# cover heating ducts using plastic sheeting



## jklingel (Dec 21, 2008)

I think you are looking for trouble if visqueen is anywhere near heat. If it does not burn or melt, I suspect the gasses it will give off when heated will not improve your health significantly. There are tapes made especially for hot ducting (not duct tape, btw).


----------



## Windows on Wash (Aug 30, 2011)

Why did you cover them with plastic?

You should have just sealed them with foil tape, mastic, or foam and layered the insulation over them.

Plastic is not proper on multiple levels and you have now installed a vapor barrier where it is likely that there should not have been.


----------



## Bud Cline (Mar 12, 2006)

Could be facing a fire risk hazard. I'm thinking the plastic should be removed immediately. If we don't hear back from you maybe you could leave a note for a family member to let us know you perished in an unexplained poison gas/fire.


----------



## Maintenance 6 (Feb 26, 2008)

Well I doubt the ducts will get hot enough to create a fire hazard or that you'll produce a whole lot of dangerous outgas chemicals, but one thing is certain and that is that you've screwed up the balance on your heating system. If they were supply ducts, the air that used to come out of them is now coming out someplace else. If they were returns, then the system may be starved for air and you may be affecting the efficiency. The other part of this is that you've got a vapor barrier separating a warm duct from a warm room. I'm not sure what kind of wierd moisture transfer scenario that creates if any.


----------



## Doc Holliday (Mar 12, 2011)

Maintenance 6 said:


> Well I doubt the ducts will get hot enough to create a fire hazard or that you'll produce a whole lot of dangerous outgas chemicals, but one thing is certain and that is that you've screwed up the balance on your heating system. If they were supply ducts, the air that used to come out of them is now coming out someplace else. If they were returns, then the system may be starved for air and you may be affecting the efficiency. The other part of this is that you've got a vapor barrier separating a warm duct from a warm room. I'm not sure what kind of wierd moisture transfer scenario that creates if any.


 
120f on average at the registers.


----------



## Maintenance 6 (Feb 26, 2008)

Takes about 451F to ignite paper. Plastic sheeting is probably close to paper.


----------



## Doc Holliday (Mar 12, 2011)

http://answers.yahoo.com/question/index?qid=20090813112027AASM7YC


----------



## Doc Holliday (Mar 12, 2011)

I'd be wiling to bet that a 6 mil thin sheet of plastic would begin to give off harmfull fumes at much lower temp.


----------



## Bud Cline (Mar 12, 2006)

> Well I doubt the ducts will get hot enough to create a fire hazard


Some times we assume too much about posters here. I always tend to err on the side of caution when I see people doing different things.


----------



## Maintenance 6 (Feb 26, 2008)

Doc Holliday said:


> http://answers.yahoo.com/question/index?qid=20090813112027AASM7YC


That converts the melting temperature to about 230 F. Flashpoint and ignition temp is higher.

http://www.inchem.org/documents/icsc/icsc/eics1488.htm

2/3s down under physical properties. Remember to convert to fahrenheit.

Bud, I tend to agree with you. Better to err on the side of safety. You never know what people are thinking when they do home projects. On the other hand, there is plenty of 6 mil poly out there that's run behind baseboard hot water heat and that operates at a higher temp than warm air ducts. I really hope that he didn't cover the registers, and I'd like to know why the poly is there to begin with. He started out soundproofing and for some reason added a vapor barrier. I'd be more concerned about the moisture drive than a fire hazzard.


----------



## Bud Cline (Mar 12, 2006)

> I'd be more concerned about the moisture drive than a fire hazzard.


True enough!

Homeowners do all sorts of off-the-wall things that are not nor have ever been considered standard practice techniques. Some of those activities are harmless while at other times there are absolute reasons why the techniques are never done.

I have no idea about combustion possibilities of poly but what-else and where-else might other things have been done that could be iffy and hazardous?

What works in one region of the country may be a bad idea in another region of the country. In this case creating moisture traps where building components should be allowed to breath may be a bad idea. I've never heard of doing what the OP has done in this case. What exactly would be the point in doing such a thing and where's the scientific evidence that such a thing is a good idea?

Just sayin'!


----------

