Faqs

A radiant barrier is a highly reflective, low emissivity foil, used as a type of insulation system to permanently reduce energy costs.  Radiant barriers are ‘technically’ not an insulation material, due to the fact they are only a thin sheet of reinforced aluminum foil, however with an air space of approximately 3/4″ or more, radiant barriers have a theoretical R-value of 53. Radiant barriers affect radiant (radiation or Electromagnetic) heat transfer, the single most efficient type of heat transfer, by reflecting that radiation away from the radiant barrier. A typical home will loose heat in the winter and gain heat in the summer and the majority of that heat is radiant heat, so stopping radiant heat transfer in both the winter and summer months is the most effective way to reduce energy cost.

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Your actual savings will vary due to many different factors including: installation location, shading, air duct leakage, air handler location, geographic location, etc.  In the South, you can expect to see a 40% reduction in heat gained through the roof, and this can translate into a 17% savings on cooling costs. Many independent studies and radiant barrier users have tested their results and reported energy savings varying from as low as 12% up to as high as 39%.  Ra-flect™ radiant barrier reduces energy costs in both summer months and winter months because it is double sided, and will keep heat in during the winter months and reflect radiant heat away during the summer. Installing a radiant barrier in your attic is the most cost effective way of reducing your heating and cooling cost and providing the quickest payback of any energy efficient material or product.

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Neither type is better or worse, however the type that you use depends on your geographic location and your application. It is very important that you choose the correct type for your location and application otherwise you may end up causing moisture problems which can lead to mold and or structural damage. We recommend that laser perforated Ra-flect Radiant Barrier be used in ALL of the southern shaded areas(hot humid climates) shown in the image below. The ONLY time when the non-perforated Ra-flect™ Radiant Barrier is appropriate in hot humid climates, is when it is used as exterior building wrap where it is located on the outside of the building insulation. Most northern states or areas of moderate climates can use either perforated or non perforated radiant barrier. If the non-perforated Ra-flect™ Radiant Barrier is used in the white states (shown below), it should be installed in the inside of the structure.

Vapor Drive Map

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The reflectivity of a radiant barrier is pretty easy to understand, the higher the reflectivity value, the more light energy(heat) the radiant barrier is able to reflect. If you look at different radiant barriers, from paints and sprayed on applications to foil rolls, you will quickly see that rolls of aluminum have much higher reflectivity values, making them more efficient than their counterparts.

But what about emissivity, why is this value so important?

Emissivity is basically the ratio of heat energy radiated by a material to the heat energy radiated by a true black body at the same temperature. Yea, I know thats a bunch of physics nonsense, so let me lay it down for you in layman’s terms. Basically, if we were to take a black object (theoretical) which reflects no light energy and absorbs all light energy that touches it, it would have an emissivity value of one (ε = 1). Any real object , weather it be black or not would have an emissivity value of less than 1.

So what this definition is really saying is that the darker an object is, the more light energy it will absorb. And subsequently, the lighter and more reflective a material is, the less light energy it will absorb. This why radiant barriers, even though they have little or no “insulative” properties, can effectively block out most of the radiant heat coming in or leaving a structure.emissivity

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20 Comments

    • Either would work fine as they both give you a little extra on the end to get your staples in. If it were me, I would recommend the 51″, its cost less per sq ft and you can cover more area, quicker.

  1. I live in Oh where winter seems to drive higher heating than summer althjough summers can be well into the 90s for over a month. Im thinking of using it on attic rafters for reflective purpose and on the attic floor for heating. Please advise. Thank you

  2. I live in the Dallas area where heat gain in the summer is the larger problem. Currently, insulation is blown in with 4″, no soffit venting, gable vents at either end of home and insulated ducting in the attic. I was going to install soffit vents with baffles and upgrade the insulation to R49 until I came across your product. Can I use your product in lieu of the baffles as it should provide an adequate barrier against insulation being blown in and blocking the newly created soffit vents. Additionally, if done in this manner would it be preferrable to cut a continuous soffit and vent each rafter space. Additiionally, would it make sense to provide powered exhaust at the gables?

    • Hey Steven,
      In your case I would recommend a combination of soffit vents and ridge vents for a fully passive system. The Radiant Barrier (perforated) can be stapled to the bottom of the roof rafters to create a physical boundary (in lieu of baffles) to stop any additional insulation from blocking the soffit vents. Typically we recommend 1 Sq Ft of attic ventilation per 300 Sq Ft of attic floor space, and that ventilation area should be evenly split between the intake (soffit vents) and the exhaust (ridge vents) for proper flow through the attic space. The radiant barrier can be run up the roof rafters to about 1′ from the ridge, so that the negative pressure created by the ridge vent can suck the attic air from both the tunnels between the rafters, and the attic space below the radiant barrier at the same time. If you choose to use gable vents, just put them up high and make sure the area of the gable vent is equal to the area of the soffit vents, no fan required.
      Adam

  3. I live in New England, 2 story colonial, existing attic insulation of R-39, 2nd floor forced hot air heating system located in attic space. Should I cover both the rafters ( left to right and bottom to top, with 2, 51″ wide strips) and also the attic floor or, just the floor? 2nd floor A/C seems to work much harder than the 1st floor unit located in the basement.

