Insulation Options
ROOF INSULATION
Roof insulation
options are varied depending on your needs.
This basic roof insulation system is designed to be well ventilated and
efficient. By combining the ceiling board, Astro-foil, fiberglass and
the use of air spaces, we have created an effective system for low insulation
needs (see drawing below). If you have greater insulation needs the use
of larger rafters and possibly this system or one of the following insulation
systems may be best for your needs.
At this time most of our customers have been using either fiberglass batting or a blown in type insulation (cellulose or fiberglass). Occasionally some people use commercially sprayed in foam. This has a high R value that allows for smaller rafters as well as completely sealing the roof and not needing a moisture barrier between the ceiling and insulation.
If you are using the low R-value insulation system descibed above this table will help you figure out what roof system will work best for you.
| Rafter Size | Ceiling Board | Fiber Glass | Astro-Foil | Total |
| 2x4 | R 1.5 | R 6.2 | R 5 | R 13.2* |
| 2x6 | R 1.5 | R 11, R 13 | R 5 | R 18*, R 20* |
*A .5 value has been calculated in for the dead air space
We have plywood patterns is available to assist incutting your ceiling material and insulation.
Blown in fiberglass or cellulose are a way to achieve a code acceptable R-value. They require a bit more labor and materials and a 2x8 or 2x10 rafter system. These materials are basically inert and serve in creating a tight seal. They require having a vented roof in order to prevent condensation problems. This is our preferred type of insulation for a well insulated, healthy structure.
With rigid or spray in foam insulation significantly higher R-values can be achieved. Up to R-19 with 2x4 rafters and up to R-30 with the 2x6 rafter system. This is a costly but effective insulating system.
