Why MVHR

Is MVHR  (heat recovery ventilation) the right solution for my build? Surely window trickle vents and standard kitchen and bathroom “purge” extractor fans are sufficient. And they’ll be enough to keep the building inspector happy. Why bother upgrading to MVHR?

What are the benefits?

As we become more aware of the harm arising from air pollution from diesel and other fossil fuel burning, we sometimes forget that most of us spend most of our lives indoors. And it is as important to pay attention to indoor air quality (IAQ) as it is outside. MVHR provides tangible benefits that are best recognised by those who already live in a home with heat recovery ventilation. However, these are the main benefits from installing MVHR…

  • Indoor air quality – keeping indoor air contaminants low, maintaining relative humidity in the healthy zone (in the range 50%, ±15%), reducing ingress of external pollution – doing all this continuously and reliably and quietly in the background;
  • Energy saving – using MVHR allows you to double-down on building air-tightness, which saves energy, hugely reduces drafts, makes the house quieter and helps the durability of the building fabric;
  • Comfort during hot weather – by helping keep relative humidity down, your home will feel more comfortable in summer
  • Open windows! You can still open windows as you do in any conventionally ventilated home.
  • Clothes and towels dry easily all year round,
  • There are no noisy bathroom or kitchen fans to disturb others, bathroom mirrors and cooking steam clear quickly

How practical is MHVR to install?

If you are extending, refurbishing or thermally upgrading your home, it is usually much easier to install MVHR at this time. Ideally, you need to consider space requirements and duct runs for the system as early as you can at the design stage, as installing it as an add-on later often makes for a less optimally designed and more expensive solution.  All of that said, MVHR can sometimes be installed independent of other building work without much difficulty. Every property and every site is different.

How complex or expensive is MVHR to maintain?

MVHR units are much simpler than domestic gas boilers in terms of moving parts and wear-and-tear. They do not require an annual service and the most important maintenance task, cleaning or replacing the filters, can be done by the end users. Electrical energy use is very low, less than £100 a year. If your building has a good level of airtightness, your savings in heating costs by using MVHR will be much greater than the energy cost of running it.

Read more about ventilation and indoor air quality (IAQ) here:

Indoor Air Quality and Ventilation (PDF, 465 kB)

Natural Ventilation (PDF, 1.62 MB)

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