MVHR & MEV Ventilation Update

Recently, the sales & management team at Fastlec had an update on the latest ventilation guidance & rule changes from Domus Ventilation Specification Manager Russell Beardsworth.

Here's some of what we learned (or re-learned)

New Part F Building Regulation Changes (Effective from 15th June 2022)

This is the 2021 edition of the approved document which takes effect on the 15th June 2022 in England.

Part F Changes Summary

Air Tightness Testing For All - Previously, air tightness testing could be done on a sample of the new buildings but now each individual building must be tested (no exemptions). It sounds like an excellent business to get into if you're looking...

Increased Ventilation Rates MEV/MVHR - Whole house minimum ventilation rates significantly increased reflecting the drive for cleaner air in the home:

Fans to Be Sized Room By Room - New guidance is included for background ventilation such as dMEV and Intermittent extractors to be sized by each individual room rather than the whole property.

We then peppered Russell with questions regarding our favourite subject, MVHR units and he was only to happy to advise.

MVHR Heat Recovery Systems

A properly designed and installed MVHR system should save around 30% off the home heating bill, so it's worth getting it right the first time and ensuring that they are properly maintained.

In order for heat recovery systems to be effective, the home must have a good degree of 'air-tightness'. Windows should also be kept closed for maximum efficiency (MVHR units usually bypass the summer months for comfort).

" Air Tightness - The resistance of the building envelope to infiltration when ventilators are closed. The greater the airtightness at a given pressure difference across the envelope, the lower the infiltration. "

MVHR and MEV systems must be commissioned to check their airflow performance and should also come with a maintenance agreement for regular servicing.

In areas of poor air quality (large towns/cities) an MVHR system with an additional NOX filter can make all the difference to the air quality in the home. This carbon filter captures up to 99.5% of NO2 pollutants that would otherwise enter the home.

PIV Mould & Condensation Control

Older, leakier homes with damp/mould issues can instead use the highly effective PIV units to remove condensation that creates mould in the home.

Ducting Recommendations

When ducting through unheated spaces and voids (lofts), make sure that all ducting in that area is well insulated to prevent condensation from forming. Thermal duct wraps now make this process much easier, even in a retrofit project.

If your MVHR/MEV unit is in the loft, then you should wrap it in thermal material or even a blanket to protect it from the cold.

Supply/extract valves should be mounted as far away from the internal door as possible, ideally diagonally opposite, so that air travels through the entire room.

Make sure that you're using fire sleeves and collars when ducting through fire-stopping or fire compartment walls.

  • Keep duct runs as short as possible
  • Use as few bends as possible
  • Avoid using flexible ducting if at all possible
  • 204x60 rigid flat duct is the best choice if possible
  • If you are using Radial ducting, then keep the runs straight

Acoustic Separation

Consider using a radial ducting system to achieve more effective privacy between rooms. Sound attenuators can also be added to the system to reduce cross-talk and overall sound levels by up to 55dB.

All in all, it was a very worthwhile few hours catching up on what's new and what's often forgotten in the ventilation industry. The sandwiches were great too!

If you'd like help on any projects you have, either new build or retrofit, then please get in touch and we'll be glad to advise and assist with designs and material sourcing.