Replies

1. 
   Mongo | Nov 01, 2002 08:38pm | #1

   Allan,

   I think you'll find hat most poeple believe the rigid provided the best overall peformance, and flex is a compromise.

   There are places where flex can be used, but it should also be used sparingly.

   Here is a recent thread regarding flex vs rigid:

   http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=24063.1

   Definitely follow up with additional questions should you have any...

1. 
   liveoakal | Nov 03, 2002 07:24pm | #2

   Mongo,

   Thanks for your reply and the link to the recent thread. It was very helpful. I have no experience running rigid ducting and need system design and installation information. There seem to be lots of useful references out there for plumbing and electrical but not much in the HVAC realm. Do you know of any good sources?

   Thanks,

   Allan

1. 
   Mongo | Nov 04, 2002 08:55am | #3

   This is a pretty good program. It asks all the right questions, is easy to interface with, and it has the ability to spit out duct sizing.

   http://www.hvac-software.com/hvac/newfeatures.asp

   When I looked into this a few years ago, they charged something like $30 to use the progam on one house...good for a homeowner...and ten times that for unlimited use...something an HVAC guy would need.

   Rigid duct isn't terribly difficult to run. Snap-together seams, proper hanger brackets, and sheet metal screws make it pretty easy.

   If you plan on insulating the duct, think about sealing all the seams before you insulate with Al foil tape. All those leaks, especially on the supply side, will ruin your efficiency.

    

2. 
   booch | Nov 06, 2002 12:56am | #4

   It sounds like you already have the house heating calculations done. It was required before I could get a permit in Northern Wisconsin. So you must know how much heat your house will need.

   Here is a strange bit of info. that could help you with the next plans.

   If your algebra is good then go to HD and get the little Paper sheetmetal duct advertising sheets they have in the sheet metal / heating section. That gives you the "what is available and air (CFM) required per cubic foot of room". Take the sheets they are free.

   Now look in the same section and you can find a slipstick that allows you to read off the cfm for given ducts. The slip stick (waxed cardboard with cutout windows and data sheet inside) will help you compute what feeders you need to supply the ducts you put in rooms. You buy the slip stick for a few bucks.

   Sit with your plans and figure what heat is needed where. Then figure out how to rout the ducts. Rest assured you can't do worse than most.

2. 
   EricS | Nov 06, 2002 01:41am | #5

   In addition to the other good info given, look into Manual D - Residential Duct Systems from the Air Conditioning Contractors of America - http://www.acca.org/

   Eric S.