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Old 12-26-2009, 08:36 PM   #1
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Insulating attic area


I am going to insulate a wall that separates two sides of a finished and unfinished attic. The wall has sheet rock on the finished side and nothing on the unfinished side, just 2 x 4 studs. It is very cold in the winter and very hot in the summer on the unfinished side which is just plywood and the roof, no insulation(I am in nothern New Jersey). It would be fairly easily to put some batts in between the 2 x 4s.
I know that the paper should face the warm, finished side, but can I use batts with paper on both sides, if I am not planning to cover the insulation with sheetrock?

Are there problems with leaving the insulation uncovered?

Thanks in advance for feedback,

Dennis

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Old 12-27-2009, 06:35 AM   #2
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Insulating attic area


Paper on one side only, toward the heated side.

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Old 12-27-2009, 08:06 AM   #3
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Insulating attic area


Well, essentially you are making your home tighter, warmer and a bit less costly to manage...so you are turning your attic space into a cold space and only heating the finished side. Good, that's what most people are doing.

But you'll have to do a few more things; since you heat the finished side during winter (and you may air-condition during the summer), it makes sense to keep that heated (and cooled) air in - hence the insulation. But you also must consider that while heating and air-conditioning, you create a higher pressure inside your home - which forces humidity outwards into your attic. That humidity will eventually cause problems if just left there to become mould. So the attic space has to be vented: roof vents on the top and a clear space to the soffits on the bottom...check out what your particular house has then get back to us...

But the best is to prevent the humidity from ever reaching the attic space in the first palce; hence vapour retarders (vr). Ideally the vapour retarder (vr) whatever it is, goes on the inside right behind the drywall. In cold climates like yours the vr could be plastic sheeting, or faced fibreglass batts or something like that. But it's placement is critical. If you can't put it just behind the drywall without tearing the walls down, then it has to go on the attic side close to the studs and behind the new insulation. This is tricky, but at least doable. Contractors faced with this dilemma usually spray-foam the stud areas because spray-foam acts as vr and insulation all-in-one and goes on everywhere.

So you have two things: vapour control and insulation. Together these add up to a warmer cheaper space to live in but you can't just do one thing and not the others. You should also report back as to the kind of insulation you have on the floor, as you can do something there too. Pictures would help.
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Old 12-27-2009, 09:38 AM   #4
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Insulating attic area


Thanks Just Bill & ccarlisle for the feedback! Much appreciated!!

Ccarlisle thanks for the info about the vapor retarder. Maybe I will spray in some insulation. I am very concerned about doing this right and not creating a situation where I create a problem like mold.

My house is a 1930s colonial and as far as I can tell there is no insulation anywhere, except in the unfinished part of the attic on the walls. There is no insulation in the floor of the attic. I am planing to do blown in insulation in the walls downstairs.

As far as vapor control, I do have a ridge vent, which is good, but no soffit vents and I am not sure if the insulation that is in the attic is put in the correct way. I will submit some pictures.
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Old 12-27-2009, 11:27 AM   #5
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Insulating attic area


And so like thousands of others, you're dealing with bringing your house - a '30s colonial - into the 21century - when the vision in those days wasn't more than a few decades beyond the very week they were built. Don't be surprised...most of the world was in a depression and graver things were on the horizon, so insulation wasn't the conversation topic it may be today.

Blown-in is good in a retrofit. Also, the vapour retarder concept can be made real by the use of 2 coats of latex paint on the LR walls. But making the house tighter will have consequences in your air quality - and that must be managed too. Are there no vented inlets at your soffits? May need a few 1" holes drilled in and capped with plastic vents.


Mould is just a visual of a problem with high humidity; that's manageable too but read some of the older posts here and get yourself an idea of what we do to control the environment we live in wisely.
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Old 12-27-2009, 01:06 PM   #6
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Insulating attic area


In New Jersey, R-15 is recommended in the wall cavity and R-49 on the attic floor. http://www.ornl.gov/sci/roofs+walls/...on/ins_16.html

"It would be fairly easily to put some batts in between the 2 x 4s." ------- You may have trouble finding R-15, use R-19 is fine. (Unless you go with foam). The unfaced side can be left exposed to the attic.
Before insulating the attic floor, you need to air seal and add soffit venting so you are not working against yourself.

