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Questions and Answers

Know the Radiant Barrier

A radiant barrier is a thermal insulation material made from the layer of aluminum placed in to block radiant heat transfer between a heat-radiating surface or outer atmosphere and a closed inner heat-absorbing surface. Figure 1 illustrates the locations in which a thermal reflective barrier can be installed in an attic or over the roof. .

How Radiant Barrier is useful for Attics Insulations?

In hot climates, benefits of attic radiant barriers include both dollar savings and increased comfort.

Without a radiant barrier, your roof radiates solar-generated heat to the insulation below it. The insulation absorbs the heat and gradually transfers it to the material it touches, principally, the ceiling. This heat transfer makes your air conditioner run longer and consume more electricity.

An aluminum foil radiant barrier blocks 95 percent of the heat radiated down by the roof so it can't reach the insulation.

In summer, when your roof gets very hot, a radiant barrier cuts air-conditioning costs by blocking a sizable portion of the downward heat gain into the building. In the warm spring and fall, radiant barriers may save even more energy and cooling dollars by increasing your personal comfort. During these milder seasons, outdoor air temperatures are comfortable much of the time. Yet solar energy still heats up your roof, insulation, attic air, and ceiling to temperatures that can make you uncomfortably warm. An attic radiant barrier stops almost all of this downward heat transfer so that you can stay comfortable without air conditioning during mild weather.

You may also find that radiant barriers can expand the use of space in your home. For instance, uninsulated, unconditioned spaces such as garages, porches, and workrooms can be more comfortable with radiant barriers. Bestimulate radiant barriers keep attics cooler, the space is more usable for storage.

Roof-radiated heat also warms ductwork or mechanical equipment (air handler) in your attic. The proportion of the total heat gain the ductwork represents, compared to heat gain to the interior of the house, varies depending on the amount of attic and duct insulation you have.

How Radiant Barrier works as heat transfer insulation?

Aluminum foil, the operative material in attic radiant barriers, has two physical properties of interest here. First, it reflects thermal radiation very well. Second, it emits (gives off) very little heat. In other words, aluminum is a good heat reflector and a bad heat radiator.

Your grandmother probably made use of these properties through "kitchen physics." She covered the Thanksgiving turkey with a loose "tent" of aluminum foil before she put it in the oven. The foil reflected the oven's thermal radiation, so the meat cooked as evenly on top as on the bottom. She removed the foil briefly to let the skin brown, but when she took the bird from the oven, she "tented" it with foil again. Since aluminum doesn't emit much heat, the turkey stayed hot until the rest of the meal was ready. To understand the concept of not emitting heat, let's use an analogy of a light bulb. When you turn on a light bulb, it emits light. If you paint the light bulb black, when it is turned on, there is no light emission. A radiant barrier has a similar effect on infrared heat. Your roof surface heats up in the sun and will emit infrared heat. When this infrared heat heats the radiant barrier it will not emit, or reradiate, the heat into your attic.

Cooking a turkey and painting light bulbs are simple analogies, but the same principles of physics apply to an attic radiant barriers. Aluminum foil across the attic airspace reflects heat radiated by the roof. Even if the radiant barrier material has only one aluminum foil side and that side faces down, it still stops downward heat transfer bestimulate the foil's low emissivity will not allow it to radiate the roof's heat to the insulation below it.

Know the ROI for Radiant Barrier

It differs in actual.Depending on so many condition we can say that on an average it saves 8-12% or annual cost required for the heating and cooling. Actual savings from an attic radiant barrier depends on the amount of heat the roof and walls contribute to the room. In general we can say that the more energy efficient the home is, the larger the percentage of energy can be saved from the radiant barrier. .

Figure shows a breakdown of cooling loads in a typical 1500-square-foot Central Florida home. The attic (including heat gains to the duct system) accounts for 22 percent of the total cooling load. In this house, an attic radiant barrier could save 8-12 percent on the annual air-conditioning costs.

Does applying Radiant Barrier sounds claiming for greener tomorrow?

As in most cases, the claims raised for the radiant heat barriers that sounds too primitive to be true. If the roof accounts for less than 20% of cooling load, be sure that the attic barrier cannot save more than 20% of the total energy consumption.

