Hello,
I am about to insulate an attic room rafter area because of the temperatures seen in summer (hot) and winter (cold). Attic floor (living room ceiling) is fully insulated with 4 inch pink between 2x4 joist with 6 inch laid perpendicualr to that. There are 36 inch hi pony walls that are insulated with 6 inch pink, but the slope up to the pan ceiling (48" x 16 feet) is uninsulated. My guess is this room was added after the fact,1930's house, and there is just no room in a 2x4 rafter space for insulation and ventalation air. I had an insulation dude come in and he told me to just fill the rafter voids full of pink or rigid foam boards after putting up a poly vapour barrier first. Lots of dusts blows into this room as there is no barrier on the ceiling. I've installed 2 turbine vents in the ceiling pan area to assist air movement from the very small soffit vents....approx. 200 sq. inches. I also want to add 2 opening skylights between rafters. My question(s): is it okay to fill in rafter space plumb full of pink. If I use rigid, shud I leave air space. Is rigid safe in hot areas like attics ie: degassing fire etc.

The place for insulation is in the attic floor, as you have. Placing another layer of 6-inch fiberglass insulation there will help your heat loss from the house in winter, or heat gain from the attic into the house in summer.

You have soffit vents, but do you have a ridge vent? If you have a vapor retarder in your attic floor / ceiling, the 200 square inches is enough for an attic floor area of juast over 400 square feet, provided you have approximately the same free area in a ridge vents, or in gable vents. Your turbine vents may be enough, but what is the floor area of your attic?

By the way, there should be only one vapor retarder in the ceiling...if you have another vapor retarder in the second layer, you should slash it liberally with a knife, so that it doesn't act as a vapor retarder.

I think you need more ventilation in the attic. I don't believe more insulation will help your problem. Insulation doesn't create heat or coolness, it just delays the passage of heat through it. Sooner or later, your attic will be just as hot after you insulate it as it is now. I don't know if you can increase the area of the soffit vents, but you can have a ridge vent installed, or even two gable vents, if you have a gable roof.

Thanks for the reply Richard,
My main concern here is that when I walk up the stairs into the attic bedroom, as I pass the floor level, I pass a thermocline. In the summer this room is very hot. In the winter very cold. There is only one window on an end wall but I plan on installing opening skylites to allieviate that problem. There are no gable ends on this house, thus no gable vents. 2 turbine vents that are situated on 12 inch by 12 inch cutouts right up on the ridge, but no ridge vents. There are also 4 typical roof vents cut in up hi near the ridge as well. They are the 4 inch x 10 inch screen type. I also have 4 of these vents cut into the roof line low down about 3 feet above the gutters on the roof so I beieve these will assist the soffit venting as well. The main house in general stays very cool in summer and is fine in winter, it's just this upstairs room that we have the problem. I am going to be pulling down the tongue and groove ceiling which consists of the pan ceiling I mentioned earlier as well as the sloped portion of the ceiling that extends down from the pan approx. 8 feet until it meets the 3 foot hi pony wall. Vapour barrier is good. I understand your comments on insulations limitations with controling temperature swings so now I wonder if I should just vent more. The sloped portion of the ceiling only has a 4 inch rafter cavity under it so as I mentioned I wanted to put rigid foam in there while maintaning a 2 inch air space to keep the continuity between the lower attic space and the pan ceiling portion of vented attic space. My thoughts were seems as how I had good insulation everywhere except the sloped portion, and pan portion of the ceiling that this is where my problems arrise from.....NO ? Will it be benificial to slip rigid between the rafter spaces? What are your thoughts on the claim that I cud fill this sloped space with insulation and forego the venting? Is foam safe in hi temp. areas such as attics. thanks

You need full ventilation, so whoever told you that you could forego it is, oh let's say, less than knowlegeable. Your air space can be as little as 1 1/2 inches, so you can get 2 inches of rigid foam in the sloped ceiling. I would use polyisocyanurate foam, which has an R value approaching 6 per inch. Then I would put as much insulation as you possibly can in the flat part of the pan...fill the ceiling joist cavity with whatever fits, and then lay unfaced roll insulation at right angles to that, making sure you maintain your ventilation path clear at the ceiling break from flat to angle. Do that and see what happens. People also use radiant barrier, which has virtually zero thickness, but I have no experience with it, and have done only minimal research on it. Maybe you can use it in conjunction with the foam and squeeze a little more insulating value.

The foam is safe under whatever heat you would get in your attic, but it must be separated from the living space by a non-combustible material such as gypsum board.

Good luck! =)

Hey Richard,
thanks again for the advice. I've read about the radiant barrier and I think it's worth the effort and cost to put it up as well as the polyiso foam. I've searched around on other sites and it does seem the consensous is ventilate ventilate ventilate !!! So I will keep god air flow thru the attic space and will cut in more soffit vents. I think there is about 30 inches of attic above the pan ceiling so I'll put in a good bit of itch there as well. I am ordering the skylites tomorrow and will start the demo next week. Thanks for the help.....oh one thing. I have vapour barrier on the entire floor of the attic, below the insulation of course,warm side of ceiling, which is the ceiling for the main house so do I put a vapour barrier on the sloped and pan portion of the ceiling in the attic room? If so do I cut and slash the original one on the attic room floor? Now with the tongue and groove ceiling I have lots of dust and debre falling into the room when the wind blows, but I guess I have to drywall the ceiling now because of the foam. Your thoughts ?