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justin76 01-06-2008 10:03 AM

attic insulation question
Hello All,

I have an older colonial house which is in need of better inuslation. I have noticed that my upstairs is constantly 3 degrees cooler than downstairs in the winter. I have decided as my first step to add additional insulation to my attic as it has only about 6 inches of older insulation, including vermiculite. The attic has a complete floor over the insulation already, and rather than pulling up all the boards, I would like to simply roll out fiberglass insulation over the floor at right angles and simply not use my attic. Is there any issue in doing this? It seems like a quicker, less messy fix to get through the winter. Will adding another 9 to 10 inches across the floor help, or do I need to pack it in under the floor for it to be effective?



USP45 01-06-2008 10:14 AM

I do not see any problems with that, as a matter of fact I may would do the same, but I would roll it out with the vapor barrior upwards, then as I roll out the second run I would use tape to seal the 2 runs together at the seam. keep doing this so the whole attic has like one giant piece of insulation. This will avoid any gaps between the runs where air can get in and out. If you want to use uncrafted just make sure its pushed snug up against the previouse run so as to avoid air flow.Then in the summer, remove it, pull up the floor boards, then install some 2x's the same thickness of the insulation across the floor, re install the insulation but remove the vapor barrior backing and install to a right angle of the original joists, re install the floor, should be a lot beter

justin76 01-06-2008 10:22 AM

That is good advice, thanks, I was told however that I should use insulation with no paper siding and no vapor barrier as the original insulation and the floor already provides this barrier. Also, I was planning on just leaving the insulation up there year round as I do not plan on using the attic. Someday should I want to use it then I would tackle the task of putting the insulation under the floor. Is there any issue with this?



AllanJ 01-06-2008 11:16 AM

Ideally the vapor barrier should be on the warm side. The floor and ceiling, even solid wood and solid plaster/mudded drywall, do not make good vapor barriers per se; there should be a specific vapor barrier.

If you use vapor barrier insulation with the vapor barrier upwards, moisture may be trapped just under the vapor barrier if there was no specific vapor barrier just above the ceiling below. If you are sure you have no vapor barrier, install the new insulation with faced side down so the vapor barrier will at least be in the middle as opposed to be on the cold side. With a known vapor barrier down below, you need to used unfaced insulation, or make proliferous knife slits in the vapor barrier of faced insulation.

justin76 01-06-2008 12:06 PM

ok, back to the vapor barrier question. I just pulled up a couple boards and it appears it is primarily cellulose insulation( white cotton kind of stuff), however in some spots it's 6 inches thick others 2 inches etc. So, do I purchase the insulation with the paper for a vapor barrier and lay it over the existing wood floor with the paper side down, or do I get one with no paper and lay it across? Just want to make sure I'm doing it best as possible. Also, under my floor are some recessed lights, that seem to have space around them from the insulation. Should I insulate over top of these when I apply my insulation since they are housed between the floor and celining?? And finally, is all this worth the trouble???



Ron6519 01-06-2008 02:59 PM

It would help if you posted where you lived.
The recessed lights are probably the type where you need to keep the insulation at least 3" away from the fixture. Unless you can confirm this is an insulation contact fixture, keep it away.
You want unfaced(no vapor barrier) batt insulation for your application. Buy the thickness your region recommends. You should be able to get the 23" wide batts. Keep the batts tight to one another and try to not step all over them when you install them. You can fix the exposed low spots by moving some of the loose stuff around to fill in the gaps and then take the batts and fill in the voids.

Shawn_Barris 01-23-2008 01:28 PM

I have a question about attic insulation. Our neighbor has what was once a mobile home that has been redone including a new scissor truss roof installed. They want to add extra insulation to the attic and they were wondering if it would be best to add the insulation between the old roof and the new roof, on top of the old metal roof, or if they should drill holes in the ceiling and fill between the ceiling and the old roof. They live in southeast Colorado where it does get very hot and gets fairly cold.

I was thinking it would be best to add between the two roofs to keep the hot and cold off of the old metal roof.

What do you think?


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