How do window actuators work?

Window actuators are electro-mechanical devices fitted to windows in place of manual window handles. They use an integrated electric motor & gearing to either operate a rigid rod (as with ‘spindle’, ‘linear’ or ‘rack and pinion’ actuators) or more commonly a semi rigid chain to operate the window.

The actuator body is normally designed to be as compact and aesthetically appealing as possible and is attached to the window frame using brackets. The moving rod or chain that projects from the actuator body is attached to the window sash – enabling it to open and close the vent.

Why use window actuators?

Window actuators make it possible to control a window or group of windows without physical interaction with the window – operating them either from a wall mounted switch or remote control. This can help with accessibility challenges and offers the potential for automation to enhance building performance.

How are window actuators controlled?

Window actuators are normally electrically powered, and most often used to open and close high level windows and rooflights. They are typically operated by manual switches, remote control, or control equipment programmed to automate them based on room and weather conditions.

What are the benefits of automated windows?

Automated windows enable the building to take advantage of intelligent ventilation based on room and weather sensor readings. By automating and optimising window opening and closing, it is possible to enhance comfort and building performance, delivering optimum room temperature, air quality and building energy usage.

Automated windows enable intelligent Natural Ventilation and are most frequently used in modern ‘smart’ buildings, and larger buildings looking to optimise indoor conditions while balancing energy use. By reducing reliance on mechanical ventilation systems, natural ventilation makes it possible in most buildings to save energy and deliver natural cooling and fresh air through natural means. These systems are normally controlled by the BMS (Building Management System) or specialist control equipment with on-board control algorithms.

Automated window systems may also be used alongside mechanical ventilation systems in a ‘hybrid’ or ‘mixed mode’ ventilation strategy– taking advantage of natural ventilation whenever possible and using Mechanical Ventilation only when extreme temperatures or weather conditions dictate.

What are the main components for simple window actuator control?

In a simple system where a mains powered actuator is being used to manually control a window, the system normally consists of the actuator(s) and a switch. 24v DC actuators also require a suitable transformer or controller. Actuators, switches and any additional sensors are wired into this controller.

Additional components may be added – for example timers or rain sensors to add an element of automation – closing windows at certain times or when it rains to maintain building security and integrity.

What are the main components of a Window Automation System for Intelligent Natural Ventilation?

In window automation systems for larger buildings and smart ventilation, the system normally comprises of window actuators, field cabling, room sensors (CO2 & temperature), local controllers, manual override switches, weather sensor and a control system – which could be a BMS or integrated control logic.

Here’s some more details about the common components that make up a window automation system:

• Window Actuators – to drive windows and rooflights to the desired opening position to allow fresh air into – or stale/warmer air out of – the space. These may be different types including rack and pinion, spindle or linear type motors – but most commonly they are chain drive actuators.
• Control units – these are particularly relevant to 24v DC window actuators which require a transformer to provide the correct power to operate and where there are larger quantities of actuators in the building to simplify local control signals. These offer a means of powering extra low voltage (24v) actuators, but can also enhance safety, simplify field cabling and create control groups. Inputs to the controllers from switches, sensors and control logic in turn operate the windows in independent groups according to how they are wired and configured.
• Rain or weather sensors – these are used to provide signals to close windows in the event of bad weather – helping protect the building and occupants. In more sophisticated systems outdoor temperature and wind readings can also play a role in optimising window positions (for example limiting them in cold, windy or extremely warm outdoor conditions)
• Room temperature and air quality sensors – These are normally combination units and may include humidity sensors too. Their job is to provide the control system and logic with a live status of room conditions. The most important factors normally being temperature (to indicate over or underheating), and CO2 which is frequently a targeted measure and used as a barometer for general air quality.
• Override switches – in most buildings it’s important to allow occupants to be able to override the system and force windows open or closed in the case of such things as a bad smell in the room, if they feel undesirable draughts or require privacy that open windows don’t allow.
• Wiring – mains power cabling to controllers (or actuators if 230v mains actuators are used), and field cabling from controllers to actuators, switches, sensors and network cabling to the head end or BMS containing the logic.
• Additional protection against entrapment – in some higher risk scenarios it may be deemed necessary to have additional entrapment protection measures. This may be in the form of advanced actuator setup (such as with WindowMaster MotorLink actuators with pressure safety function), pressure-based seal detection systems, or more sophisticated presence detection systems. If these are a requirement, early risk assessment and coordination during the design stages is a must to understand options and residual risks – often a more holistic approach to design and window positioning can provide a higher performance and lower risk solution.

System schematics for a simple manually controlled window actuator control solution

In a simple domestic style installation with a single actuator or group of actuators to control, here’s an example of a typical schematic.

For 230v mains motors the system typically sees actuators wired back to a centre retractive rocker switch, in turn wired back to an appropriate mains power supply (normally RCD protected). Please note different manufacturers require different cabling requirements – please refer to specific actuator datasheets and installation instructions.

When more than one, or a group of actuators need to operate together on a window or as a group, they often require additional wiring connections local to the windows (and this should be considered in terms of the number of cable core provisions).

Schematic for 24v DC actuators in a simple arrangement:

24V DC actuator control solution features a small control unit – fed from mains power, with a switch input and wired out to the actuator.

Systems can grow in sophistication – from the addition of convenience components in small buildings – like rain sensors, thermostats or timers – to large and complex systems delivering whole building intelligent automated natural ventilation.

Many of the approaches taken by designers, and the performance requirements set out for the individual components, will have been derived from guidance in standards like the building regulations, or by modelling and analysis of the building requirements with specialist input from the design team according to the specific building type and needs.

Systems can therefore vary between different types and sizes of buildings, but here’s a typical example using BacNet based window controllers:

Schematic of a larger window automation and natural ventilation system

Featuring a multi zone control panel taking multiple manual override inputs, a BacNet BMS network input for control signals, and grouped ‘motor lines’ out to common groups of actuators in each zone, with up to 4 no. 1A actuators per motorline, and up to 20 actuators per controller.

What are the different types of window actuators?

The most common types of actuators in domestic, commercial and public buildings are electrically driven chain drive actuators. Electric actuators use 230v AC or 24v DC motors and gearing to operate a rod or chain which in turn operates the window.

Linear actuators also known as spindle actuators use a rod system and must be mounted to enable the drive to pivot on its mount as it operates the vent. While there are pneumatic and hydraulic actuators for vents these tend to only typically be used in agricultural or industrial applications and will not be covered in this guide.

What are spindle actuators, rack and pinion or linear window actuators used for?

Spindle actuators have historically been used on large rooflights requiring high forces enabled by the rigid rods, and where actuators are largely out of sight and have less visual impact. The evolving capabilities of chain drive actuators has seen them take the place of many linear actuators.

Linear or spindle actuators use a rigid rod arrangement rather than a chain resulting in a longer assembly that must project somewhat into the space enabling them to pivot as they extend to drive the window open.

More recent manufacturing technology, motor, gearbox and chain designs have made it more feasible to use chain drive actuators cost effectively on high load applications, often making the solution more discrete and aesthetically appealing.  Chain drives are more compact and are less intrusive into the space.

Where are chain drive window actuators used for?

Chain drive actuators are commonly used for out of reach façade windows and rooflights. They provide a compact and aesthetically acceptable solution to remote window operation and automation, with high forces and chain lengths available to suit a wide range of applications.

What are the benefits of chain drive window actuators?

Chain drive actuators have become the most popular type of window actuators as the semi rigid chains are designed to recoil into a compact enclosure that can be fitted close to the window sash and frame making them aesthetically more desirable. They offer a discrete and robust solution to automating windows.

Which manufacturers make the best window actuators?

There are many high quality and respected manufacturers of window actuators that produce robust and dependable products. Teal Products have supply agreements and stock a range of solutions from recognised manufacturers including WindowMaster, Aumueller, Topp, Mingardi, Comunello and Geze.

