duct work for new A-Frame cabin


  #1  
Old 07-31-01, 06:14 AM
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I am building an A-Frame cabin on a cement slab and I am wondering if I can run my heating and a/c duct work and cold air returns on exterior walls specifically between the rafters? I am using 2x10 rafters.
 
  #2  
Old 07-31-01, 04:18 PM
lynn comstock
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Space is the issue.

Your idea would require the insulation in the wall space used for ducts to be reduced. The duct probably should have insulation and a vapor barrier as well. This would be space for a 5 or 6 inch inside diameter duct at best.

Going to custom made rectangulat ducting would get a larger duct into the space at a larger price.

The next thing to watch is turns or elbows. Each 90 degree turn is equal to at least 30 feet of metal ducting or 15 feet of flexible ducting. (The friction factor of flex duct is approximately double that of metal ducting.) Keep the turns to a minimum. If any branch has more turns between the fan and the grille, the airflow out of that grille will be reduced unless you upsize the duct to compensate for the added restrictions of the extra turns.

The ductwork is the hardest part of the job to do correctly. Design like the Pros: you can buy Manuals C, J, S, D and T for residential design. Go to http://www.acca.org/redesign/catalog/Category.asp?cid=3 to order these reference manuals. They are well written for layman or pro to use.
 
 

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