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
  • REFERENCES
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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 and IAQ 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

and POLYISOCYANURATE FOAM and IAQ panels and

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:

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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