House tightness
Is there any thing in the code (North Carolina) that states the ventilation, natural or mechanical, is at an acceptable rate. I have ran a blower door test on a new residential and got 867 cfm50 with 2.95 ACH50.
I don’t think that there is any thing in the code but I want to make sure that the house is safe regardless of the code requirements.
By my calculations, Natural ventilation required is 6174 cfm and mechanical is 49.6cfm. I understand that “safe” has to do with many factors of the home but could someone explain to me the outcome of my calculations and what that means for this home specifically. In other words, How do I make sure this home has the recommended or required ventilation.
3 bedrooms, 1960sqft, 9′ walls
Thanks
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Replies
Matt,
There are at least two questions here:
1. Does the state of North Carolina require that new homes have mechanical ventilation systems? (I think the answer is No, but I am not an expert on the North Carolina residential code.)
2. Are there any risks to omitting a mechanical ventilation system from a house with an air leakage rate of about 3 ach50?
Concerning the second question, you'll probably get several answers. Here's my advice: at the very least, install high-quality Panasonic bath exhaust fans in all of your bathrooms, and equip them with 24-hour programmable timers. That way, if your house feels stuffy or has a problem with high indoor humidity, you can use the exhaust fans to increase the home's air exchange rate.
I don't have the NC Residential Code in front of me but IIRC the only mechanical ventilation requirement is for bathrooms without operable windows. However it's considered minimal good practice to install exhaust fans in all bathrooms and at the kitchen range.
Thanks guy for the answers. Ventilation is important but I guess there is no set "healthy" point of ACH as of now. I am surprised its not in the code book. I bet that will be coming up in the next revision. I will take both of your advises.