What are the differences between different window actuator manufacturers

Most manufacturers have evolved toward similar styles of actuators – all seeking to find the most compact, aesthetically acceptable, versatile and reliable solution. Some manufacturers focus on 230v mains motors, while others offer advanced features like MotorLink to reduce noise and improve control.

MotorLink from WindowMaster is a technology platform for 24v DC actuators that allows motors to operate at lower and quieter speeds when changing position for ventilation, but faster operation when needed for closing on rain. They also enable direct communication with the control system or BMS, allowing control algorithms to send windows directly to a % opening position – simplifying control algorithms and improving comfort and building performance. They also enable custom force settings to reduce health and safety risks.

Most manufacturers offer different sized actuators, with different chain length and force capabilities, in different colour options, with various brackets to suit the application.

What are the benefits of 24v DC window actuators?

24v DC actuators are normally used for automated windows & natural ventilation in larger buildings. They offer safety benefits when running cabling through or around window frames & are more capable of frequent operation at higher loads, as well as helping simplify field cabling when there are larger quantities of motors

When dealing with larger numbers of motors needing control in groups, extra low voltage 24v actuators can help reduce cabling requirements as up to 20 actuators can be powered and controlled by one local controller and mains power source – rather than having lots of power cables, switches, inputs and relays that might be required to control mains actuators.

24v actuators are also the norm for smoke ventilation solutions and AOV’s (Automatic Opening Vents) as batteries in smoke panels offer a practical and cost effective solution for the required power backup in the event of mains power failure during a fire, compared with generators or uninterrupted power supplies (UPS) needed for mains powered smoke ventilation equipment.

What are the benefits of 230v AC mains powered window actuators?

Mains powered actuators are often used for simple single zone or smaller manual control applications where push button control will suffice. In these instances, they can provide a cost-effective solution as they don’t require the additional transformer/controller needed for 24v actuators.

Should I choose a 230v or 24v window actuator?

The most important factor is to understand the operating (load & opening stroke) requirements of the window, before identifying which actuators would suit the application. For simple manual switch control 230v actuators may suffice, otherwise where rain sensors or other inputs are to be used 24v offers more flexibility

What are the standard colours of window actuators?

Window actuators normally come in a range of standard finishes – often powder coated in black, white or silver, or in anodized aluminium finishes. Special colours may be possible depending on product & require early consideration to understand cost & lead time for special production runs or after-market wet painting.

When special colour finishes are considered, it’s also important to consider the bracket colour too (and cabling arrangements!). Occasionally it becomes cost effective and practical to consider a colour matched cover profile to obscure the actuator, brackets and cabling. These can be designed at point of window design and manufacture to emulate the window profile and clip over the actuator arrangement making a tidy and cost-effective solution.

For special finishes please contact sales@tealproducts.co.uk with the desired RAL colour and gloss level for a price and lead time.

Do window actuators offer good security?

Achieving good security with automated windows involves ensuring windows are sufficiently closed (with automation offering a benefit over manual windows) & that actuators are securely fitted to the windows with appropriate fixings. If best practices are followed, window security can be better than a manual handle.

Using appropriate riv-nuts and bolts normally provides a high level of security – typically in line with secure by design standards – as when properly fitted, a closed window secured by the actuators is no easier to open than other traditional manual handles and the most vulnerable point of the window becomes the glass rather than the frame assembly and actuator.

Building design also plays a part in maintaining good security – particularly when seeking the benefits of out of hours ventilation like night cooling or night-time ventilation. In these situations, designing opening vents to be more difficult to reach from outside, higher up the façade, on the roof or with protective planting can help to reduce security risks.

Even with windows marginally open, the strength of the actuator chain and fixings can offer a very high level of security and make it very difficult for potential intruders to defeat – however, as with any window, a common-sense approach and assessment of security/vandalism risks should be considered depending on the specific building and location.

Where additional security measures are required, it is normally possible to use chain drive actuators in conjunction with locking motors that are used to engage a window locking system like an espagnolette locking system. These are an additional motorised device, synchronised with the window actuators, to operate a sliding locking system within the window.

What is the maximum width of a window for a single window actuator?

The maximum width is normally 1100-1300mm, however, this figure depends on two factors – the weight of the window and the ability for one actuator to be able to deliver sufficient opening force, and the ability to be pull the window to a tight seal from a single pull point – which depends on flex of the window profile.

The flex of window profiles against the seal around their perimeter depends on the material, thickness and design – so can vary between different windows systems.

Actuator suppliers and window manufacturers normally offer datasheets and guidelines for both factors. For example, there are normally system specific guidelines for the number of closing points for windows using traditional cockspur handles, and this often mirrors the requirements for actuators.

Physical testing can also be used to test the capacity for an actuator to seal a window – either by air pressure test, or simple indicative ‘paper’ pull tests at the edges of the windows – depending on the application.

For very wide windows (or parallel opening windows) it may be necessary to have as many as 4 actuators on a window, and these must be synchronised to ensure they operate together and don’t skew the sash or prevent the window from closing correctly. Sometimes this requires additional setup on site or specification of the requirement for synchronised sets of actuators at point of supply, as well as additional cable cores to enable the actuators to sync. Seek advice from manufacturers datasheets or contact sales@tealproducts.co.uk

Can window actuators be used for smoke ventilation and AOV’s?

24v DC actuators are commonly used in AOV and smoke ventilation applications. As these products are covered by extensive product standards and regulations, they must have been integrated as part of the AOV manufacturing and delivery process, and have satisfied extensive testing, certification and quality control.

Replacement of existing actuators to smoke vents and AOVs needs careful consideration to ensure the solution is fit for purpose and meets relevant industry guidance. For more information please contact us, or see our guide to smoke ventilation systems here.

How do you control window actuators?

Window actuators may be manually controlled from a wall switch or remote control, or automated, or both. Where windows or rooflights are predominantly manually controlled, they may still have an element of automatic operation – eg by timer or rain sensor to close windows at end of day or rooflights in the event of rain

Larger buildings normally have more sophisticated control solutions that monitor room conditions like room temperature and CO2, and incrementally open and close windows to optimise comfort, air quality and energy performance – controlled either by modular controls with onboard logic attached to sensors and weather station, or by integrating with the BMS (Building Management System).

For more information on understanding and design of automated windows and intelligent natural ventilation, read more below.

How many window actuators does a window need?

The number of actuators needed for your window depends on the size of the window; This dictates the load that the actuators need to deliver to open and close it, and the number of pull points needed to be able to pull the window closed tight around its full perimeter and deliver a good seal according to window type.

The first thing to check is how many push/pull points the window company recommend to be able to exhibit a good seal across the window width. This normally follows similar guidance to the number of cockspur handles required on a manual window to achieve the same.

Typically for aluminium windows the maximum width for a single pull point, (manual cockspur handle or actuator) is normally between 1100-1300mm but it depends on the flex of the aluminium profile when pulled tight against the seal.

The window must be rigid enough with the number of pull points to not flex against the seal such that windows are not properly airtight at the edges. If the system provider cannot advise on this, or if you have an existing window – normally you can match the number of manual cockspur handles fitted.

If the handle operates an espagnolette (integrated sliding) locking system then the locking system would need removing, fixing open or additional espagnolette locking motors might need considering. Please contact our team for guidance.

How long does a window actuator stroke need to be?

The stroke of the actuator depends on how far you want the window to open from its closed position to achieve sufficient ventilation. The maximum stroke must not be more than the maximum opening limit of the window. A range of standard actuator strokes are available & some have adjustable strokes or can be factory set.

One thing to consider is that long strokes often require the chain to be able to handle higher loads at full extension whilst maintaining their rigidity, meaning the chains must be chunkier and subsequently the housing must be larger to allow the bigger (and longer) chain to recoil fully inside. Strokes of 200-300mm are common for domestic and comfort or natural ventilation applications.

