With so many new forms of insulation available today, how does one decide what is the most cost effective and energy efficient product or method? We have compiled this information regarding types of insulation, how they work and where/when to use them.
First, let’s get a quick understanding of how heat is transferred in or out of our home. To best understand this, we consider one of the points in the laws of thermodynamics which is – hot air tends to move toward colder air in an effort to equalize the energy system. During colder winter months we run our furnace to provide heat inside our home. This heat takes over the cooler air inside the house and also is absorbed by the building materials that make up our home. Eventually this heat pushes its way through the walls and the roof to make its way to the cooler air outside. This process happens in the same fashion during the summer months but since we are cooling our home inside, the heat energy from outside is always trying to force its way in.
Now we’ll move on to the types of insulation that are used to inhibit heat transfer.
Fiberglass batt insulation is one of the most common insulations used in home construction because of a few reasons. It is a very inexpensive and fairly effective product for resisting heat transfer. Keep in mind that fiberglass batts are “mass” insulation meaning that it uses its thickness and density to slow down heat transfer, but eventually the heat will transfer completely through to the colder side. The effectiveness of fiberglass insulation is measured in R-Value which simply describes the Thermal Resistance of the material. The higher the R-Value number is, the longer it takes heat to transfer through it.
Cellulose insulation which is commonly called “blow-in” insulation is another “mass” insulation. It is typically manufactured of recycled materials such as paper, cardboard and cotton. It is a loosely packed material that is “blown” into your attic using a special machine. The R-value is determined by how thick the insulation is blown onto your attic floor area. Typically, it needs to be installed very thick to achieve high r-values. Once again, this products composition is designed to absorb or slow down heat transfer but the heat will eventually escape.
Radiant Barrier Foil is a different approach to attic insulation and works in a completely different way than fiberglass and cellulose insulation. Radiant Barrier is not a “mass” insulation so it is not designed to absorb or slow down heat transfer. Therefore it has no R-Value. It utilizes reflective properties to re-direct heat back towards its source. This means that very little heat energy is transferred through a radiant barrier. In some warmer climates such as the southern United States, a radiant barrier may be all that you need to keep your home substantially cooler in the summer. In moderate climates during colder months a radiant barrier foil can be used to enhance a mass insulation’s r-value and will help re-direct heat toward the inside of your home.