Radiant Barrier And Roof Temperatures
Summary: Radiant Barriers DON’T harm roofing materials or void shingle warranties.
Because radiant barriers reflect the radiant heat rays that strike them back in the opposite direction from which they came, modest concerns have been raised about the possible increase in roofing temperatures and the effect of increased temperatures on roof shingles.
According to the Reflective Insulation Manufactures Association’s independent study, a radiant barrier may cause an increase in shingle temperature between 2-5 degrees Fahrenheit on a hot summer day. Given that shingle temperature at that time is in the range of 160-190 degrees, this increase is negligible and does not accelerate shingle degradation. Although roofing manufacturers were concerned about shingle failure in the years when radiant barriers were first used, it is no longer an issue. Roofing material warranties are not affected by the installation of radiant barriers.
The Florida Solar Energy Center also conducted a study on the use of radiant barriers under shingle roofs and found that properly installed radiant barriers do not void the warranty for the shingles.
Radiant Barrier Scams And Exaggerations
There is a lot of misinformation about radiant barriers out there. Beware of scams, such as paint-on radiant barriers, or too-good-to-be-true statistics about the energy savings they can bring, especially in cooler climates. Minnesota officials, for example, have advised against radiant barriers for state residents. This was in response to aggressive radiant barrier marketing efforts in that state. Consult with your state, local, or regional planning department about whether a radiant barrier is a good investment in your climate.
How Much Will I Save On My Heating And Cooling Bills
Your savings on heating and cooling bills will vary, depending on many factors. Savings will depend on the type of radiant barrier application, the size of your house, whether it is a ranch style or a two story house, the amount of insulation in the attic, effectiveness of attic ventilation, the color of the roof, the thermostat settings, the tightness of the building envelope, the actual weather conditions, the efficiency of the heating and cooling equipment, and fuel prices.
Research on radiant barriers is not complete. Estimates of expected savings, however, have been made using a computer program that has been checked against some of the field test data that have been collected. These calculations used weather data from a number of locations to estimate the reductions in heating and cooling loads for a typical house. These load reductions were then converted to savings on fuel bills using average gas furnace and central air-conditioner efficiencies and national average prices for natural gas and electricity.
If you want a better estimate based on your local fuel prices or other equipment efficiencies, you may use the worksheet in the Appendix. Local fuel prices may be obtained from your local utilities.
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Does Radiant Barrier Work In Winter Or Cold Climates
If you live in a colder climate, you may wonder if there is any benefit to installing a radiant barrier in your attic. I was surprised to learn that there are in fact energy saving benefits for northern states.
Does a radiant barrier work in winter? A radiant barrier can reduce energy loads by up to 10% in winter based on independent studies. By reducing heat transfer from the living space into an unconditioned attic, a properly installed radaint barrier can complement the energy-saving efforts of traditional insulation.
I ran across multiple studies during my research that found deductions in heat transfer from the conditioned space, especially when the radiant barrier was layed across the attic floor over the insulation instead of being stapled to the rafters. To avoid condensation issues, a perforated radiant barrier may be the best choice for this application.
The Office of Scientific and Technical Information found heat loss was reduced by 6-8% in their study . Another study, focusing on thermal performance and using a climate simulation process found the reduction in heat transfer to be closer to 10% depending on the material and installation approach used .
This YouTube video was posted by a gentlemen in New England. He gives his first-hand experience of the benefits that he has seen from radiant barrier installed on the attic floor in a cold climate.
What Is Radiant Barrier Reflective Insulation And Irccs
Myths & Misconceptions About Radiant Barriers, Reflective Insulation and Interior Radiation Control Coatings
RIMA International is dedicated to distributing reliable reflective insulation, radiant barrier or interior radiation control coating product technical information to consumers. This information will help expose exaggerated claims made by those who have misrepresented their performance. We invite readers to view the technical and library pages for comprehensive discussions on technical issues.
Listed below are some of the more common misrepresentations found on the internet and in some literature.
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The Attic Doesnt Have Ductwork
An attic with ductwork remains cool during the summer. However, if you have an older home, chances are you have an unconditioned space.
