# Exterior wall insulation ideas wanted...



## Blackwolf (Feb 27, 2012)

I have a small house that I just bought 24' X 32'. It is a 1951 GI style single story on a crawlspace. It needs new siding to replace the 12" clapboard style hardboard siding that is in really rough shape in some places. It has the 3/4" compressed fiber under sheathing and faced fiberglass insulation in the 2x4 bays. Most of the insulation seems to be falling apart in the walls. 

I am looking for ways to get the best R-value and make the walls airtight yet keep breath-ability. Any suggestions? My thought so far is to hang higher density unfaced batting in the bays then go over them with 1 1/2" polyisocyanimide foam sheathing with reflective facing (facing out) then sheath with 7/16" OSB with the reflective foil/vaporbarrier coating. After that I was going to put on thin fan fold insulation and vinyl siding. The foam panels would be run horizontal and the OSB vertical so that the seams would be as closed to air infiltration as posible. Then the OSB seams would be sealed with reflective tape (maybe the foam too just because).

Any better ideas? Problems with this set up? I thought about spray in foam but I want to be able to get into the bays at some later point from inside to do electrical and other systems upgrades when I redo the drywall. 

Also, the sills are directly on the open ends of the cinder block foundation and have gotten soft as have some of the joist ends and rim joists and plates. Everything above the floor is good, under that it becomes an issue due to the lack of proper drainage from the previous owners. I am trying to figure out how to jack up the exterior walls to replace the sill plates and add some sort of barrier between the block and wood. Then I want to waterproof the outside of the foundation and put in a drainage channel around it. 

I am thinking about interior foundation insulation and vapor barrier on the ground and up the walls inside the crawl space (probably roofing membrane rubber). The foundation is two blocks high with a center wall supporting the center of the house. The roof is gabled along the 32' E&W sides and there are no other load bearing walls although there is a center wall in the house that I'm sure helps support the ceiling joists a little bit.

Any good ideas and information for these projects?

Thanks in advance for the help!


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## joecaption (Nov 30, 2011)

Post some pictures.
Not thrilled with your wall plans, sounds like you will be adding more then one vaper barrier. A sure way to have mold in the walls again.
Really need to address all the issues under the house and at the bottoms of the walls before anything else is worked on.
Once all that old siding is removed your going to find all kinds of funky stuff going on inside those walls. Mold on the back side of the inside walls for one.
If the plan is to rewire then doing it while the siding is off would be a good time to do it.


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## Gary in WA (Mar 11, 2009)

Where are you located?

Do you mean the black Celotex- fiber sheathing holding your walls in shear? http://www.inspectapedia.com/structure/Fiberboard_Sheathing.htm

The plywood or OSB installs directly on the studs, insulating sheathing on top of that, depends on location.....Are there vents in the crawlspace?

Gary


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## Blackwolf (Feb 27, 2012)

I haven't gotten into the exterior walls too much yet. Just a small amount in the bathroom. The exterior sheathing is something like buffaloboard I think. Its brown, fibrous and is like fluffy particle board. I am not planning on doing as much with the outside walls until I get a bit of the drainage and floor joist/sills problem fixed. I am trying to get ideas to have the maximum r-value I can get for a 2x4 wall within reasonable expense. I thought maybe a couple of separated reflective foil layers would help. 

The reason I was thinking of putting the iso foam sheathing on before the OSB would be to isolate the studs with insulation to reduce thermal bridging. Since the wood is a low r rating and can transfer temp difference better than insulation materials. Originally I was going to build a perimeter wall to make a thermal break and sound proof thick walls, but that would be mostly impractical as would the original intent of building exterior straw bale walls. That was because before we got this house we were looking at buying land and building a bale house or earthship.

I want to get the house really well insulated so there is little energy input needed to maintain temps. I also need to incorporate moisture control and get the crawl space under control. A lot of that was because the previous owners did a lot of dumb things that channeled drainage into the foundation. I am planning on putting in a vapor barrier on the ground and up the foundation walls and probably waterproof the outside of the foundation and put in perimeter drainage on the outside. 

I also have a silver solution I am spraying in the crawlspace that should kill the existing mold and help prevent recurrence until I can get the area tight. It is vented and not overly wet. Its only average 18" from floor joists, (two blocks high but ground is higher in places.) and the joists are I believe SYP. The sills are 2x6 I think and placed directly on the block blocks are open cavity and the sills overlap. I plan on having to jack up the house slightly to replace the sills and also put some sort of barrier and flashing to keep the wood directly off them.

I will try to post pictures soon and fill in more details. Please feel free to ask me what questions you need that would help get a better picture of what I am working with and am considering doing. Also, any alternative ideas and suggestions would be helpful. I am mostly still assessing the property more indepth and doing tear out and excavation work to start. I am in the planning stages for the actual repairs because I want to get things together first, have a clear understanding of what I am going to do and how, and figure out order and priority for the projects. I want to do it right the first time, and be able to reuse some materials when it comes time for the additions to the house. I try to plan to have things put in place for easy tie ins and upgrades so I don't have to waste new materials as temporary work.


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## Blackwolf (Feb 27, 2012)

joecaption said:


> Post some pictures.
> Not thrilled with your wall plans, sounds like you will be adding more then one vaper barrier. A sure way to have mold in the walls again.
> Really need to address all the issues under the house and at the bottoms of the walls before anything else is worked on.
> Once all that old siding is removed your going to find all kinds of funky stuff going on inside those walls. Mold on the back side of the inside walls for one.
> If the plan is to rewire then doing it while the siding is off would be a good time to do it.


Actually everything above floor level is surprisingly clean and minimal mold even in the really water damaged bathroom. The insulation (faced fiberglass) was falling apart, some from rodents getting into the wall space from outside. I probably will do the electric from the outside as I can, I just am not sure about the expense and mess of foaming the bays. I know it is the higher r value and a vapor barrier of itself, but I don't know about getting into the bays later for other upgrades down the road then. I would imagine it would be a mess to try to fish wires through. Also I do plan on adding on to the house over the next few years so those walls will become interior eventually.

I do have some pics and such up on a blog I am trying to start so I can look back later on what all I have done. Its at http://littlehousealmostontheprairie.blogspot.com/

Thanks again.


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