Reflective Insulation: properties, uses, technical data

Reflective insulation in buildings, composition, installation & technical data
- List of typical uses for reflective insulation
- Technical data for single & double bubble foil laminated reflective insulation products
- Definition of reflective insulation; definition of radiant barrier insulation; what's the difference between reflective insulation & a radiant barrier?
RADIANT BARRIERS - separate article
Questions & Answers about reflective insulation used in buildings, mechanical systems, & other locations;
References

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This article describes the properties & uses of reflective insulation in buildings and other applications.

Also see our article on RADIANT BARRIERS, an update of an earlier Solar Age article on foil-based insulation products.

Foil-based Reflective Insulation material identification, insulation R-values, insulation characteristics, applications, & technical data

What's the difference between RADIANT BARRIERS [a separate article] and REFLECTIVE INSULATION [discussed here] ?

Watch out: In understanding insulation, radiant barriers, and reflective insulation products it's worth noting that you may find products labeled as "insulation" that are a simple single thickness aluminum foil radiant barrier, and you may find insulating blankets covered with aluminum or even kraft paper and aluminum labeled as a radiant barrier product. It's confusing.

A radiant barrier works principally by serving as a single layer of aluminum foil, possibly reinforced with fibers or paper backing, used to reflect heat outwards (keep the attic cooler) or inwards towards the building interior (avoid losing heat, keep the building warmer).

Reflective insulation is a similar insulating and energy conserving product that adds an air cushion, usually in the form of plastic bubble material, between layers of aluminum foil to improve the insulating value or R-value of what would otherwise be a simple radiant barrier.

Thickness & composition distinguish among radiant barriers (thin) and reflective insulation (thicker) and foil faced insulation (much thicker)

Some radiant barrier products may comprise multiple layers of aluminum foil or foil plus paper.

While the air layer trapped between these layers improves the R-value of the product, in our OPINION, products less than 1/4" in thickness remain, in our book, a radiant barrier.

Products that are made up of at least two layers of aluminum foil, separated by bubble or other material that is 1/4" thick or slightly thicker are reflective insulation.

The double-layer kraft and aluminum "ALFOIL house insulation blanket" shown at left works principally as a radiant barrier. As we discuss at RADIANT BARRIERS, " Dead air trapped between the double layers of foil above the kraft paper provided a slight increase in the R-value of this product."

Still thicker insulating products, such as foil faced fiberglass insulating batts that are 1" or more in thickness, we refer to as foil faced insulation, not simple reflective insulation that will be described further here.

How is Reflective Foil Insulation Constructed - what layers, what materials?

Reflective insulation is usually made using two layers of aluminum foil that has been laminated or "glued" to the surface of two layers of plastic "bubble wrap" or air bubble material.

Or in some older reflective foil building insulation such as the "Double Layer" ALFOL Type II Double Layer insulating product shown at left, you may find as many as four layers comprised of

Kraft paper (outer layer, printed with the company's information (at the bottom in our photo)
A doubled layer of kraft paper, possibly coated on one side with a bituminous moistdure barrier
A layer of aluminum foil (at the top in our photo).

In newer reflective insulation constructed using a layer of bubble wrap, the rounded surface of the air bubbles keeps the two layers of foil separated and the individual bubbles, by trapping or enclosing air, ensure that there is a still-air insulating barrier between the two surfaces of foil, thus improving the R-value of the reflective insulating material.

The bubble-trapped air means that no air movement by convection should occur within the reflective insulation. Such air currents would reduce or even eliminate the R-value of insulation just as air currents in walls, floors, or ceilings will increase heat transfer through those structures.

When used under a roof or in an attic floor (not our first choice) the aluminum foil on both surfaces of the reflective insulation means that the same insulation layer will reflect heat outwards (back towards the roof) from the upper surface of the reflective insulation in summer, and it will reflect heat downwards or inwards (back towards the building interior) during the heating season.

