Reflective Insulation: properties, uses, technical data
REFLECTIVE INSULATION - CONTENTS: 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?
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.
We expand on these definitions at the end of this article.
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 moisture barrier
Two or more layers 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
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 refrigeration and air conditioning coils inside of HVACR equipment
Properties & R-Values of Reflective Insulation Products
Single Air Bubble Layer
Double Air Bubble Layer
effectively zero for foil
effectively zero for foil
Class A/Class 1
Class A/Class 1
-60F - 180F
-60F - 180F
Weight per sq. ft.
[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).
Question: identification of reflective insulation vs. radiant barriers
Can you by any chance help me identify this type of insulation ? I have never seen it before. Thank you in advance.
I myself would like to learn more about this stuff since it is the first time i have ever seen it and i am curious and would like to learn more. I spent many hours trying to find any thing about this product to no avail please send me a link to the thread so i can follow along . - Anonymous by private email, 2016/10/23
[Click to enlarge any image]
The reflective insulation shown above was found by the reader and is reported to be installed in a single family home in Altadena California. The home was built in 1951.
Looks to me like an early radiant-barrier type "insulation" product. I'm unsure what sort of paper was used inside the foil to give it more air space and thus improve its insulating rating. On the off chance that the paper is an asbestos product I'd take care not to make a dusty mess. We discuss reflective insulation such as your product here at REFLECTIVE INSULATION.
Separately, at RADIANT BARRIERS we discuss a similar product, radiant barriers, another reflective product. What's the difference between reflective insulation and a radiant barrier? It depends on your information source, as not everyone will speak with equal precision.
Watch out: it's possible that the paper baffles shown in the reflective insulation in your photograph are asbestos paper.
Definition of radiant barrier
A radiant barrier is a single sheet of reflective foil used to reduce un-wanted heat loss or un-wanted heat gain by placing a heat reflecting material at a strategic location. In buildings that's typically in an attic and most-often on the under-side of roof rafters or on the upper side of an attic floor.
A radiant barrier might also be placed in a wall or over a basement or crawl area. Historically aluminum foil but perhaps reflective mylar in more recent applications.
Definition of Reflective Insulation
Reflective insulation improves on the concept of a radiant barrier by using two or more layers of heat reflecting material, typically bound together to form a blanket. The blanket may be simply hollow or it may contain internal baffles such as shown in our reader's photograph above. However you'll note that except for material used to provide individual air chambers reflective insulation is hollow.
Reflective Barriers on Other Insulating Products
Other fiberglass insulating products are sold with a non-reflective kraft-paper facing that also aids insulation installation as well as sold as un-faced fiberglass batts. Products that combine a reflective barrier with fiberglass or another insulating material may be referred to as "reflective fibrous insulation" (Fay 1988).
Foil-faced fiberglass insulation is a more-widely-used contemporary insulating product found in building roofs, ceilings, attics, walls, floor. This product combines a foil faced paper on one side of the insulation. The foil facing improves the insulation's perfomance by reflecting heat as well as by serving as an air barrier, and the facing also aids in insulation installation by providing a paper flange that canb e stapled to the building framing rafters, ceiling joists, wall studs, or floor joists.
Unlike reflective insulation, foil-faced insulation combines the foil facing with a thickness of insulating material, typically fiberglass batts.
Research on Reflective Insulation
While the insulating properties of multi-layer or multi-wall metallic materials are reflected in earlier patents ca. 1900, a surge of multiple-layer metallic reflective insulating materials began in the United States in the 1920's, possibly with the development of improvements in the economical production of thin aluminum sheeting or foils.
Andrews, Bernard R. "Heat-insulating-wall construction." U.S. Patent 1,522,708, issued January 13, 1925.
Benedict, Edward L. "Thermal insulating building unit." U.S. Patent 2,101,836, issued December 14, 1937.
Illustrated at above / left.
Abstract: This invention relates to thermal-insulating building units, that is to means for thermally insulating structures of all sorts suchas houses, ships and the like, and has for its object to provide a unit for such use which is easier to handle and place in position as well as easier to ship than are the present thermal insulating units.
