Attic – Cellulose, flex duct, electrical
Sorry about the cryptic subject line –
I’m really wanting to go ahead with sealing up leaks and blowing cellulose in our hip roof attic with appox. 2,000 sq ft of area to cover.
Last year, central A/C was installed with all duct work and handler being installed in the attic. Several days ago I heard some first hand accounts of flex duct outer plastic skin disintergrating after several seasons in a hot attic.
So, the question goes….
1. Is blowing cellulose over the flex duct and completely covering it common practice ? I’m hoping the cellulose insulation will help protect the flex duct. There is also the matter of the compressed fiberglass board trunk lines. How about blowing cellulose over them ? Accepted practice ?
2. When additional wiring needs to run through the attic, could the new ones be stapled onto the trusses above the insulation ?
3. What is your experience with having to deal with existing wiring that ends up under the cellulose ? Just dig into the cellulose and go for it ? I can’t think of another way but to shove it out of the way and then put it back in place.
4. I am used to being able to crouch around in the attic with boards placed at strategic spots. Even if I have all the wiring in place before blowing the cellulose, there will be occasions when I have to wade through a sea of cellulose. Or is there another solution ?
These have been lingering questions while I drag my butt on getting this done.
(This probably doesn’t need to expand into attic venting, etc.)
Thanks for your help,
Alan
Replies
Alan,
Someone else will have to help you with the electrical stuff. As far as the flex duct goes, there is high quality flexible duct and there is garbage. My preference is to use flex duct as minimally as possible or not at all. As far as covering the ducts with blow-in stuff, that is certainley acceptable, though the duct work should be sealed and insulated (ductbaord is already insulated as is most flex) first. Check for any dampers that may need to be accessible and mark them in some way so future loaction will be possible.
In many areas, romex can be stapled to the surface of joists/trusses in an unfinished area but check locally with your building department. If not, or if you just want a sturdy installation, run a 1x4 at a convenient height and staple to that. If you have 16" spacing, ripping some CDX would be cheaper and stiff enough. But I found it kind of bouncy over 24".
With regard to the electrical, usually it's a "no-no" to staple to the top of the floor joists in an attic. What code typically calls out is for "runners" to be laid on both sides of the wire so that when people are walking around on the joists, they step on the runners, not the wiring.
As for stapling to the bottom of rafters/trusses, that's more a question for the local inspector. In the basement, for instance, it's a "no-no" because people love to use the wiring as a clothes line. If your attic is such that that wouldn't happen, you can probably get away with it. Again, the way around that is to attach some 1x2s to the trusses/rafters and staple to those.
Thanks for the replies -
Our flex duct is R-6 and our installer claims most use R-4.
They did a quality job and came highly recommended, so I'm not concerned about leakage.
Burying the flex duct under cellulose couldn't hurt I suppose.
(I heard the Fed will start requiring thicker compressed duct boards for better energy efficiency.)
As for the wiring, runners is a great suggestion.
This isn't a walk around attic - even at the peak I have to stoop slightly because it's a low pitch hip roof.
I've run most wires closer to the eaves on runners nailed to the joists. Have to crawl around in those areas so there won't be any foot traffic. 1x4 or 1x2 runners along the trusses sounds like a good solution and there shouldn't be any problems with the town inspector.
So....I still haven't heard from someone who has had to work through cellulose that is already in place. Blow the stuff in the attic and hope you never have to go up in there in the future ?
Luckily the air handler is next to the attic access hatch.
thanks again,
Alan
Runners not only help with the inspection, but if you're up there, banging around, it's too easy to grab the romex when you trip on something. The runners ought to be secured to every joist/rafter because they'll function as handrails at times.
"I still haven't heard from someone who has had to work through cellulose". Well, it just one of those occupantial hazards. Like you said, scoop it aside, do the deed, shovel it back in place. A bother, but hopefully an infrequent one.
Of course make sure that any recessed lighting is "IC" rated (insulation compatible). And maybe elevate your walkway above the level of the cellulose. And don't worry about whether the wiring was rated for "free-air" or for being submerged in insulation - no one else does.
David Thomas Overlooking Cook Inlet in Kenai, Alaska