Discussion in 'Roofing and Siding' started by drewdin, Mar 18, 2013.
Do i just insulate the attic floor or am I supposed to insulate the attic roof? Thanks
Logical question. Assuming you have proper ventilation from the eaves, Just insulate between the attic joists. If you insulate between the attic floor joists, you are not required to insulate the attic rafters. Don't skimp! Attics take more insulation than exterior walls. Most of the home's energy (cold or hot) escapes through the roof. Check your local codes and go an extra step. You'll be happy with the outcome.
If you have a "normal" home with insulation in the sidewalls and attic vents of some sort you would insulate the area between and above the ceiling joists and leave the rest of the attic uninsulated and open to air flow. The area where you live dictates how much insulation is needed in the attic. That is conventionally the way homes have been built and insulated for years. There is now new thinking concerning the need for ventilating attics and ways of insulating those spaces. One popular, although more expensive alternative, is to have foam insulation applied to the bottom of the roof deck and all gable ends etc foamed to create an air tight insulated space of the attic. The claim is this causes less than a 5 degree temperature increase to the roof deck and helps the house heat and cool better particularly if you have heating and cooling duct work in the attic. Go to the internet and look up two part insulating foam. There are volumes of information concerning the subject if you are interested. You can olso have foam applied in a conventional way between the ceiling joists. You can buy loose insulation and blow it in with a blower supplied by the place where you buy your insulation and do the project yourself. They should assist you with how much you need and how to blow it in.
If you are insulating the ceiling make sure you have soffet vents and install air shoots against the roof deck to keep air moving.
Fireguy: Insulating the roof in a cold zone is questionable, as the one spot that will have the least amount of insulation is above exterior wall and there is no longer any air flow to carry heat away. Ice dams can become a problem.
Yeah Neal I know there are many factors to be looked at. I don't think I have ever seen that one talked about in all the all the stuff I have read. If you design a home for foam insulation probably increase the heal height at the wall plate to compensate.
My son-in-law was getting mold in the upper corner of their bedroom on the outside wall. Finally tracked it down to lack of blown-in insulation at the wall plate and inadequate bathroom ventilation causing constant condensation from the cold spot and high humidity in the room. When we added onto his house we redid insulation/ventilation to fix the problem.
I live in Boston so it gets cold and hot as hell here always with a ton of humidity. Right now i don't have any insulation in my attic, just had the ridge and soffit vents added last year (House is from 1927). I want to make sure that when i do put insulation up there I do the right thing.
I know I need at least 18" of insulation on the attic floor, and I can only do the ceiling bays that dont have the airvents on the side.
Is there a specific insulation you guys recommend? Thanks
Air shoots are 4 ft long, you staple them to the roof sheeting and intall a little batt insulation over that wall. That will stop the loose insulation from falling into the vent and prevent the wind from blowing the loose around.
right now I have them goin 4' up the side, ill need to add more 4' extensions to the ridgevent and then cover that with insulation?
I think the Boston Insulation Code calls for R38 minimum in the attic for new construction. Get there or higher if you can. You MUST have the chutes Neal is recommending to guarantee proper ventilation. Which kind of insulation you use it optional ... blown-in is popular but has to be carefully applied for good coverage. Inspect carefully.
I checked the R value of blown in cellulose. If Villa is correct and Boston calls for an R-38 attic rating then you must use 10" of blown in cellulose to meet that standard. I would use more. It is hard to get to much insulation. Make a stick with a mark at whatever depth you decide to use and keep checking the depth of your insulation as you install it. Make sure you plenty out against the outside edges as you go to keep that edge from being to cool or hot.
If you already have 4' air shoots then you should not need any more length. All the shoots are for is to keep the insulation from obtructing air flow from your soffit vents into the attic space. By placing batt insulation or any kind of barrier that keeps your blown-in insulation from falling out into your soffit and plugging your vents you have done all that is required to keep the air moving up through your soffit vents, through your air shoots and out the peak of your roof. I have used fan fold siding backer nailed on the outside of wall sheeting and trimmed to fit against the air shoot to hold insulation from falling into the soffit area. If your soffits are already in place that will probably not work for you, but you can most likely get the batt insulation in that area.
Since we are talking blow-in, here is an Owens-Corning video which (while heavily branded) goes through the basic steps for you to do it yourself. Not sure about the costs compared to having a company do it for you. The keys are eave ventilation with the chutes, complete coverage and proper depth.
As Fireguy can explain -- any dumb monkey can hold a hose, right?
Villa; What are you saying about firemen: That's a great clip.
Just a few points on prep work before you get going. some 1927 house still were balloon framing, so you are looking for cavities between the studs on the gable walls at the ceiling level. They need to be blocked with wood, plywood, drywall or what ever.
All holes drilled thru wall plates for wiring should be chaulked with fireproof chaulk. Pot lights should be the ones rated for insulation.
If not they need a box built over them about a 1 foot cube lined with drywall. Insulate the cube with batts. and then I would put down 6 mil poly for vapour bearier as you likely don't have one now. Tape the joints with red Tuck tape and stick down the edges with acoustical sealer. Yes it is a pain to wrap the joists and walk on later is a neat trick too. You can staple in place on the joists.
If you stop all air flow from below you get full value for the insulation.
That is a great add-on post, Neal ... These are essential things to look for whether its an old house or a newish one. A lot of newbie DIYers would not think to check for pot light fireproofing. Appropriate boxes are readily available and MUST be used before the blown-in is shot.
And, yes, anybody can shoot insulation (even a fireman) but not everyone can hold his hose.
Thanks Guys, i Don't have any pot lights but i believe that they are balloon walls as when i was taking down the walls in the bathroom some of the attic insulation came out.
I can see the air shoots going down to the eaves, i'll make sure i put something there to prevent the soffit vents from being filled.
That can easily be checked from the attic, right now i only have 4" of insulation up there. its pretty much even with the studs. Would it be worth putting some wood down so I have something to walk on and then put insulation on top of that?
I wish my attic was as clean and nice as the one in the video!
Having a catwalk is a good idea as when you are done you will not be able to see the joists.
Having lived in that area I had Mass Electric pay for adding insulation in mine. It was part of their energy conservation program. Even if you're with Boston Edison you should check if they have any rebate programs for adding insulation. You should also look into adding fire blocks into your balloon framed walls, which are a potential nightmare if you have any sort of fire in your house.
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