Insulating ducts in crawl space

[czechsonofagun]

I need to insulate ducting in the crawl space. Some of the ducts (6" diameter) are laid in the 8" joist and it is impossible to wrap them with fiberglass insulation.

I figured I could use aluminum buble wrap and staple it to the joist, I am sure it will work for heating but what is it gonna do in summer when the same duct is used to cool the house. I am afraid it will not prevent condensation on the ducting.

What do you think?

here is the ecofoil application:

crawl space insulation, insulating a crawl space, insulate crawl space

[dave1949]

Is there good info on the effectiveness of reflective barriers? I put Slab Shield, a similar product, under my slab along with 2" of styro-foam. Of course, I have no way of quantifying the effectiveness of the Slab Shield. For the price, it seemed worth throwing it in just in case it actually worked.

How useful would it be to coat your ducts with spray foam? I don't know if the heat in winter would deteriorate the foam, but the ducts would be well insulated and sealed.

[LD1]

Its pricy, and I dont know about the application, but have you considered spray-foam?

[czechsonofagun]

That would be actualy neat, to encase the duct in foam. Kinda scary to go with spray foam gun in crwal space, it is hard the way it is.

[riptides]

I have to revisit my crawl space on the old part of my house. The insulation did not hold. I am thinking about this kit.

https://sprayfoamsys.com/store/do-it...foam-kits.html

[kenmac]

You probably don't want to do it,but the correct way would be to remove the duct and wrap it with insulation & re install. I've done it many times. Insulation will stay together with the proper staple gun

[newbury]

Have you calculated the cost of heat loss/cooling loss versus the cost of the project?

For example my house in Virginia has old style windows. Based on past energy consumption and giving a 5% rise annually in energy costs, if I replaced ALL the windows the estimated pay back for energy savings would be about eternity. That's assuming new Lowes energy efficient windows (about $150), my labor and tools and the cost of natural gas/electricity. We just don't spend that much on heating or cooling.

When I put in storm windows about 30 yrs ago at $10@ payback was soon.

[edlegault]

Can you cut rigid 2" foam board and lay up/glue onto the ductwork and then wrap the foil bubble wrap around that? The foam board is light weight. Staple and/or duct tape the bubble wrap around the foam board. There is almost no insulation value with the bubble wrap alone.
Or.... run completely new, properly insulated ducts through ceilings and walls.

[czechsonofagun]

newbury - I know what you mean. VA does not need that much for heating to pay off savings.

I am only concerned with condensation in summer, if there is a heat escaping to the crawl space, so be it, not a big deal. But I dont want the duct to rust because it is dripping wet 4 month a year.

[kenmac]

didn't you just have a unit installed ? If so, that should have been figured in with install price.Is the duct insulated inside ? Alot of older homes that were heat only weren't insulated inside (old code) when I add A/C or upgread I insulate outside. new code here is R 8 insulation