Ventilating the Homes of the Future

By Ruth MacEachern

Product Manager

Ruth MacEachern, Product Manager at EnviroVent, looks at how building regulations are changing and how this will mean better indoor air quality for the homes of the future.

“These are interesting times.  The way we heat and ventilate our new build properties is changing and currently there are two regulatory documents that have been issued ahead of coming into effect in June 2022: Approved Document F- Means of ventilation (ADF), and Approved Document L- Conservation of fuel and power (L1A/L1B) (ADL) in England. 

The proposed updates to Building Regulations will pave the way towards the Future Homes Standard, which is due to be introduced in 2025. This brings with it a focus on thermal efficiency, increased air tightness and indoor air quality.  

Approved Document F has many proposed changes that will affect how ventilation is specified for new homes.  One of the most fundamental is that whole house ventilation rates will be increased from 13l/s to 19l/s for a 1-bedroom property and up to 43l/s for a 5 bedroomed property. This increase will make it more challenging to meet ventilation rates, particularly in smaller properties, such as one bedroom apartments, where, in the past, intermittent fans would have been used in ‘wet rooms’ rather than systems like MEV (Mechanical Extract Ventilation) for cost reasons.  The updated building regulations also mean that intermittent fans are now no longer suitable for very airtight dwellings, so a ‘systems approach’ is the natural choice.  Unsurprising, Scotland, with its increased airtightness and ventilation requirements has already moved away from allowing trickle vents and intermittent fans.

Increased airtightness

Updates to Approved Document L mean that new homes will be required to be increasingly airtight. Solving the problem by adding large numbers of windows with trickle vents may appear counterintuitive in a house which has been designed to be extremely airtight.

So what does this mean for new homes?

There are a number of options available to housebuilders.  The most effective in meeting the new regulations is undoubtedly MVHR, which is becoming an increasingly popular choice.   These whole house ventilation systems supply fresh air from outside into a property, as well as extracting air throughout the property.  MVHR also includes a heat cell which recovers between 70–95% of the heat from the exhaust air and greatly improves the energy efficiency of buildings – this meets the minimum heat recovery requirements of building regulations, which have been increased from 70% to 73%.

These systems are highly effective at keeping humidity low and indoor air quality high throughout the home. To prevent overheating in warmer weather our energiSava® MVHR unit has an automatic bypass function which means air is no longer passed over a heat cell and room temperature air is supplied back into the property.

The proposed new regulations also contain, for the first time, Approved Document O for mitigating overheating in England.  Overheating is becoming more of an issue due to increased airtightness in new homes and large glazed areas being more popular. Requirement O1 states that ‘reasonable provision’ needs to be made in residential buildings to be able to reduce the occurrence of high indoor air temperatures.

When working with Approved Document F, Approved Document O gives guidance for removing excess heat from residential buildings. If this is to be corrected via windows or openings, the amount of ventilation required is likely to be in excess of the current purge ventilation rates under ADF. In some situations, particularly in urban areas or near airports, railways or motorways, it may not be practical to carry out natural ventilation through opening windows.

Although an MVHR system like energiSava® will switch to bypass and will drop the temperature slightly, in cases where overheating arises. 

Mechanical Extract Ventilation (MEV) systems are another popular option with housebuilders.  These centralised systems help to reduce excess moisture by using multiple points in which to extract air. MEV systems provide year-round good indoor air quality, protecting a home from condensation, damp, and mould.  The MEV unit is usually located in the loft or hallway cupboard in an apartment to provide ventilation to the whole property. 

Another option for new and refurbished homes is DMEV, which is a decentralised version of the MEV, with individual fans located in wet rooms, such as bathrooms, kitchens and ensuites.  These provide continuous ventilation or it can be boosted automatically either by plug cords, which are often fitted to light cords. 

Systems change

Another major change that housebuilders are noticing in the updated Approved Document F is the removal of Systems 1 to 4.  System 1 will change to Natural Ventilation, this involves intermittent fans in wet rooms such as kitchens, bathrooms and ensuites, the reference to System 2/Passive Stack has been removed;  System 3 is now known as Continuous Mechanical Extract and System 4 is Mechanical Extract Ventilation with Heat Recovery

Some of the guidance on ventilation can sound quite complex, but this has been made easier to understand as, there is now only one document: The Compliance Guide has been integrated into Approved Document F. To simplify things, the updated Approved Document F contains separate guidance for dwellings and non-dwellings. Positive Input Ventilation systems are still an option providing they meet the F1(1) requirement in Approved Document F in England, Wales and Regulation 23 in Scotland:

There shall be adequate means of ventilation provided for people in the building.

For the first time, Approved Document F also includes upgrades to existing homes.  When major refurbishment work is being carried out such as new windows or doors, insulation, loft conversions, then PAS2035 is the official document that complies.

Support for housebuilders

Although ventilation is still not seen as one of the ‘primary’ services in a home, like electricity and heating, its importance is being heightened by the changes to Building Regulations.  It is critical not only to specify the right type of ventilation system but also to ensure it is installed correctly to ensure the safe and comfortable running of the house. 

Now, more than ever, it is essential that an installer is a competent person and on NHBC sites this means having successfully passed an NICEIC Domestic Ventilation course.  Following the course, the installer then needs to gain the experience to be able to be fully competent in installing ventilation systems.  Updates to building regulations means that instead of a percentage of properties being inspected to meet requirements, every property will be inspected, therefore driving up industry standards.

Here our technical department can offer invaluable support to housebuilders and contractors, which can include toolbox talks to the installation team, guidance either via telephone, online call or even in person on large volume projects, supported by a new build area sales manager.

We’re working closely with housebuilders and housing associations on pioneering net zero carbon schemes.  This includes Barratt Developments’ Z House, a new concept in homes which is set to go beyond the Future Homes Standard, with a carbon reduction of 125%.

Birmingham housing association, Midland Heart, is building Project 80, a development of 12 homes which will meet the Government’s Future Homes Standard, reducing carbon emissions by up to 80%.    Homes here will be fitted with our MVHR systems.

Ventilation requirements are often thought of as being quite recent additions, but they have actually been written into building regulations for over 30 years. 

In recent years there has in some areas been an over reliance on trickle vents to provide adequate ventilation, which was not a problem when the requirements for air tightness were much less stringent.   The systems approach is a much better option for new and refurbished homes and should make the whole process much simpler and straightforward for housebuilders.  The ultimate beneficiaries will be homeowners with much improved indoor air quality in the home and no issues with condensation.”

Confused about the changes to the Building Regulations that will shortly be coming into effect in June 2022? Don't worry, we have created a hub that includes our building regulations bitesize webinar recordings, our next upcoming webinars and free resources to easily understand the changes: Click Here