Insulate Behind Air Duct

[dieselscout80]

I need to put insulation behind the air duct shown in the attached pic.

What is the best way?

The easyest seems to be spray foam, but small cans are going to be pain.

I tried adding a hose to the small cans to reach behind the duct and that seems to kinda work, butto fill the 24' of 10"x16" cavity is going cost a lot.

Do they make spray foam in larger cans?

 

[Travelover]

Can you slide in sheet foam?

 

[dieselscout80]

Can you slide in sheet foam?

In part of it yes, but where the air duct stepps up in dia no.

 

[Snaker]

I bought some bags of styro-foam crumbs that were packaged as cement block basement wall insulation. Idea is to pour into the top of the wall and let the crumbs fall to the bottom. The walls do feel warmer. Maybe you could use that. Say staple a 2 ft strip of plastic to the bottom of the studs, stuff that full, add another strip of plastic, stuff that, etc.

 

[dieselscout80]

I bought some bags of styro-foam crumbs that were packaged as cement block basement wall insulation. Idea is to pour into the top of the wall and let the crumbs fall to the bottom. The walls do feel warmer. Maybe you could use that. Say staple a 2 ft strip of plastic to the bottom of the studs, stuff that full, add another strip of plastic, stuff that, etc.

The studs are getting fiberglass batts with plastic between the block and the batts.

I'm just trying to figure out how to insulate the floor joist cavity behind the air duct.


I called a spray foam dealer and he said that it would be a waste of my money for him to come out and do this small area. He recommended that I get on Ebay and buy some 2 part spray foam like tiger foam. He said it was cheaper on ebay. He also told me to get a couple of spare guns in case I had to stop for a while.

I like it when a company/contractor doesn't try to waste my $$$.

 

[NC tractor driver]

Can you take the duct down, insulate the cavity, then reinstall the duct?

 

[dieselscout80]

Can you take the duct down, insulate the cavity, then reinstall the duct?

I was hoping to not have to do that.

That would mean I'd know the ducts was sealed tight when I was done.

 

[tony binkowski]

there r contractors that spray urathane foam.

 

[tulenutn2o]

How about some reflectix insulation. Only a 1/4"-3/8" thick. Is that a return or supply duct?

 

[crbr]

I need to put insulation behind the air duct shown in the attached pic.

What is the best way?

The easyest seems to be spray foam, but small cans are going to be pain.

I tried adding a hose to the small cans to reach behind the duct and that seems to kinda work, butto fill the 24' of 10"x16" cavity is going cost a lot.

Do they make spray foam in larger cans?

I am finishing up the same type of project in my basement. Framed and finished. For my floor joists space, I hired a service distributor to come in and spray my entire band of joist area with Icynene (Icyneneｮ Spray Foam Insulation & Air Barrier Material ? Energy Smart Foam Insulation) and it is well worth the money and planning. I then had my CMUs filled with the same type of foam from the outside by drilling a hole in every other cell and filling with insulation. On the inside, between the CMUs and the stick framing, I placed a sheet of R6 blue sheet insulation, then filled the framing with R11 fiber.

To answer your question, foam doesn't come in large cans that I am aware. Again, the Icynene product will serve you well along the open areas of which you speak. Maybe you can make out the installation from a few pics I posted below. I'd also consider cutting the blue sheet insulation and piecing it in behind tha duct.

Prime and paint the drywall before the ceiling and trim. Works very well for speedy painting.

I'm wrapping up my suspended ceiling this weekend, electrical, ceiling fan, air diffusers, and all. Next is the flooring (as my walls are already easily painted.

If I never touch another piece of drywall for the rest of my life, it will be too soon. Dang what a DIY chore.

.

 

[bironacad]

South Carolina? Are you worried about heating or cooling? Money or performance? Where is the duct carrying the air to? I was in HVAC business but need to know what you are trying to accomplish. Here duct work in an unconditioned space must be insulated to a level similar to the wall it is against, if the wall is R 12 the ductwork gets R12. The duct in your picture is insulated a tad. If you are worried about costs for heating and cooling 1/3 of your heat loss/heat gain happens through the top portion of a basements uninsulated wall. Blocks having hollows allow for cold air to sink all the way to the bottom of the wall. I live in a climate where we by law had to insulate to two feet below grade, (dirt below two feet is pretty good) now our building code states that we insulate the entire wall to min R8 right to the footing. If you are having troubles with air flow you might want to get someone with air distribution system experience to give it a look. Air duct is limited to the smallest restriction, once you have reduce a size going back up will drop air velocity and inhibit performance. Your climate is moderate?

Hope this helps

 

[dieselscout80]

South Carolina? Are you worried about heating or cooling? Money or performance? Where is the duct carrying the air to? I was in HVAC business but need to know what you are trying to accomplish. Here duct work in an unconditioned space must be insulated to a level similar to the wall it is against, if the wall is R 12 the ductwork gets R12. The duct in your picture is insulated a tad. If you are worried about costs for heating and cooling 1/3 of your heat loss/heat gain happens through the top portion of a basements uninsulated wall. Blocks having hollows allow for cold air to sink all the way to the bottom of the wall. I live in a climate where we by law had to insulate to two feet below grade, (dirt below two feet is pretty good) now our building code states that we insulate the entire wall to min R8 right to the footing. If you are having troubles with air flow you might want to get someone with air distribution system experience to give it a look. Air duct is limited to the smallest restriction, once you have reduce a size going back up will drop air velocity and inhibit performance. Your climate is moderate?

Hope this helps

I'm finishing the basement that was partically finished before.

The duct is a supply for the upstairs rooms and may get a duct added to it for the basement bathroom.

When I get done the wall will have insulation from the top/ceiling down about 4 feet.

We are not having any air flow issues.

SC climate well I'm from Montana so I'd say it's miserably hot for nine months and the about right for three months.

 

[bironacad]

I'm finishing the basement that was partically finished before.

The duct is a supply for the upstairs rooms and may get a duct added to it for the basement bathroom.

When I get done the wall will have insulation from the top/ceiling down about 4 feet.

We are not having any air flow issues.

SC climate well I'm from Montana so I'd say it's miserably hot for nine months and the about right for three months.

I imagine Montana worries more about heating? Anyway what you will be concerned with is condensation on cold ductwork in a warm moist space. The ducting we use here for residential is sheet metal and we would wrap it with foil backed fiberglass, your ductwork appears to be a flex duct with insulation already on it. Because your ambient temperature from room temp to outside temp would not be relatively large I would imagine that minimal insulation would be OK. Again though an inspection from a local installer would give you local procedures and practice and would be you best bet for an accurate strategy or approach. A couple of bucks now could save you headaches later. Get the right information, like they say when in Rome do what the Romans do. Maybe talk to your neighbours as to what is what for your area. Hope this helps. :thumbsup:

 

[buckeyefarmer]

I would move the duct out away from the wall.

 

[dieselscout80]

I would move the duct out away from the wall.

I think that will end up being what I have to do.