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Do Radiant Barriers Save Cooling or Heating Energy? InspectAPedia®  -     Radiant barriers can save on cooling cost and may save a little on heating costs as well Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices

This article discusses the effectiveness and installation options of radiant barriers as building energy savers. Sketch at page top and the text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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Article on Radiant Barriers as Energy Saver in Attics or Building Walls

The two links below provide a photocopy of the original two page Solar Age article "Radiant Barriers, they cut cooling bills and help a little on heating too", on the performance of radiant barriers in buildings. Just below the links we provide radiant barrier information updates, radiant barrier product photographs, and we summarize information on radiant heat barriers. RADIANT BARRIERS part 1, PDF form, how radiant barriers work, how radiant barriers save energy - use your browser's back button to return to this page RADIANT BARRIERS part 2, PDF form, second half of the radiant barriers article from Solar Age. "Radiant barriers are highly cost-effective in hot climates because they sharply reduce cooling loads. They work as if by magic, but the magic is based soundly on principles of physics." This article explains the science of radiant barriers (summer heat travels through attics primarily as radiant energy, so when the sun heats up the roof to 190 degF (black roof) or perhaps 160 degF (on a white roof surface) heat is conducted through the roof materials to the roof sheathing where it radiates heat to the area below.

Where to Install a Radiant Heat Barrier, & Which Way to Face the Foil?

Our radiant barrier photos just above show the installation instructions printed on the kraft paper facing of ALFOL, an aluminum foil radiant barrier "insulation blanket" product sold and installed in many homes in the 1940's. The waterproof kraft paper covering of this radiant barrier "insulation" product faces down into the attic space - a design later research showed was not the best performer. Dead air trapped between the double layers of foil above the kraft paper provided a slight increase in the R-value of this product.

A radiant barrier interrupts the radiant heat transmission using a reflective barrier (see our page top photograph of a radiant heat shield installed in a 1950's home). Research by the Florida Solar Energy Center (FSEC) found that radiant barriers work best when installed with foil-face down (towards the building interior) and applied under the roof sheathing.

This roof heat transmission mechanism explains why air conditioning equipment or duct work located in a hot attic or roof space will have to work extra hard to cool the building unless it is adequately insulated from these hot conditions.

What are the Energy Savings from Radiant Heat Barriers?

... a radiant barrier will cut cooling costs by 10 to 15 percent when added to a house with R-19 ceiling insulation. Adding an R-11 batt to the R-19 batt would save only about 5 percent.

Remember, this advice was for Florida, primarily a cooling climate, not a heating climate. Cooling cost savings are a net advantage in the U.S. about as far north as Baltimore.

In the only northern city they modeled - Chicago - the extra insulation outperformed the radiant barrier on an annual basis,due to the much better winter performance of the insulation. In general, wherever the cooling load is large enough to justify installing central air conditioning, a radiant barrier is worth considering.

Besides the radiant heat barrier article linked-to above, we need to issue a radiant barrier warning and to raise a question or two about this energy savings approach:

Radiant barriers are not a substitute for insulation in cold climates

In older homes built between 1950 and about 1965 we have found radiant barriers installed alone, with no building insulation. In cold climates such as New York and New England, an uninsulated home may be cooler in summer with a radiant barrier installed, but this system provides only modest heat loss savings in cold weather.

In the our radiant barrier "insulation" photograph at left and home shown in our page top photo of a radiant heat barrier, the foil was sold as "insulation" and no other insulation was installed. Each was a costly house to heat in cold weather - the new owners would want to install insulating batts in the attic floor.

In the Solar Age article above, radiant heat barriers are installed under the roof on a building at which insulation has been installed in the attic floor as well as the building walls. That's the way to do it.

Installing radiant barriers as a substitute for actual building insulation performs poorly. Radiant barriers work best blocking radiation of heat downwards towards the occupied space. In cold climates the radiant barrier actually prevents desired heat gain in the home during daylight hours. The Solar Age article above correctly concludes that while a radiant barrier may provide a small net heating cost savings (over no insulation at all) a better approach would be to add insulation to the building. "According to ASHRAE data, a radiant barrier at a 45 deg. slope with heat flow upward is worth about R-2.5."

The article adds that installing radiant barriers on building walls is less effective than under roofs. "A radiant barrier facing a 3/4" [air] space provides about R-3. If the barrier is included as part of an insulation system (such as foil faced insulation that includes this material as a vapor barrier) that's great. But don't use radiant barriers as a substitute for wall insulation.

Radiant barrier researchers think roof venting is unnecessary - are they right?

According to the Solar age article above, researchers think that venting the roof cavity above the radiant heat barrier is unnecessary because "... the radiant barrier does such a good job of blocking attic heat gain".

What is missing from that analysis is a more comprehensive consideration of how building work in all weather and moisture conditions, especially in cooling and humid climates, and also missing is a possible impact on roof shingle life when the roof is allowed to heat to the highest possible temperatures.

We prefer to provide under-roof ventilation in buildings, not just to permit hot attic air to escape in summer (drawing in cooler air from outside at the roof eaves), but also to permit un-wanted moisture to escape year-round. Failure to adequately ventilate attics has been shown to lead to condensation in cold weather and in some homes, severe mold contamination.

In our references list below we provide links to the full set of US Department of Energy Documents giving extensive research data and installation advice for radiant barriers. Of those documents, we recommend in particular, the following:

• "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.

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.

