Light-Weight Concrete Wall Insulation for buildings

Use of light-weight concrete insulation such as Thermal Krete™ as a wall cavity insulation material
- Does use of light weight concrete insulation eliminate the need for wall vapor barriers?
- Is there a problem using Thermal Krete™ in thick double-framed walls in superinsulated houses?
- Does use of AirKrete cementious foam insulation affect structural integrity of a building?
- Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
Questions & Answers about how light weight concrete insulation
References

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This article discusses the use of light-weight concrete building insulation (such as Thermal Krete™ in building wall-stud cavities. Table at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

For a complete listing of types of building insulation, their properties, and how to identify or use them, see INSULATION INSPECTION & IMPROVEMENT. Readers should see INSULATION R-Values & Properties for a more extensive table describing the properties of different insulating materials.

Properties of Light-Weight Concrete Building Insulation

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

Q&A on Wall-Cavity Concrete Building Insulation - PDF form, use your browser's back button to return to this page. Original article, Solar Age Magazine, Nov. 1983, , adapted and updated for InspectAPedia.com December 2010.

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Topic: What do you think of using light-weight concrete insulation such as Thermal Krete™ in Walls?

Question: What is the Effectiveness of using Cementious Foam Insulation in a Super-Insulated Building Using Double-Wall Construction

What do you think of using light-weight concrete insulation such as Thermal Krete™ as an insulating filler for double 2x4 walls?

Would use of lightweight concrete insulation eliminate the need for a moisture and/or air barrier? - Lane Felker, Jefferson MD

Answer:

Thermal Krete™ (discussed at "Product Update," Solar Age 11/83) is a special magnesite concrete that is pumped into wall cavities in a way that traps air bubbles. It insulates to about R-4 per inch.

Can I install light-weight concrete insulation in a super-insulated double-framed building wall?

According to Thermal Krete™ company president Fred Moer, the thickest cavity in which Thermal Krete™ has been installed is a 2x8 framed (rafter depth nominal size 2" x 8" is actually about 1.5" x 7.5") cathedral ceiling. The company should be consulted regarding lightweight concrete installations in cavities beyond 8-inches thick.

The weight of the material (4-5 pounds per cubic foot) could bow out drywall in a double-framed super-insulated building wall design, or the water from the larger volume of concrete could damage building materials.

See our discussion of super-insulated buildings and double-framed wall studs at INSULATION CHOICES.

Do I need a moisture barrier on a light-weight concrete-insulated wall?

Thermal Krete is fairly permeable to water vapor, so a vapor retarder is recommended.

Do I need an air barrier on a light-weight concrete-insulated wall?

As for air leakage, you should be primarily concerned about places where the concrete does not penetrate, e.g. under soleplates (sill plates), through ceiling penetrations, and out through interior partitions. Thermal Krete's manufacturer, Omni Tech Energy Products, welcomes inquiries.

Structural Properties of Air-Entrained or "Foamed in Place" Concrete Insulation such as AirKrete® Insulation

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

Q&A on the Effects on Structural Integrity of Using AirKrete® or similar Air-Entrained foamed-in-place cementious insulation products - PDF version, use your browser's back button to return to this page. Original article, Solar Age Magazine, December 1985/January 1986, adapted and updated for InspectAPedia.com December 2010.

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Question: Will insulation retrofit using AirKrete Cause Problems with the Structure of the Building?

I am renovating a 100-year-old house that is a mix of timber frame and stick frame construction, with massive diagonals at the corners. At some point a second story was added, and later a balloon-framed addition.

I had planned to cut fiberglass batts to fit the stud spaces but I'm beginning to think that foam-in-place insulation might save enough on labor to offset the higher material cost.

Would a foam such as Air Krete® cause any problems with the structural integrity of the house due to pressure during application, or will it actually strengthen the framework? - Stephen Ortado, contractor, White Stone, VA.

Answer:

AirKrete® is a cementious foam with the consistency of shaving cream and an R-value of about 4 per inch. (See our table just below, and see INSULATION R-Values & Properties to compare various insulation products.).

When foamed in place, AirKrete® (and similar products such as discussed above), has finished expanding and flows around obstacles. So it places little stress on the structure of a building. After it sets, the foam is dimensionally stable, and there is no shrinkage problem.

Because it has no structural strength, AirKrete or other cementious foam insulating products will not make the building frame any stiffer.