    • If you already have R-39 on the floor of your attic, I would only recommend adding the Radiant Barrier at the roof rafters to keep the attic cooler so the AC is not working as hard during the summer. Lower attic temperatures will equate to a more efficient AC blower unit int he attic.

    • If you are using 2″ of spray foam you really don’t need to use any Radiant Barrier. 2″ of spray foam should take care on all of the radiant heat transfer.

  4. I want to use this stapled to my rafters. My attic has forced air ventilation (two fans) & sofit vents so insulation is not blocking airflow there. Because of this, should I use perforated or non-perforated? I should think airflow in the summer would keep condensation from forming and dripping + in the winter humidity is low enough not to have condensation. I live in Atlanta and have about R30 on the attic floor (batts + blown on top)

    • Perforated radiant barrier is always recommended in an attic situation as it allows water vapor to pass through the product without creating a vapor barrier on which water can condense.

  5. I’m very interested in this product. I live in South Louisiana and I have an older home. My attic insulation is in decent shape, but my electric bill is outrageous. I looked at adding more insulation, but am comparing to the cost and effectiveness of adding a radiant barrier in the attic. I was wondering though, I have an electric attic fan in the attic as well. If I staple the radiant barrier over my rafters, will the fan cause any issues when it kicks on? I obviously will not cover the fan itself with the barrier. Thank you for your time and advice.

    I also tried to order a free sample of the product to see for myself before making a purchase. I filled out the form a few times but when I click submit it would bring up a screen of codes and errors. Can I please be mailed a sample of this product? I would like to see it before I purchase a large quantity.

    • You didnt mention if your attic fan is in the roof or at a gable end, but if you do install the radiant barrier on the bottom of your roof rafters, you will want to leave the radiant barrier off where your attic fan is located, so that it can continue to ventilate your attic properly. I always recommend removing electrical attic fans and opting for a ridge vent and properly sized soffit vents to ventilate an attic without using electricity and instead relying on the venturi effect at the ridge.

  6. I’m about to replace a 20,000 SF. flat roof that currently has no insulation in the truss system. I want to place 2 layers of Owens Corning Foamular (2″ R-10 per layer), then a layer of your perforated barrier on top, before installing the roof membrane. Does this sound proper, or am I possible going to have roof issues down the road ?

    • Unfortunately Our product will not work well in that type of configuration. When a radiant barrier is sandwiched between two materials (insulation and membrane) it becomes a conductor and its emissivity and reflective properties do not allow it to reflect and dissipate the radiant heat. In your case, your best bet is to put down your two layers of the poly-iso insulation board and then a 1/2″ or 3/4″ layer of cover board (protects from people walking on the insulation board, it has R-value but a little more dense) and then choose a white or light colored roof membrane as the lighter the color the more radiant heat it will reflect.

  7. For an existing attic, I installed the perforated barrier along the roof rafters of the downstairs attic. For walls facing the attic that have batts of insulation, can I fasten the barrier over the existing insulation? We have soffit vents, a large gable vent, and a ridge vent. Should the gable wall below the gable vent get the barrier installed? Then the upstairs attic has soffit vents only and no ridge vent. Is it okay to install the barrier all the way to the ridge without adding any ventilation at or near the peak?

    • I generally recommend leaving a gap at the ridge when there is a ridge vent in that location so that the attic can continue to ventilate properly. However, in your case in the upstairs, the ventilation happens out of the gable, so it really is not necessary. Your other question regarding the gable wall below the vent, I would recommend installing some radiant barrier there, especially if it is a West of South facing gable, as some heat gain will come from that side of the structure.

  8. Would this product work for a small (8×8) a-frame child’s playhouse? It gets pretty cold in the winter but luckily the kids like to play outside! Would like to improve the body heat retention in a safe and low cost method. Are smaller quantities available or must I buy the huge roll?

    • I cant say for sure if there would be a noticeable difference in the playhouse during winter, because it all depends on the specific situation. Does the playhouse have doors? How low is the ceiling? Wind? The product definitely reflects radiant heat, that I can tell you, but how it would perform in that specific situation is not something I can really speculate on. Now your other question about different quantities, there is a drop-down box for each of the products (perforated or non-perforated) and you can select the size and square footage you need and the price will adjust respectively.

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