Longer strokes up to 1000mm are available, but forces, opening limitations, actuator size, risk of fall and actual need should be assessed; Natural ventilation typically gains the most airflow from opening distance in the first 200mm of opening due to air pressure differences around the building – particularly where there is some cross ventilation.

It should be noted that the maximum actuator chain stroke stated would normally need to include the length of chain required to bridge the gap between the actuator mounting point and the sash (see below). Also, that the clear gap for opening area calculations between the window frame and sash will be the functional chain stroke less the depth of the frame and cill. See calculating the free area.

What is the geometric free area of a window?

The geometric free area of an open window is a measurement or calculation of the rectangular clear area between the open sash and the frame through which air can flow. It is an expression used to indicate the realistic area through which air can flow unrestricted through an open vent at the throat of a window.

The triangles at the side are often ignored but may be taken into consideration depending on the needs of the building and method of assessment.

A simple geometric free area calculation of a top hung window is a x b, where ‘a’ is the smallest clear opening between the sash and most prominent part of the window frame or building, and ‘b’ is the clear width of the inner window frame.

More accurate calculations use the clear gap at right angles to the sash (indicated by the yellow square) which is the more realistic pinch point of the opening. This is slightly smaller than measuring from the leading edge of the sash – consider this as a representation of the diameter of the largest ball that could be passed through the window as the leading edge protrudes slightly further than the actual restriction at right angles from the sash to the most prominent edge – normally either frame or cill.

How do I find the operating load for window actuator selection

The load on the actuator is dictated by the window, as a function of the window orientation, hinge arrangement, dimensions, weight (frame material & glass thickness) & how far it needs to open. Depending on these factors it’s possible to either calculate or measure the approximate load required to operate the window.

How much force does a window actuator need to operate a window?

The force required to open or close a vent is an important factor in window actuator selection. The force required is dictated by the window specifications and arrangement, and there are two main approaches to find the operating force – calculation or physical test – and to prove actuator suitability.

The orientation of the vent/window plays a major role – for example side hung windows have little force required to open and close aside from overcoming hinge friction.

How do i calculate the load or required force of an actuator for Top Hung Windows

Top hung windows on butt hinges see an increase in the actuator force required as the windows open and pivot from vertical (where the sash weight is fully supported by the hinges) up toward horizontal where the actuator bears more of the weight. It’s relatively easy to calculate approximate loads involved.

Top tip: If a load is known in Kg it can be multiplied by 10 for an approximate newton force.

Useful calculators like that from WindowMaster can also help with these types of estimations. https://www.windowmaster.com/resources/calculators/actuator-finder/

How do you assess actuator forces for top hung windows on projecting hinges or friction stays?

Unlike with butt hinges, top hung windows on friction stays or projecting hinges require less force to open as the scissor action of the hinges extends the sash partially under its own weight, however this requires more closing force to overcome the lift to pull the hinge geometry & sash back up to the closed position.

It can be more complex to accurately calculate the force required with this window and hinge arrangement as the hinge type, dimensions, location and sash weight create many factors and complex geometry making it more difficult to calculate. Ideally a physical test can be used to establish the operating forces.

Force gauges are designed to measure such things accurately, but simple devices like fishing weigh scales or luggage scales with a hook connected to the sash and pulled in the same plane as the actuator chain can give a good estimate of the operating load.

Otherwise, engage window designers and hinge providers for calculations and estimates with a safety factor applied. For large quantities of windows of the same dimensions it is normally recommended that a mock up unit be built and tested with the actuator before mass manufacturing or order of actuators.

One other factor with projecting hinges is ensuring that if the hinge geometry allows the sash to drop when it opens, the path of the chain must not conflict with the frame. This can be assessed using a mock up window build or through technical drawing assessment of window and hinges – ensuring the actuator brackets and mounting position account for any potential chain path issues.

How do i calculate the load or required force of an actuator for Bottom Hung Windows?

Bottom hung windows required mainly a pull or tension force to lower the sash open & pull it closed. Those on butt or barrel hinges can be calculated. Bottom hung windows should also be fitted with restrictors for health & safety to protect the sash from falling in the event of actuator mounting or chain failure.

How do i calculate the load and required force of an actuator for Side Hung Windows?

Side hung windows require relatively low forces to open the vent as the full weight of the sash is supported by the hinges throughout the range of operation. Actuators only have to overcome the operating and friction forces of the hinges. Manual calculation or physical testing can confirm operating loads.

How do i calculate the load or required force of an actuator for Parallel Opening Windows?

Parallel opening vents are self supporting but have a friction force to overcome the multiple hinge geometry, and require multiple push and pull points (4) using synchronised actuators to ensure the sash operates evenly and in parallel. Manual calculation or physical testing can confirm operating loads.

This arrangement can be more complex to calculate and a test can be useful to confirm operating loads – otherwise an estimate with safety factor may be sufficient. Normally 4 synchronised actuators are required per window to ensure parallel operation, and they share the operating load between them.

What are the two main methods to establish operating load on a window actuator?

1. Estimation based on window size – this method is simple for some window types and can be used with top and bottom hung windows on butt or barrel hinges. The load is a function of the sash weight – which can be determined by the sash size, and a calculation of the estimated sash frame weight according to material, plus an estimation of the glass weight according to total thickness of all panes of glass, and glass unit size. The maximum opening angle is the final factor. Heres a useful calculator from WindowMaster that takes a lot of the effort out of calculating approximate loads, opening distances and free area:

https://www.windowmaster.com/resources/calculators/actuator-finder/

1. Physical test of the actual or a mock up window – for more complex arrangements with scissor hinges or friction stays, the existing unit in situ or a test unit can be rigged and physical measurements taken.

Specialist equipment and load scales can be used, but often a simple fishing weighing scale or luggage scale can be used. The hook end is attached to the sash where the handle is normally fitted, and the window is operated through its entire range – pulling in the same plane as the actuator pushes open, or pulls closed – and the maximum load observed. If the load is given in Kg then it should be multiplied by 10 to give a newton force (ie a measured load of 9kg is equivalent to an operating load of 90N / 90 newtons). Most actuators have a load capability stated in Newtons, so for example a 300N actuator can operate with forces sufficient for a load up to 30Kg. It should be noted that the force and load bearing capability of an actuator can diminish as the actuator chain extends to extreme opening distances, so please check the actuator data sheet and specifications.  Eg

Fitting window actuators

What mounting brackets do I need for my window actuator

Most manufacturers offer a range of brackets to suit different applications – as well as guidance and drawings showing typical arrangements according to common window profiles, window opening orientation and mounting arrangement. Brackets must be securely mounted with sufficient clearance for the application.

The main factors that dictate which brackets to use are

• Actuator design
• Window orientation
• Frame depth / profile
• (Alignment with chain mounting on sash)
• (Clearance required for chain path)

Most manufacturers offer a range of different brackets accordingly – normally with drawings showing the different arrangements. The bracket has to hold the actuator body securely against the frame while the chain bracket provides the connection between the end of the chain to the sash – which can normally be released with a bolt or split pin for installation (security bolts may also be used).

For shallower windows (or long chain lengths) that require the actuator to pivot to prevent undue stress on the actuator, chain or window, it may be necessary to use pivot brackets that allow the actuator to rotate slightly on the bracket as the window position changes.

Brackets must be secured in the correct positions to align the actuator body and chain in the correct locations – normally having the chain centred on the window (or placed evenly when more than one actuator is fitted on the sash).

The bracket profile must allow for the actuator to be mounted at the correct height for the chain to clear the frame when operating, while ideally sitting directly behind the chain mounting position on the sash.

Most applications will use a small chain bracket for the chain to sash, with some form of right-angle bracket made of cast aluminium or pressed steel for the actuator.