Be safe, Gary
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Old 12-27-2009, 01:59 PM   #7
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A few things,

I haven't seen any mention of the fact that there should be (and most codes now require) an air barrier (solid material fastened and sealed at all ends and joints) on the attic (colder) side of this assembly. Your wall should ideally have interior painted drywall, insulation which fully fills the cavity at all areas, penetrations into the cavities foamed or caulked, and then a rigid air barrier on the attic side. Foam sheathing is nice for that and eliminates thermal bridging, but be mindful of what materials are permitted to be exposed in that area for your area.

In theory, your house will only be under more moisture driving pressure differences due to HVAC if there is inadequate return ducting. A good rule of thumb is that if the pressure in your house goes positive relative to the outside when the air handler is running then you have dominant return leakage to the outside or inadequate return ducts. If your house pressure relative to the outside goes negative, then the reverse (dominant supply leakage to the outside). Of course your house can go positive or negative to the outside due to several other factors, but as far as concerns about what the HVAC system can cause, then the above factors are primary.

Good luck on your attic finish.
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Old 12-27-2009, 04:41 PM   #8
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Yeah, well ideally, the OP would rip off the siding to put rigid sheeting or Typar all around the house to prevent air movement and act as a primary defense against the penetration of rain water - but how realisitic is that?

The siding does a lot of that job - and until we know what that siding is and what's beneath it, there's no point in supplying all the possibilities. But inside the attic, you could get by with rigid insuation/vb all-in-one , but it would trap some of the moisture in the insulation. Best get the vb as close to the walls as possible...
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Old 12-27-2009, 06:02 PM   #9
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True, but the way I read the original, it appeared to me that the homeowner has access to both sides of the attic knee wall. While the house as a whole can't be improved without a MAJOR investment of time, effort, and finances, he can properly treat the attic sidewalls.

No argument here, just trying to give the most professional advice possible since I happen to be a professional in home energy and building performance. I know at some point, I will need some professional information from someone else here as well.

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Old 12-27-2009, 07:58 PM   #10
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Insulating attic area


Thanks for all the great info!! Much appreciated!

Please bear with me because I still trying to understand the vapor barrier. Will this give me problems: Say I put insulation batts in the wall that have paper on both sides, with the idea that the wall on the cold side is never closed with sheet rock or anything? I am thinking I would rather not have open insulation on the wall as the kids like to get toys out of this storage area (cold side), and I don't want bits of insulation blowing around.

Do I need to put plastic down before the insulation? or latex paint?

Putting rigid foam over the insulation to seal it sounds good and I assume that would mean using insulation with paper on one side facing the warm wall.

Last edited by Densec; 12-27-2009 at 08:01 PM.
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Old 12-28-2009, 07:38 AM   #11
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Yes, I see what you mean, Energyrater...and I agree. You have a better understanding of your countries codes than I do - so I don't venture very far into that area.

For example, we don't see fibreglass batts that have paper on both sides, so I can't answer the OP on that one either.
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Old 12-28-2009, 12:08 PM   #12
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Quote:
Originally Posted by ccarlisle View Post
Yes, I see what you mean, Energyrater...and I agree. You have a better understanding of your countries codes than I do - so I don't venture very far into that area.

For example, we don't see fibreglass batts that have paper on both sides, so I can't answer the OP on that one either.
To be honest, I haven't heard of such a product either. I have seen batts encapsulated in white or clear plastic, but I am sure that that is not the product described by the OP.
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Old 12-28-2009, 12:56 PM   #13
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Check with your local Building Department as to : if you need an interior vapor barrier; if you need to air seal the wall on the attic side with a housewrap or not. The map is split need/not need the vapor barrier and only you know your address: http://www.buildingscience.com/docum...ecommendations

Paper faced batts cannot be left exposed in attic. There is too much water vapor in the air to cause mold. This insulation is safe but may require covering, as I said: http://building.dow.com/na/en/safetouch/index.htm

Regular latex paint is a vapor retarder, but special vapor barrier primers may be accepted by local B.D., as a substitute for plastic or faced batts. The foam board would also require their approval.
Be safe, Gary

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