AIR CONDITIONING, COOLING & VENTILATION
Ringing the changes in ventilation requirement for new dwellings
Mark Isles, new build sales director at EnviroVent, takes a look at what the changes in ventilation regulations mean for the industry and how to meet the challenge of meeting more stringent ventilation requirements with increasingly airtight dwellings
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2022 was a year of significant change in the ventilation industry. Major updates to Approved Document L and F were introduced in a move towards the Future Homes and Building
Standard. This includes the ambitious target of reducing carbon levels in new homes by 75% by 2025. So what are the key changes for dwellings?
Well, the updated standards require all new build homes to be future-proofed with low carbon heating, effective ventilation and world- leading levels of energy efficiency.
Important changes
An important change in the updated Building Regulations is the increase in the whole dwelling ventilation rates in a property.
Between the 2010 and latest updates there has been an increase of 6l/s per person with a one-bedroom property which was previously at 13l/s, now 19l/s. This is a significant increase and will affect decisions in terms of choosing a suitable product to be able to comply with the regulations. In many cases, intermittent fans are no longer suitable for very airtight dwellings. The requirements for background ventilation
in relation to Continuous Mechanical Extract Ventilation (MEV and d-MEV) in England have also been changed. This usually takes the form of trickle vents in windows, but through-wall ventilators can potentially be used, however both options usually require factoring in during the design phase as retrofitting can be costly and time consuming. In the previous regulations, if a property had an air permeability of 5 or greater this was considered to be fairly leaky and therefore no background ventilation was needed. In properties with an air permeability of less than 5 and therefore more airtight, there was a requirement of 2,500mm2 of background ventilators in each habitable room. The latest Building Regulations updates changed all this, to ensure that properties of all air permeabilities use trickle ventilation in habitable rooms. The ventilation level has also increased to 4,000mm2 per habitable room and the guidance states that the total number of background ventilators must not be fewer than the number of bedrooms in the dwelling, plus an additional two ventilators.
A further change is the addition of Section 2 and Appendix B to Approved Document F which relate to indoor air quality and volatile organic compounds (VOCs). This includes a list of harmful contaminants, exposure limits, time and advice on action to be taken should the property exceed safe levels.
Many within the new build sector are therefore
increasingly looking to specify whole house ventilation systems, even for smaller properties, as they can be a more efficient way to meet the regulations. The most effective in meeting the new regulations is undoubtedly MVHR, which is becoming an increasingly popular choice.
Systems change
Another major change to Approved Document F was the re-naming of the ventilation methods. In the previous Building Regulations, these were referred to as Systems, which have been changed to:
• System 1 became Natural Ventilation with Intermittent Extract Fans and Background Ventilators
• System 2 which was Passive Stack Ventilation (PSV) has now been removed (but can potentially be used in situations where suitable).
• System 3 is now known as Continuous Mechanical Extract Ventilation (MEV and d-MEV).
• System 4 has become Mechanical Ventilation with Heat Recovery (MVHR).
• Alternative ventilation systems, such as Positive Input Ventilation (PIV) could be specified on the requirements of Regulation F1(1) on the basis that ‘There shall be adequate means of ventilation provided for people in the building’ and that compliance can be proven, for example, with a BBA Certificate.
Overheating mitigation
The issue of overheating has been addressed for the first time in the updated Building Regulations, with the release of Approved Document O: Overheating Mitigation, which is causing an additional challenge. The document concentrates on two main methodologies, the Simplified Method and Dynamic Thermal Modelling which look at many variables to determine whether further action is required to reduce the risk of overheating. 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. A fabric first approach is often taken, with mechanical cooling seen as a final option once all other options have been explored.
For anyone working to Passivhaus standards, a certified Passivhaus MVHR system is the key to ensuring that buildings can breathe effectively.
6 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2023 Read the latest at:
www.bsee.co.uk
For a summary of all the key changes to ventilation Regulations, take a look at EnviroVent’s series of webinars ‘Building Regs Bitesize’ for quick and easy to understand content on all the changes to the Future Homes and Building Standard legislation in the UK Approved Documents F, L and O. For more details visit https://www.
envirovent.com/help-and-advice/ building-regulations/
Increasing airtightness
In addition, updates to Approved Document L mean that new homes are required to be increasingly airtight.
Latest Building Regulations have increased
energy efficiency requirements from 70% to 73% and, as a result of the current energy crisis affecting homes, this need to recover heat and save energy is particularly important to homebuyers. Because of recent Building Regulation changes, the new build sector is working more closely than ever with ventilation manufacturers to ensure requirements are being met. The results will speak for themselves in terms of the homes of the future having better indoor air quality and a lower carbon footprint.”
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