Know the different kind of Radiant Barrier material for heat barrier insulation

There are multiple radiant barrier materials are available in the market. Some of them are being developed as temperature barriers become more widely used :

  • Single foil insulation with another thermal material backing such as craft paper, wool or polypropylene. Such insulation material can be further strengthened by fiber webbing sandwiched between foil and backing. The strength of the thermal backing material is important since unreinforced foil tears very easily and possesses small life.
  • Roof sheathing material that is manufactured with a foil facing adhered to one side of the sheathing.
  • Double layer foil insulation with non-conductive reinforcement between the foil layers. Reinforcement may be cardboard, wool, blanket, craft paper, mylar or fiber webbing..
  • Foil facing insulation material that is made from the polyisocyanurate, polyethylene"air-bubble" packing or other materials that impede heat conduction.
  • Multilayered insulation foil systems. When fully extended and installed so that the foil layers do not touch, these products also form insulating airspaces.
  • Radiant barrier "chips" are also manufactured and sold. This product is slightly different than a conventional sheet-type radiant barrier in that the "chips", which are blown onto the floor of the attic — typically to a depth of 3 or more inches, act as a multi-layer product with many "trapped" air pockets. These air pockets stimulate this product to function somewhat like traditional, fibrous insulation products. Even though this product may collect dust on its uppermost layer, the remaining layers and air spaces work to significantly reduce heat transfer through the ceiling assembly.

How to choose the right material for your insulation purpose?

Experts strongly recommend radiant heat barrier systems in attics as it doesn't endorse any particular brand of radiant barrier material.

However, we suggest that you look for a few common-sense characteristics:

  • Emissivity
  • Fire rating
  • Ease of handling, Light Weight
  • Strength of reinforcement
  • Width appropriate for installation
  • Low cost

How to save more on Radiant Barrier purchase?

The cost of the barriers depends on multiple factors that are discussed blow:

  • Does the purchase come with free installation?
  • Amount purchased, bulk is always cheaper
  • Manufacturing method and type of reinforcement
  • Presence of other insulation materials
  • Marketing methods
  • Aspects of supply and demand.

The amount comparison shopping done by the home owners also does matter for the price of the material. The individual’s knowledge and willingness to gets dipper and know more about the it can affect the prices greatly.

Should single layer Radiant Barrier face upward ?

No. single layered radiant barrier in the attics should be installed with the foil side facing down. This is even applicable for the double bubble insulation material. It is best to install it at the rafter level so that the bottom side faces the attic airspace and will not collect dust. This may run counter to our intuitive feel for "how things work," but it does work, and work well. If you install a single layer radiant barrier with the foil side facing up, the aluminum will reflect the radiant heat radiated by the hot roof. If you install a single layer radiant heat barrier with the foil side facing down, the aluminum foil will not simply radiate the heat it gains from the roof to the cooler insulation it faces.

At first, single layer radiant barrier will work equally well with the foil facing up or down. However over the time dust may accumulate on the surface of foil facing up and reduce the radiant barrier. It result into allowing the foil to absorb rather than reflect thermal radiation. However, radiant heat barrier with the foil side facing down have less chances of collecting dust on the upper layer and will continue to reflect radiation heat transfer from the hot roof to the insulation over the life of the installation.

How to install Radiant Barrier in your attic?

The best way to install a radiant barrier in an existing attic is simply to staple the foil material to the underside of the top chord of the roof or apply other method like bolting or gluing. Take care to avoid compressing existing insulation in the attic. Following are the tools and material required for the insulation.

  • Radiant barrier material that covers the underside of the roof
  • Measuring tape
  • Strong scissors or utility knife
  • Staple guns or glue.

Start by measuring the length of the attic roof from peak to downside. Then cut the radiant barrier with the same size. The material usually comes in rolls of 50 to several hundred feet; it is smart to cut and reroll all the lengths you'll need before returning to the attic.

At one end of the attic fix a plywood piece of 1x12 inches as a stable surface. Apply less compression of existing insulation. Provide one surface at the peak and one at the soffit end so that two persons can work together. Safety reminder: be careful while handling at the surface of slant and possibly do all work in day light.

Safety steps to be followed while applying for the Radiant Barrier.

