Roof Color - what is the best color for a roof?

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
References

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This article describes the effect of roof color on shingle (or other roofing material) life and the effect of roof color on building cooling load. We provide a table of the effects of various roof colors on building cooling loads and costs.

Choices of Roof Color & Effect on Energy Use & Roof Shingle Life

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. This website provides un-biased articles about many common roofing materials, installations, inspection, defects, roofing repairs, and products.

The question-and-answer article about the effects of roof color on building temperature and on roof life discussed here quotes-from, updates, and comments an original article 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.

Light colors would be in order there.

Roofing Color Effect on Cooling Costs

Table 2-18 Roof color and cooling Loads (C) J Wiley, S Bliss

As explained in Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

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.]

-- Adapted with permission from Best Practices Guide to Residential Construction.

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.).

See

E. I. Griggs, T. R. Sharp, J. M. MacDonald, Guide for Estimating Differences in Building Heating and Cooling Energy Due to Changes in Solar Reflectance of a Low-Sloped Roof, U.S. Department of Energy, Oak Ridge National Laboratory Report #ORNL-6527, 1989. Web search 02/01/2011, original source http://epminst.us/otherEBER/ornl6527.pdf
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.

Q & A: What is the Best Roof Color? - How does roof color choice affect energy usage and shingle life? - PDF form

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Technical Reviewers & References

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

Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
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
"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.
E. I. Griggs, T. R. Sharp, J. M. MacDonald, Guide for Estimating Differences in Building Heating and Cooling Energy Due to Changes in Solar Reflectance of a Low-Sloped Roof, U.S. Department of Energy, Oak Ridge National Laboratory Report #ORNL-6527, 1989. Web search 02/01/2011, original source http://epminst.us/otherEBER/ornl6527.pdf
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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