Understanding Cool Roofs and Insulation For Energy Efficiency

05 Dec

Can you benefit from a Cool Roof? Or are you better off investing in more insulation? No doubt, a cool roof can help many building owners save money while protecting the environment but not everyone should rush to get one.Your money might be better spent on attic insulation depending on where you live as well as your specific attic situation.

The U.S. Department of Energy has published an excellent guidebook on cool roofs (link below). The guidebook was created to help builders and home owners understand how cool roofs work. Read more

Best Available Research on Attic Fans and Power Ventilators

09 Jul

Do attic fans lower the cost of cooling your home?

Solar attic vents are not good for energy efficiencyAre solar attic fans worth installing? Common sense suggests they would be but are powered attic fans really a good idea for energy efficiency based on research and science? I have a master’s of science degree and my initial belief was it made sense. It just seems logical that a cooler attic would lower the cost of cooling the house in summer. While researching radiant barriers for the attic and reflective paint (Kool Seal Premium White) for our metal roof, I came across a few articles strongly suggesting powered attic fans were a dumb, and possibly dangerous, idea based on science. Here’s what I found so far and why I removed my attic fan:

  • The Scientific Spin on PAVs (powered attic ventilators – fans): Cooling off hot attics with powered attic ventilators (PAVs) seems like a good idea. After all, doesn’t cooler attic air mean less work for the HVAC system, longer shingle life, and reduced energy costs? Unfortunately that’s more myth than fact.
  • Drawbacks Of Powered Attic Ventilators:Powered attic ventilators, already suspected of using more energy than they save, can also create excess moisture, structural problems, discomfort, and combustion safety problems for home occupants, according to a recent study. John Tooley of Natural Florida Retrofit, and Bruce Davis of Alternative Energy Corporation’s Applied Building Science Center in North Carolina, presented “The Unplanned Impacts on Houses by Powered Attic Ventilators” at the 1995 meeting of the Energy Efficient Building Association.The paper describes research conducted on eight homes over a period of three months. As a result of this research, Davis said that he wouldn’t recommend the use of powered attic ventilators. He emphasized, “If someone chooses to use a powered attic ventilation strategy, they need to do additional performance tests and take responsibility to be sure that it won’t cause other problems.” The potential for hazardous conditions is particularly high in homes with combustion gas appliances, because the ventilators can create negative pressures that cause backdrafting.
  • Energy Star: Attic Fan Ventilation – Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. However, if your attic has blocked soffit vents and is not well-sealed from the rest of the house, attic fans will suck cool conditioned air up out of the house and into the attic. This will use more energy and make your air conditioner work harder, which will increase your summer utility bill.
  • Ask the Builder: Powered Attic Fans – Attic Insulation Facts: “I used to recommend PAVs [powered attic ventilators – fans] for houses, but I don’t anymore.”
  • Building Science, Unvented Roof Summary Article

The best solution appears to be making sure your attic is well insulated and well-ventilated using passive vents and natural air flow. Inspect your attic insulation and ventilation, or have a contractor do so for you. Just add more insulation or natural (passive) ventilation, if needed. Both measures will reduce the cost of cooling and heating your home; no electricity required and they are perfectly quiet.

ADDITIONAL ENERGY EFFICIENCY RESOURCES

  • Contact the local power company website and local energy associations for more information on constructing an energy efficient home in your area.
  • Building Science Corporation, Unvented Roof Summary Article: Excellent resource with in-depth research and hard-core science. Building Science is dedicated to teaching and providing factual information concerning building science and energy efficiency. This resource is used extensively by builders “in the know” when it comes to energy efficiency.
  • Building Science Guides and Manuals: Good place to start if you want reference documents for some of the most important building science topics.
  • Building Science Information Sheets: Fact sheets and overviews; another great place to start for those relatively new to the field.
  • Energy Star : The Energy Star website has extensive information on energy efficiency.
  • Geothermal Heat Pump Consortium: Geothermal is the most energy efficient method known today for heating and cooling. However, you will benefit by first making sure your home or building is insulated properly and as air tight as possible (within the limits of the appropriate building codes and safety concerns) before considering an expensive geothermal system.