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INSULATION & VENTILATION INSPECTION & IMPROVEMENT
AIR BYPASS LEAKS
AIR LEAK DETECTION TOOLS
AIR LEAK MINIMIZATION
AIR SEALING STRATEGIES
ASBESTOS IDENTIFICATION IN BUILDINGS
ATTIC LEAKS, CONDENSATION & ATTIC MOLD
BATHROOM VENTILATION
BASEMENT LEAKS Moisture or Mold
BASEMENT HEAT LOSS
BLOWER DOORS & AIR INFILTRATION
BRICK LINED WALLS
BUCKLED FOUNDATIONS due to INSULATION?
CATHEDRAL CEILING INSULATION
CRAWL SPACES
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
ENERGY SAVINGS in BUILDINGS
ENERGY SAVINGS PRIORITIES
ENERGY SAVINGS RETROFIT CASE STUDY
ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE
ENERGY SAVINGS RETROFIT OPTIONS
ENVIRONMENTAL HAZARDS
FIBERGLASS INSULATION
FIBERGLASS HAZARDS
FIBERGLASS MOLD
FRAMING DETAILS for BETTER INSULATION
FRAMING DETAILS for DOUBLE WALL HOUSES
FREEZE-PROOF A BUILDING
HEAT LOSS CALCULATIONS
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HEAT LOSS DETECTION TOOLS
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  BASEMENT HEAT LOSS
HEAT LOSS R U & K VALUE CALCULATION
HOUSEWRAP AIR & VAPOR BARRIERS
HOUSEWRAP - TYVEK INSTALLATION DETAILS
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INSULATION & VENTILATION INSPECTION & IMPROVEMENT
INSULATION CHOICES
INSULATION FACT SHEET- DOE
INSULATION IDENTIFICATION GUIDE
  Asbestos Identification in Buildings
  Asbestos-Free Insulation Materials
  Balsam Wool Batt Insulation
  Cotton Insulating Batts
  Cellulose loose fill insulation
  Concrete insulation, light-weight
  Fiberglass Insulation
  Foam Board Insulation
  Foam Insulation Types - Visual Id
  Homasote & Other Insulating Board
  Icynene Foam Spray Insulation
  Insects & Foam Insulation
  Mineral Wool - Rock Wool Insulation
  Mold in Fiberglass Insulation
  Mold in Foam Insulation
  Paper Duct Insulation
  Perlite Insulation
  POLYISOCYANURATE FOAM INSULATION
  POLYSTYRENE FOAM INSULATION
  RADIANT BARRIERS
  Urea Formaldehyde Foam Insulation UFFI
  URETHANE FOAM Deterioration, Outgassing
  Vermiculite Insulation
INSULATION MOLD
INSULATION LOCATION for BASEMENTS
INSULATION LOCATION for CAPES, CRAWLSPACES
INSULATION for GREENHOUSE or SOLARIUM
INSULATION MATERIAL IDENTIFICATION GUIDE
INSULATION R-Values & Properties
Insulation Values of Log Home Walls
INTERIORS of BUILDINGS
MOISTURE CONTROL in BUILDINGS
Mold Growth Resistance of Foam Insulation
MVOCs & MOLDY MUSTY ODORS
ODORS & SMELLS DIAGNOSIS & CURE
RADIANT BARRIERS
ROT, FUNGUS, TERMITES
  TERMITE SHIELDS vs TERMITICIDE
ROT, TIMBER FRAME
SOLAR ENERGY SYSTEMS
SOUND CONTROL in BUILDINGS
STAIN DIAGNOSIS
THERMAL MASS in BUILDINGS
THERMAL MASS in UPSTAIRS
THERMAL TRACKING & HEAT LOSS
  Ceiling Thermal Tracking Marks
  Wall Thermal Tracking Stains
  Floor Carpet Thermal Tracking Stains
  Air Bypass Leaks Marks on Insulation
  Thermal Tracking to Diagnose IAQ
  Stains HVAC Supply Registers
  Pet Stains on Floors
  Pet Stains on Walls
  Human Occupant Stains on Walls
  Stains from Candles, Woodstoves, Fireplaces
  Other Stains on Indoor Walls & Ceilings
  What to Do About Thermal Tracking
VAPOR BARRIERS & AIR SEALING at BAND JOISTS
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
  Air Bypass Leaks, Thermal Tracking
  ATTIC CONDENSATION CAUSE & CURE
  BATHROOM VENTILATION
  Blocked Soffit Intake Vents
  BRICK VENEER WALL INSULATION
  CATHEDRAL CEILING INSULATION
  CRAWL SPACE VENTING & Dryout Procedures
  BLOWER DOORS & AIR INFILTRATION
  HEAT LOSS: How to Calculate Heat Loss in a Building
  HOUSEWRAP AIR & VAPOR BARRIERS
  HUMIDITY LEVEL TARGET
  ICE DAM PREVENTION
  MOISTURE CONTROL in BUILDINGS
  Crawl Space Ventilation
  MOISTURE CALCULATIONS
  MOISTURE PROBLEMS: CAUSE & CURE
  ROOF VENTILATION SPECIFICATIONS
  ROOF VENTING ENERGY SAVING DETAILS
  ROOF VENTING NEEDED?
  Soffit Ventilation
  VENTILATION DESIGN PROBLEMS & SOLUTIONS
  WHOLE HOUSE VENTILATION Strategies
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING

• 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."
  
• 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.
  Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in BUILDINGS, and other topics.
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• 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.
• "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.
• "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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