15/07/2013
INSULATION AND RADIANT BARRIER FOIL—WHAT’S THE DIFFERENCE?
Fiberglass insulation depends on R-Value (resistance) alone to insulate against summer heat gain and winter heat loss. Thin layers of fiberglass do virtually nothing to stop reflective heat or energy transfer. Fiberglass insulation is also affected by changes in humidity or moisture levels. A 1% to 1-1/2% change in the moisture content of fiberglass insulation can result in up to a 36% decrease in performance.
Unlike fiberglass insulation, reflective insulation or radiant barrier foil products, such as Enerflex, are not affected by humidity and moisture changes and will continue to provide energy savings and insulation value no matter what the moisture level is. Reflective radiant barrier foil also has additional uses for which fiberglass insulation is not applicable, such as radiant heating systems, or any under or over concrete slab applications. In these uses, reflective insulation is the better, if not only, choice to use.
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. These types of insulation do not BLOCK heat—only slow it down. Therefore, after a period of time, 100% of the heat radiated would eventually transfer through the insulation. The rate in which this heat eventually transfers through an insulation material is the material's R-Value. If you want to reflect the heat—stop it in its tracks—you need a radiant barrier.
As a home owner, the challenge is how to keep the heat in during winter and how to keep it out during summer. There are three ways in which heat goes from warm spaces to cold spaces:
1.Conduction is direct heat flow through a solid object such as a wall or a ceiling.
2.Convection is heat movement through air, occurring when air is warmed. The warm air expands, becoming less dense and rising.
3.Radiation is the movement of heat rays across air spaces from one warm object to a cooler object.
The heat we feel from a wood stove or a space heater is radiant heat. All objects and bodies give off radiant heat. Even the insulation in your attic gives off radiant heat to the cold attic space in the winter and to the living space in the summer. Regular insulation won't stop radiant heat loss. Radiant heat must be reflected with a radiant barrier.
WHAT IS A “RADIANT BARRIER”?
With increased attention being paid to home energy reduction, radiant barriers have lately been in the green building spotlight.
So, what exactly is a radiant barrier and what can a home owner expect from one?
Radiant barriers, like Heat Shield, are materials that reflect the radiant heat of the sun. They are installed in roofs and walls of a structure. Do they save energy? Yes. But be careful to understand any savings claims that may be made. For example, a claim that a product reflects 90% of radiant heat does not mean it will reduce cooling bills by 90%.
So how do they decrease heat? First let’s understand the three ways heat is transferred: With conduction, heat is transferred from one molecule to the next. Holding a beer bottle warms the beer. This is bad. Insulation mitigates this. Convection involves moving air, and a fan is an example of how to reduce this type of heat. Radiant heat is a bit harder to understand. Terms like “electromagnetic waves” and “high-energy particle transmission” are thrown about in its explanation but for purposes of this post let’s just say radiant heat is noticed by you when it hits the air around you, your car seats or your home’s roof. Heat from the sun is absorbed by roofing materials and reradiates to the air in your attic. That’s why attics get so hot. This heat energy then gets absorbed by the attic insulation and ceiling drywall, then is reradiated into the living space, making the room warmer.
A radiant barrier reflects that radiant heat. Shiny aluminum foil facing a heat source reflects over 90% of the radiant heat that strikes it. How much can it save you in cooling costs? Depends on your climate, shading from trees, how much insulation you already have in your attic, and to some extent, how well the attic is ventilated. Some studies indicate the most energy saving benefits are in homes that have duct work or HVAC equipment located in the attic. Leaky ducts draw in the hot attic air causing your system to work harder to cool 140 degree air rather than the air in other living spaces.
Radiant barriers like Heat Shield can cool attic temperatures 20 to 35 degrees. The radiant barrier creates a cooler attic which helps reduce cooling costs. Obviously there are comfort improvements to be noticed in the rooms just below the attic.
WHAT ARE RADIANT HEAT BARRIERS?
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WHAT IS RADIANT HEAT AND HOW DOES HEAT SHIELD RADIANT BARRIER FOIL REFLECT HEAT?
An easy way to understand the concept of radiant heat is to stand in front of your grill during a cookout. The heat you feel standing next to the grill is considered radiant heat. A radiant barrier will reflect that heat. Heat that is radiated doesn’t necessarily have to come from the sun.
Heat Shield radiant foil barrier is installed inside your attic, beneath the roof sheathing, so how is it expected to reflect the sun’s rays? The answer is it doesn’t have to reflect the sun’s rays to work, but it does reflect the radiant heat generated from those rays.
On a hot day, heat from the sun is absorbed by the roof and warms up the sheathing below, which radiates heat towards the attic floor and conventional insulation. All materials emit radiant heat to varying degrees based on their surface temperature. However, installing a radiant foil barrier like Enerflex will reflect up to 96% of this radiant energy back toward the roof.
The result: The top surface of the insulation is up to 30° cooler than it would have been which reduces the amount of heat that moves through the insulation to the living areas below.
HOW TO INSTALL HEAT SHIELD?
Heat Shield can be installed either...
1. Under the roof tiles on the rafters or
2. Above the ceiling board
WHERE CAN YOU USE HEAT SHIELD
Residential Houses / extensions
Commercial buildings / shop houses
Supermarkets / hypermarkets
Restaurants / hawker centres
Warehouses
Factories
Bird Houses / Farm houses / Barns
…..basically in any buildings roof/walls where you want to effectively control the temperature
Also
Automotive roof / train coaches roof / boats etc.
HOW TO INSTALL HEAT SHIELD?
Heat Shield can be installed :
- Under roof tiles
-Above ceiling board.
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