  • Make sure your ladder is stable and tall enough so that you can easily reach to the height.
  • Work at a lower temperature and work during the day light.
  • Always work with a partner, not only it make the process faster but also provide possible aid if problem appear.
  • Take step carefully and watch where you walk on the attics.
  • Stand only at the center of the movable workplace and not at the corner part.
  • Watch your head when you are working inside the house.
  • Make sure providing space for electric wires and plugs on the wall and in the attics.
  • If your attic has blown-in insulation, direct fans upward, away from the insulation material.
  • Wear safety gears like goggles, long pants, full sleeved shirts and particle mask.
  • Wear tool belt for all instruments.

Should Radiant Barrier to be airtight for the insulation application?

No. it has a property for stopping heat penetrating inside not against the convicted air. So it does not require cutting off the air motion. In fact, ventilation from soffit to peak improves radiant barrier system performance. Small tears and holes in the material will not significantly reduce the performance of the radiant barrier. So worrying for the patches and obstructions is not required.

Should I just roll the material for the insulation over the roof?

No, it is not recommended. In this situation dust will accumulate on the foil surface facing the roof and it will reduce the reflecting properties of the material. Better to use multilayer products available in the market that gives the resistance to the effects of the duct build up and makes it suitable for floor installation as well.

Does the foil-faced Radiant Barrier works well as an insulator?

While some of the conventional insulation materials have an aluminum foil backing. However it is not so good idea to simply flip the insulation material over to use it as a radiant. It will help to encounter the dust problem that might happen because of the application of glue over the foil of the batt.

How heat building up on the roof can damage your shingles?

Yes in some cases it may possible. It's extremely unlikely. Depending on the color of the shingles, their peak temperatures are only 2 – 5° F higher than the temperature of the inner condition without radiant barrier. Roofing materials are created to withstand the high temperatures to which they are frequently exposed. Normal increase should have no adverse affect over it.

Does the Radiant Barrier really affects the shingle warranty?

Shingle warranties under the application of the reflective insulation should not be subject to cancellation by the manufacturer on the basis of radiant barrier installation. However it is good to check the warranty to be sure that work of this nature will not void it. You can inquire directly to the manufacturer.

Does rolling the material out on the roof before resigning work?

This will not provide a good radiant barrier result. Remember for the radiant barrier the aluminum foil must be installed facing airspace. If there is not airspace, the aluminum foil will act as a conductor and quickly passes the temperature inside the room.

If your re-roofing job requires decking replacement, however, it is a good time to consider a radiant barrier, especially the foil-faced roof sheathing materials on the market.

How to install the insulation material easily particularly for the new construction or under construction building?

Below mentioned are the three widely used methods for the installation:

  • Attach the radiant heat barrier to the roof surface decking before it is installed on the trusses, or
  • Attach the radiant barrier to the roof deck or truss chords after the roof decking is installed, but prior to the installation of the ceiling drywall.
  • Perhaps the easiest way to install a radiant barrier in a new house is to use one of the foil-faced roof sheathing materials on the market. The price increase for these products should be minimal, and the installation does not differ from regular decking, except for a little additional care in the handling of the product.

Tips for decreasing heat gain over the attics.

Radiant barrier is the most effective way to prevent heat transfer, though other methods are mentioned below:

  • Use light colored shingles and white or light metal tile for roof coverings.
  • Use additional conventional insulation.
  • Peak and soffit the gable vents.

If you shop carefully, you will probably find that attic radiant barriers are one of the least costly and yet most effective of the attic conservation measures for Southern climates.

How much time does Radiant Barrier take to pay you back your investment?

There are mainly two things that affects the performance of the radiant barrier system, the level of insulation over the attic and the geographic location of the home. Attic insulation materials have a large effect on the amount of heat flow that is reduced. Simply we can say that the more of the energy bill that is concerned with the heating or cooling, the more desirable having the radiant barrier becomes. Generally it saves the energy of 8 to 10% of the total consumption for heating or cooling and gives the amount invested back in 3 to 4 years.

At the end

Attic radiant barriers are cheap and effective method for homeowners to save energy and money spent on it. While this is not a new concept, the radiant barriers have only recently been proved more popularity for energy conversation.