Patch or Replace Plenum

[LarryLeveen]

Helping a friend who has a 1-foot hole in the plenum of her forced air heating system. I haven't been under the house, but a few estimators have for rodent invasion and crawl space cleanout/vapor barrier replacement and re-insulation (both are trashed).

UPDATE -- here are two pix I was sent by someone he was under the house doing an estimate:

Thinking about it and considering the estimates, I am concerned that a simple patch (if a 1-foot hole can be considered simple) won't suffice; I wonder if the rest of the plenum might be about to fall apart. I'd like to know what folks think based on their experience — is the rest of this thing about to crumble, and should we just replace the whole dang thing? Sorry I don't have more info or better images. Thanks.

 

[Stuff]

Without more info it would just be a guess to know the condition so all is speculation. Unlikely, but if it is fairly new and was properly taped and had mastic it could still be solid. Even if solid there could be an issue with mold since is in a crawl space with compromised vapor barrier. Fiberboard is easy to install and easy to patch. Also easy for rodents to get through. Another issue is what got tracked in to the rest of the system. May need to be cleaned out.

Patch it now to get the heat working properly and to keep more stuff from getting in the system. Then get quotes for replacing as much as possible with metal. Metal ductwork installation requires skill, experience, planning, design, and labor so some places won't do it.

 

[Sponsor]

 

[LarryLeveen]

Without more info it would just be a guess to know the condition so all is speculation. Unlikely, but if it is fairly new and was properly taped and had mastic it could still be solid. Even if solid there could be an issue with mold since is in a crawl space with compromised vapor barrier. Fiberboard is easy to install and easy to patch. Also easy for rodents to get through. Another issue is what got tracked in to the rest of the system. May need to be cleaned out.

Patch it now to get the heat working properly and to keep more stuff from getting in the system. Then get quotes for replacing as much as possible with metal. Metal ductwork installation requires skill, experience, planning, design, and labor so some places won't do it.

I hope you saw the images I added to my original post -- please check them out.

I appreciate your thoughts -- especially about what might have gotten in the plenum and system as a whole. There were definitely various critters in there -- rats, cats, a raccoon at one point -- plus the potential for mold from the toasted vapor barrier. Ironically, might the huge hole in the plenum have helped keep things drier down there than they would have been given a crappy vapor barrier, or does the heat actually help pull in soil moisture through increased evaporation?

I am inclined to recommend considering a full replacement of the plenum, but we'll see when estimates can be done (the place that services the furnace was a MONTH out for just estimating what to do), and what the costs are.

Is there a problem with me suiting up (I own a respirator and goggles) and just placing a board or something over the hole just to try and block it on a super temporary basis? I think the plenum isn't fiberboard at all, but just slabs of insulation with wood at the corners and covered with foil. I don't know (but can find out by looking directly) how structurally sound it is to put anything on it. I'm thinking that a cat was camping out on it at night and enjoying a toasty, heated bed -- maybe with "room service".

Any additional thoughts and advice are welcome.

 

[Cacher_Chick]

I would be more apt to hard pipe a single trunk to a central location in the home to keep it from freezing, until is can be done correctly and completely.

 

[Stuff]

That is a bit more than a one foot hole. Second picture looks like the fiber board separated from the barrier has fallen in. Wonder if something was sleeping on top to get warm and fell through.

How much effort do you want to put into this? As long as the house is still getting heat and it isn't smelling too bad you could let it go until the professionals show up. The install looks normal as there was insulation and vapor barrier. Is that really wood? Fiberboard duct is basically a slab of insulation with a foil side folded into a square with only one corner needing sealed.

Installing hard pipe would be a lot of effort for a temporary repair but would make sense if none of the current system can be reused.

See what you can get at your supply store. Cut off the top square, pull out whatever is inside, be careful vacuuming as it is fragile, then cover and seal. A piece of fiberboard and good tape at a minimum for a temp repair. If no fiberboard then find some other type of board insulation. Don't do multiple layers of plastic as moisture gets trapped inside.

See if others have some real experience with this as I am a diy and have worked with sheet metal and round ductwork but have stayed away from the fiber stuff.