Table of building insulation costs (C) Daniel Friedman High R-Value Building Insulation Choices Described

  • INSULATION CHOICES & PROPERTIES - CONTENTS: Properties of various building insulation materials: fiberglass insulation, expanded polystyrene insulation, foil-faced polyisocyanurate insulation, and extruded polystyrene.
  • Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
  • POST a QUESTION or READ FAQs about High R-value insulation products & choices
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Building insulation choices & properties:

This article discusses the properties of various building insulation materials: fiberglass insulation, expanded polystyrene insulation, foil-faced polyisocyanurate insulation, and extruded polystyrene.

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Building insulation properties of fiberglass insulation, expanded polystyrene insulation, foil-faced polyisocyanurate insulation, and extruded polystyrene

Foam insulation sprayed in a crawl space - this is not mold - Daniel Friedman 04-11-01The table of insulation properties at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

"Insulation Options, a few facts to help you choose among foams and fibers":

This article explains the insulating properties and relative costs of common building insulating materials including fiberglass insulation, expanded polystyrene insulation, foil-faced polyisocyanurate insulation, and extruded polystyrene.

The insulation figure of merit, "cost of insulation per square foot R-value, is explained as a means of comparing insulating materials. While the insulation cost data in the original article dates back to November 1983, the concept of using an R-value normalized cost to evaluate insulation is useful today.

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.

See POLYISOCYANURATE FOAM INSULATION for details about polyisocyanurate insulation use.

The polystyrene family of insulations are discussed and are recommended particularly for insulation below grade using expanded polystyrene (EPS or beadboard) and extruded polystyrene (such as Styrofoam® - photo at below left, or Foamular®).

Crawl space insulation with foam board (C) D FriedmanThe article pointed out that in the 1980's there were more than 150 different manufacturers of EPS/beadboard and only three or four of extruded polystyrene.

Claims (perhaps by competitors) that EPS absorbs water are dismissed as nonsense - the material is used to float docks. The article also discusses the use of polystyrene insulation as a non-structural building sheathing (permitting insulating over building band joists and headers) and as an added control of air infiltration.

Problems reported with use of polystyrene as non-structural sheathing where horizontal wood siding is installed included loose clapboards, cupping or cracked clapboards, and nail pulling due to thermal movement of the foam. The article concludes:

The wood problems are attributed to the tendency of these relatively impervious insulations to aggravate thermal and moisture cycling in the siding, since they soak up little heat and moisture themselves. One solution may be to strap out the siding, though this reduces the savings obtained by eliminating the sheathing in the first place.

See POLYSTYRENE FOAM INSULATION for details about polystyrene foam board insulation use.

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Current High-R Building Insulation Products for Super Insulated Buildings

Spray foam roof (C) D Friedman The high-R insulating panel building products currently in most common use are POLYSTYRENE FOAM INSULATION


also polyurethane spray foam
(URETHANE FOAM Deterioration, Outgassing).

These materials have a typical R-value of about R-5 to R-6 per inch, though when installed with a radiant surface (that might help) and a 3/4" air gap, the R-value is increased substantially - as we detail below. Fiberglass batts, which are still most-widely used in residential construction, are about R-3 per inch.

Here are some currently-available high-R building insulation products as well as some specialty very high-R insulation materials:

  • Aerogel has an R-value of about R-10 per inch, is 99% air and insulates up to 37 times higher R-value than fiberglass. The material is costly, and fragile, factors that have limited its use in residential construction. Work is in process to produce a less costly version.
  • Barrier Ultra-R super high-R building panels, produced by Glacier Bay, use Aerogel and are rated up to R-30 per inch, or in Barrier Ultra-r™ panels, R-50 per inch. The Ultra-R™ R-50 insulating panel is a rigid polypropylene-encased vacuum insulation panel that is custom made to the client's specified dimensions. The panels are also available with a fiberglass coating on one or both sides. (Used in refrigeration applications.)

    The company also produces acoustic panels that are Ultra-db resistant and lightweight. Unlike the appliance insulation panels discussed in the original Q&A above on miracle insulation, these Aerogel based panels will continue to retain some, though reduced insulating value if punctured, performing at perhaps R-9 per inch.

    The product is used in marine refrigerators, but in the future may be available as a residential construction product. The company is researching specialized products in medical, transportation, and aerospace applications.
  • CERAMIC INSULATION - version of high temperature treated PERLITE INSULATION
  • Eco-Panel polyurethane foam core structural insulated panels (SIPs) are produced by Eco-Panels Corporation. The 3-inch thick panels include structural elements and panel locking devices.

