What tape should I use to seal leaks in forced air heating system

duct-tapeductsductworkforced-airheating

I have some of this duct tape Nashua 557 Premium Grade Flex Duct Tape. Is this the correct stuff to use to seal leaks in a forced air heating system, or is there something else I should be using?

Note:

It says it's rated for Class 1 ducts, I haven't been able to find out what exactly a Class 1 duct is yet though.

Best Answer

Looking at the specifications on the page you linked to, it appears to be made of the same basic materials as other duct tapes: plastic coated fabric with a rubber adhesive. Premium Grade it may be, but I think you'll run into the same problems -- it'll get brittle and crack with age. I've used aluminum foil tape where I've needed spot repairs; Home Improvement 1-2-3 says to use duct mastic when installing ducts.

I found this article very useful: Can Duct-Tape Take The Heat?

Duct Tape Cannot Take The Heat

Although our testing has not been able to differentiate amongst other sealant products, the data shows that cloth duct tape is not a good sealant for use in ducts that operate at much above ambient temperature. We believe this is due to the rubber adhesive, but cannot state so definitively. For the most part, cloth backing and rubber adhesives go hand in hand. Thus it is not surprising that the other sealant products have not demonstrated any of the failure modes we have seen in the duct tapes. There are a few products that use rubber adhesives with non-cloth backing and we intend to test these in the future.

To address your side note about Class 1 ducts: from the scope for UL 181 Standard for Factory-Made Air Ducts and Air Connectors

Class 0 - Air ducts and air connectors having surface burning characteristics of zero.

Class 1 - Air ducts and air connectors having a flame-spread index of not over 25 without evidence of continued progressive combustion and a smoke-developed index of not over 50.

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