A radiant barrier can do the job just as well and prove less expensive in the long run. They can reduce the heat in your home and thus reduce the need for energy-sapping air conditioning at the same time.
If the heat transfer between your home and the exterior is relatively high, your HVAC system struggles to maintain a comfortable temperature. This instance is where the radiation barrier proves invaluable. It stops heat waves from moving through your home, thus reducing heat retention by about 10%.
Is Spray Foam Bad For Shingles
One of the biggest fears people have is that spray foam will make shingles curl because they overheat. This misconception came about when people believed insulation was a heat source and were concerned about having a hot roof. In actuality spray foam is a barrier between two areas of different temperatures, for example, your attic space compared to your snowy roof.
If you dont know the term hot roof, Im sure youve heard of an unvented attic. If your roof deck has been insulated, that means your attic space is now part of your homes conditioned space. This method of insulating the attic can actually be good for your roof because it can help prevent ice dams.
The Florida Solar Energy Center did a study a few years ago during the peak summer months in Floridaa state that gets much hotter than New Englandmeasuring the temperatures of roof shingles above an attic with a radiant barrier. Depending on the color of the shingles, the study found the shingles peak temperatures were between 2- and 5-degrees Fahrenheit higher than the temperature of shingles in the same conditions without a radiant barrier.
What this study means is that you can insulate the roof deck of your home with foam insulation without any adverse effects to your shingles. Foam insulation creates thermal resistance, which is keeping the hot air out during the summer and the cool air inside.
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How To Tell If Your Radiant Barriers Are The Source Of The Problem
This is an easy diagnosis. All you have to do is take a quick peek into your attic. If your radiant insulation is installed on the roof trusses or decking, reflective side in, you should be fine. If its been laid over the top of the fiberglass insulation on your attic floor, youve got your insulation contractor to blame. Talk to an insulation specialist about removing your existing reflective insulation and getting it re-installed properly. If you dont, and youre already experiencing problems with moisture buildup, its only going to get worse.
What About My Shingle Warranty
Shingle warranties should not be subject to cancellation by the manufacturer on the basis of radiant barrier installation. However, it may be wise to review the warranty to be sure that work of this nature will not void it. You may want to inquire directly of the manufacturer. Any changes in warranty should be substantiated in writing.
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Will Radiant Barrier Damage My Shingles
This is a valid concern based on the concept of what a radiant barrier is designed to do. It is essentially intended to reflect radiant heat away from the attic. Since it is installed under the roof, it is reasonable to conclude that additional heat buildup will result in the shingles and possibly cause damage. To find out the facts, however, we need to look at the research.
Does a radiant barrier cause roof damage? According to the Florida Solar Energy Center, shingles only heat up by an additional 2 to 7 degrees compared to shingles that are not over a radiant barrier. This depends to some degree on the color and type of roofing shingles installed. .
Although the variance in heat buildup with a radiant barrier is minor, it is worth noting and understanding the difference in roofing color as it relates to attic temperatures.
Darker color roofs absorb light more readily than light colors. The darker your roof, the more light is absorbed and the hotter the roof will be. The lighter and more reflective a rooftop is, the cooler the roof which means less heat is radiating into the attic. .
My point to this is not that you need to go out and buy new roofing material that reflects heat. The point is that if you have a darker roof as many of us do then you will likely benefit from a radiant barrier even more!
Your Roof Will Not Bake By Adding A Radiant Barrier
So, adding AtticFoil Radiant Barrier to your roof redirects the heat being absorbed by your home and therefore keeps your attic, and ultimately your home, more comfortable and energy efficient. The small increase in your overall roof temperature is not enough to have a significant impact your roof, shingles, or any other part of the roofing assembly.
For more information on the effect of radiant barrier on exterior roofing materials, you can read the technical bulletin published by RIMA here. Below are the details of a little test we did to further prove these facts. Our results were consistent with those of national/government testing.
A view of the inside of the test attic. Three pieces of AtticFoil Radiant Barrier Foil insulation are attached to one side with a single strip extending off to the side.