Inward opening windows are slightly more complex in that the actuator needs to be mounted behind the bracket that opens the window inward – normally using a z bracket or swan neck arrangement. Occasionally it may be necessary to consider mounting the actuator to the sash due to lack of clearance on the frame, and in these instances cable placement needs careful consideration as it will need to be able to articulate with the sash as it opens and bridge sash to frame at the hinged side of the window.

Examples of different window actuator brackets and mounting arrangements:

How do you fit a window actuator

Window actuators are normally installed to mimic the normal position of the window handle(s) – the body of the actuator fitted to the frame on brackets, with the chain fitted centrally to the sash (in the case of a single actuator) or at evenly spaced distances when there are more than one.

Specific guidance depends on the actuator and window. The most important factors to consider are (described for a top hung outward opening window):

1. Horizontal alignment of the chain bracket on the sash: chain bracket mounted to the sash centrally to the width of the sash (for 1 actuator, or equally spread for more than one)
2. Horizontal alignment of actuator body on frame: positioned so that chain exit from the actuator aligns to the chain bracket’s horizontal location
3. Vertical alignment of actuator on frame: just high enough for the chain to clear the frame throughout its range of operation, good fixing position of motor brackets into the frame material.
4. Vertical alignment of the chain bracket on the sash: aligned to the vertical position of the actuator, with a good fixing position into the sash material and a position that does not put the glass at risk during fixing.
5. Fixings: rivnuts or fixings appropriate to the frame material
6. Cabling: think about cable routes – where does it need to get from (from which side of the actuator does it exit) and to (where will the controller be located, or adjacent actuator or junction box when connecting multiple windows), and best methods of fixing cabling to minimise impact on aesthetics (eg plastic containment, cover profile etc).

Note on cabling – where more than one actuator is fitted to a window, the actuators must operate together and be synchronised to prevent skewing of the sash and ensure trouble-free long-term operation. Depending on the actuator this may require 3-5 cable cores and specific actuator settings or programming – please refer to actuator specific datasheets and installation guidance.

Proper fixings are needed to ensure safety, longevity and good security – rivnuts and bolts are the norm for hollow frames (Aluminium, UPVC etc), with fitting guides offering more information.

UPVC windows may require additional strengthening to secure the fixings depending on load – often having aluminium inserts provided during manufacture within the profile.

Most manufacturers provide drawings and instructions showing how to install the actuator and the correct brackets according to the application.

One other consideration is cable routing – with some looking to integrate or pull cabling through the window profile – early consideration of this prior to fitting windows can help achieve a tidier installation, and factory prep of wire ways, draw wires and grommets can make installation easier. Other options for cable management may include surface mounted containment or cover profiles to obscure the cabling and actuator.

Different actuators have different standard cable or ‘tail’ lengths. These may be extended to reach local junction boxes or controllers using appropriate electrical connections (depending on voltage), often using Wago, bullet and/or choc box connectors. Ideally these connections should be accessible for maintenance and/or continuity tested prior to enclosing.

Once actuators are fitted, any window friction stays should be set to minimum friction, and the actuator should be tested and commissioned to ensure it operates correctly and does not exceed the window limits or put undue strain on the window or actuator.

What fittings should you use with a window actuator

Appropriately sized rivnuts and bolts are the most common fittings for window actuators to UPVC,  aluminium or steel windows according to manufacturer specific guidance. UPVC windows may require additional metal reinforcement within the profile during manufacture, and Timber windows use appropriate screw fixings.

How do you commission a window actuator

Once window actuators are mounted, they should be tested and commissioned to ensure they open and close correctly without putting undue stress on the window or actuator. Different manufacturers have different guidelines but normally require a function test and routine to set the closed position.

Cable tests: It is common for continuity tests to be carried out on any field cabling to prove connections and ensure there is no cable damage prior to commissioning actuators. Insulation or ‘Megger tests’ should NOT be conducted when connected to actuators, controllers or other electrical components.

Appropriate power supplies: Mains motors must be operated using a 230v AC power supply, while 24v DC actuators should have final commissioning using the dedicated controllers or power supplies. On sites without available power or controllers during build, actuators are often set into the closed position using temporary 24v DC power supplies such as a drill battery or similar to allow temporary operation to achieve a weather tight and secure window that can be fully commissioned once controls and power are available. Mains power must NOT be connected directly to 24v actuators.

Checking for restrictions: Any temporary holding devices, existing handles or locking equipment not associated with the actuators should have been removed, and friction stays adjusted to their lowest friction setting. Checks that the maximum chain stroke does not conflict with any maximum window opening limitations.

Adjusting stroke: It is critical to ensure the actuator does not conflict with the maximum window opening as it moves to its maximum stroke, and it may be necessary to set the actuator stroke at this stage according to requirements. Depending on type this may be done by manual adjustment on the actuator, digital programming using specialist equipment on site, or should have been completed at the factory (if a specific none standard stroke is required this should always be mentioned at point of enquiry/order as this can be cost effectively achieved at the factory and reduce time and complexity on site).

Setting the home position: Once final transformer/controls are in place final commissioning normal involves driving the window fully open and closed to check operation, and for some actuators setting the closed position – often by repeatedly driving windows to the closed location until their ‘zero point’ is set (please refer to manufacturer’s instructions as different manufacturers have different needs and ways of achieving this).

Operational test: The actuator is operated to its fully open and fully close position multiple times and the window and actuator operation are observed to ensure they operate smoothly without unexpected stress.

Record keeping: Records of cable testing and actuator commissioning are normally kept as part of sign off, for O&M manuals and for future reference with details of actuator model, brackets, fitting arrangements, specific settings or adjustments made and successful testing.

What maintenance do window actuators require?

Most actuators are ‘sealed for life’ and require little maintenance other than ensuring chains are occasionally cleaned to prevent build-up of dust and contaminants, and perhaps greased according to manufacturer instructions. Actuator manufacturers guidance should always be followed.

How long does a window actuator last for?

Most actuators are tested to 10,000 full load, full stroke operations (see manufacturer datasheets), and expected to have a life span in-excess of 10-20,000 operations in normally use. This normally equates to a life expectancy of more than 10 years depending on application, with many lasting 20 years or more.

Replacement actuators are available from Teal Products, with many brands and models available from stock for next day delivery when required.

What is Natural Ventilation?

Natural ventilation is the principle of using outside air to maintain good levels of indoor air quality & comfort by controlling building openings. Building design & the extent & timing of openings are key to balancing the airflow provided by wind & thermal buoyancy to deliver optimum comfort & energy efficiency.

What are the benefits of Natural Ventilation in buildings?

Natural ventilation has the potential to offer a very effective means of providing healthy and comfortable indoor climates in buildings while saving energy compared to traditional mechanical ventilation. The UK climate and generally good air quality is particularly well suited to natural ventilation.

What’s more, as windows are also required for natural daylight – making them openable and controlling them properly to provide the right amounts of fresh air at the right times rather than using mechanical fans and air conditioning equipment, has the potential to provide a very cost effective as well as healthy, comfortable and energy efficient solution in most buildings.

What is mixed mode or hybrid building ventilation using natural and mechanical ventilation?

If extremes of weather are expected to make it more difficult to achieve a balanced climate using Natural Ventilation alone, then supplementary mechanical ventilation systems may be employed alongside natural ventilation in a ‘mixed mode’ or ‘hybrid ventilation’ approach.

This uses mechanical systems only when conditions dictate, making it possible to get the best of both worlds – energy efficient and user preferred natural ventilation when conditions allow, with mechanically optimised ventilation provided by lower capacity* mechanical systems only when required in extreme conditions.

*By utilising the benefits of Natural Ventilation, night cooling and pre-emptive-ventilation when possible, the load on the mechanical systems is normally lower than when pure mechanical systems are used. This can make hybrid or mixed mode ventilation an appealing and cost-effective approach for modern buildings.

