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Insulating an older masonry building inside above grade and below

This building is located in the upper peninsula of Michigan. It is a church of about 40 people, with limited resourses. It has been heated with an oil furnace since it was built in 1955. The furnace has failed this winter, and they want to switch to propane. Our church is in the lower part of Michigan and our men's group is willing to go up and do the work of insulating and drywalling the interior walls of this building, with all labor donated.

The interior walls on the above grade portion are cement block with brick on the outside. The bricks appear to be 3" x 12" in size if that means anything as to the content of them. The basement walls are cement block waterproofed and the in contact with the earth.

I have been researching the best ,cost effective way to accomplish this and am becoming more and more wary of doing the wrong thing .

My first method was to install 1" of closed cell rigid foam directly to the blocks and then apply 1" nailing strips of wood with another layer of the 1" rigid foam between the nailers. This would only give approxomately 8.4 R value and the people feel this isn't enough.

The second and most expensive option was to use metal 3" z chanels with sprayed closed cell foam 2-3" thick giving an R value of 13 to 18.

My third was to use a solid layer of 5/64" reflective insulation against the blocks, then the 1 or 2" nailers with another layer over the nailers and drywall over the top trapping air for the added R value. This I think would give a conservative estimate of near R-20.

Are any of these methods viable? Should I be concerned about moisture condensation? Or should I use one method above grade and another below grade? Which would work best?

Darwin Thompson

Asked by Darwin Thompson
Posted Sun, 03/02/2014 - 20:36
Edited Mon, 03/03/2014 - 06:08

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3 Answers

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The reflective insulation solution is a non-starter--it will provide very low R value in spite of any claims by the manufacturer to the contrary.

I would probably use the thickest rigid foam boardstock you can get away with, install 1x4 furring strips over that, install 3/4" foam board between the furring if you have the energy, and then install drywall. The foam against the block should probably be installed in multiple layers with staggered joints that are taped. I have not insulated against above-grade block before, so don't have a firm recommendation on the foam type, but know that you could use XPS, bet that you could probably use EPS, and wonder if you might even be able to use foil-faced polyiso. Others here will add info on appropriate foam choices.

All of this will mean you need to detail the window and door openings, deal with any electrical on the walls, and so on. If you can have someone there send you photos, and post them here, we can probably offer suggestions on some of those details.

I'm not a big fan of spray foam, although I have used it. The cost is high pretty much everywhere, and I bet Michigan's UP is no exception. Problem are rare but they do happen. Spraying cold surfaces is problematic. You may get big variations in thickness. For a project such as you are describing, I would load a box truck with foam board, furring strips, fasteners, and everything else you need, and keep the whole thing firmly under control so your volunteers can perform during the time they have.

Answered by David Meiland
Posted Sun, 03/02/2014 - 22:45

2.
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One thing worth considering, and I hope someone else will comment on it: up to this point, this masonry building has had the benefit of heat loss from the interior to help dry the brick. It has also been able to dry to the interior if needed. Insulating the interior will change this dynamic, perhaps to the detriment of the brick. I have very little experience with brick, it's just not used for walls much up here in the northwest... but I think you should investigate this angle.

Answered by David Meiland
Posted Sun, 03/02/2014 - 22:49

3.
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Darwin,
Here are links to two article that you may want to read:

How to Insulate a Basement Wall

Insulating Old Brick Buildings

David is absolutely correct about the reflective insulation; in the locations you suggest, it is basically worthless.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 03/03/2014 - 08:06

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