Insulation is a pretty popular word in all types of construction because it is required by building codes and it can cost and / or save an owner big money, especially over time. On flat and low slope roofs it must be considered closely in new construction and in roof replacement situations.
Your building code will dictate how much insulation you need when you build something new and sometimes may dictate what to use when you are reroofing. An important thing to know is that when putting on a new roof, it is a good time to evaluate how your home, office or church is doing in the insulation department.
Make sure you consult your roofer when deciding what to install.
Roof insulation is designed to keep heat or cold in or out of the building effectively. Insulation is measured by R Value. This is a measurement of the resistance of a building material to heat flow. The more resistance to heat flow in the material, the higher the R Value will be.
The most commonly used roof insulation is a rigid board called polyisocyanurate insulation and it is definitely good stuff. It comes in different thicknesses and therefore different R Values. One inch thick “iso board” has an R Value of about 5.5 whereas one and a half inch is R9. The R value goes way up, but normally we do not install more than R30 on a roof. It may be installed in layers too.
Roofers attach insulation to the roof deck or sheathing and then install a single – ply membrane roof such as TPO, E.P.D.M., MODIFIED BITUMEN or even a built up roof system on top of it.
If your building is too hot in the summer or too cold in the winter, adding more R Value on the roof may contribute to fixing the problem. Old buildings sometimes have none at all.
Robert Andrews, II