BMD
first read this article to check out the alternatives:
[broken link removed]
If you are still happy to go with MHRV, here are a few things to note:
- Mechanical Heat Recovery Ventilation (MHRV) will only work at anything like its suggested efficiency in a pretty airtight house (<5cum/sqm/hr is a good target) so take care of airtightness as your first priority.
- select a system with a very low fan power (<1W/s) as a high fan power probably means that you are spending more keeping the unit running than you will save in heating (from a CO2 point of view at least).
- make sure the installers know what they are doing (easier said than done!). The ducts proposed should be as large as possible, should be round in section and smooth, with gently swept bends and the ducts and heat exchanger should be installed inside the insulated envelope of the building (to miniminse condensation in the ducts).
- position the heat exchanger to minimise duct lengths as much as possible.
- 85% efficiency should be the minimum to look for from the unit.
-and ensure that the extract and intake duct positions dont ruin your elevations!
As for picking a supplier, ask for the technical details and your BER assessor should be able to input each one into the DEAP software to see which one gives the best performance and payback period.
I don't know your proposed heating system, but also look at combining your HRV with other systems to maximise synergy. I know for instance that
propose such a combination. I have no relationship with the company, but it is worth looking at.
another useful and related thread is here:
[broken link removed]
As with most things, its more complicated than just picking a supplier, but if you read the above links you will (perhaps sadly) know more than most of the reps
!