Sarking, or insulation foil, is a flexible plastic sheeting with foil laminate applied to one side. It is applied on top of the rafters and under the battens the slate tiles are mounted to.
Sarking has several benefits which include:
- Provides good weather protection during the installation of slate tiles
- Prevents dust from entering your ceiling cavity
- Creates additional insulating to your ceiling batts
- Offers temporary weather proofing if your roof slates get damaged
A Byproduct of Space Program Technology
Outer space is much more brutal than Melbourne weather. Interestingly, though the benefits of foil insulation were well known decades ago as the result of the space program, only more recently have those benefits been applied to home insulation technology.
Foil insulation provides a “radiant barrier” that works equally well to retain heat in your home during cold weather and inhibit solar radiation (heat) from entering during hot weather. Heat transfer is accomplished through the infrared spectrum and foil thwarts that transfer so effectively that it’s used in outer space.
The conventional batt insulation in your home only slows down this transfer and becomes a radiant sponge in the process—soaking up heat only to leach it toward the cold. A little known law of temperature exchange is that heat seeks out cold. Summer heat seeks out the cooler air in your home. In the winter, cold is not actually coming in, heat is going out.
Understanding this nature of temperature exchange will help you realize why your home heats up noticeably at the end of a summer day and into the evening. Once your batt insulation is overwhelmed with stored heat from the day, it begins radiating it inward toward your cooler living space.
Foil inhibits this process by bouncing the heat back toward its source, therefore keeping you cooler in the summer and warmer in the winter, all while reducing energy bills. You may not think of a new slate roof as being a means of reducing energy bills, but because we use sarking on all slate roofing projects, you’re getting this additional benefit too.