Common Uses of Reflective Building Insulation

Unlike RADIANT BARRIERS that were used in lieu of fiberglass, mineral wool, or foam insulation in building floor, wall, or ceiling cavities, reflective foil based bubble-interior building insulation is not used in modern residential construction as the primary cavity insulation material. Rather the product is used in more industrial settings and in special applications as we list here:

Animal barns, poultry buildings, stables
Commercial buildings, garages, workshops
Concrete curing blankets
Garage door lines
HVAC duct wrap, especially as a retrofit product
Packaging for products that need to be protected from temperature extremes during shipping
Storage facilities
Survival blankets
Temporary-occupancy buildings such as temporary jails or shelters
Transportation truck and trailer cargo liners
Window coverings or insulating window shades
And in these special applications:
- Reflective insulation boards or blankets behind freezers, woodstoves [watch out, overheat risk, may not be UL approved],
- behind radiators,
- behind refrigeration and air conditioning coils inside of HVACR equipment

Properties & R-Values of Reflective Insulation Products

Property	Single Air Bubble Layer	Double Air Bubble Layer
R-value [b]	4.9	5.0
Reflectivity	0.96-0.97	0.96-0.97
Permeability	effectively zero for foil	effectively zero for foil
Emissivity	0.03-0.04	0.03-0.04
Fire Rating	Class A/Class 1	Class A/Class 1
Temperature Exposure	-60F - 180F	-60F - 180F
Puncture resistance	63 psi	66 psi
Weight per sq. ft.	0.8 oz	1.25 oz

Notes: [a] Based on industry standard sheet [on file]; [b] R values obtained from a C236 hot box test. Watch out! these ratings were taken from the entire building cavity including the surrounding air space and thus reflect the R-value of the wall, floor, or ceiling the cavity represented, not the R-value of the material itself. Because building construction and air leak properties vary widely we question these numbers. The original document for double air bubble layer reflective insulation: 15 (D), 7.31 (H) and 5.4 (U), and for single bubble layer reflective insulation 14.5 (D), 7.0 (H), and 4.9 (U).

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Technical Reviewers & References

