mechanical ventilation requirements
I have a 3 family house in Essex County NJ (Zone 4A) and am looking into redoing the siding, roofing, and window replacement in the next year, but have some concerns about adding in more than 1.5 inches of foam board insulation under new siding which make wrap the house in an air barrier. The house currently is heated with a boiler/hydronic baseboard and cooled with through the wall air conditioners (two apartments on ground floor) and window units (one apartment on top floor). The two ground floor apartments have bathroom and kitchen exhaust vents, but the top floor apartment does not. I am considering adding in central air to the top apartment at some point in the future since I’ll be living in that unit for the next several years and am considering conditioning/air sealing the attic above it which would potentially seal the entire building. The attic currently has R-30 in 2×6 floor joists and insulated 2×6 rafters. At what point should I consider adding in a mechanical ventilation system to this setup (If any), and are there any that you could recommend to be installed through exterior walls for the bottom units? Thank you for all the information you’ve put out so far and any knowledge you could share regarding my question would be very appreciated.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I don’t think mechanical ventilation ever hurts., provided the intake air air is adequately filtered. In leaky homes it gives you more control over a phenomenon that is going to happen anyway. One continuously operational system could potentially ventilate the entire house and manufacturers typically provide you with ashram guidelines for sizing.
One erv runs just two fans (which ought to be ECM so power usage would be minimal) continuos ventilation has low cost requirements and therefore lower installation costs. So it may be worthwhile regardless of how well sealed your house becomes.
In mild weather with no wind and closed windows, even a leaky house provides inadequate ventilation.
General misconseption that leaky houses don't need ventillation. Since you don't know where the leaks are and the leaks are generally not evenly distributed, you can end up with rooms that have no air exchange at all especially with radiant heat.
For retrofit, your best bet is a couple of spot ERV units. There are a bunch out there, Lunos, Vent-us, Continental Fan ECO-FLO.
If you are doing any bathroom reno, a WhisperComfort Spot ERV is not much more than a decent quiet bathroom fan.