What types of buildings can use Natural Ventilation

Natural ventilation is common in UK homes and widely used in education, healthcare, and commercial buildings. With growing awareness of carbon emissions and climate change, it’s being revitalised as a preferred way to cut energy use compared with mechanical ventilation, while maintaining a comfortable indoor climate.

Getting the best performance from Natural Ventilation

To gain maximum benefit and optimum performance in terms of room conditions and energy consumption, control of the ventilation is key. Traditionally this would have been through manual control of windows. More recently, studies have shown that manual control is suboptimal – often resulting in too much or too little ventilation, manifesting in overheating spaces, poor air quality, or excessive heat loss and energy usage in winter.

Modern capabilities through automation enable most larger buildings to save significant energy while delivering excellent indoor climates by automating windows or vents for intelligent and controlled automated Natural Ventilation.

Natural ventilation uses natural forces to move air through a building. Its therefore important that whenever possible a building is designed to optimise air flow and therefore the potential effectiveness and performance of natural ventilation.

Natural ventilation uses the natural forces of wind, pressure differences around the building, and thermal buoyancy of warm air to move air through the space – therefore designing enough openings in the right places in the building, and controlling them correctly, is key to capitalising on the potential of natural ventilation. A holistic approach to building design always achieves better results, and the design would normally incorporate the principles of cross ventilation and stack effect, as well as working in harmony alongside other systems.

Can all buildings use natural ventilation?

We are fortunate in the UK that most buildings can take advantage of the benefits of natural ventilation for much of the time. There may be circumstances where buildings may be better served by alternative means of ventilation – these may include poor outdoor air quality, high noise levels or privacy needs.

Depending on the challenges specific to the building, it may be possible to use natural ventilation some of the time in a mixed mode arrangement, for example at times when outdoor air quality or noise levels permit. Operating Natural Ventilation based on outdoor air quality and noise sensors has been successfully employed in city centre locations.

How do I optimise the performance of natural ventilation?

For optimum indoor climate and energy efficiency, Natural Ventilation must be properly controlled. In homes with few users, manual control can be acceptable, but in larger buildings with more complex needs, automated Natural Ventilation offers superior performance, ensuring better airflow management and energy savings

To get the very best indoor climate & energy performance, Natural Ventilation must be properly controlled. In domestic settings with few users & ‘ownership’ of the ventilation, manual control is often adequate, but in larger buildings with more complex ventilation needs – automated Natural Ventilation achieves better performance.

It is unrealistic for building occupants to have a constant awareness of changing room and outdoor conditions – particularly in larger more densely occupied buildings where no single person is responsible for controlling ventilation. In addition, even with the advent of traffic light systems to indicate varying air quality and room temperature, it’s often difficult for users to know the best window positions to achieve optimum ventilation and energy performance. Regular changes in status can also become obtrusive leading indicators to be ignored.

Individuals most often react to extremes – rooms that are too warm, too stuffy or too cold – often being the triggers for actively intervening with ventilation – however, this often means action is too late, and the lag in response or lack of physical presence in the spaces mean rooms are not maintained in an optimal state of comfort or energy performance.

One other such example is counter intuitive operation of the ventilation – for example limiting openings only for air quality in the height of summer when outdoor temperature is higher than indoor temperature. The assumption by many occupants might be to throw windows open on a very hot day, but this can have a detrimental effect on indoor temperatures and overheating.

In addition, certain highly beneficial natural ventilation strategies are difficult to deliver manually when buildings are not occupied – for example maintaining acceptable security while also delivering optimised night cooling or pre-ventilating spaces before they are occupied or heated.

What is night cooling?

Night cooling is the practice of taking advantage of ‘diurnal’ temperature differences (it typically being cooler at night) to implement additional ventilation and cooling to rooms that need it at night during the summer. This is most practically delivered by using automated Natural Ventilation.

Night cooling allows the air in the space, the building fabric, and the contents of a space to be cooled while people aren’t present. Done carefully this allows more elasticity of the space the following day to be able to absorb some of the thermal gains from heat contributors (solar gain, heat from equipment and people) slowing the onset of overheating, delaying and reducing overall peak temperatures to more acceptable levels.

Strategically incorporating higher levels of thermal mass in the space and fabric of the building can further help exploit the benefits of night cooling. Thermal mass uses denser materials (or phase change materials) that can be accounted for as part of ventilation, heating and cooling strategies to help stabilise operating conditions by absorbing or emitting heat according to preferred room setpoints.

Night cooling can help to reduce overheating by many hours in a day and reduce extremes of room temperature, often by as much as 5-10 degrees C. It can provide a means of keeping otherwise uncomfortable rooms at a much more desirable temperature.

What is automated or intelligent natural ventilation?

Automated natural ventilation is an intelligent approach to optimising natural ventilation openings and performance by using control devices, sensors and control logic. The system may typically use the BMS or onboard logic to control ventilation components like windows, louvres or rooflights using actuators.

What is window automation in buildings?

Window automation is one means of delivering high performance automated natural ventilation to enhance indoor conditions & building energy consumption. It typically uses actuators fitted to windows, controlled either by the BMS or outstation logic, & has been extensively proven in education and commercial settings.

How will I know if Natural Ventilation will perform – modelling performance for overheating and air quality?

For larger buildings like schools, universities and offices seeking to utilise automated windows for natural ventilation, the building design will normally require modelling to prove thermal comfort, air quality and energy performance based on the opening area and arrangement of windows.

For Natural Ventilation to work well and maintain good levels of comfort and energy efficiency, it depends on sufficient, well-placed openings in the building, controlled appropriately according to internal and external conditions, utilising the natural forces of wind pressure and natural buoyancy to move enough (but not too much!) fresh air through the building in a considered way.

There are several guidance documents that offer a starting point on what to expect and the requirements in terms of performance, depending on the type of building and occupancy, however every building design is different and therefore there is normally a need for assessment of expected performance using static calculations, simulation and modelling during the design stages.

This may include thermal and energy performance assessment using software packages like IES, SAP, or full CFD analysis using weather files and building material, occupancy and location data to provide a more in depth look at anticipated performance.

There are different schools of thought on how to best arrive at the required chain stroke or free area required, how to calculate the geometric free area of a window opening, and best practices around optimum window positioning – but here’s some guidance from us;

How much free area is needed from the windows for naturally ventilating a room or building?

Design guidance such as AM10 offers a starting point, stating that the free area of windows in a room should be a minimum of 5% of the floor area. However, other regulations state a need to achieve certain building performance in terms of maximum temperatures & CO2 levels which are normally proven through modelling.

Where modelling is conducted by trial and error assuming a starting number of windows with assumed openings, where possible use smaller standard actuator strokes (deducting approximately 70mm for the chain required to bridge frame and mounting) for running initial calculations on free area.

For example, 250mm chain strokes are commonly available, and these will typically offer around 180mm clear opening on an aluminium window profile. If the building performance modelling passes – you will have access to a range of compact and cost-effective actuators to deliver the indicated performance. Otherwise, you can consider going to a larger chain actuator such as 400mm (offering c. 330mm clear opening – providing the windows allow) or adding more opening windows.

More and better distributed opening windows has the benefit of better air distribution compared with fewer, larger openings – helping to achieve better comfort and air quality across the space and reducing draughts by spreading the required volume of fresh air across more openings with smaller apertures.

The geometric free area may be calculated based on the rectangle between the edges of the sash and frame at the fully open position (see above). This is a simple geometric calculation or can be measured with the window in situ/or factory.

Different methods of performance assessment will dictate whether to include the triangular elements at the sides of the window. When there is a linear string of opening windows side by side, these triangles cannot be used as the extra opening cannot be exploited due to limitations from the adjacent window. There is also some debate as to whether air can flow through the main rectangle and triangles at the same time without flowing across the window rather than through it – so triangles are often ignored for geometric free area unless modelling software instructs otherwise.