A vapor barrier is recommended according to the product specifications and also according to Jay Savery, an East Coast manufacturer of the material, because the foam is very porous to moisture flow.

The table below summarizes the properties of various types of cementious building insulation and was excerpted from the more extensive table of insulation properties found at INSULATION R-Values & Properties.

Insulation Material ⁹	R-Value¹	Density²	Perm³	Absorption⁴	Flame Spread ⁵	Smoke⁶	Toxicity⁷	Aging Effects
Concrete, uninsulated	0.08¹⁸ - 0.3125¹⁷							Typical residential weight concrete 8" wall = R 2.5
Concrete-insulated	0.85 - 1.2	12-88	Varies	Varies	0	0	0	Insulated forms available
Concrete, air entrained	3.90²¹
Air Krete®²⁶	3.90²⁶	2.07 lbs/cuFt²⁶	0.1457 in/sec coefficient, or 0.3407 in/sec flow rate at 68 degF H2O²⁷		0²⁶	0²⁶	no	Cementious foam insulation, fireproof, non-toxic, non-shrinking, also used for acoustical sound proofing; MgO cement (Magnesium Oxide); 6 mil poly vapor barrier required

Notes to the Table of Building Insulation Properties

R-Value is expressed as rate of heat loss per hour per square foot per inch of thickness of material per deg. F - see "R" value definition at Definitions of R K U values
Insulation density is expressed in pounds per cubic foot of material
Permeability is expressed as the water vapor permeability of the material per inch of thickness. These numbers are most useful to compare one insulating material to another.
Absorption is the tendency of the insulation to absorb water in percent by weight. This is important for assessing the risk of mold in some materials
Flame Spread is a measure of fire resistance of the material. Use these numbers to compare one insulating material to another.
Smoke is a measure of fire safety - that is, the relative amount of smoke produced if the insulation is exposed to flame or combustion
Toxicity is a measure of fire safety - that is, toxins given off if the insulation is exposed to flame or combustion.
Polystyrene may be in molded or extruded forms and like some other plastic or foam insulations may be in open or closed cell form. (Closed cell foams are more moisture resistant). Polystyrene also is referred to as molded expanded polystyrene (MEPS), expanded polystyrene (EPS), and extruded polystyrene (XPS) - the most common foam board insulation product. MEPS & XPS are used in insulated structural panels and in insulating concrete forms (ICFs).
Links to details: Insulation product names in the first table column include links to articles that help identify and provide the properties of each insulating material listed.
Open vs. closed cell: Foam insulation densities vary among closed-cell vs open cell forms. Open cell foams are typically about 1/2 lb/cubic foot; Closed cell foams are more dense and rigid, typically about 2 lb/cu. ft.
C or Thermal conductance of these materials is the reciprocal of the R-value. C is known only when the k, the thermal conductivity of a material is known. k is the heat transmitted through a 1-inch thickness of homogenous material per square foot per hour when there is 1 degree of temperature change. k= (BTU * inch) / sq.ft. * hour * degF.
Air film: This table of R-values does not consider the insulating characteristic of the air film on each side of a surface nor the effects of wind on the air film or on the material itself. Some of these materials are more resistant to wind-caused heat transmission than others.
Moisture: Closed cell foams resist moisture uptake (good) but if construction is improper they can trap moisture (bad) leading to rot or mold problems in other building materials.
Insects: Exterior foam board on foundations can ease attack by wood destroying insects.
Fire & smoke: Foam insulation products present fire-smoke hazards and usually they must be protected with a fire barrier (usually 1/2" drywall).
R-Values for wooden log walls given by the U.S. DOE are in error except for square log walls. D-logs and round logs that are given a nominal log thickness, say 6" logs are calculated by DOE as having an R-value of just over 8. This is incorrect for non-square logs because the cross section of the log is 6" only at the log's widest point. A correct assessment of the R-value of a wooden log wall needs to be calculated based on the average wall thickness, considering the variation in thicknesses over the curvature of the logs. Therefore the DOE's value is on the "high" end of the R-value of a log wall.
R-Values of uninsulated concrete: Concrete Homes Magazine web search 5/18/2010
R-Value for concrete, glass, other materials, Wikipedia web search 5/18/2010 citing Ristinen, Robert A., and Jack J. Kraushaar. Energy and the Environment. 2nd ed. Hoboken, NJ: John Wiley & Sons, Inc., 2006.
E-Star Colorado. Energy Saving Calculations. Energy Living Alliance, 2008. Web 05/18/2010
U.S. Department of Energy, DOE Handbook, see http://buildingsdatabook.eren.doe.gov/TableView.aspx?table=5.1.3 18 May 2010. The DOE in turn cited these sources
- ASHRAE, 1997 ASHRAE Handbook: Fundamentals, p. 24-4, 22-5
- DOE, Insulation Fact Sheet, Jan. 1988, p. 6
- Journal of Thermal Insulation, 1987, p. 81-95
- ORNL, ORNL/SUB/88-SA835/1, 1990
- ORNL, Science and Technology for a Sustainable Energy Future, Mar. 1995, p. 17
- ORNL for vacuum insulation panel
Wikipedia, web search 5/18/2010 R-Values per Inch
EcoHaus UltraTouch cotton insulation batts batts http://www.ecohaus.com/C-121/ultratouch+batts Web search 5/18/2010
Icynene product information see http://www.icynene.com/icynene-insulation/ - Web search 5/18/2010
ICC Legacy Report ER-2833 - Cocoon Thermal and Sound Insulation Products, ICC Evaluation Services, Inc., http://www.icc-es.org - Web search 5/18/2010
HomeFoam®, Home Insulation Corp. - see http://www.homefoam.ca/articles/Why_HF.htm - Web search 5/18/2010
Home Foam® does not contain formaldehyde, fibrous particulate, HFCs¹, CFCs² or HCFCs³ and is a zero-ODP⁴ product. The Saskatchewan Research Council (SRC) advises that even sensitive individuals may take occupancy just 24 hours after application is complete.
Air Krete®, Air Krete Inc., P.O. Box 380, Weedsport NY 13166-0380 –Keene Christopher, Principal Telephone: (315) 834- 6609, Retrieved 05 Dec 2010, AirKrete® Green Insulation Specifications, original source: http://www.airkrete.com/ Specifications for AirKrete® can be found at http://www.airkrete.com/pdf/072101specification.pdf
AirKrete® Water Permeability Coefficient, 03/02/2005, letter provided by AirKrete, retrieved 05 Dec 2010, original source: http://www.airkrete.com/testResults_files/PermRating.pdf

