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| I have a 1930s brick house in the Washington, DC suburbs with a large attic -- you can stand upright in it. It is accessible from a permanent stairway with a door at the bottom, at the bedroom level. There is one louvered vent to the outside, approximately 18" square. The attic floor is framed in 2x8s and filled (or mostly filled) with some sort of cotton-type loose insulation. It seems to be in fair condition, but I would need to pull up a lot of floorboards to get a complete assessment, which I'd rather not do. The roof is very steep and the insulation (TWO layers!) that had been stapled to the rafters years ago was sagging, falling down and disintegrating, so we ripped it all out. The question now is: what, if anything, do we put back up there? (The attic is used for storage only.) |
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| You have insulation at the roof line and under foot up there???? |
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- Posted by energy_rater_la (My Page) on Fri, Dec 7, 12 at 15:12
| you would increase the insulation value of the attic floor by blowing enough inches to meet requirements in your area. less than 8" isn't much for your climate. best of luck. |
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| Ionized: yes. We pulled out all the old insulation above the attic floorline -- it was breaking up, sagging, falling down, etc. What's under foot is the unknown quantity and quality under the floorboards, which seems to be a few inches of blown-in, resting on top of paper-backed batts. There is blown in at the eaves. It appears that various previous owners pursued overlapping theories on insulation. Somebody evidently believed "the more the better," but I'm reading in some places that it is a mistake to insulate between the rafters. I'm inclined now to leave it all open and see how we survive the winter. |
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| "...but I'm reading in some places that it is a mistake to insulate between the rafters." It depends on the climate and the house. Sealing the attic and insulating at the roofline is a good thing for a lot of houses in the hot, humid South US. |
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- Posted by energy_rater_la (My Page) on Fri, Dec 7, 12 at 18:44
| Ionized, insulation other than foam is often used in cold climates. just not here as the high temps in summer & high RH have educated code to NOT do this here. OP..I agree that going thru the season is the best again check into code insulation Rvalue requirements. insulation at roofline & insulation at attic floor when you wrote overlapping of insulation..this is best of luck. |
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| Energy_rater, OP has insulation at the house ceiling/attic floor, a (poorly) vented attic and MIGHT have insulation at the roofline. In the OP's second post it says " above the attic floorline" which is not the same as the roofline. Maybe it does not matter since it is gone. I am just trying to figure out what was going on up in that attic. DC is pretty hot and humid in the Summer, but they have to deal with a little ice and snow. I am quite aware of the historical insulating strategies there and much further North since I have lived in the mid Atlantic. What I don't know is if sealing the attic is a good thing in that area. If it is, he might consider it. If the attic is to be left vented, it needs more ventilation than one 18" square vent. As Energy_rater wrote, you need more insulation and gaps are not good. I think that you have little choice but to pull up the floor to add more insulation. Pay attention to the weatherstripping on the attic stair door and insulation around the encloses stairwell too. |
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| ionized: what exactly do you mean by 'the roofline?" I will say this, that there was insulation between the rafters for many years and there is no evidence of mold, moisture damage or condensation anywhere. If I let the attic get cold this winter, will I be increasing the chance of condensation? I'm not sure it's "poorly" vented. It's a 75-year old house and it's dry as a bone up there--or has been up to now. |
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- Posted by energy_rater_la (My Page) on Sat, Dec 8, 12 at 14:37
| bppark you and ionized are talking about the same install. just our climate Louisiana...putting insulation that absorbs rather than seals moisture at the roof line..between roof rafters is not done. with our high humidity & hurricane damages roofs it is against code (which is minimal allowed by law) to put batts, cellulose & blown fg (bibs). building practices are climate specific. but a standard is to air seal attic floor to blown insulation over batts is a good thing. check buildingscience.com for cold climate info. best of luck. |
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- Posted by mrconstinc (My Page) on Mon, Dec 10, 12 at 6:13
| Nice job pulling the insulation from the rafters, it was useless. I sounds like you may have blown or poured rock wool under the boards, you can have blown in added under the boards by pulling just a few boards. Then I would recommend 10 to 12 inches added on top of the boards. My recommendation is blown in cellulose. |
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| "ionized: what exactly do you mean by 'the roofline?" I meant between the rafters, under the roof deck. If your attic is vented, there is no point to having insulation there. |
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- Posted by energy_rater_la (My Page) on Tue, Dec 11, 12 at 16:59
| I'd not put cellulose but a blown fiberglass. 1930's houses were not built tightly. cellulose contains small fibers that enter the house via holes in ceilings. put cellulose in a house with a lose air chose an insulation that won't easily enter better yet...improve that air barrier best of luck. |
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