ENERGY EFFICIENCY PRODUCTS

Whether or not you are using an attic fan and you own a fireplace, a great product to consider is a fireplace plug. Battic Door sells several energy conservation products including a simple fireplace plug; stops drafts and saves energy by sealing the chimney when not in use:

Fireplace Plugs Save Energy Stops Fireplace DraftsThe Fireplace Draft Stopper is an inflatable urethane chimney plug balloon pillow measuring 38″ x 16″. A round Fireplace Plug is also available. It is quickly and easily installed in the fireplace just below the damper level. The Fireplace Plug can be adapted to work in almost all fireplaces. Even if you have an unusual construction, the Fireplace Plug can be successfully installed in less than 2 minutes.

The Fireplace Plug is provided with 5 “slittable” areas that can be cut to provide an opening for a damper handle. As the Draftstopper is inflated it seals around the damper handle sealing the opening (helps reduce energy costs). Easy, quick and clean installation.

 

Will You Reduce Energy Costs by Painting Your Roof White

08 Jul

My metal roof was red, hot, and desperately needed painting. After spending some time inspecting the roof, I quickly realized how incredibly hot the red paint became even on a modestly hot spring afternoon. Why repaint the roof red since it gets so hot? I thought there must be a better solution so I started investigating roof paints. Fortunately, I wasn’t the only one wondering if a lighter-color roof would reduce heat gain inside the attic and save energy. Also, I quickly learned a lot about “reflective” paints, radiant heat, and the best ways to insulate the attic to reduce cooling and heating costs.

One research article I found informative and one I recommend reading is, Cool Roofs For Hot Climates by Dan Parker, a senior research scientist with the Florida Solar Energy Center (2003). The following is from the article:

Reflective roofs work because they stop the rooftop heat before it ever gets going. The sun’s rays hit the roof at the speed of light, and at the speed of light they bounce back into space. White or light-colored materials work best, but some new dark pigments reflect enough invisible infrared radiation to reject a lot of solar energy. And whether you’re applying tile, metal, membranes, or even asphalt shingles, choosing a more reflective version seldom adds cost.

The figure below graphically depicts the best solution for energy efficiency is a reflective white metal roof:

energy savings research white roof

After reading this article and numerous others, I painted my metal roof with Kool Seal® Premium White Elastomeric Roof Coating which I purchased at the local hardware store (ACE Hardward has it here in Richmond, VA).

Additional Metal Roof Information

Roof Costs and Energy Savings: According to the Metal Roofing Alliance, white-painted metal roofing has the highest solar reflectance value of any roofing product available and can save you up to 40% of your annual energy bills.

According to statistics from McGraw-Hill Construction Research and Analytics®, the number of homes with metal roofs has more than tripled over the past decade, moving metal from 3% of the overall U.S. market to 10%.

Some homeowners’ insurance programs allow discounts for homeowners with specific weather-resistant metal roofing products. Contact your insurance agent to determine if your home qualifies.

metal roof benefits fire resistant

Photo taken after the 1991 Oakland, California firestorm. Burning embers destroyed all of the homes in the neighborhood, except the masonry home that was roofed with Stone-Coated Steel Roofing.  While all of the neighbors fought (without success) to save their homes by watering down their asphalt roofs, burning embers did not ignite the steel roof. The house with the steel roof survived while all others around it were destroyed. (SOURCE: Metal Roofing Alliance: Lower Your Insurance with Weather-Resistant Metal Roofing)

Kool Seal® Premium White Elastomeric Roof Coating

FEATURES AND BENEFITS
(SOURCE: Provided by the manufacturer, see product description, surface prep, etc. here – PDF)

  • Energy saving up to 35%
  • Reflects 90%+ of the sun’s rays
  • Designed to be durable in any climate
  • Higher solids for better coverage
  • Forms a thick rubber-like blanket of protection
  • Expands and contracts – clings to your roof in all temperatures
  • Protects against moisture
  • Cured elastomeric film is mildew and algae resistant
  • Helps to absorb sound
  • Environmentally compliant
  • Soap and water cleanup – while wet

Energy Efficient Roofing Video by Tod Miller

Other Useful Articles Pertaining to White Roofs: