Insulation, Radiant and Vapor Barriers - Add batts over cellulose in attic?
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tom855
10-18-04, 11:00 AM
I'm in a 6 year old two story house. Heating seems to cost us a small fortune. Attic has blown in cellulose. In some portions of the attic the insulation had been smashed down from workers walking up there to do repair work, add an attic vent fan, etc. I'm guessing in at least a portion of the attic the R value of the insulation has been pretty dramatically comprimised. I understand that cellulose is supposed to be very popular and effective, but it doesn't see to work so well in an area that gets some traffic.
In our geography (Maryland) I understand the recommended R value is R49. I'm thinking about rolling R30 or R38 on top of the cellulose. I realize this is going to reduce the R value of the existing cellulose dramatically since in theory the stuff could get smashed down to the width of the 2x4s in the trusses.
Given the poor state of some of the attic cellulose, do you think I could gain anything in terms of insulation value by putting batts on top of the cellulose? I guess at a minimum I'd have the R30 or R38 of the batts, but given the fact they would be perpendicular to the studs, I'm not even sure that's the case.
I "think" I'd be better off but any guesses on the effective R value in a setup like that? I really appreciate your input!
In our geography (Maryland) I understand the recommended R value is R49. I'm thinking about rolling R30 or R38 on top of the cellulose. I realize this is going to reduce the R value of the existing cellulose dramatically since in theory the stuff could get smashed down to the width of the 2x4s in the trusses.
Given the poor state of some of the attic cellulose, do you think I could gain anything in terms of insulation value by putting batts on top of the cellulose? I guess at a minimum I'd have the R30 or R38 of the batts, but given the fact they would be perpendicular to the studs, I'm not even sure that's the case.
I "think" I'd be better off but any guesses on the effective R value in a setup like that? I really appreciate your input!
Ed Imeduc
10-18-04, 11:11 AM
If you go Batt's be sure and NO PAPER on them
I understand that cellulose is supposed to be very popular and effective, but it doesn't see to work so well in an area that gets some traffic.
Lost here why are how? Id go with more cellulose . In a fire in the home the fiberglass will melt and let a fire get through. Where as the cellulose will just turn black not burn are melt. Make sure you put in rafter foam vents so air can get up in the attic from the vents in the over hang . Whit that much insulation.
ED ;)
I understand that cellulose is supposed to be very popular and effective, but it doesn't see to work so well in an area that gets some traffic.
Lost here why are how? Id go with more cellulose . In a fire in the home the fiberglass will melt and let a fire get through. Where as the cellulose will just turn black not burn are melt. Make sure you put in rafter foam vents so air can get up in the attic from the vents in the over hang . Whit that much insulation.
ED ;)
tom855
10-18-04, 11:54 AM
I understand the issue of the paper backing - I'd absolutely use batts with no backing. Only issue with more cellulose is then that gets crushed as well so I'd like to stay away from more of the fluffy white stuff. Have you ever heard of anyone adding batts on top of cellulose?
Ed Imeduc
10-18-04, 03:02 PM
Yes you can do it. just so they have no paper on them for a V/B. Batts just will not be as tight as the cellulose can be.
ED ;)
ED ;)