AIR CONDITIONING, COOLING & VENTILATION
Ventilation requirements are changing – what you need to know
Ruth MacEachern, product manager at EnviroVent, looks at how ventilation requirements are being tightened in the updated Building Regulations due to be released in June 2022
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une 2022 will see significant changes to Building Regulations being introduced affecting 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 for new homes, which is due to be introduced in 2025. This new standard focuses on reducing carbon from homes by 75% by 2025, which could potentially lead to Passivhaus standards becoming the norm.
As the Government moves towards its Net Zero target, homes are becoming more airtight, which means they have increased ventilation requirements. It also makes it more difficult to meet ventilation requirements for very airtight dwellings through conventional methods, such as intermittent fans and trickle vents in windows.
So how will new homes meet increased ventilation requirements?
A ‘systems approach’ to ventilation is therefore set to become much more common, with MVHR (mechanical ventilation heat recovery) and MEV (mechanical extract ventilation) likely to be increasingly widely specified.
MVHR, as a whole house ventilation system, supplies 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. In the new regulations, MVHR efficiency requirements 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 outside air temperature is supplied back into the property. The updated Building Regulations due out in June 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 (ADF), 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. An MVHR system will
switch to bypass and will drop the temperature slightly, in cases where overheating arises. Mechanical Extract Ventilation (MEV) systems are another popular option for new homes. 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 (IAQ), 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 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 by pull cords or light switches. For the first time, Approved Document F also includes upgrades to existing homes. When major refurbishment work is being carried out such as installing new windows or doors, loft conversions, then PAS2035 is the official document that applies.
Systems change
Another major change in Building Regulations 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 Supply and Extract with Heat Recovery. Some of the guidance on ventilation can be 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.
Rising importance of ventilation
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. Correct installation is also essential to ensure the safe and comfortable running of the house. There is a drive in the ventilation industry towards raising standards through accessibility to quality training and ensuring that all installations are carried out by fully trained competent persons. This has become a more pressing issue as the new guidance states that each ventilation system will be assessed to ensure they are compliant with latest Building Regulations, therefore driving up standards. On NHBC sites, installers of ventilation systems need to have successfully passed an NICEIC Domestic Ventilation course. After completing this, it is essential to gain the experience to be able to be fully competent in installing ventilation systems. In recent years there has been, in some areas, an over-reliance on trickle vents to provide adequate ventilation, which may now be insufficient to meet the updated regulations. Architects and housebuilders may therefore be required to review their ventilation design systems to ensure that latest regulations can be met. As householders are now spending longer at home than ever before, due to work changes as a result of the pandemic, poor IAQ is therefore becoming an increasing problem. It is linked to a number of conditions, ranging from asthma and allergies to lung cancer, chronic obstructive pulmonary disease (COPD) and cardiovascular disease. For new homes and major
renovations, increasingly whole house ventilation is being adopted as a much more popular option for meeting the requirements of building regulations. There is therefore an opportunity here for installers to become trained in whole house ventilation system design and installation to meet future homes requirements.
10 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MAY 2022
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