Basement wall insulation guide:
This article discusses the quantity and location of basement foundation wall insulation and the energy cost savings that will be achieved.
We also discuss use of stucco, reinforced stucco paint, and other protective coverings for foundation exterior insulating board.
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Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
I plan to insulate the outside of a concrete-block basement foundation wall with extruded polystyrene board insulation, but anything over 1-inch thick will make for a difficult installation and be aesthetically questionable.
What minimum thickness or R-value is necessary to make a foundation wall insulation project worthwhile?
Do you recommend fiberglass-reinforced stucco paint or conventional stucco as a protective coating to be applied over the exterior-applied foundation insulation? -- George Ciechanowski, Pleasantville NJ
According to computer simulations performed for a house in Columbus Ohio (Solar Age, 7/83 p. 47) with a heated basement, insulating the exterior foundation wall to R-5 will result in a 57 percent reduction in heat loss through the basement walls.
Insulating the basement wall to R-10 will increase savings to 70-percent.
In many cases - with heated basements in particular - the added heating cost savings will justify the expense of going to two inches or more of solid foam insulating board on the foundation walls. However, as you can see, one inch of insulating foam is certainly worthwhile.
As for real stucco vs. reinforced stucco paint, the former is tougher and a more durable product. If you choose stucco paints to coat your foundation insulation, get one that is specifically recommended for application over foam insulating board and follow the instructions.
Surface preparation (such as washing off dirt and debris) is important, as is keeping water from getting from behind the finish. (Such as due to roof runoff splash-up against the foundation walls due to poorly-maintained gutters).
Other foundation protection covering options include 1/4-inch fiber cement board, pressure-treated plywood, or special fiberglass panels made for this application by Trend Products.
This article is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
The text below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
The question-and-answer article about foundation insulation options and foundation insulation protective coatings, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Also see FOUNDATION WATERPROOFING
AkroGuard, Omega Products, International, 1681 California Ave, Corona, CA 92881, Tel: 800-600-6634, 951-737-7447, Fax: 951-520-2594, Quoting from the company's product description:
AkroGuard is a field applied, non-cementitious, [acrylic] flexible coating that when used with AkroFill creates a water-resistive barrier over approved substrates.
Basic Uses: AkroGuard is designed for use as a water-resistive barrier and air barrier over approved substrates and with the AkroFlex EIF Systems. Complies with ICC-ES Acceptance Criteria for Water-resistive Coatings (AC212).
AkroGuard may be applied to the following substrates:
Thanks to reader J. Campbell for pointing out this product, March 2010.
- Gypsum sheathing
- Fiber-faced ghpsum sheathing
- Wood-based sheathing
- CMU/Poured-in-place and/or tilt-up concrete/masonry
- Cement board
Krystol Hydrostop, Kryton Corporation, "Crystalline Waterproofing" masonry sealer. MSDS for Krystol Hydrostop WB [copy on file as /exterior/Krystol-hydrostop-wb.pdf ] - from Kryton Corporation. Masonry sealer.
Vi-Cryl CP-10 (Trowel Grade) & Vi-Cryl CP-11 (Spray/Brush) Weather Barrier Coatings, Childers Corporation. We discuss the use of this coating here: Quoting from the company's product literature [copy on file as /exterior/Vi_Cryl_cp-10-11.pdf ] - ,
VI-CRYL CP-10/11 weather barrier coating is unsurpassed for the mechanical protection and weatherproofing of thermal insulations both outdoors and indoors, in hot, cold, and dual-temperature service. However, since it is a ‘breathing’ coating (vapors under pressure will pass through it) it should only be used over insulations in lowtemperature, or dual-temperature service when the insulations themselves are vapor barriers.
VI-CRYL CP-10/11 has also found use throughout the thermal insulation industry as a coating used over closed cell polyethylene and polyurethane foam insulations. Industry experience has demonstrated that all weather barrier coatings may blister when applied over polystyrene board.
This effect may be limited by the use of white colored coatings. VI-CRYL CP-10/11 weather barrier coating in its Metallic Gray color is the ideal companion product to Aluminum and Stainless Steel Jacketing. VI-CRYL CP-10/11 gives superior mechanical and chemical protection to any irregular shape or surface where the application of Childers Metal Jacketing Systems is impractical.
Also see FOUNDATION WATERPROOFING
The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.
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