Summer has kicked in again in the nort east and the heat in the attic is very high.When i read the temp of the ceiling its 94 degrees, so the bedrooms are tough to cool.
Any ideas on easy extra insulation in the attic? blown fiberglass at the moment. I was thinking of installing foam sheets to the underside of the rafters and gable ends. Not real sure if this be effective. I should note the bedrooms are cool in the winter too.
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Replies
How much blown f/g is in there now? Assume the attic is vented roof, correct?
I had blown celulose in my last home. My first upgrade was to just add more cellulose. It helped a lot. My second upgrade was to add rlls of (free ) 6" f/g acroos the joist and over the cellulose. It helped even more.
Maybe just adding more of what you have is the simplest solution. I would be carfull of foam on the underside of the rafters unless I was sure ech bay was vented.
dave
If the attic is vented (and it should be) insulation up near the roof isn't going to help. You don't say how much insulation you have now, but adding insulation can be helpful.
For the heat, the best thing to do is get the hot air out of the attic. Powered attic fans can help, as can whole-house fans.
It is vented and has powed fan assistance. Blown fiber glass to about 2' deep. Still very hot up there!
Allow me to disagree with your point of view. Unvented attics IMO are a much better solution of keeping the hot and the cold out than the vented kind. Fewer cracks, fewer potential leaking points, etc. See the research at buildingscience.com re: what difference it made to have a unvented vs. a vented attic in Las Vegas, NV. In full sun, the difference came out to just 17 degrees Fahrenheit at the roof deck and the shingle temp was still in-spec.Vented roofs are a leftover from some research the DOD made in the 1940's, IIRC. IMO, nothing beats a well-insulated roof deck (exterior, if possible) since you gain attic space, can install air-moving appliances up there in the conditioned space, and reduce infiltration/exfiltration significantly. Since we were restoring a 1872 Mansard, we had no choice but to insulate from the inside. 6-8" of Corbond under the roof deck later and the rooms up top stay warm in winter and cool in summer. True, cheapo asphalt shingles may have an issue with being warmer than they otherwise would be, but we're in MA and we went for DuraSlate instead. Our fake slate has yet to show any signs of curling, cupping, flaking, or the myriad of other issues people associate with the stuff. Presumably, the material has something to do with it (recycled car bumpers, not rubber as with some fake slate)I maintain that one of the reasons we only have 0.2 ACH is that the roof deck is tight. The lack of a stack effect in the home also helps comfort-wise, as the individual floors stay at their respective temperatures, despite a 3-story, open stairway connecting them. For me, the "hot roof" here was an essential step towards reducing our heating and cooling requirements 4x per square foot over the course of the renovation.
Edited 6/10/2007 8:53 am ET by Constantin
I agree with what you say, but I don't think that it applies to the poster's question. Converting from a vented attic to a non-vented attic seems to be considerably beyond what the poster was interested in.
Perhaps it's beyond the scope of what the OP was looking for... but his idea of going for insulated panels on the rafters is pretty similar to spray foam being applied to the roof deck.I guess the question is whether the OP wants to deal with the expense of a professional spray foam job vs. DIY... corbond is not something I'd DIY unless I had the equipment to do it right.
Constantin,
I have a question about your insulated attic. I am considering having spray foam installed in my attic. The installer says that if do the underside of the roof deck, I have to add an air supply and return from the HVAC system to the attic. The only reason that I am considering doing the underside of the roof deck is that I want to later add HVAC equipment up there to handle extra rooms for an anticipated remodel. Otherwise, I would just have them insulate the attic floor. Did you have to put a supply and return for your attic?
Thanks
- Kevin
I have a AH up there to handle the upper floors. No dedicated inlet outlet for the attic though. There is no insulation between the floors below and the attic. Given the location of the AH, adding a inlet, outlet would be easy. I guess I wonder why such an inlet/outlet config is necessary? Also, our "attic" is tiny... think 20x20 Mansard pyramid-top (i.e. 5' at the center). Temperature-wise, it will go above 80 degrees occasionally. If the top floor had the ac going (it usually doesn't) then the space under the roof would be cooler also. If you're thinking of putting the HVAC up there, I'd definitely make it part of the conditioned space. AC systems (even well-installed ones) are notoriously leaky. If it leaks into the conditioned space, you have fewer losses to contend with than if you try to cool the outdoors... never mind other issues such as escaping cold air causing hot humid summer air to condense in various places.IMO, if an air handler is to be installed in an attic, it better be sealed and part of the conditioned space.
Edited 6/21/2007 11:08 am ET by Constantin
When i read the temp of the ceiling its 94 degrees
Which is something I'm too familiar with down south. Sun heats the shingles all day, until they hit a sort of "terminal" heat. That heat is transmitted to the deck, then down into the rafters, and to a certain exten, into other framing members attached to the roof.
You used the term "read," are you using an IR thermometer? It can be better to use an actual thermometer, or a contact thermocouple. But, I'm biased, I've been gathering data on attics and things for far too long now <g>.
"Why how measured?" Well, you say there's at least a foot of insulation on the ceiling already. What I suspect is that you have a "northeastern" style forced air layout, supplies low, and returns high--dieal for heat, less so for cooling. So, what you may have is a "puddle" of air that gets very little disturbance (the way bedrooms can), that just sits up against the ceiling and stays there.
What you may need is to run some fans, to "break up" those air masses. But, that's a guess.
Hard call. It's 0017 here, temp has come down to 82º, RH is 68%, the remote in attic has cruised down to a balmy 96º; our heat Index has broken the century mark over the last two days--heat is part of my life.
I had the same problem. Blow cellulous a foot deep on top of what you got. You can do it your self with a hellper. Takes less than a day. Will help with winter and summer.