Insulation, Radiant and Vapor Barriers - Adding attic insulation
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tvshooter
10-21-05, 10:14 AM
My house was built in 1964 and is in Maine. I bought it back in March of this year. There is about 6 inches of blown-in insulation in the attic crawl-space. The home inspector I hired before I bought the house sent me a written report of everything I needed to know about the home, including the suggestion that I could add more insulation up there to realize additional energy savings. He specifically wrote in the report that if I go with the pink roll type of insulation (which I'm going to do), make sure it doesn't have a vapor barrier. He didn't specify why, and I'm getting conflicting information from other sources now that I'm getting ready to do it. As part of the fee I paid his company for the inspection, I can consult him anytime for advice on these matters. However, as you'd expect, he isn't returning my phone calls (which is really annoying me given the amount of money I forked over for him to spend 45 minutes in the home and I had to go up in the crawl space to tell him what was up there). Anyway, I was wondering if anyone on here could offer some insight as to why I shouldn't have a vapor/moisture barrier, or if they feel that's bad advice. Thanks in advance!
Concretemasonry
10-21-05, 10:26 AM
You probably already have a vapor barrier on the warm side of your ceiling.
If you do, he was correct in telling you to not get another vapor barrier since you would possibly be trapping moisture between the barriers. If you get 1/2 to 1% of moisture in the fiberglass you kill the insulating value.
If possible, apply the rolls perpendicular to the joists to insulate the areas the original fiberglass always misses. If you have trusses, you would probably would be better off with blown insulation that eliminates this classic roll insulation shortcoming.
Dick
If you do, he was correct in telling you to not get another vapor barrier since you would possibly be trapping moisture between the barriers. If you get 1/2 to 1% of moisture in the fiberglass you kill the insulating value.
If possible, apply the rolls perpendicular to the joists to insulate the areas the original fiberglass always misses. If you have trusses, you would probably would be better off with blown insulation that eliminates this classic roll insulation shortcoming.
Dick
tvshooter
10-21-05, 01:19 PM
The insulation that is there now IS the blown-in stuff, not the rolls. I'm ADDING the rolls over the blown-in. Could there still be a vapor barrier under the old blown-in? And if so, how would he know since he never went up there? If I don't find any type of barrier under there, should I then get the rolls WITH it?
Ed Imeduc
10-21-05, 01:35 PM
like said dont dont get any rolls of insulation That have a V/B or paper on them. To go over what you have now.
Make sure you dont block off any air from vents out in the over hang of the home.
ED ;)
Make sure you dont block off any air from vents out in the over hang of the home.
ED ;)
Concretemasonry
10-21-05, 02:59 PM
Do not add rolled insulation with a vapor barrier. Get the unfaced type.
If you have trusses, you will have trouble insulating over the bottom chords (joists) because of the diagonals. Blown in avoids this problem.
If you do not have trusses, just unroll the fiberglass.
To find out if you have a vapor barrier, move the blown in inslation aside to see if there is plastic between the ceiling sheet rock and the joists.
Even if you do not have a vapor barrier, do not buy insulation with a vapor barrier unlees you plan on removing the blown in inslation you already have. If you really feel you have to have a vapor barrier you can buy a vapor barrier paint.
P.S. You still will have holes everywhere you have ceiling fixtures.
Dick
If you have trusses, you will have trouble insulating over the bottom chords (joists) because of the diagonals. Blown in avoids this problem.
If you do not have trusses, just unroll the fiberglass.
To find out if you have a vapor barrier, move the blown in inslation aside to see if there is plastic between the ceiling sheet rock and the joists.
Even if you do not have a vapor barrier, do not buy insulation with a vapor barrier unlees you plan on removing the blown in inslation you already have. If you really feel you have to have a vapor barrier you can buy a vapor barrier paint.
P.S. You still will have holes everywhere you have ceiling fixtures.
Dick