Rigid Foam Insulation over existing wood siding

Gary in WA

Avoiding Potential Insect Problems

When insulating a foundation you need to consider that, although insects don't eat foam board, they can easily tunnel through it. Insect burrows reduce the R-value and structural integrity of the insulation. For these reasons, some manufacturers treat their foam products with an insecticide, usually a borate compound. Many building jurisdictions also mandate treating the earth around the building with insecticides. These jurisdictions may also want an inspection area several inches wide and all around the foundation of a house kept bare of insulation board. http://www.energysavers.gov/your_hom.../mytopic=11620
Water resistant, not waterproof: a Class 3 vapor retarder = vapor semi-permeable: http://www.panhandleinsulation.com/b...materials.html to be a vapor barrier (vapor impermeable), Class 1- would need to be 8” thick.: http://www.buildingscience.com/docum...gs?full_view=1
Has anyone read any new info on sticky window tape on the sheathing instead of on the house wrap? Capping windows with aluminum VS flashing with aluminum 5 window manufacturers and Typar, Tyvek, and a few others still have the old way as mentioned.


Be safe, Gary

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Hexar

Thanks guys, I appreciate the comments and advices.

How about these steps:
1. take out the existing wood sidings, and inspect/repair the sheathings
2. build out the window openings with 2x4, this will give me a solid nailing base for the windows,
3. then install 1.5" rigid foam insulation, and bring the foam up to the new 2x4 nailers built in step2.
4. tape the edges/seams of the foam
5. install house wrap, seal and flash according to the dow.com recommendations.
6. install vertical furring strips (for sidings to be nailed to)
6. install the windows, and flash/tape them
7. install sidings.

there are some images and videos I found on the internet/youtube.



http://www.youtube.com/watch?v=12DvyHjqu4Y
http://www.youtube.com/watch?v=dSqpKyiWbsA

but these videos show flashing over foam which is what dow suggested...

Gary in WA

Now you’re into rain screens: http://www.greenhomebuilding.com/pdf/RainScreen.pdf

http://www.nchh.org/Portals/0/Contents/Article0440.pdf

http://www.coastalcontractor.net/article/135.html

Be safe, Gary

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ccarlisle

I repeat:Why do you insist on putting the house wrap after the insulation, when the diagram shows you don't...?

Hexar

Thanks GBR for the docs, they are VERY helpful!

Hexar

Sorry ccarlisle,
I did not "insist" on putting the house wrap outside of insulation, I thought the diagrams, especially the ones from dow.com show that the house wraps are outside of the everything, except the sidings?

Hexar

this page shows using two layers of felt, one on each side of the foam...

http://www.hammerzone.com/archives/e.../prep/wall.htm

Tom Struble

housewrap should be directly under the siding,that's where your drainage plane is,not under the foam,the foam should be considered a sheathing extension and the windows and doors packed out to the level of the foam,then wrb installed on top of the foam,


nice illustration op that's how i would approach this project

closed cell foam is about as good an air barrier as your going to get

and again it no more suseptible to insects than any other non treated wood based sheathing,good building practice and keeping everything atleast 8'' above grade will help keep the insects at bay

Skuce

Millions and million of rotted sills.

What's yours?

GreginAlaska

How long did it take to rot them? We put rigid foam and vinyl siding over T-111 about 10 years ago, it was still OK when we sold the place 4 years later. We sold it to people we know and everything still looks ok on the surface anyways.

Did you guys know that Quadlock has a retrofit system for putting foam over an existing wall?

Tom Struble

more likely caused by window,door or roof leaks or built too close to grade
foam insulation has proven itself over the years,are there some problems and disadvantages to it...yea sure just like every other building product

it all comes back to building practice...

Hexar

Hi Guys,
I finally started!

I took the sidings (on one half the wall) down today, and I am glad I did! There are lots of problems hidding inside. I think the previous window installer did not do a right job.

This is a window (facing north), I think he did not:
1. flash the window
2. insulate the gap 100%, so the cold air can go from the trims into the gap and into the window frame, and into the space between the two window panes, and from there into the room.

No wonder the window is very drafty in the winter, and fully of condensations!

[img]http://lh3.ggpht.com/_gU9oEcKzhUA/S7...0/P1020884.JPG[/img]

I have a question now:
The red lines I drew on the pictures should be where the rough opening is, correct? I should tear down the white frame and the pink/redish sill when I un-install the window, correct?

Thanks!

Hex

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Do Over Gal

Every single house that I have done in my 15 yrs of construction I have realized if you want the correct answer you go straight to the source. The issue of house wrap is this ....you can blow smoke through one side and not the other which make the outside air stay out and lets the inside air out. This means the house can breathe !! I was told by a Tyvek rep visiting our local Spahn N Rose lumbar yard that the wrap is to be put OVER any insulation on any older home . New construction can be very well insulated from the inside before sheet rock is put in place. The wrap , capped nailed over what ever insulation you use on the exterior , allows the house to breathe. If you cover the wrap with your insulation you are not allowing the wrap to breathe. Personally have had to re-do other homes that were full of mold due to the application of foam over wrap. Not fun when insurance adjuster shows up or general contractor for your lending institution. It's very simple to pick up the phone and call your state agency to find the codes where you live and call your insurance company.

Input from a person that has been there is better than no input at all !!

jogr

Sorry, that's not true. Tyvek isn't directional. It stops air flow either way. It is permeable to water vapor (either way also).

There seems to be a regional difference in the use of Tyvek with foam board insulation. In some areas contractors put the Tyvek under the foam and in others they put it over. Both probably work fine if the flashing is done correctly for the approach taken and both probably fail if the flashing is incorrect.

Chemist1961

The DOW site shows wrap over foam, however again there are regional breakdowns on their site.
Despite regional differences, think about warranty, if you don't do it their way and have an issue forget it.
Once you cure the leaky drafty home remember your ventilation may need to be addressed. My air sealing of the rim joist and behind baseboards has reduced the draft tremendously. Caulking inside has reduced the ACH, (air change per hour) rating by close to 50% in my 35 year old brick/stucco home. I am now just over 3.5ACH, down from 6.4 and approaching the level of new construction
If I continue with house wrap and insulation to replace the upper level stucco as I plan on I will need to add an HRV!!!You need to be aware of this as you will experience a HUGE change in your retrofit