The new Part F raises the bar for domestic ventilation, given the need to ensure air quality in more efficient house constructions. Lee Caulfield from Titon explains further
Ventilation plays vital role for ensuring occupants’ health within a home, and getting the right system in place at the design stage is essential. There are many forms of ventilation available currently for the residential market, but a number of factors influence the selection process.
Approved Document F of the Building Regulations states that an “adequate means of ventilation,” must be provided, but since the update to these Regulations in June 2022, there are now three types of ventilation identified (it was previously four, but passive stack ventilation was removed).
The ventilation types identified in the new Part L are as follows:
- Less airtight dwellings: natural ventilation with background ventilators and intermittent extract fans
- Highly airtight dwellings: continuous mechanical extract ventilation (MEV) and mechanical ventilation with heat recovery (MVHR).
A highly airtight dwelling is defined as that with a ‘designed’ air permeability lower than 5 m3/ (h·m2) at 50 Pa, and an as-built air permeability lower than 3 m3/(h·m2) at 50 Pa; and dwellings are assumed to have an infiltration rate of 0 air changes per hour.
For less airtight dwellings, there is an element of mechanical ventilation within the ‘natural ventilation’ option, which can make things a little bit misleading. However, a less airtight dwelling is defined as: a design air permeability higher than 5 m3/(h·m2) at 50 Pa; an as-built air permeability higher than 3 m3/(h·m2) at 50 Pa; dwellings are assumed to have an infiltration rate of 0.15 air changes per hour.
The changes in classification indicate the Government’s intention to make sure that in future, homes are provided with adequate ventilation and have increased ventilation rates. With the Future Homes Standard being implemented in 2025, the need to build homes with more efficient energy consumption, and therefore more airtightness, poses a question for designers about what mechanical ventilation system to put in place.
MVHR: an energy-efficient solution
The most efficient use of energy and utilising heat recovery to achieve air quality is mechanical ventilation with heat recovery (MVHR), which is suitable for houses, flats, or apartments. MVHR works by combining supply and extract air, extracting moisture-laden, stale air from wet areas, such as kitchens and bathrooms. The heat from the extract air is recovered by the heat exchanger in the unit, and is recycled into the supply air entering a dwelling.
A MVHR unit can be located in a number of areas, such as the ceiling void, loft, cupboard, or garage. Designed to recycle up to 92% heat and utilising low powered electronically commutated (EC) centrifugal motors, it is a system that ticks all the boxes for futureproofing homes. Ideal for lowering Dwelling Emission Rate ratings, the performance of MVHR units will be confirmed in SAP (the Standard Assessment Procedure) for their performance and energy consumption.
Specify early
If a MVHR system is added into a design at an early stage, it is easier for the building’s aesthetic aspects to absorb the system’s design and layout. Becoming an integral part of the home, it also allows the occupant to be provided with healthy replacement air, with the added protection of filters as per standard ISO16890 – which will absorb particles that would normally enter a dwelling.
Going forward, MVHR will become more standard within ventilation designs due to how they comply with legislation changes and developments. Not only are they ideal to fight against common issues with mould and condensation as a direct result from poor ventilation in a home, MVHR units also ensure that air is continually passed through a home to remove contaminants, and keep the air circulating.
Lee Caulfield is ventilation system sales director at Titon