mobile home hvac ductwork


  #1  
Old 06-10-05, 09:22 PM
mvintx
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mobile home hvac ductwork

I want to replace the ductwork under my mobile home. It has a single 5 by 12" rectangular duct about 60 feet long. Can I replace it with round metal or flexible ducting and what size should I use? Thanks.
 
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Old 06-13-05, 06:16 PM
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Mobile Home Ductwork

The ducts in moblie homes are designed for a higher than normal static pressure. I suggest sticking with the original size unless a re-design is done.
 
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Old 06-14-05, 03:03 PM
mvintx
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Thanks, Grady. The area of the original duct is approx 60 square inches. An 8" flex duct has about 50 and 10" about 70. Since I can't seem to find 9" ducting, should I go with the 8 or 10?
 
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Old 06-28-05, 08:08 PM
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mvintx

Sorry for the delay in replying. If you are usuing flex duct (I don't suggest it under a moblie home), go with the 10". Nine inch round metal pipe should be available at an HVAC supply house. Just make sure you insulate it well with foil faced duct wrap then over wrap it with heavy plastic. You could also use 8x8 square metal duct. What ever you use be sure to seal the seams & joints with mastic.
 

Last edited by Grady; 06-28-05 at 08:10 PM. Reason: Another option
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Old 08-18-05, 05:45 PM
mvintx
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Thanks for the reply, Grady. I've settled on ten inch round metal duct and then taper down to eight inch about halfway to each end. Thanks for the insulating tips.

Marshall
 
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Old 10-01-05, 11:01 AM
mvintx
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finished ductwork project

For anyone who's interested, I've finished the new ductwork under my single-wide MH. I used 8 and 10 inch metal ducting along with Ts and 90s to connect the register boots. All connections had to be secured with sheet metal screws, then the seams taped over and mastic applied over all the joints and taped seams. It looks great. Too bad it's hidden under the floor. Installation took about four days (working alone). Thanks to everyone for their tips.
 
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Old 10-01-05, 05:39 PM
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Thumbs up Congrats

Hope you insulated well & covered the insulation with heavy plastic. I think you will notice a major improvement in air flow.
 
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Old 10-01-05, 11:07 PM
mvintx
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Well, I haven't COMPLETELY finished it because I still have to reinstall the furnace, set the AC unit outside and hook everything back up. I also haven't hooked the water up yet and I'm waiting to do that before I insulate and seal everything up. I did talk to someone who used sheetmetal to seal the bottom of their singlewide and then blew in insulation. That might be the route I take. He doesn't have to worry about critters eating through the plastic.
 
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Old 10-02-05, 02:33 AM
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Metal vapor barrier

I think I would use heavy plastic then cover it with aluminum if you want to do metal. The plastic will provide a better vapor barrier & the metal will be your critter barrier. Not sure about blowing in insulation. Never seen it done on a MH. Fiberglass roll or batts is the norm.
 
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Old 10-02-05, 07:33 AM
mvintx
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Thanks, Grady. Good idea on using plastic and then aluminum. It would certainly be easier to put up than sheet metal. As far as insulation, I'm not completely sold on the idea of blowing it in versus placing fiberglass bats in between the floor joists. The blown-in insulation is a bit cheaper. The last time I priced R19 bats, it was going to cost me about $450 at Home Depot. What sort of plastic would you recommend? The black polyethylene (sp) at Home Depot or should I use a product specifically designed for mobile homes?
 
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Old 10-02-05, 04:56 PM
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Plastic

Nothing specific, just the heavier the better.
 
 

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