Warming passive make-up air for exhaust only ventilation
I need advice on where to locate and how to condition (or at least protect occupants from the cold flow) incoming make up air. I need to bring the rigid vent pipe on the exterior (unconditioned crawl space) under the floor and enter through my 12” insulated floor baysup. There is no suitable wall or soffit entry point for the intake. I can install more than one intake if necessary.
I have 3 draws: (1) an electric clothes dryer, (2) a single 80 -120 CFM bathroom exhaust fan and (3) a 120 CFM range hood; plus a small wood stove. The Prestige boiler is direct vented.
Is an 8” diameter intake sufficient or too much? (the space is 1000 sq’; 14” cathedral ceilings; Lake Ontario, NY; caulked-to-death envelope; airtight drywall; HD cell insulation; 2 occupants)
Do I need more than one passive, make up air, intake vent?
How do I warm the incoming air?
In my situation, the air cannot be dropped on or behind a radiator and I do not want to use an independent or dedicated heater for this purpose.
Would it be good to empty the air into a closet – a laundry closet for example – or perhaps to run rigid pipe or a plywood chase upwards (from the fresh air intake at the floor level) towards the ceiling and allow the air to mix as it spills out ? I could use through the wall vents to allow a feed of fresh air into adjacent rooms. I assume an interior vertical stack like this would increase the fresh air inflow rate and add to air exchange even when appliances and fans are not running.
Do need to use a 24 timer to turn on the bathroom fan for routine cycles of exhaust-only ventilation in the heating season?
By the way, I spoke with the Aldes tech and he says passive vents are not sufficient to overcome stack effect or supply sufficent volumn of air for the range, cloths dryer and bath fan to work to their efficiency ratings. He advise power venting the make up air and linking the supply side fan electronically to the other exhaust fans. I am inclined towards the passive air supply / exhaust only solution.
Posted Feb 7, 2013 2:32 AM ET
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