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  1. #1
    Join Date
    Jan 2012
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    New Jersey
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    23

    Default 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Hello,

    On the third floor of my house (attic), there is a small bedroom that has been made with two doors in it - 1 door is a closet and the 2nd door opens into the "attic" where the bulk insulation is. What is in there is wrong. The rafters are sealed up tight with fiberglass that has a black and firmer, heavier side facing the warm part of the house. There is no insulation under the floor from what I can tell by looking into a few decent sized cracks and holes. Also, the straight wall next to what is the small bedroom does not have any insulation on it.

    I had Home Depot come by and take a look and for them to do everything - it would be an expense of about $2700 including the removal of all of the stuff in the rafters and to cut 4' x 4' chunks in the floor to blow in R19 (which, I don't think is enough - I'm thinking a minimum of R38 if not R76 by doubling it). We live in NJ - it gets cold in the winter and hot in the summer. My wife and I would like to do as much of this as possible but the take down and disposal of the old stuff seems to be a project which will be a royal pain.

    Assuming there is no insulation of any kind under the floor, can you just lay out insulation rolls on top of the floor or does it have to go in between the joists? Is there any harm if you have insulation on top of a flat wood surface, 4-6" of space, more wood below that?

    Anyone have any suggestions on what they would do? I believe the square footage of the floor was around 320 SF - give or take.

    Thanks.

    Steve

  2. #2
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    I just had this done last year in my house, they drilled small holes in the floor in the unfinished attic and blew in cellulose under the floorboards, and then they added 12" on top of the floor, on the kneewalls on the attic bedrooms they used fiberglass batts, they cut holes in the roof and blew in 16" into the attic celing and blew all down the slopes to the knee walls, and then capped the 4 holes in the roof with vents. All the exterior walls were filled with cellulose also. Just make sure they don't cover up all your soffit vents if you have them, I did not realize this until I saw insulation coming out of the soffit vents, now I have to cut a hole to get get behind the sheetrock into the attic space which I just had replasterd after the insulation was done. This was a very expensive project, It cost around $5300.00 in boston,ma, so your price seems average for just the attic, I would get multiple quotes on this, I had prices all over the map for the same work descrition. Good Luck !

  3. #3
    Join Date
    Jan 2012
    Location
    New Jersey
    Posts
    23

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Hi - good to know. But, my question still is do you have to into the joists if you have a floor - can you just lay down OVER the floor let's say two rolls perpendicular to each other over it?

  4. #4
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Yes you can lay insulation batts over the floor, there will be an airspace under the floor between the joists, this will not be airtight, unless the joists are sealed off from the soffits at the ends, the soffits willl let air in under the joists and into your living area below, you could seal off the ends with spray foam to minimize air movement under the floor joists, either way it will work, but you may not save as much in energy! Good Luck!

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Quote Originally Posted by Steven413 View Post
    Hello,

    On the third floor of my house (attic), there is a small bedroom that has been made with two doors in it - 1 door is a closet and the 2nd door opens into the "attic" where the bulk insulation is. What is in there is wrong. The rafters are sealed up tight with fiberglass that has a black and firmer, heavier side facing the warm part of the house. There is no insulation under the floor from what I can tell by looking into a few decent sized cracks and holes. Also, the straight wall next to what is the small bedroom does not have any insulation on it.

    I had Home Depot come by and take a look and for them to do everything - it would be an expense of about $2700 including the removal of all of the stuff in the rafters and to cut 4' x 4' chunks in the floor to blow in R19 (which, I don't think is enough - I'm thinking a minimum of R38 if not R76 by doubling it). We live in NJ - it gets cold in the winter and hot in the summer. My wife and I would like to do as much of this as possible but the take down and disposal of the old stuff seems to be a project which will be a royal pain.

    Assuming there is no insulation of any kind under the floor, can you just lay out insulation rolls on top of the floor or does it have to go in between the joists? Is there any harm if you have insulation on top of a flat wood surface, 4-6" of space, more wood below that?

    Anyone have any suggestions on what they would do? I believe the square footage of the floor was around 320 SF - give or take.

