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Question DetailsAsked on 12/20/2015

my house was built in 1952. we have discovered that there is no insulation in the outside walls.

Inaddition the outside walls are lapstrake redwood and donot hole paint well. What can be done to insulate etc.

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You can get a number of opinions on fiberglass batt, blown-in fiberglass, blown-in cellulose, foam-in-place foam insulation (open cell and closed cell), even shredded blue jean materials for retro-insulating walls in the Home > Insulation link in Browse Projects, at lower left.

Obviously, if you are taking off the interior plaster or drywall or the exterior redwood to remodel so you will be opening up the wall then all options are open, and I would strongly recommend proper vapor barrier (in the right place in the wall depending on your climate) and batt fiberglass stapled at the top to prevent slumping.

For blown-in insulation installed through about 2" holes in the drywall in each stud bay, fiberglass and cellulose are the common ones. I emphatically recommend against cellulose or jean material - first putting organic material in a wall makes no sense to me - I have seen too many cases where it got damp and molded because it holds moisture terribly - and also settles a LOT after installation. Fiberglass avoids most of the moisture retention issue but also settles some, leaving a gap at the top over the years (as does Batt which is not fastened well at the top).

Foam-in-place foam insulation, also done through holes in the stud bays, does a better job of filling the stud bays and avoiding settlement, and is generally a much better insulator - but if used wrong can cause moisture problems, especially with the significantly cheaper open-cell foam. Is also significantly more expensive than the alternatives.

My recommendation - have an architect or very experienced energy auditor check out your house, including ceiling and such - and a formal energy audit with blower door infiltration test would be a good idea too, to evaluate WHERE your largest energy losses are. In houses with interior drywall or plaster, unless the outdoor temps are quite high or low for extended periods, it is not uncommon for air infiltration around piping and windows and doors, and convective (airflow) losses to the attic, to be larger and more economically fixed than conductive losses through the walls, even if uninsulated. Of course, that is not commonly the case in the desert or the arctic, for example, where the sheer number of heating or cooling degree-days overwhelms the airflow losses.

BTW - in a 1952 home, count on most likely NO vapor barrier under the drywall (for most climates), and at most tarpaper (building felt) under the siding, which is likely pretty well deteriorated by now - so before putting a lot of money into blown-in insulation you might consider the entire wall system and what should be done to make it more energy efficient - which might mean removing the siding, putting in a sprayed-on vapor barrier (to the extent possible without removing the drywall), insulating the wall, putting on proper housewrap water barrier, then the siding - which might or might not be chosen to be what you have on there now.


As for the redwood not holding paint - it has natural occurring chemicals, inclluding oils, that cause it to be quite resistant to rot and insects, but also prevent most paints from sticking. Especially since the white lead paints have been banned - they did a good job of adhering to cedar and redwood and such. Your solution wiht that - though a problem if already painted (might require flipping the boards over if in decent shape otherwise) is a penetrating oil-based sealing stain specifically formulated for redwood like Olympic Maximum Penetrating Stain and Sealer or similar.

Answered 4 years ago by LCD

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