Big house air exchange ?
We just bought a new (to us) house in Calgary, Alberta. Its a 2 story, built in 2007, 5,000 ft^2 finished, including the basement, 9 foot ceilings throughout.
Its appears to be a very well built home. Its probably pretty air tight.
The house has an on demand natural gas hot water heater and hot water storage tank feeding heat exchange coils in dual forced air heat exchange units, one for the main floor and one for upstairs. The basement has its own recirculation fan and ducting and in floor hot water heat coils. The house also has dual AC.
4 to 6 people live in the house at any one time.
I'm concerned about how much air moves in the house. I estimate the volume of the house to be about 52,000 ft^3. (52 x 37 x 9 x 3) Given a recommended air change rate of 5 per hour, that leads to a ventilation rate of 4300+ CFM.
The house has no where near that much air movement. The only "normal" ventilation that I am aware of is
- bathroom fans in 5 bathrooms, which are generally never on
- natural gas stove hood vent, which is not usually on
- leakage from the flue on the natural gas fireplace
- 1 clothes dryer vent
- the hot water heater is high efficiency and uses PVC piping for the exhaust to a vent on the side of the house.
The builder also installed some sort of booster recirculation fan system. There is a switch on the main floor. You turn it on and you hear a louder fan noise and the air flow from the vents increases dramatically. The current owner says it great in the summer time and it keeps the house very fresh.
The house does not use conventional rectangular air vents for the supply to the rooms. It uses small, round (2" diameter) vents and a lot more of them. They seem to move a decent amount of air normally and a lot of air when the booster fan is turned on.
We currently live in a similar sized house to the one we bought. It has a big, noisy, bathroom style ventilation fan in the ceiling on the upper floor controlled by a switch on the main floor. When the air in our current house feels stale or is smelly because of cooking (down draft natural gas cook top built into the island, no vent hood) we turn it on. Having done that, the air in our current house always seems a bit stale. The new house has no such fan set up.
We are about to do some renos in our new house prior to moving into it.
What changes, if any, would you make to the air ventilation system on this house ?
Given that we live in a cold climate and the volume of air a house like this seems to need, would you install an air to air heat exchanger so that the ventilation rate can be kept up without spending a lot on heating the incoming air ?