Basement heat loss (C) Daniel Friedman Insulation Location & Quantity for Basement Foundation Walls

  • INSULATION LOCATION for BASEMENT WALLS - CONTENTS: How much insulation to put on basement walls, where to insulate. Heating cost savings amount achieved by insulating basement walls. Advice on use of reinforced stucco paints vs. real stucco on foundation insulation. Use of polystyrene insulation on foundation walls
  • Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
  • POST a QUESTION or READ FAQs about insulating basement foundation walls
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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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Proper Amount & Location of Basement Wall Insulation

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.

Basement Foundation Wall Insulation Thickness, Location, & Energy Savings


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


Energy Savings from Insulating the Basement Wall

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.

Readers considering adding insulation inside or outside a basement foundation wall should also
as well

Use of Stucco vs. Reinforced Stucco Paint on Foundation Insulation

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.

Weather Barrier Coatings, Mastics, Sealants, Adhesives used on Buildings, Building Sheathing & Building Foundation Coatings


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:

  • Gypsum sheathing
  • Fiber-faced ghpsum sheathing
  • Wood-based sheathing
  • CMU/Poured-in-place and/or tilt-up concrete/masonry
  • Cement board
Thanks to reader J. Campbell for pointing out this product, March 2010.

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.

  • Krystol T1 and T2 waterproofing system is brush-applied onto concrete surfaces to become an integral part of the concrete. It contains Kryton's renowned waterproofing chemicals and is durable and self-sealing.

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.


The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.

  • Q&A on Basement Insulation - PDF version, use your browser's back button to return to this page


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