A few questions about ducts

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joshuab93
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Joined: Mon Nov 23, 2009 12:28 am

Mon Nov 23, 2009 12:52 am

Hello everyone. I have reviewed most all of the other posts about ducts and could not find the answers to a couple questions I have. I was hoping someone could steer me in the right direction if nothing else. I am in the process of a total rehab of my 1982 Manatee singlewide. Years ago, before I started this project I had already removed an existing Intertherm heating unit and installed a package ac/heating unit. I simply sealed off the opening in the floor of the closet where the heater had been and attached my supply from underneath, thus using the existing under-floor trunk for my package unit. This coupled with the return I added worked ok. I now know that there are calculations you are suppose to do, etc but at the time I just went with what I had. With all of that said, I have since completely removed the insulation, and trunkline under the home. I am going to replace the package unit with a new one. I noticed that the trunk line I removed is rectangular and is aluminum. There is no insulation on it. Is this because it was buried in the actual floor insulation? I'm assuming that would catch any condensation. So would the new duct, that I will have to have fabricated, need to be wrapped with insulation or will it be ok once I've put the new floor insulation back in place all around it? Also, has anyone on here moved their vents from the floor to the ceiling? I'm also building a pretty elaborate roof-over that I have contemplated closing in and adding more insulation. If I did this, I could use round flex but would have to build distribution boxes, cut holes in the old (existing) roof to drop my registers. The only problem with this option is how to attach the register boxes to the flimsy 1x trusses. I apologize for the lengthy post and I know everyone is busy this time of year, but any suggestions and/or advise would be much appreciated. Thanks.


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Robert
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Tue Nov 24, 2009 4:47 am

Hi,

The duct is not insulated to allow heat transfer into underbelly to keep water pipes from freezing. If the skirting and underbelly is kept sealed tight with even insulation in the belly, there will be minimal condensation from the duct.

You can wrap them, but would need to wrap the water lines as well. That would be what I would do if doing renovation as intense as yours.


As for roof-over and ceiling registers, better first be sure your roof truss system can handle any added weight.

Next, how would you get to the ducts to repair if needed once all is completed.

Also, during winter, the heated air would remain more around ceiling than down at floor level.


I would post about roof-over in the mobile home repair forum and talk to JD there about it.



Thanks,
Robert
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joshuab93
Posts: 3
Joined: Mon Nov 23, 2009 12:28 am

Tue Nov 24, 2009 3:45 pm

Robert, thanks for the reply. I didn't realize that about the heat transfer to the water lines. After replacing the floor insulation and sealing it off with plywood I had planned on running my water lines (new) exposed underneath the plywood. I wold wrap them of course. After replacing numerous areas of rotten joists I figured if I did it this way and had a leak it would be found easily on the ground below and without any damage to wood. I just wasn't sure if the metal duct would condensate enough to cause mold or anything in the insulation. As for the roof-over, It's not supported by the trailer. It's supported by 4x6's cemented into the ground. None of the framing is even touching the trailer. (Though if I close it in it will.) I live in North Florida so I'm not so much concerned about the warm air as I am the cooler air in the house. Another reason I would like to move the vents to the ceiling. After looking at the register boxes at Lowe's,etc it looks like they all need to be nailed or screwed from the side into a truss. However,with this trailer it looks like it will be a pain because of the tiny truss system used back then. Too bad they don't make a push in type register box that uses clips like recessed can lights. I had planned on having two distribution boxes on the existing roof (covered by the new roof, of course) connected by my 12" supply line. Then off of each box I would branch out with my 8". The mobile home is only a 14x56 so I only need 6 vents. I didn't think about having to get to it to make repairs until you mentioned it. Thanks for the heads up.

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Robert
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Tue Nov 24, 2009 7:39 pm

Hi,

You're very welcome, happy to help. Would definitely keep it from touching home(roofover).

As for water lines, slide on the pipe insulation (foam type), then wrap all in foil backed insulation.


That should take care of it and still allow it to be noticeable if it leaks.


Take care and best wishes,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?

joshuab93
Posts: 3
Joined: Mon Nov 23, 2009 12:28 am

Wed Nov 25, 2009 9:00 am

That sounds like a good way to go with the pipes. Thanks for the tips. With the size of the project I've gotten myself into I'm sure I'll be back to this site in the future.Take care.
--Josh


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Robert
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Wed Nov 25, 2009 7:21 pm

Hi Josh,

You're very welcome, happy to help. Come back anytime.


Take care and best wishes,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?

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