    The company offers a super-insulated 8.5-inch thick structural insulated panel and also produces roof panels. The 2.5 pound polyurethane foam used in these panels provides about R-7 per inch; 4-inch panels are rated at R-26, 6 1/2inch panels at R-40.
  • Hightherm R-24, Supertherm R30, and Superthermal R60 wall panels are produced by Supertherm. Wallpanel® uses 18 gauge steel studs spaced 16" on center, staggered to support 24" o.c. roof trusses, combined with high-density (two pound) polystyrene foam insulation. The higher density polystyrene foam insulation permits achieving an R-30 wall panel that is 6" thick (rather than 7" with lower density foam). The panels are finished with an insulating ceramic coating and are warranted for 25 years.
  • Low-E Housewrap Insulation™, is a patented insulation consisting of a closed micro-cell foam core that is heat laminated to foil or polyethylene facings. This foam board insulating product is thin, provided in rolls, intended as a thermal break wrap that is moisture, rodent, and insect resistant.

    The Low-E Manufacturer states that it outperforms 3-4" of fiberglass insulation. As the product literature points out, "All of these components are referred to as a system R-Value. A 3/4" air space facing the aluminum is ideal because convection currents cannot begin to move in an air space this small. The aluminum actually increases the R-Value of the air space it faces. Low-E is manufactured using a 1/4" polyethylene foam core with scrim reinforced double-sided aluminum facings. It can be used in all facets of the building industry where conventional insulations are used. It can be used alone or in conjunction with mass insulations for high R-systems. " The product is also advertised by some distributors for insulation retrofit products, attics, basements, under-slab insulation, etc.
  • Precision Panel R28 (R-4 to R-7 per inch) Laminated EPS foam core Structural Insulating Panels (SIPs) are produced by Precision Panel Co. located in Idaho, ships insulating panels world wide. The 4-inch thick EPS foam core panels are laminated with exterior sheathing (OSB) and an interior sheathing (OSB or ?). The foam core panels are prepared with window and door rough openings and accept edge splines or top and bottom plates for construction. They include wire chases and are cut to customer specifications.
  • STRAW BALE CONSTRUCTION has been considered a high-R building method for a long time and is discussed at STRAW BALE CONSTRUCTION
  • STYROFOAM™ Brand Spray Polyurethane Foam R 6.1 per inch, (CM Series) produced by DOW Chemical is a "two-component, spray-applied polyurethane foam that creates a seamless, monolithic barrier for protection against water vapor and air on the interior of steel stud walls. This closed-cell, 2-pcf spray foam successfully incorporates the Enovate 3000 blowing agent from Honeywell. This product is designed as a filler for the Thermax Wall System discussed below.
  • Super Therm® insulating ceramic coatings produced by Superior Solar Barrier, are used on buildings as well as freezers and refrigerators, intended as an impenetrable exterior coating. The coating uses a vacuumed microceramic hollow particle (ceramic bubbles) containing a gas,and providing minimal heat conductivity. The particles are distributed in a coating vehicle.
  • Thermax™ Wall System, DOW Chemical, "addresses design considerations for commercial steel stud applications and is not relevant for most residential applications. THERMAX™ Exterior Insulation R6.5 per inch, consists of a glass-fiber-reinforced polyisocyanurate foam core faced with nominal 4 mil embossed BLUE™ acrylic-coated aluminum on one side and 1.25 mil embossed aluminum on the other.
  • Tuff-R™ and Super Tuff-R™, Dow Building Solutions, have an R-value of R 6.5 per inch. Note that the R-value of this insulating board is increased to R-9.3 per inch if construction includes a 3/4" air space. These are closed-cell polyisocyanurate insulating foam core board products.

    The foam core is sandwiched between a choice of exterior faces including aluminum foil, tri-plex aluminum foil, or polyester kraft paper combined with reinforced aluminum foil. One board side is blue, the other is radiant aluminum foil. These products must be covered with a minimum of 1/2" drywall or equivalent thermal barrier in building applications. See POLYISOCYANURATE FOAM INSULATION.

    Also see Q&A on use of Rigid Foam Insulating Board - [PDF]

    Also see the Dow Product Literature for Tuff-R insulating board - [PDF]
  • Vacuum Super-Insulated R-28 Panels from RParts are sold as an alternative to aerogel products. The panels are produced by a third party manufacturer using DOW INstill foam cores sealed at high vacuum in a special multi-layer gas impermeable barrier membrane film.

Original Solar Age Magazine Article on High R Insulation Choices

Links to the original article in PDF form immediately below are preceded by the expanded/updated online version of this article above.


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