Do You Have To Have Ac Registers In The Attic That Is Spray Insulated

Michel Thres1987 · Monday, 9 May 2022

Quote:

Originally Posted past tps7742 View Post

We just had a house built with spray foam. Perchance I missed it in this thread simply information technology is my understanding that the ac is designed for the sealed homes that take a fresh air return to keep the humidity at a desired level. I am not sure how this works in a house y'all accept spray foamed and non new?

A couple of things...
i) Outside air is non used to control humidity, information technology is used to command he quality of air in the home; to avoid things like sick firm syndrome and dirty sock syndrome. Humidity is a pocket-sized part of that equation and, in our climate zone anyhow, unremarkably ways a dehumidifier, ERV or upsizing the equipment.

2) Semi-conditioned attic is the mode to go for foam envelopes. As others have said, at that place will exist no air movement with the foamed envelope (no attic ventilation). this means that the attic Will stack humidity and you will either demand to add a dehumidifier or utilise the A/C to do the job; over again this will mean upsizing as you are adding load.

iii) As long equally yous are getting a bid to foam the attic get a bid to foam the ducting also (if information technology is canvass metal); it is a lilliputian over kill but it volition last forever.

Every bit stated earlier, foamed envelopes accept no passive attic ventilation. Information technology sounds similar your insulation provider knows what they are talking about. But Delight accept a qualified HVAC company expect it over to requite y'all the recommendations on workout the attic. If yous are going to use the existing equipment it may non exist big enough due to the extra load.

Also, you may not take enough outside air coming in for the new sealed envelope, this will demand to be checked also.

I have done many retro fit homes where cream cathedraling (cranium foam merely)was done and nosotros usually end up adding outside air ventilation and either upsizing the equipment or calculation a dedicated dehumidifier.

Typically I run across well-nigh ane ton of A/C needed for each 200 CFM of outside air requirement, or in a typical 2500 square foot dwelling house we employ a 90 pint dehumidifier.

Become this right or you will be battling musty smells, bio growth and comfort issues for years to come up.