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Keeping Your Home Cooler with a Radiant Barrier


On the Job in Florida, Larry Janesky, President and Owner of Dr. Energy Saver, installed a radiant barrier in an attic to make this homeowner's home more comfortable and to help reduce the cooling bills. Florida's warm sun causes most roofs, which absorb the sun's heat, to get really hot. That heat is then transferred to the attic where it can reach scorching temperatures as high as 140 degrees! When the attic, like this one, stores the air ducts, the 55-degree air in the ducts is surrounded by the 140-degree heat before it reaches the living space-- making the air conditioner work much harder than needed to keep the house cool and comfortable.


Installing A Radiant Barrier

Installing A Radiant Barrier

One of the big issues in a southern climate is reducing the cooling load. We have air conditioning to cool a house, but what is making it hot? Well, it is the sun. It is a hot roof and we can reduce the load on the air conditioning system and make the house more comfortable by installing a radiant barrier. Let's take a look. When this roof heats up to 150 degrees, or more, from the sun in the summer this heat will radiate down into this attic and make it incredibly hot. The air in this attic could be 130 or 140 degrees. Now look at what we have here, this is a supply duct. This supply duct is taking cold air from the air conditioning system that we paid to cool and cooling it down to approximately 55 degrees and just trying to distribute that 55 degrees air to all the rooms in the house. Well we are running this duct 55 degrees air inside through 135 degrees attic, unbelievable an 80 degrees difference between the air on this side of the duct and inside this duct and there is just a little bit of insulation on this duct.


Radiant Barrier

15 or 20° Difference in the Temperature of this Attic.

A radiant barrier is a reflective surface that we are going install not against the roof deck, but at least an inch away to reflect the heat from the roof back out so that heat doesn't radiate down this way and heat this attic so much. Now it is not going to keep the attic cool per se. We are still going to have a hot attic, but it is not going to be as hot. This could make it as much as a 15 or 20 degree difference in the temperature of this attic.


Spray Foam Seals It Tight

Cooler Attic

Now if we put this thermal imaging camera up a little we can see that the space just above the radiant barrier is 113 degrees or so. So we have a 20 degree differences between the spaces above the radiant barrier compared to the space below the radiant barrier. That is going to make this entire attic 20 degrees cooler huge difference over a 1200 square feet of roof and these ducts aren't going to be in such a hot hostile environment. Not as much heat would go through the ducts and add to warm that air, as it is coming from the air conditioning system to the rooms, and the ceilings will be a lot cooler. It will also prevent so much heat radiating down through the dry wall and ceilings on to you.


Blown Insulation

A Cooler More Efficient Attic

Here is another example of the roof temperature question with radiant barrier. Right here we have radiant barrier and that part we do not and it has been about an hour, an hour and a half in this direct sun that since we installed it. It is about 123, 124 degrees over here and over here where there is no radiant barrier it is about 117 so it is a 7 degrees difference here on this side of the house where there is direct sun, full sun, about a 7 degree difference and that is what the studies show is typically a 5, 7 degree difference. Again well within the design limitations of the shingle so it is no problem. It is very comfortable up here in this attic now that we have the radiant barrier installed. This makes a dramatic difference in how much heat is beating down on your ceilings

Full Video Transcript Below:

Hey. I am Larry Janesky from Dr. Energy Saver. You know we have Dr. Energy Savers all over the United States and in our country we have so many different climates. We have coastal climates. We have mountain climates. We have dry hot climates like in the southwest. We have cold climates, we have mixed humid climates and we have hot humid climates as represented by where we are today, in Central Florida. One of the big issues in a southern climate is reducing the cooling load. We have air conditioning to cool a house, but what is making it hot? Well, it is the sun. It is a hot roof and we can reduce the load on the air conditioning system and make the house more comfortable by installing a radiant barrier. Let's take a look. When this roof heats up to 150 degrees, or more, from the sun in the summer this heat will radiate down into this attic and make it incredibly hot. The air in this attic could be 130 or 140 degrees. Now look at what we have here, this is a supply duct. This supply duct is taking cold air from the air conditioning system that we paid to cool and cooling it down to approximately 55 degrees and just trying to distribute that 55 degrees air to all the rooms in the house. Well we are running this duct 55 degrees air inside through 135 degrees attic, unbelievable an 80 degrees difference between the air on this side of the duct and inside this duct and there is just a little bit of insulation on this duct. So, what's happening is we are cooling the air at the air conditioning system and then heating it partially before it gets to the rooms that we want to cool? This makes absolutely no sense and here in lies one of the big issues for homes in any climate, really. It is the reverse when you have a cold attic and heated duct same idea, but in reverse.

There are several strategies we are going to take to make this home more energy efficient and one of them is going to be a radiant barrier. A radiant barrier is a reflective surface that we are going install not against the roof deck, but at least an inch away to reflect the heat from the roof back out so that heat doesn't radiate down this way and heat this attic so much. Now it is not going to keep the attic cool per se. We are still going to have a hot attic, but it is not going to be as hot. This could make it as much as a 15 or 20 degrees difference in the temperature of this attic. Now, 15 to 20 degrees doesn't sound like a lot, but when you multiply that over the entire square footage of this ceiling and these ducts it makes a big difference. When we talk about surfaces and how they influence the space that we are in we have to talk about the temperature of those surfaces, the temperature difference and how big those surfaces are and this is just the whole top of the house is 15 to 20 degrees cooler and that is gong to make a huge difference in the comfort and the cooling bills for this homeowner.

All right, well, we are in the process of installing the radiant barrier in this attic and it is the middle of the day now and the roof is beginning to heat up. It will get a lot hotter throughout the day and if we look at the temperature here on our thermal imaging camera, the bottom right, in that bulls-eye there is 92, 93 degrees on the bottom of the radiant barrier. Now if we put this thermal imaging camera up a little we can see that the space just above the radiant barrier is 113 degrees or so. So we have a 20 degrees differences between the spaces above the radiant barrier compared to the space below the radiant barrier. That is going to make this entire attic 20 degrees cooler huge difference over a 1200 square feet of roof and these ducts aren't going to be in such a hot hostile environment. Not as much heat would go through the ducts and add to warm that air, as it is coming from the air conditioning system to the rooms, and the ceilings will be a lot cooler. It will also prevent so much heat radiating down through the dry wall and ceilings on to you.

Here is another example of the roof temperature question with radiant barrier. Right here we have radiant barrier and that part we do not and it has been about an hour, an hour and a half in this direct sun that since we installed it. It is about 123, 124 degree over here and over here where there is no radiant barrier it is about 117 so it is a 7 degree difference here on this side of the house where there is direct sun, full sun, about a 7 degree difference and that is what the studies show is typically a 5, 7 degree difference. Again well within the design limitations of the shingle so it is no problem. It is very comfortable up here in this attic now that we have the radiant barrier installed. This makes a dramatic difference in how much heat is beating down on your ceilings. At Dr. Energy Saver our work is very difficult, but we take great pride in what we do. It makes a big difference for home owners just like you. Give us a call today and give us the opportunity to make your home more energy efficient and more comfortable. Dr. Energy Saver Contact us for a home energy evaluation and written estimate.

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