Negative Pressure from Bath Fans
I am nearing the end of a home renovation and need to make some decisions on bath fans.
I am a homeowner working with a builder who is not very familiar with HP building so I am trying to manage as much of that aspect as possible to make the home both comfortable and efficient.
I have no clue what we will net on blower door score once our windows and WRB are installed. If we are over 3 I might opt for aerobarrier with a goal to get us to 1 ach50. If we are at or under 3 I might save the money.
So, as I look at bath ventilation I am wondering if I need to worry about depressurizing the house when the primary bath is in use. That bath will have a 150CFM fan, the other two baths will be 50cfm. There is no gas in the home, we are all electric. I did plan for mechanical ventilation using the Lunos system (no room for ducts) but they do not correct for imbalance created outside systems. Is the potential negative pressure caused by the primary bath or some combination of the 3 something I need to worry about? Not sure there is anything I can really do at this point but figured I’d ask. Also, not sure how it is different than a 400cfm kitchen hood (which would not require make-up air). Perhaps I answered my own questions. If so my follow-up would be at what ach50 level do you need to worry about negative pressure in these amounts?
The location is Southern California in case that matters.
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