FOCUS: DOMESTIC & RESIDENTIAL LIVING Fresher air, healthier homes
Natasha King, product manager at Vent- Axia, explains how amended Building Regulations will affect social housing and what it means for M&E contractors specifying for social housing stock in the retrofit market
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n December 2021 amended versions of Approved Document Part F (Means of Ventilation) and Part L (Conservation of Fuel and Power), were published with Part F hailed as a vital step to improve indoor air quality.
With a focus on both health and energy efficiency for the first time, this latest version of the regulations is a welcome change since the COVID pandemic which showed the importance of healthy homes. The social housing market has been set the
hard task of lowering carbon emissions to help the Government reach its carbon targets under the Future Homes Standard and on the road to Net Zero. Previously, when energy efficiency measures were added to housing stock there was no stipulation that ventilation should be added too. As we know from the Housing Ombudsman’s recent report ‘Spotlight on Damp and Mould: It’s Not Lifestyle’, mould is a huge problem in the sector and adding energy efficiency measures without considering ventilation, especially in properties where occupancy is an issue, has caused problems with condensation and mould in housing stock. Part F sets out significant ventilation changes
from previous versions with a key addition to the Building Regulations being a new sub section ‘Installing Energy Efficiency Measures’ in existing properties. The regulations look to minimise entry of external pollutants and ensure humidity and pollutants are extracted effectively and efficiently. They also set minimum levels of fresh air which all add up to ensuring good occupant health. This is set to drive adoption of low carbon ventilation as an industry standard and will have a major positive impact on indoor air quality (IAQ) in homes. The new Energy Efficiency sub-section sets out that: “When carrying out energy efficiency measures to an existing dwelling, an assessment should determine what, if any, additional ventilation provision is needed, based on the estimated impact of the work.” This side of energy efficiency improvements has been overlooked in the past but is vital. If ventilation is not considered, as buildings become more airtight to improve efficiency moisture is unable to escape resulting in condensation, mould and poor IAQ - which leads to ill health and damage to the fabric of homes. Therefore, this positive new move will help protect health and wellbeing of households as well as protecting buildings.
Calculating ventilation
Depending on what energy efficiency measures are installed in a home, the amount and type of ventilation required varies. So, how is it worked out? Part F provides two options for calculating the new ventilation requirements, when energy efficiency measures are added. Option A)
offers a simplified method which looks at what energy efficiency measures have been added and whether they are minor (e.g. roof insulation, cavity wall insulation) or major (e.g. installing external or internal wall insulation over 50% of external wall area, replacing more than 30% of windows and doors) and then it works out if more ventilation is needed. This method should be appropriate for the majority of existing dwellings. (There is a helpful table on page 23 of the Regulations (Table 3.1) that clearly sets this out.) Alternatively, option B) provides the alternative of expert advice from a consultant or someone that is signed up to a competent person scheme like the NICEIC or a trade body. This means that suitably qualified M&E contractors can offer this expert advice which is most likely required if a property is significantly different from its original construction when it comes to energy efficiency measures. With the simplified method, for a home that falls under Category A (a maximum of two minor changes and no major changes) it is likely no additional ventilation will be required. However, for Categories B and C, more than three minor changes, and/or one or more major measures, it is likely that additional ventilation will be required. This could be provided by the inclusion of either intermittent extract fans to wet areas and trickle vents that meet Part F; continuous mechanical extract with smaller trickle vents in habitable rooms only; or balanced supply and extract (normally heat recovery) without trickle vents. This, along with Appendix D in Part F, provides an excellent tool to work out if additional ventilation is required.
Airflow
Another key change within Approved Document F is the whole dwelling ventilation rates, which have been increased by almost 50%. Any mechanical ventilation that’s added must be commissioned to provide adequate ventilation and air flow rates must be measured. M&E contractors need to consider this big change when specifying ventilation to best meet the airflow rates.
The minimum whole dwelling ventilation rate for the supply air should meet the higher of the two following results:
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A minimum rate of 0.3 l/s per m2 of internal floor area
18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2022
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A minimum rate determined by the number of bedrooms - as set out in Part F. e.g for 1 bedroom it is 19l/s (a 46% increase from 2013 edition of Part F) and for a 5-bedroom dwelling it is 431/s (a 48% increase from 2013)
Ventilation solutions
So, what are the ventilation options for existing dwellings? The number of ventilation options have changed since the previous Regulations and ventilation systems are no longer categorised 1-4. There are now three main ventilation systems in Part F:
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Natural Ventilation (previously System 1): background ventilation and intermittent extract fans
Continuous Mechanical Extract Ventilation (previously System 3): continuous mechanical extract (MEV)
Mechanical ventilation with heat recovery (previously System 4): continuous mechanical supply and extract with heat recovery (MVHR)
Passive stack ventilation (system 2) has been removed and other system types, such as Positive Input Ventilation (PIV), may be used to for compliance but expert advice should always be sought.
For social housing refurbishments, there are number of ventilation options available to help provide effective ventilation and comply with the new Part F including: continuous extract ventilation such as the Lo-Carbon Revive and Lo-Carbon Response 7, intelligent filter-less fans; decentralised heat recovery ventilation systems like the Vent-Axia Heat Save; and Positive Input Ventilation, such as Vent-Axia’s Lo- Carbon PoziDry Pro PIV and Lo-Carbon PoziDry Compact Pro.
The new Building Regulations mark a positive and vital change to how ventilation is viewed when refurbishing social housing. The importance of good IAQ has been recognised for some time and now that it is an essential part of the Building Regulations, homes will be healthier as well as more efficient. They will also ensure that social housing
providers are better able to meet their duty of care to provide homes free from condensation and mould.
Read the latest at:
www.bsee.co.uk
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