It is also good practice to take the rectangular free area at right angles to the sash which is slightly smaller than the simple rectangle from the inside trailing edge of the sash to cill or frame (this aligns with the approach for smoke ventilation calculations). The rectangular free area can be found using assessment of drawings or measurement of the window.

The Teal Products tech team are also at hand to offer guidance on opening areas.

Modelling and assessment software may also require alternative methods of area calculations like effective free area or equivalent free area.

What are the regulations for natural ventilation and automated windows?

In the UK, several key regulations and design guides govern and offer guidance on natural ventilation in buildings to ensure acceptable indoor air quality, comfort, and energy efficiency.

Here’s a summary of the main ones:

Regulations

1. Building Regulations Part F (Ventilation)

1. • Specifies requirements for sufficient ventilation to maintain good indoor air quality.
   • Sets minimum ventilation rates for different types of building
   • Includes guidance on background ventilation, purge ventilation and mechanical vs. natural ventilation systems.

1. Building Regulations Part L (Conservation of Fuel and Power)

• Focuses on energy efficiency, regarding the design of ventilation to minimise energy usage while ensuring a good indoor climate.
• Encourages natural ventilation as a means of reducing reliance on mechanical systems and improving energy consumption.

1. Approved Document B (Fire Safety)

• Covers smoke and heat control in buildings, which can involve natural ventilation systems to assist in smoke extraction. (For more information on smoke ventilation see our ultimate guide to smoke ventilation)

1. CIBSE TM52: The Limits of Thermal Comfort: Avoiding Overheating in European Buildings

• Offers guidance on thermal comfort in naturally ventilated buildings with a method of assessment and focus on reducing overheating to acceptable levels without relying heavily on mechanical cooling.

1. CIBSE TM59: Design Methodology for the Assessment of Overheating Risk in Homes

• Provides criteria for assessing overheating risks in residential buildings – particularly relevant for naturally ventilated homes.

Design Guides

1. CIBSE Guide A: Environmental Design

• A comprehensive guide to achieving acceptable thermal comfort -including natural ventilation strategies.
• Provides details on ventilation rate calculations and headline design considerations.

1. CIBSE AM10: Natural Ventilation in Non-Domestic Buildings

• A guide specifically for designing natural ventilation systems in commercial, education, and healthcare buildings.
• Covers approaches, principles, control strategies, and case studies.

1. BB101: Ventilation, Indoor Air Quality, and Thermal Comfort in Schools

• The go-to standard for ventilation in schools (and other education settings) – focusing on natural and hybrid ventilation to enhance indoor air quality and thermal comfort.

1. BS EN 16798-1:2019 (formerly EN 15251)

• A European standard adopted in the UK – providing guidance on indoor environmental input parameters, including ventilation rates for different building types.

1. BS 5925: Code of Practice for Ventilation Principles and Designing for Natural Ventilation

• Focuses on the design principles for achieving effective natural ventilation in buildings, particularly in urban and complex environments.

Why are actuators and window automation used in schools?

Schools & education buildings are well aligned to the use of intelligent natural ventilation. The desire to achieve better room conditions, reduce dependency on mechanical ventilation, use natural ventilation wherever possible, & need to achieve real world performance requires something more robust than manual windows.

There is also a desire to improve the performance of existing school buildings whose performance is often not up to current standards, with automating windows offering one pragmatic means of achieving that.

What are the requirements for Natural Ventilation in UK schools?

The design and performance requirements for natural ventilation in schools are set out between the Building Regulations, BB101, Department for Education (DfE) standards, and CIBSE guidelines to ensure good indoor air quality, thermal comfort, and energy efficiency.

The key document for school ventilation is BB101: Ventilation, Indoor Air Quality, and Thermal Comfort in Schools.

What are the performance requirements for natural ventilation in BB101?

BB101 sets out clear minimum requirements for schools including minimum ventilation rates of fresh air, maximum CO2 (carbon dioxide) limits in classrooms, maximum acceptable indoor temperatures and offers guidance on air quality and noise, summarised below.

Key Design and Performance Requirements for Natural Ventilation

Excerpt from BB101: All occupied spaces should be provided with ventilation for warmer weather, preferably by using, cross flow natural ventilation or ventilation systems with equivalent ventilation effectiveness, and night cooling.

1. Ventilation Rates

• Adequate Fresh Air Supply:

• Indicative minimum 5 l/s per person during normal teaching activities.
• Proposed normal 8 l/s per person.

• CO₂ Concentration Limits:
  • Should be designed to keep CO2 levels below 1200 ppm most of the time during the occupied year in a new school building  (below 1750ppm most of the year for a refurbished building)
  • Should not exceed 1500 ppm as an average over the school day.
  • Maximum concentration allowed to exceed 2000 ppm for not more than 20 minutes consecutively each day.

2. Thermal Comfort

• Overheating should be assessed using BS EN 15251 and CIBSE TM52 adaptive thermal comfort model (this replaces the former 120 hours per year above 28°C). Adaptive thermal comfort considers factors like outside temperature, the number of hours above acceptable indoor temperatures, the degree of overheating above the acceptable temperatures, and the maximum temperature of exposure. These are normally assessed using software and dynamic thermal modelling.
• Draughts should be carefully considered and avoided.

3. Air Quality Standards

• Schools should maintain good indoor air quality particularly where outdoor air quality may be a challenging factor, by providing effective natural or hybrid ventilation systems that can manage pollutants, allergens, and CO₂ levels.

4. Noise Levels

• Good acoustics are essential for learning environments and BB101 refers to  BB93 (Acoustic Design of Schools):
  • Natural ventilation systems should generally not exceed 45 dB(A) in teaching spaces during operational hours.
  • Acoustic treatments or quieter natural ventilation designs (e.g., attenuated vents) may be required to meet this standard particularly where outdoor noise is a challenge.

6. Control Systems

• Natural ventilation systems should be user-friendly and allow for manual override and purge ventilation where appropriate.
• Automated systems (e.g., window actuators or hybrid systems) are encouraged in large or complex spaces for optimal performance, particularly in managing temperature, air quality and energy performance.

Designing systems for automated natural ventilation – what are the practical design considerations for a naturally ventilated building?

Early consideration, a holistic approach and co-ordination between different design disciplines and building packages is key to achieving successful natural ventilation design. Vent positioning, adequate openings and control must all be considered early on to mitigate risks and ensure high levels of performance.

Building orientation and solar shading are also an important consideration to get the best from Natural Ventilation.

Following design guidance, best practices, taking industry expert guidance and modelling outcomes will all help to ensure the building is delivered cost effectively, right first time and will achieve expected levels of performance.

What are the different natural ventilation strategies?

Natural ventilation strategies take advantage of natural forces caused by wind pressure, building form, and thermal buoyancy.

What is single sided ventilation?

Single sided ventilation uses vents on one side of a space. These may be at high and low level to help improve air exchange, but ventilation is limited by one direction of airflow. It can normally provide effective ventilation in smaller perimeter rooms with lower occupancy, or wider shallow rooms with more vents.

The ability to be able to harness wind pressure differences is more difficult in single side spaces and the preference is normally to employ cross ventilation or stack ventilation wherever possible.

The limitations of single sided ventilation are due to the inability to create pressure difference across the space to encourage airflow and distribute the air more evenly and across the space. In simple terms, the impact of wind on a single sided façade is to pressurise the space rather than supply air at the windward side for it to be drawn out by lower pressure on the leeward side of the space. As a result, single sided ventilation depends on local air temperature differences between inside and outside, thermal buoyancy and localised air turbulence to exchange air.

BB101 suggests that as single-sided ventilation relies solely on openings on one side of the room this has a limiting depth for which it can achieve effective ventilation, typically 5.5m or 2 times the room height, making it more suitable for shallow rooms, perimeter offices or smaller space.

