Efficiency of compressor assisted HRV

[montreal]

The reason behind winter ventilation is the homes tightened up in Canada over 20 years ago with building codes. Home onwers also weatherstripped homes sealed them up.

Humidity building up in these sealed homes is as you point out the main reason for the growth of HRV in Canada. Thus they often come wired with humidistats. HRVs were also prescribed in parts of the country where radium gas occurs naturally in the soil below the basement slab.

Lately, these same HRV are being promoted as essential to achieving the desirable 0.3 ACH ever since indoor fresh air has become a cultural must, if not for any other reason.

Hoyme in Alberta sells a passive ventialtor that works off of the furnace fan, but the principal seems wasteful, could be blowing out some pretty warm air.

I did a calculation on what would be the financial impact on my electric furnace bill if I simply had a push/pull pair of ventilators doing 100 CFM continuously. The bill would have risen by $225. So if a commercial HRV can save 70% of this, then we can see how many years it would take to recover the capital cost of a HRV. But what price do you place on benefit of fresh air in the dead of winter?

Another thing which discourages my experiment is that my home was built in 1979. It has no continous poly vapour barrior, just the kraft paper backing of the fiberglass batts that are stapled as they overlap the studs. On the exterior under the siding are rolls of 4' wide building paper stretched horizontally around the house instead of Tyvec. I am left wondering how much natural infiltration I am getting anyway and to what degree this infiltration compromises my device which is trying to generate a balanced flow of air?

I once read that some builders connect an exterior duct directly to the cold air return air plenum. The furnace fan causes a pressure buildup within the interior of the house relative to the exterior so that warm interior air is forced into the wall insulation thereby pushing further towards the outside the location where the dew point would otherwise occur within the wall cavity. Having a greater thickness of batt insulation that is warm and dry provides a greater overall benefit, especially when the wind is driving cold air into the wall cavity from the exterior.