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veesubotee 12-13-2008 01:41 PM

Q's about duct insulation
 
After morning recovery, my new modulating furnace runs long cycles at low firing rates and airflow. Because of the reduced airflow, I'm losing a lot of heat to the basement through the ductwork (not leakage). I want to insulate the trunks and runs to reduce the radiant and conductive heat losses.
At Home Depot, I picked up a package of 6" (tubular) duct insulation to evaluate. I installed it on the first section of the farthest (and longest) run. It was rather difficult to work with, as I had to slice it, then rejoin it. It also seemed kind of flimsy, but it did work as I could not detect heat on its surface, and the duct temperature before and after the insulation was the same. The R value is 6 (has aluminum facing).
Because I had to slit it, the aluminum facing separated from the fiberglass. I've ruled out using this type of product.
I'm looking at Reflectix insulation, in which all layers are bonded together, so cutting and pasting would go much easier (time and labor-wise).
It appears to have an R value of 3, but when installed with an airspace, it has a value of about 6.
I'm looking for input and answers to some questions. First, I want to make sure that the product does NOT have an adhesive coating. Second, it mentions the use of 'spacers' to achieve an airspace. I did not see any examples of spacers on their website, but from an illustration, it appears that they are using narrow strips of the insulation, itself, to create the air space.
Can anyone validate the use of the product to create air spaces? Ditto, with regard to adhesive coating.
I would also appreciate any other input (or tips) with regard to using/installing this product.
Thanks for your help.
V

Marvin Gardens 12-13-2008 03:16 PM

I think you are overdoing this. The insulation you got from HD will do fine. Anything over R6 is overkill.

If you have a lot to do get a large roll. They are 4 feet wide and 50 feet long. You can wrap it twice if you want more insulation.

Basements like a little heat also since there are water pipes and is especially important in colder climates.

veesubotee 12-13-2008 03:32 PM

Quote:

Originally Posted by Marvin Gardens (Post 197537)
I think you are overdoing this. The insulation you got from HD will do fine. Anything over R6 is overkill.

If you have a lot to do get a large roll. They are 4 feet wide and 50 feet long. You can wrap it twice if you want more insulation.

Basements like a little heat also since there are water pipes and is especially important in colder climates.

Thanks. Actually, I was thinking about leaving some of the runs unwrapped. I'm more concerned with some of the most distant runs (really long and convoluted), as the temperature drop is quite noticeable.

V

Marvin Gardens 12-13-2008 03:44 PM

Make sure you use the silver tape with the fiber strands in them. They are tough and resist tearing.


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