This ia an overlay of thermal image over the regular image. You can clearly see where the foil is stapled up. There is about two feet at the bottom with no foil and about 18 from the top due to where the three pieces ended. We also did not put foil over the last rafter bay on the left to show clearly where the foil ends.
This image shows the roof over the radiant barrier measuring 7ºF hotter than the area without a radiant barrier . Typically, the roof temperature over a radiant barrier will increase less than 10ºF which should not have a significant impact on the performance of a roof.
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Your Roof Gets Direct Sunlight
The primary job of a radiant barrier is to reduce heat gain from a hot roof, and a roof that gets more sun exposure will get hotter. If you live in the northern hemisphere and your roof is south-facing, a radiant barrier will be more effective on that side.
You may also want to consider installing a radiant barrier in barns or outbuildings that are poorly or not at all insulated. Buildings with metal roofs could benefit greatly from radiant barriers, since metal can get very hot under the sun.
An Interesting Fact About Roof Temperatures And Buildings Without Radiant Barriers:
Without a radiant barrier in place, radiant energy from the sun heats the roof decking and then radiates from the roof decking into an attic and is absorbed by any existing heat absorbing insulation in the attic. As the sun sets and the attic temperature begins to level itself with the outdoor ambient temperature, the attic insulation is still radiating the heat it has absorbed throughout the day.
In essence, the heat absorbing insulation is similar to a hot piece of coal in your attic that is slowing emitting heat throughout the early evening therefore, extending an increase in roof temperatures into the early evening than if a radiant barrier had been in place.
Without a radiant barrier in place, your existing insulation and roof stay hotter into the early evening causing your air conditioning system to work harder and longer into the evening to keep your home cool.
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Your Roof Isnt Shaded
A radiant barriers main job is designed for is to reduce heat gain. A roof exposed to the sun completely will get way hotter than a shaded one.
So if you live in the northern hemisphere and your home faces south, get a radiant barrier installed to offset the heat. Besides a house, you can also install it over a barn or outbuildings with poor or no insulation, including buildings with metal roofs that can bake under the sun.
Does Spray Foam Damage Roof Shingles
Has anyone ever told you that spray foam insulation will damage your roof shingles and void your warranty? Guess what? They are wrong!
Founded in 2007, The Green Cocoon has more than 14 years of experience insulating attics. As a result, we have heard many stories about shingles. But, the biggest fear is that your roof shingles will be damaged by spray foam insulation. Consequently, we are helping alleviate homeowners fears by showing them the benefits of having spray foam insulation.
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What Is The R
This question is often asked and is an indication that there is still some confusion between radiant barriers and reflective insulation. Radiant barriers are always installed with the reflective, low-e , surface facing an open air space. Because of a radiant barriers low emittance and high reflectance, it can block about 90 97% of the radiant heat that strikes the surface, significantly reducing the total heat transfer in and out of a building. However, due to variations in building construction, location and climate one cannot assign a unique R-value to this application. Calculations can and have been made for very specific applications, but every given application requires its own evaluation.
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Whats The #1 Radiant Barrier
If youre considering a radiant barrier, go with the best.
LP TechShield Radiant Barrier is Americas original and #1 brand of radiant barrier sheathing. You cant go wrong with it.
Theres one more reason to trust the homes you build to this proven performer. Its backed by a 20-Year Transferable Limited Warranty. So you and your homeowners get two decades of peace-of-mind protection.
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Radiant Roof Barriers: Are They Rotting Your Roof
Roofs can rot, especially in areas of high humidity and heavy moisture. While radiant barriers take much of the blame, rotting roofs are usually caused by poor ventilation, not radiant barriers. Ventilation allows fresh air to replace the existing air and circulate within an attic. This keeps the attic, and your roof, at a moderate temperature in summer and winter, and extends the life of your roofing materials. While improperly installed radiant barriers can cause moisture problems, its relatively rare. Usually poor attic ventilation is to blame for any moisture or rot problems you experience with your roofing.
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