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Worth it to upgrade room from R12 to R20 for extra warmth/energy savings?


jimbob's Avatar
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04-22-09, 05:41 PM   #1  
Worth it to upgrade room from R12 to R20 for extra warmth/energy savings?

We have a back room which is generally colder then the rest of the house. The house is about 30 years old, is 2x4 construction, and has 30 year old R12 insulation with the paper vapour barrier. I was thinking it wouldnt be that much expense, just the effort, to take down the exterior wall (wood paneling - rest of house is plaster), rip out the old insulation, tack on a 2x2 or 2x3 to the existing 2x4, and re insulate with R20 and plastic vapour barrier.

Will this make enough of a difference to make it worth the effort and cost?


Last edited by jimbob; 04-22-09 at 06:08 PM.
 
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Perry525's Avatar
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04-23-09, 11:36 AM   #2  
I expect you find that when sitting near a window or the outside wall you get cold.
With R12 insulation you effectively loose the use of two foot of space alongside a wall or window as the area is too cold.
The best solution is to fill the space with expanding foam insulation or polystyrene sheet cut to a tight fit between the frame, filling the space completely.
Taking care to fill all holes and spaces with expanding foam - if you leave holes, cracks or gaps then the passing wind will suck all your expensive heat from your home through these gaps.
Then you have a problem. The timber frame will conduct your heat away to the outside as it is not as good an insulation as polystyrene.
The next step is to cover the total inside of the room with one or two inch thick polystyrene, stuck on - don't use metal fixings as these will conduct heat to the wood frame and on to the outside.
Then cover the walls and ceiling with plaster.
Five inches of polystyrene in total will give you a room that is warm, pleasant to live in and cheap to heat.
This will save you money year after year.
Perry

 
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04-23-09, 12:02 PM   #3  
A 30 year old house is probably sheathed with plywood, if so it is a good air barrier. You could leave the insulation you have in place and add 2" polyisocyanurate (sp) the foil faced stuff, about r=7 per inch over the studs and then use long screws to apply sheetrock over that. Carefully detail around the windows and seal all penetrations with fire rated foam.

Don't forget to upgrade the attic and air seal the rim joist below if there is a basement. Insulating the exposed foundation to raise the floor temperature helps as well.

Bud

 
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05-13-09, 06:36 PM   #4  
So I just took a look at getting this project going. Took off some of the paneling and what I assumed was R12 is actually R7!

So I think the new plan is to take down the panelling, rip out the old R7 and put in new insulation and drywall.

I notice you can get R12 or R14 in 3.5" thickness. Seems like a no brainer - is there a reason I would choose r12 over r14?

So after I put in new insulation would it be a good idea to add that rigid foam board insulation on top (1" thick would give me R5 more), then just pull the outlets and frame the window sill an extra 1" out?

If I did this do I still need vapour barrier?

Or should I just stick with R14 (twice what it was) and vapourbarrier?

 
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05-13-09, 08:17 PM   #5  
Hi Jim,
Definately the R=14, actually I thought the high density 3.5" was R=15 but esentially the same. Given the risk of energy costs going higher, and higher, if you can fit it in your budget, the extra one inch will be nice. All taped and sealed, a foil faced foam is a vapor barrier. The common polyisocyanurate foil faced foam (big box stores) is R=7 per inch. It is also going over the studs so it reduces the thermal bridging. Use some non-expanding can foam, I like Dap as it has almost zero expansion, and seal around doors and windows. R=14 plus R=7 plus air sealing, and reduced bridging and you will certainly feel the difference.

As I have mentioned on other posts, I am applying 3.5 inches of rigid on the outside, because I need new siding and windows. If I were replacing my sheetrock, it would be on the inside. The goal is something close to r=30 for the walls. But I live in north country and my business is evaluating homes for energy performance. You have to go with where you live and how much you want to do. All I can do is PUSH. Sorry

What you are considering is still very good.

GL
Bud

 
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05-14-09, 07:16 AM   #6  
Posted By: Bud9051 Hi Jim,
Definately the R=14, actually I thought the high density 3.5" was R=15 but esentially the same. Given the risk of energy costs going higher, and higher, if you can fit it in your budget, the extra one inch will be nice. All taped and sealed, a foil faced foam is a vapor barrier. The common polyisocyanurate foil faced foam (big box stores) is R=7 per inch. It is also going over the studs so it reduces the thermal bridging. Use some non-expanding can foam, I like Dap as it has almost zero expansion, and seal around doors and windows. R=14 plus R=7 plus air sealing, and reduced bridging and you will certainly feel the difference.

As I have mentioned on other posts, I am applying 3.5 inches of rigid on the outside, because I need new siding and windows. If I were replacing my sheetrock, it would be on the inside. The goal is something close to r=30 for the walls. But I live in north country and my business is evaluating homes for energy performance. You have to go with where you live and how much you want to do. All I can do is PUSH. Sorry

What you are considering is still very good.

GL
Bud
Thanks for the info. I live in Ontario so it can get chilly up here.

I can get either of these at R14. The Roxul is a touch cheaper per sq.ft. Is one of them a better option?

PINK FIBERGLAS sup /sup Insulation - R-14 PINK FIBERGLAS Insulation - 15 In. x 47 In. x 3.5 In.; 78.3 sq. feet - 428193 - Home Depot Canada

Roxul - Roxul Comfortbatt R14 For 2x4 Studs 16 In. On Centre - 415001 - Home Depot Canada

And would you mind telling me which of the following rigid insulation is best for this application? I dont see one with foil facing? Would I use traditional vapour barrier over this?

http://www.homedepot.ca/webapp/wcs/s...chLevel=level1

And one last question - this will become a playroom and things will be hung and attached to the walls. Will screwing through this and using drywall plugs be an issue for the vapour barrier?


thanks for the help.

 
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05-14-09, 10:38 AM   #7  
Not familiar with Roxul but looks fine, perhaps others will comment.

If you can't come up with the poly iso foil faced, or other foil faced, add a layer of 4 mil poly as a VB.

The r=7 is nice and it seems like someone should have it up there.

Bud

 
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