[Greenbuilding] best practice

John Straube jfstraube at uwaterloo.ca
Thu Mar 17 06:39:37 CDT 2016


Very difficult to take such claims seriously: “not worth it” depends entirely on the cost of the doing “it” and what “it” gets you. Too many practical and economic variables to be able to make such a statement.
Adding insulation between the framing will be massively impacted by thermal bridging.  You will have a hard time getting airtightness to the same level as from the exterior.
But, if you are willing to live with an equivalent R10 wall (after all the thermal bridging at studs partions and floors) and an airtightness probably in the 2-5 ACG at 50 range, then ripping apart the entire interior is the cost.
Removing the exterior siding is also a lot of disruption but the disruption is outdoors.  Good design will allow you to get exceptional airtightness, adding just 2” of insulation will get you the same R-10, and you will be able to improve water control so that the house framing lasts a very long time.  Add 4” of, say, rockwool/EPS and you get R20, real R-value (nothing in the studspace) or drill holes in exterior sheathing, blow in cellulose, add 4” of rockwool/ EPS and you are now close to real R-30.
With the reliable and high airtightness, and the uniform high R-value you can now heat or cool this place with small and simple HVAC, and not have to think about upgrading again for another long time…
In my experience, the performance of the between studs retrofits is always significant less than an exterior wrap, and the difference matters to occupant comfort and energy use in a very noticeable way.
I guess, though, I am just another design professional in my young 40’s  ☺

John

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Sacie Lambertson
Sent: March 16, 2016 21:43
To: Greenbuilding <Greenbuilding at lists.bioenergylists.org>
Subject: [Greenbuilding] best practice

A good guy and relatively young architect (in his 40s, 'young' by my standards), tells me it is not worth taking off the siding of an old 1883 house to add insulation and an air space to the outside.  He says the added expense is not worth the additional insulation. That the extra R-value above R 23 in walls is thermodynamically not money well spent as long as the house is very tightly constructed in the retro-fit.

The siding is original and in very good shape.  The interior has full dimensioned 2x4 walls.  The rooms are too small for me to want to build a double wall on the interior.

What he suggests I do is simply used closed cell foam between the wall framing.

I would appreciate your comments please.

Sacie


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