Passivhaus Affiliate

Research Report - The Case for MVHR

Category: Guidance

The Case for MVHR, Passivhaus Trust, 2020

Mechanical Ventilation and Heat Recovery (MVHR) systems are one of the ventilation options in domestic dwellings in the UK.  They extract warm but potentially stale and humid air from wet rooms and pass this over a heat exchanger which transfers the heat to air from outside, providing 100% fresh and filtered air to the building.

These systems are more costly and more extensive than alternative ventilation mechanisms.  There is also a widely adopted rule-of-thumb that MVHR systems are only effective in more airtight buildings.  As a result, MVHR systems remain relatively niche in the UK, with most dwellings still being fitted with trickle ventilation and single room extract fans.  In particular, MVHR systems are rarely fitted in retrofits unless particular attention has been paid to improving airtightness.

This paper seeks to challenge this convention, demonstrating that the perceived need for high levels of airtighness is based on outdated assumptions, and suggests that MVHR systems are, in fact, desirable in nearly all domestic situations, either new-build or retrofit.


The case for MVHR

                

 

 

Download full report (PDF)

 

   

 

Published: April 2020

 

Further information

Technical Guidance - Good practice guide to MVHR for single dwellings


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