One objection to the use of metal foil has been the inconvenience in handling and shipping it or else the inconvenience in inserting it. One suggestion contemplated the foil being attached to a foundation for giving it strength. If the foundation is rigid and easy to insert between studs, beams or other framing members, it is not convenient for shipment. On the other hand, if the foil'is mounted on paper and made easy for shipment in rolls, considerable labor expense is required to properly space and mount the foil sheets between the framing members.
It has been customary to crumple up foil sheets and mount them between the framing members. Theobjection to this practice is that the spacing and therefore the efiiciency of the spaced foils will not be uniform and in fact there is not enough certainty that the foils will be spaced apart everywhere. Metal foil is so light and thin and easily torn that its insertion in a building has not been considered altogether easy.
Under this invention metal foils are mounted in pairs with an intermediate foundation and the unit being constructed so that it is easier to assemble and insert in place, yet unusually well adapted for shipment without danger of being torn.
Referring to the drawing Fig. 1 shows a folded insulating unit according to this invention.
Fay, Ralph M., and Theodore R. Rohweder. "Reflective fibrous insulation." [JPG] U.S. Patent 4,726,985, issued February 23, 1988.
Abstract: A laminate of foil and kraft paper is adhered to the upper face of fiber glass insulation so that the exposed foil reflects radiant heat entering the attic through the roof of a building structure. Relatively thick kraft paper supports the very thin layer of foil without causing a fire hazard due to the use of an inorganic adhesive, such as sodium silicate, to bond the two together and also due to the use of a fire retardant water-based adhesive to bond the foil-kraft laminate to the fiber glass. The laminate is preferably perforated to prevent it from functioning as a vapor barrier.
Hnilicka, M. P. "Engineering aspects of heat transfer in multilayer reflective insulation and performance of NRC insulation." In Advances in Cryogenic Engineering, pp. 199-208. Springer US, 1960.
Al-Homoud, Mohammad S. "Performance characteristics and practical applications of common building thermal insulation materials." Building and environment 40, no. 3 (2005): 353-366.
Ghahremani, A. Moayed, and E. Freel Singleton. "Reflective insulation blanket with retaining clips." U.S. Patent 4,590,727, issued May 27, 1986.
Guo, W., X. Qiao, Y. Huang, M. Fang, and X. Han. "Study on energy saving effect of heat-reflective insulation coating on envelopes in the hot summer and cold winter zone." Energy and Buildings 50 (2012): 196-203.
Olson, Fletcher M. "Insulating material." U.S. Patent 1,726,040, issued August 27, 1929.
Olson, F.M., 1927. Insulating material. U.S. Patent 1,651,539. [Shown below]
Wheeler, Donald B., "Heat reflective insulation." U.S. Patent 2,879,554, issued March 31, 1959.
Abstract excerpt: the present invention'relates to a heat reflective in sulation. More particularly it covers an insulation which can be made up in collapsed form and can be conveniently expanded and mounted in a building to provide a minimum of two and a maximum of four layers of air spaces, each of which may have a reflective surface. This application is a continuation-in part,of my cc,- pending application, Serial No. 665,821, filed Jun'14', 1957, and a continuation-in-part of my copending application Serial No. 720,873, filed March 12, 1958,
Zupon, Lawrence, David Dejarlais, James Gambatese, and Stephen Neff. "Reflective insulation." U.S. Patent 6,797,356, issued September 28, 2004.
Abstract: A reflective insulation system. The reflective insulation system includes a reflective layer such as aluminum, a layer of fiberglass, and a layer of vapor retarding material. A first side of the layer of fiberglass is bonded to the reflective layer by a deposit of hot melt glue. The second side of the layer of fiberglass is bonded to the layer of vapor retarding material by a second deposit of hot melt glue. The vapor retarding layer may be a plastic material, such as polypropylene or a reflective material, such as aluminum.
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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
"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.
Asbestos: How to find and recognize asbestos in Buildings - visual inspection methods, list of common asbestos-containing materials
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print).
Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
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:
2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
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.
"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
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 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.
The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
"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
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.
Re-Bath, tub lining products is a bath tub relining manufacturer and distributor located in Tempe, Arizona - see rebath.com
Rubblestone Wall Filler: See this Lartigue House using exterior-exposed rubblestone filler between vertical timbers of a post and beam-framed Canadian building.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, $69.00 U.S., 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: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a ten percent discount on any number of copies of the Home Reference Book purchased as a single order. Just enter HRBUS10 in the order payment page "Promo/Redemption" space.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones