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Old 09-29-2010, 08:12 AM   #1
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Insulating a remodel


I have an old converted 4-season room that I'm remodeling. It's about 200 square feet, with a sloped ceiling. 3 walls plus the ceiling/roof are exterior. I have it down to the studs right now. I'm trying to figure out the absolute best method of insulating this room, because it's cold and sits on a concrete slab.

When the walls were framed out originally, they had to shim 3/8 - 1/4" of the exterior sheathing for whatever reason.. so my 2x4 cavities are actually slightly deeper than the standard 3.5".

I was thinking about putting 3/8" foam board in between each cavity, spray foaming it tight with Great Stuff, then putting up R-15 faced insulation on top of that. Is that a bad idea? Will I create a double vapor barrier effect by doing that? Is it overkill?

And as far as the ceiling, it's 2x10 rafters, with the roof on top (no attic or anything), so I want to maximize the insulation for that as well, going with R-30c and baffles. My concern is if I want to put in any recessed lighting, the cans take up 7.5", so there'll be spots with hardly any insulation. Should that be a concern?

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Old 09-29-2010, 01:32 PM   #2
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Insulating a remodel



Hello Chigundo!
I am Gregg with the Home Depot in Chicago. Sounds like you have a real fun project on your hands. Your plan is pretty solid, but I would recommend a few things. First of all I would check your local minimum code for insulation in exterior walls and non-attic ceilings. Minimum requirements are a good starting point, and I always aim to beat them.
I wouldnít use the foam board in the walls, although itís a brilliant idea for the situation. I think you would get more out of a thicker kraft faced fiberglass. After putting the regular fiberglass insulation between the studs I would use a vapor barrier, plastic sheathing and tape the seams, to protect from moisture. On the ceiling you have a few options. You can use regular fiberglass, a blown in fiberglass, or a blown in cellulous product. I would use regular fiberglass. When it comes to the can lighting, I would just make sure you use IC cans, or Insulation Contact air tight cans, they wonít have a drastic affect on the over insulation of the room, especially when they are on.
The floor is fairly easy to warm up. There are certain types of underlayment you can easily install over the slab. They usually have a plastic grid on one side and wood on the other, Itís made to raise the subfloor off of the concrete to allow air and moisture to pass underneath it. It also makes the floor a lot easier on the feet. You can see what Iím referring to here,
http://www.homedepot.com/buy/lumber-...nel-53672.html
Or tile over and underfloor heating system,
http://www.homedepot.com/webapp/wcs/stores/servlet/BuildLinkToHomeDepot?linktype=product&id=100641174 &cm_mmc=socialmedia-_-fieldteam-_-fw35-_-underPIP
I have Some important questions: What insulation was in the room before? How old is the room? What kind of floor was there before, and what do you plan to put in? Is there lighting in the ceiling already? Let me know so I can further assist you. Gregg @ Home Depot



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Old 09-29-2010, 01:41 PM   #3
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Insulating a remodel


Thanks, Gregg!

The room is quite old, hard to say how old, but inside the walls used to be old R-11 crushed by previously blown in cellulose.. it was a mess. The ceiling had a thin layer of fiberglass and a huge open cavity above it.. by sistering in 2x10 rafters along the previous 2x8's, we were able to convert the flat ceiling to a sloped ceiling.

Floor is just concrete, but we were planning on going with the DriCore route after I figure out all this insulation madness. Drywall should go up first before the dricore right?


As far as putting up a vapor barrior, do you think it's best to go with un-faced insulation for the walls and ceiling, then staple 6-mil plastic up? I heard the paper does a better job of letting out enough vapor while the plastic totally blocks it.. which could be bad?? I'm in New England.
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Old 09-29-2010, 09:56 PM   #4
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Insulating a remodel


". by sistering in 2x10 rafters along the previous 2x8's, we were able to convert the flat ceiling to a sloped ceiling' ----- when you removed the flat ceiling with the ceiling joists, did you install a structural ridge to keep the walls from spreading out?
Last page: http://www.cciccweb.org/files/Framing.pdf

Fiberglass batts would be my last choice in a wall in a cold climate. You get convective loops around and inside the batts, unless high density and any installation less than laboratory perfect will suffer. Notice about no vapor barrier, that is scientific, not my opinion.
http://findarticles.com/p/articles/m...6/ai_n8582994/

http://www.energysavers.gov/your_hom.../mytopic=11530

Convective loops, density: http://www.buildingscience.com/docum...archterm=insul

The vapor barrier on the walls is a bad idea: Page 2: http://www.ecohomemagazine.com/energ...gy-claims.aspx

I’ll get back to you soon about the ceiling.

Gary
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Old 09-29-2010, 11:32 PM   #5
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Insulating a remodel


As far as the vapor barrier on the walls, your idea of rigid foam between studs is a good one: “For example, in Zone 6, high density spray foam with an R-value of 11.25 or more can be used on the interior cavity side of exterior OSB sheathing installed on a 2x6 framed wall with the remainder of the cavity insulated with a fiberglass batt or cellulose and a Class III vapor control layer.” Find your climate zone and the outside cladding, with or without foam there: http://www.buildingscience.com/docum...ecommendations Notice the wall assembly can dry to either inside or outside without plastic vapor barrier inside. (Class I)

The ceiling can/or not be ventilated. The recessed lights will melt snow above and cause ice dams. (Are they necessary?) If ventilated and foam board used rather than fiberglass, read the reasons for the differences: notice the map and figures 7-12: http://www.buildingscience.com/docum...on?full_view=1

As your addition was a converted screened room, patio slab, you may get some moisture coming up through the slab as I doubt any vapor barrier plastic was under it at install. I would go with Gregg’s correct idea of a plastic grid underlayment system the big box stores carry rather than a heated floor which would wick the capillary water below the slab to it and add additional un-wanted moisture vapor inside the room. End of this article: http://www.buildingscience.com/docum...ms?full_view=1

Gary
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Old 09-30-2010, 07:25 AM   #6
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So if I don't go with any foam (because it's very expensive), you're saying that I shouldn't use a vapor barrier with fiberglass?
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Old 09-30-2010, 07:30 AM   #7
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Quote:
Originally Posted by GBR in WA View Post

Fiberglass batts would be my last choice in a wall in a cold climate. You get convective loops around and inside the batts, unless high density and any installation less than laboratory perfect will suffer. Notice about no vapor barrier, that is scientific, not my opinion.
http://findarticles.com/p/articles/m...6/ai_n8582994/
That article keeps referring to "our climate", and I think in that case it's North Carolina.

I'm in Connecticut.. New England is definitely a "vapor barrier on the inside wall" kind of state from everything I've read.
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Old 09-30-2010, 12:48 PM   #8
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Insulating a remodel


Hey Chigundo,
The Kraft-faced insulation is considered a vapor barrier, so you can use just that, but using the un-faced with the plastic over it should be better for your situation. The paper allows more air movement through it, whereas the plastic will completely stop it, which isnít a terrible thing. When installing a vapor barrier remember that the barrier goes on the warm side of the wall. In your case that would be the inside. I would still check what the minimum code is for your area. Just give a call to your local building and zoning inspector and see what the code is for exterior walls. I would say that using the un-faced with a plastic vapor barrier is still your best route.
You are correct about the DRICore. Put up your drywall first because you need a ľĒ gab between the wall and the DRICore.
Keep me up dated with what you are going to do and what the code is for your area. Donít forget to take lots of pictures of the process. Itís fun to see the progression of such a big project!

Gregg @ The Home Depot

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