# Increasing R-value Northeast



## johnpma (May 21, 2009)

Working on insulating the crawlspace beneath a satellite room in my home. Next up is increasing the R-value for the 2X4 walls in the room above this crawl space.

I've searched this to death and found my best two options would be to remove the existing sheet rock and build out the 2X4 walls to 2X6 walls and move electric boxes out, re insulate, and re sheet rock
or
install 2" rigid foam against the sheet rock, tape seams, fill gaps, extend electric boxes, furring strips then new sheet rock.

Of the two which would give the better results while saving $$$$$

What other options might I have? It would be three exterior walls


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## JustinK (Oct 4, 2009)

First option would be cheapest. Foam sheets are expensive. An other option would be air seal the addition put the savings in to more efficient heating source or keep in your pocket. It will take a long time to get that savings back unless the 2x4 wall are improperly insulated.


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## Windows on Wash (Aug 30, 2011)

I would not put foam to the inside of the home. That will make that outside stud surface extremely cold and super low dew point.

If there is R13 in there, spend the money on air sealing and insulating the home. It will pay for itself much, much, much quicker and make the entire home more comfortable.


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## johnpma (May 21, 2009)

Thanks!! What do you mean by air sealing?? Just caulk & can insulation?? What I forgot to mention is I'm not really sure what is in the walls now. I've been told R-13 and the sheet rock is in horrible shape as the room was all wall paper in the 70's


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## JustinK (Oct 4, 2009)

Here are some of the locations where air leakage occurs in a typical house:

Plumbing and wiring penetrations through floors, walls and ceilings
Chimney penetrations through insulated ceilings and exterior walls
Attic access hatches, doors and drop-down stairs
Recessed lights and fans in insulated ceilings
Weatherstripping around windows and exterior doors
Cracks, gaps & holes in drywall or plaster
Electrical outlets and switches, especially on exterior walls
Gaps around window and door trim and baseboard moldings
Dropped ceilings & soffits
Leaky basement windows
Rim joists in the basement or crawl space

It might be worth it have an professional come and do a blower door test. This will determine where air leaks are. You can choose to fix it yourself or have the company do it. 

If you are planning on replacing drywall then it would make sense to build out the wall for more insulation.


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## johnpma (May 21, 2009)

if I intend to build the wall out what would be the best choice to insulate with? just faced fiberglass R-19??

I guess this is the route I'll go so I can update the wiring in the room as well


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## Windows on Wash (Aug 30, 2011)

Kraft faced fiberglass batts of the proper depth would be okay here.

Please don't miss all the opportunities for air sealing and do not put rigid foam to the interior.


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## JustinK (Oct 4, 2009)

You can get R21 fiberglass to fit in 2x6 wall.


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## High Gear (Nov 30, 2009)

How about a window upgrade ?


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## Gary in WA (Mar 11, 2009)

R-13 recently became code minimum, in the '70's would be R-11 or even R-9 (left-over from phase-out). I installed a lot of R-11 when first starting out in '73.... itchy memories- lol. Interior foam board application depends on the permanence of the exterior sheathing/siding and of the FB itself (thickness/facings). It is harder to air-seal and the cavity does run cooler- if the siding is open enough to allow drying to the exterior, as WoW said. It will only mold/rot in the summertime so it can be risky from a moisture standpoint. 

Bringing the walls to R-19- still a low density insulation (faced or not) is same as existing R-11, also low density- except seal wiring holes. Much better; Justin's FG R-21 or even R-25 OR a Roxul at R-15 or 23 (without the convective loops inherent with low-density fiberglass batt); pp.45-47; http://www.buildingscienceconsultin...010-03-10_When_R-Value_Doesn t_Measure_Up.pdf

http://www.roxul.com/files/RX-NA_EN/pdf/ROX2346_USA Res_Eng_Sp_web_06_13.pdf

If you go batts, don't side stud staple for same loops. If you go XPS (depending on siding/WRB), cut to fit between studs, canned foam them, add some rigid foam board strips (thermal break the temp. bridge) on the stud edges to room, add a wood 2x2 sleeper for drywall fastening, fill cavity with Roxul, ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Gary


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## Gary in WA (Mar 11, 2009)

Are you still here, or did you "hang up"? 

If the siding/sheathing is vapor open, FB on the inside will not add to the amount of moisture diffusing through and into the cavity-- it is acting as a vapor retarder to reduce the moisture drive. This, along with closing the gaping holes in wiring/drywall (ADA) caulked as well, you are severely limiting the moisture now able to pass through- from the inside. Exterior leaks are problems- with or without foam inside. Because of the foamboard thickness, it is required to dry outward---- it may be set-up that exact way. Without more info- siding type/sheathing, etc.--- I can only tell you basic guidelines. 

Gary


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