14" Supply Line Running along rafters in attic

[rogressem]

About 30 feet of my 14" flex duct (non metallic) supply line is running along the peak of my attic, adjacent to the rafters. I don't really think its compressed much, but its wedged up there by the supports pieces that run from one rafter to the other (see photo in link below). Floor to peak in this attic is about 15 feet or so, so its up there.

I've often wondered if there is any significant advantage to running the supply line much lower in the attic so that 1) its not so close to the hot roof and 2) the hottest spot in the attic is up high were the flex duct it running.


http://picasaweb.google.com/lh/photo...eat=directlink

[kls-ccc]

I would guess that there is not a lot of temp difference in the attic between the peak of the roof and ceiling joist. One advantage is it won't get smashed by anyone crawling around in the attic. Disadvantage is you can't blow more insulation over the top to help insulate it more. If the system is working fine I don't think I would worry about it. If you have issues with rooms at the end of the duct then you may have a size issue more than a location issue

[rogressem]

Thanks. I've suspected there really isn't that much temp differnce too - I've wondered about radiant heat coming from the roof - maybe I'll just measure it.

I do have some issues with the temps coming from registers on that side of the house, but that will be a separate post - I need to gather more details before I ask that question (lengths, sizes of ducts, etc)

I would guess that there is not a lot of temp difference in the attic between the peak of the roof and ceiling joist. One advantage is it won't get smashed by anyone crawling around in the attic. Disadvantage is you can't blow more insulation over the top to help insulate it more. If the system is working fine I don't think I would worry about it. If you have issues with rooms at the end of the duct then you may have a size issue more than a location issue

[REP]

What I am looking at is fine for about 6 six inch flex runs and a ton and a half.
You should be very proud to own such a fine design and install.

[Shophound]

There is a pretty significant temperature difference between attic floor and attic peak during hot weather, especially if the attic is not well ventilated.

Additionally, that particular flex duct in the photo appears to have a black jacket on it, not the reflectorized mylar or foil jacket. The black jacket is a radiant heat absorber, wheras the reflectorized jacket repels radiant heat gain, to a large extent.

A 30 foot run of 14" flex isn't the most optimal configuration for minimizing friction loss, either, even if it is relatively non-compressed.

You may wish to consider adding a foil based radiant barrier below your roof deck to reduce heat gain to that 14" flex duct.

[pstu]

I measure a considerable difference in temperature between high and low positions in the attic. Easily 15F on a hot sunny day. But... there are tradeoffs in every choice you make and it is not proven this leads to a problem in your house, is it?

Hope this helps -- Pstu

[beshvac]

I believe too there is significant heat there, I don't see a ridge vent and in Virginia it gets hot quick, and noticable how high you get in the attic.