We just finished installing an a c air handler with rigid round metal ducts in our attic.
Spray foam attic ductwork.
The 1 800 square foot brick ranch in climate zone 4 dates from the 1960s but the previous owner installed both a furnace and ductwork in the attic just four years ago.
Closed cell foam is very expensive especially the first lift 1 5 in this case.
The question is which type brand to use.
Note that this isn t a good idea if you have a very airtight high performance home or if your home simply isn t large enough to provide the air needed for combustion.
Attics with spray foam insulation are so cool.
The attic will stay within a few degrees of the living space.
After you seal the duct work you would have more than enough left over to do the box sills which would add to your efficiency.
These allow the furnace to use air from your home for the combustion process.
Our plan is to insulate the ducts with spray foam.
A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents.
This is a job that you can probably do yourself with a portable spray foam kit.
We mean that literally by the way.
Nothing unusual about that.
Please note that only the supply duct work should be sealed.
Earlier this year i got a question about a home that had spray foam insulation in the attic.
The installation was done by a hvac pro.
When you insulate the top of your attic with spray foam you re bringing your attic into your home s envelope.
These cost about 400 for 200 board feet.
We are located in southern ontario canada.
The unconditioned space also houses his hvac system.
When we seal the attic with spray foam it s as tight as a butter tub.
You have to bring in fresh air in a tight home like this so i hope you are putting the v back in hac.
Spray foaming the roof deck is definitely the way to go over foaming the attic floor.
One huge benefit of the spray foam insulated attic is that conditioned air leakage from the ac furnace duct system is contained and used to condition the attic.
As a result you can reduce the temperature in your attic by a lot anywhere from 120 degrees to around 95 during peak summer.
In a vented attic all of that expensive airflow is lost to the environment.
In my opinion the presentation at the doe link you posted seems to have lost sight of the rationale for using closed cell foam on attic ducts.
The doe and building america specifically did a lot of research on what s required to bury ducts in ceiling insulation.
Where allowed foam it green can be sprayed onto duct work to maintain temperature eliminate condensation and reduce vibration.
The ah furnace cabinet will be inside conditioned space as will the duct work.
The spray foam contractor installs louvered grilles between your attic and your living space.