    Thanks.

    Steve
    If there is an air space under the floor then putting insulation on top of the floor won't benefit much at all.
    The reason being the space under the floor is in the cold zone. You want insulation in direct or intimate contact with the ceiling of the space below.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Actually its the insulation between the joists of a floored attic that doesn't do much good. The joists act as short circuits for heat conduction from the ceiling below to the attic floor. The attic floor becomes a large radiating surface.

    If there is no attic floor, the the short circuiting isn't as bad as the only radiating surface is the top edges of the joist. It it can be improved by insulating over the top of the joist. But, you have to watch out for the edges. The joist bay on each end of the attic should be insulated as should the ends of each bay. This is to prevent an uninsulated belt from forming around the edge of the roofline.

    From your description though, it sounds like the attic is being treated as a conditioned space and it is done correctly. The vapor barrier should face the warm side of the house and there should be a gap between the insulation and the underside of the roof sheathing. The wall between the attic and the bedroom would not need any insulation if the exterior wall of the attic is insulated. Also, there should be no vents in the attic itself.

    If you do not plan on using the attic as storage and energy conservation is your goal, then remove the current insulation, insulate the wall of the bedroom, remove the flooring and insulate with R30 covering the joists. Based on your dimensions and description of your house, your heat loss through the roof probably less than 15% of your total heating bill. Insulating to R30 will probably reduce your total heating bill by 10% or less. Spending a lot of money on more insulation will only disappoint you, the money would be better spent on windows, doors and walls.

  7. #7
    Join Date
    Jan 2012
    Location
    New Jersey
    Posts
    23

    Smile Keith - I am so glad you posted

    Keith (and anyone else):

    I just had an energy audit and obviously the attic was an area of evaluation. The auditor who was one notch shy of a physics professor compared to the Home Depot guy which was sort of frightening and also confusing/frustrating - until I just read your post. EVERYWHERE I read,see, etc. - nobody says the rafters should be insulated - except you and this guy as of today. His take was this:

    1. The insulation that is in place, isn't very good (not even R19 value) but based on how it was done and when (he estimates 40+ years ago) is done correctly for the house. He is not a fan of fiberglass.
    2. There does appear to be a space between the rafter wall and the insulation but the soffit vents appear to be closed and he said you want them closed.

    His suggestion is to pull out the present insulation and replace it with a combo of foam boards on the rafters followed by cellulose blown in. He also suggested that even though there is a 4th bedroom up there -there is attic space above and around it and that it also needs to be insulated and sealed even though you can't see it as there are finished walls around and above it. He seemed to be quite educated with the convection/conduction stuff.

    I kept questioning the rafter area and the whole "breathing" thing - he says there are plenty of places for the house to breathe and kept on stressing that insulation techniques have changed but a lot of contractors simply won't embrace the change. With his suggestion the foam panels act as the vapor barrier (I think). He spent 4 hours on the energy audit, which was free (NJ Dept. of Energy approved company) and did the pressure test in the doorway as well which was an incredibly revealing on the amount of leakage my home has in places such as electrical outlets. Now he goes and plugs all sorts of info into a computer and I'll regroup with him in the next week and see what we will do. FWIW, in NJ to get any rebates for energy fixes, you have to use a company like this to have an energy audit done.

    Thanks.

    Steve

  8. #8
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Glad to see you brought in a pro on this one, I had the same thing done here in boston, ma. They required the audit to get the utility rebate. Just make sure the insulation contractor you hire does things correctly and doesn't cut corners, its your house and you have to live in it, so once there gone and the work is signed off your done,if you have any issues after that point good luck trying to get them back to correct any issues, I got the run around for months about fixing a blocked soffit vent issues and a furnace issue, So get a local reputable company and tell them what you want, you will love the energy savings if you insulate the whole house. Good Luck!

  9. #9
    Join Date
    Jan 2012
    Location
    New Jersey
    Posts
    23

    Default Re: 100 year old attic - insulation is wrong - which scenario makes the most sense?

    Good to know - is your attic "sealed" with vents closed off?

    Steve

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