Spray foam insulation, a/c blowing in attic

Home is brand new, Curious why this would have been done? Attic has spray foam insulation, and a supply register intentionally installed in attic
It also has an air purifier/dehumidifier if that makes a difference

Two words… “Conditioned Space”.


Yes, it is “conditioned space”, so its not a complete waste of a/c, but it is also not necessary either… Unless I am missing something. Any other conditioned attic I have seen did not have this.

I don’t see a problem.

Energy.gov prescribes the exact system in your pictures.

Insulate the attic or roof of a new home by installing spray polyurethane foam insulation - either open cell or closed cell - on the underside of the roof deck.

  • Design and construct a roof /attic assembly with no vents.
  • Install spray polyurethane foam insulation (and additional insulation other than spray polyurethane foam if desired) in the roof cavity to levels that meet or exceed the current adopted building and energy codes.
  • Install thermal or ignition barrier (coating, gypsum board, or other material) over spray polyurethane foam insulation if necessary based on the material properties of the spray polyurethane foam or as required by code. Note that not all spray polyurethane foams require thermal or ignition barriers.
  • Seal any penetrations from the home into the attic through the attic floor.
  • Provide conditioning, dehumidification, or controlled ventilation to the attic.
  • Ensure the home has good ventilation.



Thanks Bert,
That made me think, it may actually be good to add air to the attic, as this would add positive pressure to the enclosed space. Instead of a negative pressure, that could bring in pollutants and humidity.
That may be the reason, I have just never seen this done with a conditioned attic space. I guess I wont comment on it, I just wanted to have an explanation in case the buyer mentions it.

1 Like

I have had the same experience here, Daniel. The few foamed attics I see rarely have a register in the attic. Then again I see a lot of new construction that ignores a host of codes and best practices.


When they decide to treat the attic like conditioned space, you have to stop thinking of it as your traditional attic and consider it more like a loft space that’s within the envelope of the house. The register in the attic is simply to provide the same advantages of heat and cooling as the rest of the house. From the pictures it appears that they decided to install the air exchange unit for the house in the attic space rather than elsewhere in the home, typically in a utility space near the furnace. Nothing wrong with that either.

1 Like

Whenever you have a closed space (air-tight), you have to condition it or nature will come calling in terms of condensation, mold, mildew, etc… You may not need to cool or heat it, but you must control humidity. In Florida, without cooling the attic, in addition to humidity it may get pretty pretty hot. If you saw an attic that had spray foam before without any means to remove humidity, you missed a big big issue.


Those are common in N/C in our area.
The whole house dehum is typically ducted to bring in outside air with a damper system. (Check the filters, they are overlooked as most people don’t know the machine is even up there.)

Some have returns in the attic, others do not.

1 Like

Un-vented, Conditioned Attic. Permitted by the IRC since 2006.


Apparently I worded my question wrong. I know it is a conditioned space… I had just never seen a supply register intentionally added when it’s not a living space.
Thanks for all the replies!

1 Like

I agree that is correct Russel.


A lot of builders here do not condition the airspace when using open cell foam. I now mark it wrong even though they say their engineers approve it.


I’ve run into this in my area too. No de-humification or airflow in the attic can’t be good, long term. I think with the foam on the underside of the roof deck the shingles get hot.

They do it in maine

Do you get paid for your sarcastic response which usually includes minimum or no help and limited information ? Hopefully not.

1 Like

Two words… “F*CK OFF”!!

Section 806 of the 2018 IRC includes many changes regarding attic ventilation. 806.5 is directly related to your question. Many of these were incorporated into the 2020 Florida Building Code https://codes.iccsafe.org/content/FLRC2020P1/chapter-8-roof-ceiling-construction#FLRC2020P1_Pt03_Ch08_SecR806