Specifications for Wall Insulation for Superinsulated Homes

As we discuss at INSULATION CHOICES , for superinsulated buildings the article concludes that a double-stud wall with fiberglass batts provided the greatest insulating value per dollar. However other insulating products may be a better choice depending on other construction details and space limitations.

Our photograph (left) shows an insulation retrofit in a crawl space where icynene foam spray was applied to the crawl space wall and between the floor joists overhead.

The article also discusses the question of air permeability of fiberglass insulation and its impact on the actual insulating value of the material compared with impermeable (to air) foam insulation products. The impact of moisture on the R-value of fiberglass insulation is also discussed (it's low). Fiberglass both gains and loses moisture more rapidly than some other insulating products.

Foil-faced polyisocyanurate insulation such as the Thermax® and Hi-R® brands are discussed - these products give the highest R-value per inch among insulating materials. Also, as we tested in the 1970's, the use of these products combined with a 3/4" air space permits achieving an additional R 2.7 provided that the foil is clean and the gap or air space is uniform.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
Air Krete®, Air Krete Inc., P.O. Box 380, Weedsport NY 13166-0380 –Keene Christopher, Principal Telephone: (315) 834- 6609, Retrieved 05 Dec 2010, AirKrete® Green Insulation Specifications, original source: http://www.airkrete.com/ Specifications for AirKrete® can be found at http://www.airkrete.com/pdf/072101specification.pdf
AirKrete® Water Permeability Coefficient, 03/02/2005, letter provided by AirKrete, retrieved 05 Dec 2010, original source: http://www.airkrete.com/testResults_files/PermRating.pdf
Omni Tech Energy Products can be contacted at 616-458-5894.
Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the InspectAPedia Bookstore
"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
"Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
"Heat Exchangers for Solar Water Heating Systems", U.S. DOE describes the types of solar water heater heat exchange methods between the sun and the building's hot water supply
"Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
"Solar Water Heating System Maintenance and Repair", U.S. DOE
"Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
"Scaling and Corrosion in Solar Water Heating Systems", U.S. DOE
www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these articles
"Active Solar Heating Systems", U.S. Department of Energy, including
"Radiant Heating Systems" U.S. DOE
"Absorption Heat Pumps & Coolers", U.S. DOE
"Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building
"Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.

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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

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