Radiant barrier insulation, installed on building rooftops, helps bring down heat during summer and prevents heat loss in winter. There are many types of roof insulation. Use of this insulation type is promoted by the energy ministry, as it helps in bringing down the power usage for heating and cooling homes. In short, it saves energy. Using this type of insulation is an excellent way of getting those power bills down, as well as enjoying a cooler summer at home.
What are Radiant Barriers Made of?
They are generally made up of thin reflective sheets. The sheets could be made up of diverse substrate materials, which are coated with a thin reflective coating of aluminum, applied on single or both sides. These base substrate sheets could be plywood, plastic, air infiltration barrier materials, or even craft paper. Some barriers are reinforced with fiber material to make them more robust and easy to handle.
This insulation type has applications in diverse fields like space technology. As mentioned above, aluminum-coated plastic sheets were used by NASA as space blankets. They protected the space probes from radiant heat of the Sun. Specialized insulation fabrics are developed from this insulation to create fire proximity suits for firefighters.
Let us see, how the installation of this barrier, used for the roofing of residential buildings, reduces heat exchange with the surroundings. All materials that have a temperature, radiate energy.
The quantity of energy radiated depends on the temperature and the 'emissivity' or 'emittance' of a material. Emissivity is a number between 0 and 1. It measures the amount of energy radiated by a material. There is another property which is called reflectivity, which measures the amount of radiation it reflects. The sum of emissivity and reflectivity is always 1. So, higher the emissivity, lower is the reflectivity and vice versa.
Radiant barrier materials have high reflectivity and very low emissivity. Generally, reflectivity of these materials is 0.9 and emissivity is 0.1 or less. Now, this type of insulation is placed under roofs and over attic floors.
Normally, Sun heats up the roof and this heat is radiated to the attic floor. Subsequently, the rooms under that roof get heated too. Now, with the barrier installed in between, most of the heat radiated by the roof gets reflected back. The insulation material underneath the reflective material is relatively cooler. Hence, heat dissipated to underneath rooms is significantly lower.
The installation is quite simple in principle. One can simply spread insulation sheets with the reflective side up, over existing ordinary insulation on the attic floor and staple it. Leave a small gap between the floor and the insulation sheets. Another way of installing it is, fixing it near the roof of the attic. There should be considerable space between the attic roof and the insulation sheets. This can be done by attaching the barrier sheets to rafters under the roof deck. A roof installation will cost more as it will require covering of more surface area.
The cost is comparatively lesser than conventional roof insulation products. Currently, it ranges from USD 0.12 to USD 0.35 per square foot. It varies, depending on what kind of product, you go for. The cost also varies according to the type of installation. The roof installation costs more as compared to attic floor installation. You could get some discount, if the purchase is made in bulk.
If you are installing it on your own, here are some things to remember.
- While installing this insulation, near the roof, remember that you need a sufficient amount of air gap, in between the barrier and the roof.
- Ensure that after the installation, your attic can breathe. That is, the water vapor rising from the house should find a vent through the barrier insulation. This can be done by using perforated barrier insulation sheets and fixing exhaust fans in the attic.
With this kind of insulation in place, you will certainly see a lowering in your air conditioning and house heating bills. So, go for radiant barrier installation as it will not only cut your bills, but save some valuable energy.