5th July 2022

Very few house designs make any serious provision for accommodating an MVHR unit or associated ducting, so the resultant system can be unnecessarily complicated and costly, people are often surprised how much space an MVHR unit requires or how much ducting is necessary to allow for the quiet distribution of air within a dwelling.

As a company specialising in MVHR, we regularly see plans for houses with vaulted ceilings, no storage areas and a proliferation of steel beams, none of which help the planning of a sensible ventilation system. Open web joists are wonderful for simplifying the installation of all the services that a modern house requires, but their efficacy is much reduced if they are caged by steel or glulam beams.

Space is required not only for the MVHR unit but that allowance should also be made for easy connections of ducting, as convoluted duct routes are inefficient. Thought needs to be given to the siting of external vents, particularly the air inlet vent, which should be in a shaded area if possible. Access to an installed MVHR unit should be made as easy as possible otherwise the end user is likely to neglect to clean or change filters.

The use of radial ducting systems has become increasingly popular recently as an alternative to rigid trunk and branch systems. These supply or extract air via manifolds to or from each room using individual, non-branching ducts. These systems offer great versatility, ease of installation, greater predictability of results and are generally quieter if correctly specified. The downside is that the manifolds and associated ducting add even more bulk to a system so provision needs to be made for this at an early stage of design. CVC Systems have also developed a CPD presentation which highlights some of the problem areas in designing and installing ventilation systems, and aims to educate and inform architects and specifiers.