How to cool a steel roof during summer

Given that hot air raises, have you considered a Passive Stack Ventilation system. Basically:

• A tall pipe coming out of the top of your loft so the hot air can raise
• You must not have bends in the pipe or it does not work as well
• The topping on the pipe must not add much to the flow resistance
• The sizing of the pipe is important (sorry can’t help on this)
  • Too wide you don’t get fast enough upwards air movement.
  • Not wide enough, you get to much air resistance
• The pipe must come out of the top of the loft and be high enough above the roof
• Soffit venting of some type so the colder air can get in at the bottom

The system will only tent to pull air though the loft when the outside air is colder than the air in the loft (just what you need).

Given the correct conditions and design, a Passive Stack Ventilation system will work forever with no running cost or maintenance. Get anything wrong and it will not work at all.

Also check that your ceilings are well sealed, otherwise all the expensive cold air from your AC will just go up into the loft and be vented out.

A skylight (and any hole in the roof) needs flashing, not caulk. The flashing should be overlapped so that shingles above are on top of the flashing, and as it goes down the side, each piece is on top of the piece below, so that any water runs down the roof rather than in your home. The flashing should go up the side and under any lip from the top of the skylight so that rain from above cannot get in behind the flashing. And then all nails should be covered in a roofing caulk and under a shingle/above flashing/other protective layer.