How Do Radiant Barriers Really Work?
To help you to understand how a radiant barrier works, let us first start by explaining a little about heat transfer. When talking about radiant barriers, insulation, HVAC systems and energy efficiency, it is important that we recognize that all of these things are about controlling heat.
You can also read a summary about what radiant barrier services we offer on our Radiant Barrier page.
If you were wondering why you might need radiant barrier, it might be helpful to read our post before you read the remainder of this article. Why Radiant Barrier?
A: Understanding Heat Transfer
Heat transfer happens in homes and building in three distinct ways.
* Conductive heat transfer (conduction)
* Convective heat transfer (convection)
* Radiant heat transfer (thermal radiation)
Conduction is the least efficient method of transferring heat, and in a kitchen analogy, that would be an equivalent of boiling water in a pot over a stove. The fire heats the pot and the pot transfers its heat to the water and the water eventually comes to a boil. The key point here is that conduction is the transfer of heat through direct physical contact.
Convection is more efficient than conduction, and in our kitchen analogy, convection would be the use of an oven to heat food. Convection heat transfer is the process by which heat is circulated in an area through the air and/or fluid. The key point here is that heat is transferred through air circulation.
Radiant heat otherwise known as thermal radiation is the most efficient type of heat transfer and the best example in our kitchen analogy would be the use of a microwave. Radiant heat is generated when heat from the movement of charged particles within atoms is converted to electromagnetic radiation. In a home or building, radiant heat refers to heat radiated from objects and materials, such as incandescent lights, concrete flooring and the sun. It is also important to note that radiant heat moves through the air without heating the air, instead it will heat the first surface that it touches, and this surface will then re-radiate that heat in the space making it feel warmer when you are in that space.
In general, heat transfer between the interior and exterior of a home or building is bad and decreases the efficiency of the heating and cooling system. There are some special conditions where heat transfer is used to increase the efficiency, such as trombe walls, thermal masses, and other natural heating and cooling techniques. But for the most part, in a typical home or building which relies on mechanical means of heating and cooling, heat transfer is the enemy.
So, it makes sense to stop as much heat transfer as possible. This is why insulation is used in all structures. Insulation is great at reducing convective heat transfer, while also reducing some radiant and conductive heat transfer as well. However, the typical amount of insulation in a home or building (anything below R39) is
simply not enough to stop the majority of radiant heat from infiltrating the structure.
Eastin Air serves Dallas and surrounding areas. We specialize in Highland Park and University Park.
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