What is cross ventilation?

Cross ventilation uses vents on opposing sides of a space. This makes it possible to take advantage of pressure differences at each side of the space to drive fresh air into and stale air out of the space using the size of the openings like large valves to control the amount of airflow.

Cross ventilation with properly spaced and distributed vents across facades helps to achieve much better coverage of ventilation in the space and achieve higher air exchanges when required in more densely occupied or larger, deep spaces. Often cross ventilation can be used in conjunction with thermal buoyancy with high level vents too – either rooflights or when associated with an atrium’s high level vents using transfer grilles into an adjacent atrium.

BB101 suggests that cross ventilation is most effective when the room depth is limited to 15m or 5 times room height. Additional stack ventilation via rooflights, ventilation stacks or atria can help to extend these limits.

What is thermal buoyancy and stack effect?

Thermal buoyancy is the principle that cool air is denser & heavier than warm air – forcing warm air to rise. The degree of the effect of thermal buoyancy depends on the temperature difference between the warm & cool air, & the height differential. High & low-level vents can use this effect to ventilate a space.

Warm air is allowed to evacuate a space through high level vents, which in turn is replaced by cooler air allowed to enter through the low-level vents. Thermal buoyancy is also known as ‘Stack effect’ and is particularly useful to help exhaust warm or stale air in a building and replace it with cooler, fresh outside air even when there is little to no wind pressure to support air exchange.

High and low-level façade vents, or façade vents in conjunction with rooflights, roof vents, ventilation chimneys or transfer grilles into atria with high level atrium vents all offer opportunities to take advantage of stack ventilation and thermal buoyancy.

What is a typical design approach for Natural Ventilation?

During the design stages Architects and Engineers will consider a range of factors to calculate and validate the suitability and required opening areas for Natural Ventilation. These will take into consideration things like:

• The use of the space (eg commercial, education)
• The type of occupants, daily and calendar usage, and occupant density
• The relevant standards that stipulate minimum and maximum performance for things like temperature, air quality and other comfort and energy factors.
• Location related challenges that may require hybrid or alternative methods of ventilation.
• The design, construction and fabric of the building that will influence things like heat gain and loss.

How many windows openings do I need?

The quantity of window openings is typically dictated by ventilation strategy, opening area requirements and fresh air distribution. Best practices encourage the use of cross ventilation with openings on opposing sides of the room, ideally automated at high level and well distributed around the space.

What free area of window openings do I need for Natural Ventilation?

Guidance on ventilation and openable window free areas can come from one of the design guides appropriate to the type of building, in addition to modelling to prove performance. Typically, according to CIBSE guide AM10 the starting point for ventilation free area is 5% of floor area.

How do you measure geometric free area of window openings for natural ventilation?

A simple geometric free area calculation of the rectangle at the leading edge of the window is a x b, where ‘a’ is the smallest clear opening between inner edge of the sash and the most prominent part of the window frame or building, and ‘b’ is the clear width of the inner frame (see illustration below).

What is effective opening area of a window?

Some natural ventilation & design guides refer to effective free area of a window & this may be required for dynamic analysis of the ventilation performance. Effective free area uses a calculation of the geometric opening size x the discharge coefficient of the window according to angle of opening – normally c. 0.6-0.7

A calculator has been made available by the ESFA – Education and Skills Funding Agency to help such calculations https://assets.publishing.service.gov.uk/media/5b7add7540f0b64350cbf814/Discharge_coefficient_calculator.xlsx

What is the best position for automated windows and natural ventilation?

Design guidance typically recommends several well distributed vents around the space, utilising cross ventilation (and/or thermal buoyancy) wherever possible. High level automated facade windows help to enhance security, reduce draughts and minimise entrapment risks.

Depending on the strategy and type of room, there are some best practices and considerations for where to position vents, and what type.

High level automated windows have a number of benefits:

• Small openings at high level in winter to control CO2 do not introduce draughts and cold air directly at body height, enhancing the possibility of mixing that air and reducing cold draughts
• Small openings higher up on the façade help to reduce the security risk for night cooling
• Automated windows at high level present a much lower risk to users who might accidentally put their fingers in a closing window. They may also allow larger openings than allowed at low level due to risk of fall and opening limitations.

Where additionally opening area may be required – it is not uncommon for high level automated windows to be supported by low level manual windows. The automated windows do most of the work most of the time, with low level windows offering additional purge function when required and the potential of low level air inlet for a degree of stack effect, exhausting warmer air through the high level opening when conditions suit.

Occasionally the high level windows may be supported by rooflights, acoustically treated louvres into adjacent spaces, ventilation chimneys, roof vents (windcatchers), or modulating fans.

What’s the best window orientation for automated windows?

High level top hung outward opening windows typically offer the best balance of performance, security, health & safety, & aesthetics. They help reduce draughts at low level in the space, minimise the risk of accidental entrapment, & limit access for security, often allowing a degree of secure opening for night cooling

They may also allow limited opening during rain compared with bottom hung and other window orientations.

Side hung automated windows:

• Side hung windows are often seen as a way of achieving quite large opening areas, however they can also introduce cold air and issues with draughts at low level in winter unless split into high and low-level units (having one or two large side hung vents also achieves poorer air distribution than more and better distributed smaller vents).
• They may also introduce a fall risk depending on height and position – often used in conjunction with screens and sometimes acoustic treatments if site conditions dictate.
• Can achieve a perceived reduction in summer temperatures by encouraging controlled airflow (a light breeze) at body height.

Why use window actuators to automate windows? Manual v Automated windows

Whether natural ventilation employs automation or manual windows in new buildings, as part of the simulation and modelling exercise certain assumptions will have to be made about when and how much windows are opened. The challenge with manual windows is that there is no certainty that they will be operated by the right amounts at the right times to deliver real world building performance.

There have been extensive studies to show that manual windows are rarely opened or closed by the optimum amounts at the optimum times. As a result of which quite often windows are left closed for too long or opened too late. This can manifest itself in either poor air quality levels (due to CO2 build up and lack of fresh air/ventilation) or overheating as a result of rooms being allowed to accumulate heat throughout the day through occupant and equipment load and solar gain. Once rooms have been allowed to overheat it can be challenging to recover the situation, often causing windows to be opened at hotter parts of the day when outdoor conditions may be less than ideal for cooling the space (ie as the outdoor temperature overtakes the indoor temperature, larger than necessary openings at high outdoor temperatures can result in compounded indoor overheating).

On the flipside, windows may be opened too much or for too long when manually operated – particularly a problem in winter and mid seasons when too much ventilation can cause discomfort or a heating demand which wastes energy, affecting the buildings energy performance and running costs.

As with many building systems, automating ventilation and using smart algorithms to monitor space and outdoor conditions and optimise window positions and ventilation rates can deliver significant improvement to air quality , comfort and energy performance.

The other benefit of automating windows is the potential to securely ventilate the building in a considered and controlled way when the building is not occupied! This allows us to take advantage of night cooling, and purge ventilation before the rooms are occupied – preparing them with ideal comfort and air quality conditions prior to users entering the space.

Night cooling in-particular is very difficult to achieve without automated ventilation – and yet it can make a significant impact on building performance and reduced overheating.

Do Traffic light systems help manual natural ventilation performance?

One of the ways building owners have attempted to address the challenges of manually opening windows by the right amount at the right times has been to introduce traffic lights systems. These have been commonly employed in schools – helping to give a visual and sometimes audible indication to teachers of when to open and close windows. They typically monitor CO2 and Temperature in the space and give prompts to when windows need opening or closing.

The slight challenge, particularly in large and densely occupied teaching spaces, is that a good number of windows or vents distributed around the space means lots of windows to open and close. And, if properly located to encourage cross ventilation, the event of opening windows can quickly satisfy the indicated demand for opening, and result in a further prompt to close windows. And so, the challenge of balancing ventilation goes on.

