The Future Homes Standard 2025 and the Changes to Part F 2021
March 31, 2021
Update to Part F of the Building Regulations:
The aim behind the update to Part F was to simplify ventilation requirements whilst aligning air tightness and system specification.
This was following a government review of ventilation and indoor air quality in new homes which showed that only three of the eighty homes monitored complied with the current standards for Part F: Ventilation, in part due to complexities within the regulation itself.
How will Part F change?
The Government began by proposing that the four system types, as listed in the current Part F, are updated. Guidance has been removed for passive stack ventilation, formerly System 2 and the remaining three systems have been renamed and guidance given on aligning these with the most suitable level of air tightness.
The aim of this is to provide more support for designers in specifying the best solution for their project based on air permeability levels.
Dwelling covered by
proposed guidance changes
Natural ventilation (formerly System 1)
A design air permeability higher than 5m3/(h.m2) at 50 Pa;
An as-built air permeability of higher than 3m3/(h.m2) at 50 Pa
Continuous mechanical extract ventilation (formerly System 3)
Any level of airtightness
Continuous mechanical supply and extract ventilation (formerly System 4)
Any level of airtightness (although MHVR efficiency will improve with increased airtightness)
When this becomes legally enforceable (expected June 2022), designers will need to seek expert advice if using a system type in a dwelling different to the above, however, SAP credits may be limited where this is the case.
In a move to make compliant design easier, the revised Part F will also change the way that whole dwelling ventilation rates are calculated. This will eliminate the need for designers to estimate the number of people in bedrooms by changing to a constant factor.