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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: ¡ A minimum rate of 0.3 l/s per m2 of internal floor area ¡ A minimum rate determined by the number of bedrooms – as set out in Part F. e.g for one 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: ¡ 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 comply but expert advice should be sought. For social housing refurbishments, there are a 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.
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Social housing
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