How can Natural ventilation be controlled to get the best performance

While natural ventilation via windows has been historically manually controlled, extensive research and occupant feedback has shown that building performance using manual windows often leaves much to be desired. Implementing effective control strategies via automated windows is one possible solution.

What are the best control strategies for automated windows?

Depending on how automated windows are controlled – whether by the BMS or onboard logic, some common control strategies help to optimise performance; From simple settings like preferred setpoints and calendar functions and incremental opening, to limiting factors like time, weather readings and night cooling.

Understanding and implementing optimum vent positioning according to the prevailing and changing room and weather conditions achieves best performance.

Other natural ventilation strategies may be considered and incorporated into control logic:

Purge ventilation:

Purge ventilation can ‘flush’ the space with fresh air and is particularly useful when spaces are not occupied (with due consideration to avoiding items being blown from desks etc). Limited opening before the day or heating cycle starts, to freshen the room and set good room air quality before the room becomes occupied, or purging rooms at known break times during the day has benefits by delaying or reducing ventilation needs during occupied times, particularly during winter.

Pre-emptive ventilation:

Begin to ventilate based on outdoor trends and changes in room conditions rather than waiting until the performance of the space has breached setpoints – if there are trends that the temperature in the space and outdoor temperature is starting to increase (without heating input), begin to ventilate in anticipation of approaching desired setpoints to slow overheating or poor air quality and prevent dramatic overshoot.

Limit openings for inclement weather:

Limit openings for extreme weather – rain is the most obvious factor where limited window openings are set, but high winds should also impose limits or reduce the degree of opening of windows. As should high outdoor temperatures – if the temperature outside is higher than that inside, limit openings to focus on maintaining indoor air quality and minimise warmer air entering the space.

Use night cooling:

Where possible identify vents that may be opened at night (and any openings that may need limits imposing according to position and security, risk of insect/animals etc). Monitor room trends and address overheating with night-time cooling – bringing air and mass in the space to temperatures that will help limit overheating the next day (without overcooling which may contribute to a need for heating).

Set deadbands and cycle times:

Monitor and adjust – but not too much! Monitor sensor readings (and ideally build a profile of how rooms react to occupancy, outdoor temperatures, changes in control logic and vent positioning), set deadbands of a degree or two so windows aren’t constantly opening and closing, and set cycle times.

Understand impact of openings on airflow and ventilation rates:

Higher wind readings will cause the same degree of window opening to ventilate more aggressively and can cause undesirable draughts – smaller initial openings (particularly at higher wind speeds) should be employed – monitoring the room conditions for the desired impact before opening further.

Prevent conflict with other systems:

If the heating is on or the mechanical cooling employed – it’s important to make sure the automated windows and other systems aren’t fighting each other. Use a lockout function or only control for air quality according to the building’s needs and best energy approach.

What is a BMS and how is it used to control actuated windows?

A BMS is a Building Management System, also sometimes known as BEMS or Building Energy Management System. They are commonly installed in larger buildings which require more complex control and coordination of heating, ventilation, lighting and other mechanical or electrical systems to optimise building performance.

Where window automation is controlled by the BMS, it is normally integrated as part of the overall heating and ventilation strategy to ensure the systems work in harmony with each other and deliver optimum performance. The BMS is set up with the preferred setpoints across the building, and associated with the sensors to monitor indoor conditions in each of the control zones, along with outdoor weather sensors to help it to optimise control.

How is a BMS programmed to control window actuators?

BMS programming is complex and would normally require specialist BMS integrators and engineer input to create control algorithms and routines based on the specific building operating parameters and performance requirements. The main control variables would be temperature, CO2 and weather.

The BMS will incorporate sensors in each room being controlled, typically monitoring temperature and CO2, as well as outdoor weather sensors. The BMS is then set up to optimise window positions according to the demand for ventilation based on room conditions, along with consideration of the prevailing weather conditions that may require openings to be limited due to wind, rain or extremes of outdoor temperatures.

A BMS controlled system would normally use 24v DC actuators, which are powered in groups per zone from a local controller. The controller can typically control up to 20 actuators (depending on type, location, load etc) in independent control groups. Each control group has an independent control input from the BMS to tell it when to open and close windows.

Modern solutions like WindowMaster’s motorlink enabled controllers, can be located close to the rooms they serve as ‘outstations’ around the building and connected to the actuators they serve as well as the BMS comms network. The controllers are connected to the BMS network using protocol like BacNet or KNX, which enables the BMS to send % position commands to actuator groups according to control needs. This helps reduce field cabling, make installations more robust and cost effective, and adds functionality like multi speed (quieter) automation, more accurate positional control and position feedback to verify operation and security depending on the components used.

Health and safety – entrapment

One necessary consideration with any form of automation is an assessment for health and safety and the mitigation of risk of injury. In most applications the risk is acceptable providing users and building occupants are aware that windows may be automated and that they should avoid putting fingers in the windows – this is often achieved by signage and/or placing entrapment risk stickers near each window which often provides an acceptable approach, however depending on window locations and types of occupants, further measures may be required.

Some occupants may present a higher risk – for example young children or other more vulnerable user groups. In these cases, good design practices like placing automated windows out of reach, protective barriers or furniture placement can help mitigate risks.

Windows with the main opening below 2.5m from finished floor level require particular consideration, where further measures may also be needed such as audible warnings or sensors. More intelligent actuators like those from WindowMaster allow additional settings to be requested and set up during commissioning that enable the actuator to detect unexpectedly high forces during the closing cycle which causes them to reopen and release the trapped object. In addition, there are sensors such as edge pinch sensors that can be fit around the window seal during manufacture which detect a point contact with any interfering object during closing and can be set up to stop the window operation, or PIR or laser sensors that monitor the space close to the window and prevent them from closing when a defined area is breached.

For more information refer to manufacturers guidance or speak to our office.

What are the Window Safety Guidelines for automated windows

Window safety applies to both manual & electrically controlled windows. Consideration should be given to the application & people exposed to the devices, with appropriate notification measures, education, strategic barriers or safety devices used to protect users from hazards like automatic closing or risk of fall.

Power-operated windows are classified as machinery under the European Machinery Directive (MRL 2006/42/EC) and should be assessed accordingly for health and safety.

Product Standards

Safety features for windows, such as locking mechanisms and friction/scissor stays, are covered under EN 14351-1. Automated windows also follow EN 60335-2-103 for safety of drive units for windows.

Risk Assessment

Risk assessments must be conducted based on the installation, use of the room and types of occupants, and how the windows are controlled.

Windows with the opening element above 2.5m normally need no further protection but should still be subject to risk assessment.

Where windows are below 2.5m, how the windows are controlled and the risk profile of occupants needs consideration – particularly where more vulnerable users may be in exposed to any risks – for example your children in nurseries.

Health and safety – risk of fall and more

Bottom hung windows should always have additional measures to prevent the sash from falling in the unlikely event of actuator, fixing or mechanical failure – such as safety scissor stays which are allowed to articulate during normal operating but provide a physical device to ‘catch’ windows in the event they are allowed to fall open. Risk of fall may also be addressed by setting window actuator limits, putting in place guard rails, bars or barriers according to risk assessments and best practices.

Summary

Automated windows have been successfully adopted in thousands of buildings to provide a high quality indoor climate, which provides significant energy and performance benefits over manual windows or traditional mechanical ventilation solutions. Actuators offer a safe and robust means of delivering intelligent natural ventilation, helping designers to meet the latest design guidance encouraging natural ventilation and real world performance, and helping building owners to achieve better performing buildings.

Teal products are at hand to provide guidance, advice and a wide range of cost effective product, service and installed solutions. Please contact our team at sales@tealproducts.co.uk.

This article was produced for Teal Products in collaboration with Northern Shoal Consulting