subject: Choose the Right Attic Insulation for Your Home [print this page] Radiant Barrier is also known as reflective barriers. They inhibit transfer of heat by thermal radiation. However, they are ineffective with regards to convection and conduction, that are two other modes of heat transfer.
When an object becomes heated it radiates that heat in the form of energy known as thermal radiation. The level of heat radiated directly is dependent upon the emissivity and surface temperature. Emissivity of a material directly depends upon the degree of heat radiated. How much energy a body reflects at a specific length is referred to as its reflectivity.
For those wavelengths at which the Radiant Barrier function, there emissivity is to be maintained low as much as .1 or below it. The wavelength generally lies within mid and long infrared spectrum that is between 3 to 15 micrometers for long structures. The value of reflectivity isn't fixed for Radiant Barrier. This is simply because both emissivity and reflectivity don't add up to one for different wavelengths. Thus, low thermal emissivity can be used to produce surfaces that are visibly dark in color. For proper performance; Radiant Barrier should face towards open surfaces like air or vacuum to ensure that there is no radiation.
The technique of applying a radiant barrier:
NASA created a material that was light, reflective and made of a plastic substrate that had a vapor deposited coating of aluminum. This is popularly known by the name space blanket. These materials are mainly used for making a protective shield for sensitive equipments, astronauts and spacecraft to protect them from radiation and also to retain the heat to avoid temperature fluctuation that is common issue in space. Radiant Barrier is much more efficient in space than on earth because heat exchange in space only takes by radiation. On earth however, heat exchange can take place through convection and conduction also which makes these Radiant Barrier less efficient.
There is another important use of Radiant Barrier that is to cut down reduction of indoor heat.
There are essentially two techniques by which Radiant Barrier can be installed-
1.Radiant Barrier Decking
2.Radiant Barrier Attic Foil.
On sunny days, the rooftop absorbs the solar energy. The roof sheathing gets heated up and radiates the heat downward to the attic floor. By placing a radiant barrier in the attic floor the heat is reflected keeping the top surface cool and at the same time preventing the heat from entering the rooms. This makes a radiant barrier an efficient reflecting system.
Attic insulation and radiant barrier are different from each other. Though their use is similar but their functioning differs as the Radiant Barrier decrease the heat radiated around them whereas the conventional technique of attic insulation reduces thermal radiation via convection. In this process the air gets trapped inside only. This method is rated by R-value. Radiant Barrier don't carry R-value since they are dependent on numerous factors.
Radiant Barrier has varying range. The cost of set up is depended upon the person who installs it. Other factors consist of the extra functions which some individuals prefer to include in it. The cost is different for a new house and an existing one.
In the end, it would be sufficient to say that Radiant Barrier is really efficient and useful. People prefer them over other means these days.
