Roof boots

The most reliable way of penetrating the roof for the plumbing to your solar thermal collectors is with a roof boot. These are usually aluminum plates with a neoprene collar around a hole, through which the pipe passes.

Roof boots are designed for sewer pipes, which are much bigger than solar thermal pipes – about 3" to 4" in diameter for sewerage, compared to ¾" or 1" for solar. However, once you add the insulation to your collector pipes, they come out about the same size so the system works very well, especially because the neoprene collar means there's no need for any additional sealing.

Use plenty of roofing cement when installing roof boots and ensure their top edge goes under the shingles, the lower edge over. You'll need a separate boot for every pipe that penetrates the roof.

Posts and rails

Some buildings do not allow access to the inside of the roof, such as historic buildings or designs like cathedrals. In these cases, you can install a post and rail system on which the solar collectors are mounted.

A roof boot is placed for each post, which has a threaded hole in it to attach the rail. The rail or beam runs the length of the solar collector array.

A post and rail configuration has the advantage of better leak protection and also allows the fasteners to be lagged directly into the rafters or trusses.