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

"Controlling Moisture in Log Homes" and the more general (but brief) DOE article series on moisture control:
Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage
"Minimizing Air Leakage in Log Homes"
"Ventilation", U.S. DOE, describes the purpose of building ventilation and three basic ventilation strategies:
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
"Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barriers
"Moisture Problems: Causes and Cures. Understanding moisture problems can steer you free of trouble", Steve Bliss: Building it Right, Solar Age, March 1983 p. 37, 38. -- Adapted with permission, from original material to form this web page article.
"Radiant Barrier Attic Fact Sheet, Introduction", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Effect of Radiant Barriers on Heating & Cooling Bills", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Important Non-Energy Considerations", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, [Radiant Barrier] Installation Procedures [for Attics]", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Appendix: Radiant Barrier Test Results", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, DATA TABLES: Cost of Radiant Barriers in Locations, Savings of Radiant Barriers by U.S. City, Average Reductions in Ceiling Heat Flow due to Radiant Barrier, Table of Typical Heating Equipment Efficiencies, Table of Cooling Load Factors for Radiant Barriers by U.S. City, Table of Cooling Load Factors for Additional Insulation by U.S. City,", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website. Spells out the full text names of AFUE, ASTM, BTU, CCF, COP, DOE, FSEC,KWH, MIMA, NAHB, NFPA, ORNL, RB, RBS, RIMA, SEER, therm, TVA, and UBC - this gives the names, not extensive definitions of these acronyms.
"Radiant Barrier Attic Fact Sheet, Key to Abbreviations & Acronyms", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Sources of Government Information", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website. Spells out the full text names of AFUE, ASTM, BTU, CCF, COP, DOE, FSEC,KWH, MIMA, NAHB, NFPA, ORNL, RB, RBS, RIMA, SEER, therm, TVA, and UBC - this gives the names, not extensive definitions of these acronyms.
"Radiant Barrier Attic Fact Sheet, Technical Panel who Developed this Fact Sheet", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website. Spells out the full text names of AFUE, ASTM, BTU, CCF, COP, DOE, FSEC,KWH, MIMA, NAHB, NFPA, ORNL, RB, RBS, RIMA, SEER, therm, TVA, and UBC - this gives the names, not extensive definitions of these acronyms.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Asbestos: How to find and recognize asbestos in Buildings - visual inspection methods, list of common asbestos-containing materials
ASHRAE resources on building insulation, dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Construction Waterproofing Handbook, Michael T. Kubal. Quoting:
... an all-inclusive, project-simplifying guide for waterproofing and construction professionals. This comprehensive answer-packed resource is loaded with the up-to-date, clearly-defined information you need on every project, including work on the building envelope, below-grade, above-grade, and remedial waterproofing.
Brick nogging used as soundproofing is mentioned in this article on Popular Forest
Brick Nogging, Historical Investigation and Contemporary Repair, Construction Specifier, April 2006. Historical use of brick in timber-framed buildings, drawing on the investigations of the Kent Tavern in Calais, VT. "Brick nogging is a European method of construction which was brought to the new world in the early-nineteenth century. It was a common construction method that employed masonry as infill between the vertical uprights of wood framing." -- quoting the web article review.
Photo of very rough in-wall brick nogging at an architects website
Dust from the World Trade Center collapse following the 9/11/01 attack: the lower floors of this building contained spray-on fire-proofing asbestos materials.
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Fiberglass: Indoor Air Quality Investigations: Health Concerns About Airborne Fiberglass: Fiberglass in Indoor Air from HVAC ducts, and Building Insulation
From the walls in, Charles Wing
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Insulate & Weatherize (Taunton's Build Like a Pro), Bruce Harley. Review quoted:
An engineer who trains builders in energy-efficient construction, Harley offers a wealth of information that will allow readers to improve their home's efficiency, saving both money and natural resources. After an introductory section that explains the underlying principles of heat transfer, insulation, and air quality, Harley demonstrates basics such as weather-stripping and moves forward through advanced projects including insulation and major upgrades. Short "Pro Tips" as well as sections labeled "Trade Secrets," "What Can Go Wrong," and "In Detail" provide a great deal of helpful information. Increasing energy efficiency is one of the easiest ways for homeowners to save money
"Insulation: Adding Insulation to an Existing Home," U.S. Department of Energy - tips on how to do your own check for the presence of absence of insulation in a home
Insulation: Selecting Insulation for New Home Construction, U.S. Department of Energy - "Your state and local building codes probably include minimum insulation requirements, but to build an energy-efficient home, you may need or want to exceed them. For maximum energy efficiency, you should also consider the interaction between the insulation and other building components. This is called the whole-house systems design approach."
Insulation Types, table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-Values & Properties our own table of insulation properties that includes links to articles describing each insulation material in more detail.
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- "A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS
Nogging: See this photo of exposed bricks on a building exterior on a building exterior in Canada. [Thanks to Carson Dunlop, Toronto - see References below].
Piquet Wall Construction: See this photo of piquet wall construction - involving timber-framed wall construction with long top girts, diagonal timber bracing, and small diameter logs placed vertically along with concrete chinking to fill in the wall plane.
Plank House Construction: weblog from plankhouse.wordpress.com/2009/01/25/plank-house-construction/ and where plank houses were built by native Americans, see
Large 1:6 Scale Plank House Construction / P8094228, Photographer: Mike Meuser
06/12/2007 documented at yurokplankhouse.com where scale model Museum quality Yurok Plank Houses are being sold to raise money for the Blue Creek - Ah Pah Traditional Yurok Village project.
Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 ASHRAE Handbook - Fundamentals, Harry J., Jr. Sauer, Ronald H. Howell, William J. Coad. Quoting
... textbook for college level HVAC courses or independent study and review, especially when combined with the 1997 ASHRAE Fundamentals Handbook. Contains the most current ASHRAE procedures and definitive, yet easy to understand, treatment of building HVAC systems -- from basic principles through design and operation. Dual units of measurement.
"Radiant Barrier Attic Fact Sheet, Introduction", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Effect of Radiant Barriers on Heating & Cooling Bills", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Important Non-Energy Considerations", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, [Radiant Barrier] Installation Procedures [for Attics]", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Appendix: Radiant Barrier Test Results", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website.
"Radiant Barrier Attic Fact Sheet, Technical Panel who Developed this Fact Sheet", U.S. Department of Energy, - PDF file. Click in the top area of this document to return to this website. Spells out the full text names of AFUE, ASTM, BTU, CCF, COP, DOE, FSEC,KWH, MIMA, NAHB, NFPA, ORNL, RB, RBS, RIMA, SEER, therm, TVA, and UBC - this gives the names, not extensive definitions of these acronyms.
Super-Insulated Retrofit Book: A Homeowner's Guide to Energy-Efficient Renovation, Robert Argue
The super-insulated retrofit book: A homeowner's guide to energy-efficient renovation (Sun builders series), Brian Marshall
Understanding Ventilation: How to Design, Select, and Install Residential Ventilation Systems, John Bower, Quoting:
Understanding Ventilation is the only book that covers all aspects of exchanging the air in houses: infiltration, equipment selection, design, heat-recovery ventilators, sizing, costs, controls, whole-house filters, distribution, and possible problems that a ventilation system can cause--all in easy-to-understand language.
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Weaver: Beaver Board and Upson Board: Beaver Board and Upson Board: History and Conservation of Early Wallboard, Shelby Weaver, APT Bulletin, Vol. 28, No. 2/3 (1997), pp. 71-78, Association for Preservation Technology International (APT), available online at JSTOR.
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