The best MVHR system is the one that you don't know is there!
March 21, 2016
We are increasingly being asked to quote for the installation of Mechanical Ventilation and Heat Recovery systems (MVHR). Self builders will be only too aware that in their quest for better insulated and air-tight properties, building regulations are becoming ever more stringent and in order to comply with Part F for ventilation there is often a requirement to install MVHR. The basic principle of MVHR is that it sucks warm stale air out of kitchens and bathrooms etc, extracts the heat to reuse, and feeds filtered fresh air back into the room. Although there is an extra cost involved, it does ensure an indoor air quality which "feels" like the outside, as well as moisture and odour management. It also avoids the need for trickle vents in windows - which as well as being irritatingly primitive, can look tacky!
As with any finely balanced system, problems can arise if it is poorly designed or installed. Good design will optimise the efficiency of the heat recovery whilst minimising the electricity consumption of the MVHR unit. The air should be delivered to the right places, in an airtight manner and installed to avoid condensation and problematical noise levels. Fairly straightforward I hear you say(!) - however this is not always the case......
Ducting should be smooth, rigid and as short and straight, (and airtight) as possible - or perhaps not!
The above installation (not an Orangehouse one!) is a classic case of questionable workmanship. In the photo below from one of our installations, note the direct runs of well-supported, effectively sealed pipe.
Some of the quality (and hence longevity) in a good system comes from using high specification kit in a well designed scheme. However the rest of it is dependent on good installation practices to achieve high levels of airtightness and efficiency.
These are the sort of subtleties that are not immediately obvious when clients are comparing quotes for the same job from different companies. These ostensibly "comparable" quotes can vary hugely in price for many reasons!!