| NRG Shield Technical Details | | Print | |
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How Heat is Transferred - Heat is transferred from one source to another via three methods of transfer: conduction, convection, and radiation. See Warranty Details Manufacturer's Certification Statement download here
Common examples of radiant heat transfer:
Conventional Insulation Most people are familiar with traditional insulating materials such as fiberglass, cellulose, Styrofoam, and rock wool. These products absorb or slow down convective and conductive heat transfers to insulate. These types of insulation do not BLOCK heat - only slow it down. Therefore, after a period of time, 100% of the heat absorbed would eventually transfer through the insulation. The rate in which this heat eventually transfers through an insulation material is the material's R-Value.
How NRG Shield type technology works. It reflects/blocks radiant heat energy instead of trying to How does NRG Shield reflect/BLOCK radiant heat? The aluminum found in NRG Shield has two properties that enable it to reflect/BLOCK radiant heat when at least one air space is provided on one side:
NRG Shield reflects radiant heat that strikes its surface across an air space from a heat source and conversely, it EMITs very little radiant heat from its surface across an air space opposite a heat source. Why NRG Shield needs Air Space No matter how you plan to install NRG Shield, it MUST have at least one air space of at least 3/4 of an inch on either side to be effective at BLOCKING radiant heat. It does NOT matter which side of the radiant barrier the air space is located. The purpose of the air space is to prevent conductive heat transfer. If NRG Shield does not have at least ONE air space on either side of it, heat will conduct from the surface touching it, then pass through the Shield, and then transfer to the next surface touching the Shield on the opposite side therefore, giving you no protection against the heat you intend to block. Therefore, as long as the air space requirement is achieved, NRG Shield will be effective at BLOCKING radiant heat regardless of your application, i.e. interior/exterior walls, siding, roofing and attic locations, etc. What Happens When No Air Space Exists Because NRG Shield requires an air space on at least one side of itself to be able to BLOCK radiant heat, NRG Shield CANNOT be installed directly underneath roofing materials where no air space exists. For example, if you install NRG Shield on top of roof decking between the felt paper and asphalt shingles, it will NOT provide any benefits as the radiant heat would be transferred through the shingles, through the felt to the Shield, and through the roof decking into the attic space (see image below). NRG Shield can be effective with an asphalt shingle roof ONLY when installed inside the attic either to the underside of the roof decking or to the underside of the roof rafters. In these attic space applications, there is an air space below the Shield. It is the existence of a single air space that eliminates, almost entirely, the pass-through of radiant heat. Everyday Example of Low Emissivity Across an Air Space The help you understand the more difficult concept of emissivity, imagine of a hot baked potato wrapped in aluminum foil. If you hold your hand close to the wrapped potato (not touching it), you would feel very little radiant heat coming off the aluminum because aluminum doesn't “emit” much heat across an air space (aluminum has a low emissivity factor). If you were then to touch the aluminum wrapped baked potato, you would feel a great deal of heat because the aluminum would then be conducting heat from the potato, through the aluminum, to your hand. Because you have lost the air space, the heat would contact (conduct) to your hand. NRG Shield is ONLY effective when at least a 3/4" air space is provided on either side of itself regardless of the location of the heat source. If the air space is on the side of the heat source, the REFLECTIVITY property works to REFLECT the radiant heat. If the air space is on the opposite side of the heat source, the low EMISSIVITY property works to reduce the amount of radiant heat that EMITs from its surface. Blocking Radiant Heat Transfers in a Home or Building All building surfaces include roofs, ceilings, and even conventional fiberglass and blown-in insulation radiate heat in varying degrees. Radiant heat from the sun strikes the outer surfaces of roofs and walls and is absorbed causing building surfaces to heat up. This absorbed heat moves through the material (via conduction) to the opposite side and is then radiated from itself into attics and living spaces increasing the temperatures inside the building. Installing NRG Shield is a MUST to combat the major form of heat transfer (radiant) that is currently not being controlled by your conventional insulation. What is NRG Shields emittance and reflective ability? NRG Shield have an emittance of only 3% and a reflectance of 97%; considerable better than the DOE's radient barrier minimum classification requirements. The Department of Energy says that this type of product must have a low emittance of 10% or less and a high reflectance of 90% or more. How does NRG Shield Benefit You NRG Shield reflect/BLOCK radiant heat; not just absorb or slow it down like other forms of insulation. NRG Shield is unaffected by humidity or ambient temperatures, unlike other forms of insulation, and therefore, perform at a consistent level at all times. NRG Shield reflects/BLOCKS 97% of the radiant heat transfer and when installed in an attic space, they can result in a reduction of attic temperature below the shield of up to 30 degrees. Lowering the temperatures above living space ceilings provides a significant benefit by reducing air conditioning loads and energy usage. NRG Shield can:
NRG Shield Testing and Approvals:
Metro Dade County Double-sided vs. Single-sided Single-sided shield have only one reflective surface adhered to a non-reflective substrate (for example, Kraft paper). Single-sided shield reflect radiant heat only from the reflective side facing a radiant heat source. Double-sided shield have two reflective surfaces, one on each side, allowing the shield to reflect radiant heat from both sides independently. NRG Shield is double-sided. Scrim & Durability In order for NRG Shield to have durability and strength, a middle "scrim" layer is present in the center of the product. NRG Shield have a reflectivity of 97% . # of Layers Many consumers have been mislead to believe that a shield with more layers is more effective than one with less layers. It is not the number of layers that makes one better than the other. Fire Ratings Shield like most building materials, must be tested and meet specific fire ratings. The fire rating of shield is determined by the flame spread and smoke development results of the surface burning characteristics test performed as part of the ASTM C1313 qualification tests. NRG Shield has the Class A & Class 1 fire ratings. Weights Many consumers have been mislead to believe that the heavier the shield is, the more effective it is. When comparing shields, the weight of the product is not typically indicative of the effectiveness of the product. When reviewing shield for effectiveness, the consumer should compare the following C1313 properties (reflectivity, tensile strength, fire rating, water vapor transmission, etc). If weight comparisons are important to you, make sure you are comparing apples-to-apples. NRG Shield product specifications list the weight based on the shield alone (not including the weight of the cardboard roll core or shipping box). For example, 1,000 sf lists a weight of 24.6 lbs. However, the shipping weight, which includes the cardboard roll core and shipping box, is 28 lbs. Perforated vs. Solid Vapor Barrier A perforated shield has small holes throughout the product that allow moisture vapor to pass through A non-perforated (solid) shield has no holes and serves as a vapor barrier.
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| Last Updated on Thursday, 18 November 2010 12:03 |
Conductive: the transfer of heat flowing through a substance (molecular motion) or to another touching substance. If you touch a pot on the stove, the heat is transferred from the pot to your hand via conductive heat transfer.
Convective: the transfer of heat in fluids, such as rising heated air, steam, and moisture. If you put your hand above a boiling pot, you will feel heat rising from the pot in the form of steam. This transfer of heat from the pot upwards is via convective heat transfer. Convective heat transfer results in warmer air rising and cooler air settling creating a convection loop termed free convection. A Convection loop can also be generated mechanically with the aid of fan or wind and is then called forced convection.
Radiant: the transfer of heat via infrared radiation rays that are invisible to the naked eye and unaffected by air currents. If you step outside on a windy sunny day, you will feel the sun's heat rays on your face. This transfer of heat from a heated source across an air space to a colder surface is via radiant heat transfer. All materials radiate radiant heat in ranges from 0% to 100%.
