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Re: GSBN:HRVs and SB


> Thanks for all the answers and advice! I think perhaps I wasn't clear on
> what I was looking for, but Paul kind of hit on it above. I'm not against
> HRVs, and understand their benefits. What I was hoping to find was an
> alternative to the expensive, off-the-shelf units that are a constant draw
> on an off-grid energy system. I was thinking that there must be passive
> and/or non-electric active means of providing fresh air in a home.

I sympathise with what you are looking for. It would be nice to have a non
mechanical solution to the ventilation problem.

First of all I would like to say this. All the experimenting I have done
have led me to believe that a commercial HRV is by far the cheapest/most
effective solution. With solar cells and battery for powering.

It is possible to make a passive system work based on chimney effect, you
just need a high stack. It will even work without heating due to atmospheric
thermal stratification. I dont have the exact numbers at hand but will look
them up for you. I would definitely install a selfmade/bought HRU (passive
Unit)otherwise you are throwing away heat (and don't dare to say you have
enough wood). You only need 25m^3/h per person. Then the ducting as low a
speed as possible this reduces the amount of resistence which means big
diameters. To get the HRU to work you have to either draw cold outside
pre-heated air (after the HRU) down or warm inside air down to the HRU. I
would definitly go for the first option. You are drawing the outside air
straight into the HRU this decreases the amount of condensation against the
outside surface of the outside air inlet duct. The efficiency of the whole
system is completely dependent on the amount of outside pre-heated air you
are able to suck down and the efficiency of the HRU.

With kind regards,
Rene Dalmeijer