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Insulating from the outside Guidance (100 yr old home)

Insulating from the outside Guidance (100 yr old home)


Old 02-16-14, 07:59 AM
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 2
Insulating from the outside Guidance (100 yr old home)

Hi All,

I had a couple of questions for you regarding an exterior foam retrofit I am
gearing up for on my house in the spring.

We live in Union NJ (I believe it's climate zone 4 except marine) and we
are doing a complete gut of the exterior of the house. We are removing the
poorly installed windows and vinyl siding.

Back story on the house: Majority of the 100 year old house has blown in urea formaldehyde foam that has failed (shrunk). Any part of the house that we remodeled on the inside (kitchen, bathrooms) have R30 batt insulation with tyvek house wrap over it.

What I am looking to do:
1) replace the windows
2) install drainwrap/stuccowrap or tar paper over the shiplap
3) install 1 inch atlas energy shield foam boards with foil back facing outwards
4)furring strips
5) replace all trim with azek
6)cedar shingles

For the foam I am planning on installing them between vertical 2x2's
(attached to the original shiplap) to offer a 1/2" vertical ventilation and
nailing surface for the furring strips. So it would be a vertical 2x2 then a
2x8 vertical piece of foam then another 2x2 etc etc.

I wanted to know:
1) What underlayment would be best to reduce the risk of moisture between the
foam and shiplap?
2) Is 1" foam with aluminum backing acceptable for my area?
3) Is the 2x2 and foam idea an acceptable one?
4) Can I put drainwrap over the locations that have house wrap on the interior?

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Old 02-16-14, 11:25 AM
Join Date: Jan 2014
Location: usa
Posts: 466
How did you install R-30 batts in exterior walls where you renovated?

Is there sheathing under the ship lap siding?

Do you have any idea what the sources of moisture are in your home and how do you control it and what is the general level of relative humidity in the home in the winter?

What will you do in the attic to control air flow from the structure and what level of insulation do you plan on having there as a final assembly?

What cedar shingles will you use and how are you attaching them....I would suspect that they will be over horizontal furring strips?

Everything you do affects something else in the insulation equation.
Old 02-16-14, 08:28 PM
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 2
Pardon the typo, it was R13 that was installed. Any all we opened, we added paper backed r13 followed by tyvek house wrap before installing Sheetrock.

The house is old, from what I can tell, the wall layers from the outside in is:
1/4 foam board
Urea formaldehyde (any part of the house untouched) or r13 (any part opened up by us)
Tyvek under Sheetrock (new work) or just plaster(Untouched parts of the house)

In regards to the venting in the attic, we do not have any and we don't plan on touching the attic or room at this point.

The house is very dry during the winter even with a new HVAC system and humidifier constantly on (28% humidity). I assume this is due to the humidity loss through the windows etc but could be wrong.

We are installing white cedar on horizontal furring strips at 5inch exposure.

Thanks for the help,
Old 02-17-14, 04:29 PM
Join Date: Jan 2014
Location: usa
Posts: 466
I know you probably don't want to hear it but if you are going through the trouble of removing the vinyl siding and backer board and windows....why not go full tilt and take the lap siding off as well.

If there is no sheathing, as you seem to be indicating, you could then have access to the urea formaldehyde insulation and remove that giving you a opportunity to really do things as they should be. Install new fibrous insulation, new sheathing, foam, air barrier, furring and new shingles. Everything can be detailed as it should be plus you will be providing the structural support of the sheathing.

After that is all done you will have to rethink your hands-off attic approach and add ventilation since you will be tightening up the air exit paths that exist now.

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