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Sealing around heating vents

I was wondering what I should use to seal around the heat ducting where it joins the wall register. I rent an apartment and am trying to cut down on heat loss this winter and also seal the apt as much as possible to block out secondhand smoke from the downstairs apartment. The converted house is quite old and the heating system isn't in great shape so where the metal duct comes out into the wall register there are pretty big gaps between the wall and the metal duct and the registers no longer will sit flush into wall as a result.

Re: Sealing around heating vents

Depending on the size of the gap maybe caulk will work otherwise you might use a can of spray foam.

Re: Sealing around heating vents

Thanks for that, do you know of any brands that are temp resistant?

I looked for high temperature caulk at my home depot but they didn't have any - they also didn't know if the spray foam was safe when exposed to heat- i have used the spray foam liberally around the apartment to block the secondhand smoke and it has been great, but considering the poor air quality already I don't want to risk chemical off gassing if I use the wrong thing.

Re: Sealing around heating vents

If I understand this is for forced air heating vents?
There shouldn't be a need for high temperature materials used for the sealing the gaps .... otherwise the vents wouldn't simply be attached to the wood structure.
The temperature is likely going to be around 100 degrees F which is not considered high temperature.

As far as off gasing I don't think there should be an issue unless there's a flame present allowing the material to burn.

Here's an example of one brand and where they recommend to be used......

However .... if you have any concerns you could always contact the company for whichever product and find out directly .

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