Sizing a HRV

Shoe Lover

Hi Folks,

Does anyone know how to calculate what size of a HRV unit you would need? We are looking at building a 191m^2 bungalow. We will be converting (hopefully) the attic during the construction phase and it will have an area of about 60m^2. I'm set on getting the HRV, but just finding it difficult to understand what I should be looking for in a unit, what is too big and what is too small.

Thanks

beyondpassive

Multiply your volume by your airchange rate and you have the amount of air you need to move per hour.

Area 250m2 x 2.5m high ceilings x 0.4 airchanges = 250 cubic meter unit. So a P..l 300F, Ze.....r 350 comfort lux or a Da.....erm _CH 5.

some peeps go for 0.33 airchanges, I think 0.4 suits Irish homes better.

Shoe Lover

Thanks very much! Just one question, you mention that you consider a 0.4 air change rate to be better for Irish homes, do you mind me asking what you are basing that on?

beyondpassive

Monitering completed projects.

By the way, What's you design airtighness, that will have a big effect on the MHRV?

Shoe Lover

No idea yet. We are still working out what specs of everything that we will be using. Ideally, we would like to be as airtight as possible but still researching everything at the min. So far we are thinking of 200mm cavity filled with beads and triple glazing. Beyond that, I'm not 100% sure of everything else. We are literally just starting!

josip

When we were getting our HRV installed, the sales guy specced a "300" unit as adequate for the size of our house and because we had limited space. The installer told us no way, that while on paper the 300 would be up to the job it would be running at 90% design, run more noisily and be more heavily loaded. So we shelled out an extra €300 for the "600" and sacrificed a little space. Don't know what the "300" would have been like, but we sleep under the "600" with no issues. I think the installer's advice was genuine because he worked for a different firm and wasn't getting a cut.