Roof Color - what is the best color for a roof? InspectAPedia® -
Choices of roofing color
Effect of roof color on energy usage
Effect of roof color on life of roofing material
Roof color choice depends on climate and amount of sunlight
Table shows roof colors and effect on cooling load & cooling costs
Effects of roof color & reflectance on cooling energy costs for buildings with low slope roofs
Questions & answers about choosing the color for a roof and the effect of roof color on building cooling load
This article describes the effect of roof color on shingle life and cooling load for a building and we provide a table of the effects of various roof colors on building cooling loads and costs.
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This website provides un-biased articles about many common roofing materials, installations, inspection, defects, roofing repairs, and products.
Also see COOLING LOAD REDUCTION by ROOF VENTS where we describe the effects of various factors together such as roof venting, radiant barriers, and roof color.
Choices of Roof Color & Effect on Energy Use & Roof Shingle Life
The question-and-answer article about Under-Basement Insulation , quotes-from, updates, and comments an original article, (see links just above) from Solar Age Magazine and written by Steven Bliss.
Roof Shingle Color Advice for Northern Climates Compared with Hot High-Sun Climates
Question:
What is the best color for a building roof? In Iowa a well-insulated roof has snow on it for most of the winter, so using dark shingles to absorb solar energy won't work.
In the summer a light colored roof will stay cooler.
So in our hot Iowa summers, when we have to air-condition, is it not better to use light-colored roofs, despite the trend toward dark roofs? -- Victor Gibson, Waterloo IA
Answer:
Roof Color for Iowa-like Climates
In the absence of specific research [back in 1985] on the subject, we polled several roofing experts.
They agreed that roof color alone has a minor effect on the overall energy balance of a well-insulated house in your area (Iowa), winter or summer.
The attic insulation level and under-roof ventilation rate are the most important factors. So for a house in your climate, choose whatever color strikes your fancy.
Our photo (left) shows heavy snow-cover on an asphalt shingle roof in Rhinebeck, NY.
Roof Color Suggestion for Hot Climates
In very hot climates (Florida, Texas, Arizona), however, roof color definitely affects the cooling load of a house.
Roof color choice also may affect shingle life in those climates.
For instance, an attic under a black-colored roof can be 30 degF. hotter than a white-roof attic in Florida, according to the Florida Solar Energy's Phil Fairey.
Tests at FSEC also indicate that simply
switching from dark to white asphalt shingles in a cooling
climate can reduce peak cooling loads by 17% and seasonal
loads by 4%.
The greatest savings resulted from
using white metal roofing (see Table 2-18 shown at left.)
[Click any image or table to see an enlarged version with more detail.]
Effects on Energy Costs of Highly-Reflective Low-Slope Roofs
The U.S. Department of Energy and Oak Ridge National Laboratories have studied and reported on the effects of roof coatings that help deal with building heat load by improved solar reflection.
The graphic shown here, [published by Oak Ridge National Laboratories at ornl.gov/sci/roofs+walls/roof/coatings.html] illustrates that a fresh-coated roof can reduce the annual cooling energy in a low-slope-roofed building by as much as 43% (uninsulated roof)
And remarkably, notice that the uninsulated but fresh-coated roof performed almost as well as a roof with two-inches of insulation. (Of course, two inches of insulation isn't much.).
T.W.Petrie, J.A. Atchley, P.W. Childs and A.O. Desjarlais. “Effect of Solar Radiation
Control on Energy Costs – A Radiation Control Fact Sheet for Low-Slope Roofs,” Proceedings on CD,
Performance of the Exterior Envelopes of Whole buildings VIII: Integration of Building Envelopes.
December 2001. Paper 146. Atlanta, GA: American Society of Heating, Refrigerating and Air-
Conditioning Engineeers, Inc., Copy on file as /roof/Solar_Radiation_Energy_Cost.pdf, original source: http://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergyBackground.PDF
"Highly-Reflective Low-Slope Roofs", Building Envelope Research, Oak Ridge National Laboratories, Andre O. Desjarlais
Oak Ridge National Laboratory,
P. O. Box 2008, MS 6070,
Oak Ridge, TN 37831-6070, web search 02/01/2011, original source: http://www.ornl.gov/sci/roofs+walls/roof/coatings.html
Insuladd® - ceramic-based paint additive to help reflect radiant heat, TECH TRADERS INC.
The Insuladd Company,
412 Waterside Drive,
Merritt Island, FL 32952,
Phone/Fax (321) 453-5060
E-mail: info@insuladd.com
Website: www.insuladd.com/, Product & Technology Review [evaluation report], web search 02/01/2011, original source: http://www.energy.wsu.edu/documents/AHT_Insuladd%5B1%5D.
pdf%20Ceramic-based%20paint%20additive.pdf, Washington State University Extension, Energy Program
Quoting from the product review authored by Geoscience’s
President, Heinz F. Poppendiek, PhD, P.E.: Insuladd is a paint additive that helps it to
reflect radiant energy. Insuladd can be added
to ordinary paint and stucco mixes and used
on both interior and exterior walls, ceilings
and roofs. On exterior surfaces, Insuladd
reflects the radiant energy of the sun to help
reduce the cooling load. On interior surfaces,
Insuladd reflects the radiant energy from
heated objects, reducing energy transfer to the
walls.
Insuladd additive is a blend of microscopic
hollow ceramic spheres. When the paint dries, these little spheres pack together, making a
tight layer with increased reflectivity.
The manufacturer claims that Insuladd paint
additive, when mixed with light-colored house
paint and painted on exterior walls, can reduce
solar heat gain through the walls by over 20%
during the summer. Energy consumption
is reduced regardless of color when using
Insuladd paint additive, but lighter colors are
better. Winter savings from the reflection of infrared radiation from interior painted walls
are less than summer savings, but the reduced
loss of radiant heat from the occupants to
room surfaces makes the space feel more
comfortable.
Poppendiek
calculated that an insulation value of R-6.0
would have to be added to the panel painted
with latex paint to match the heat flux of an
Insuladd-painted panel.
Product & Technology Reviews (PTR) are developed for
Northwest electric utilities. EnergyIdeas Clearinghouse engineers
review published literature for objective, independent test
results. No primary testing was conducted by the reviewer for
the preparation of this document. PTR factsheets describe the
technology, discuss available data, and suggest additional testing
needed to verify energy saving claims.
The link to the original Q&A article in PDF form immediately below is expanded/updated by the preceding online version of this article.
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Additional technical contributors & reference sources for this article are listed below.
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"Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
T.W.Petrie, J.A. Atchley, P.W. Childs and A.O. Desjarlais. “Effect of Solar Radiation
Control on Energy Costs – A Radiation Control Fact Sheet for Low-Slope Roofs,” Proceedings on CD,
Performance of the Exterior Envelopes of Whole buildings VIII: Integration of Building Envelopes.
December 2001. Paper 146. Atlanta, GA: American Society of Heating, Refrigerating and Air-
Conditioning Engineeers, Inc., original source: http://www.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergyBackground.PDF
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