What about integrated PV, so the roof covering is not needed.....

Other question, what do you do about the noise of the rain beating down on a tin roof?

Posted By: cjardOther question, what do you do about the noise of the rain beating down on a tin roof?

Put 500 mm of warmcel or similar underneath it and you hardly hear the rain.

Re the warmcel comment, I had another thread on here recently where I was querying whether it was a good idea to put mineral wool under some roof lights that I will eventually remove and slate over.. but in the interim what could be done to reduce condensation risk to the the materials that would remain. Generally the wool was considered a bad idea, so I'm now seeing a a bit of conflict of opinion surely, with the "put warmcel so it touches the underside of the outer skin.."

I think I've posted our roof construction before, but I'll repeat it.
From the outside down:

- aluminium standing seam surface
- 'metal' membrane (i.e. a breathable membrane with what looks like scotchbrite pad on top)
- 2 x 9 mm external structural ply, overlapped
- 450 mm deep cavity formed of timber roof structure, filled with warmcel
- panelvent HDF board
- Intello membrane
- plasterboard & skim

So no ventilation but ostensibly breathable to some degree both top and bottom. The theory is that condensation/vapour under the metal drains across the top of the membrane, through the tangled plastic wool. Vapour/condensation anywhere underneath the ply is buffered by the warmcel and escapes via the Intello when conditions are suitable.

Posted By: Gotanewlife

Posted By: djhThe theory is that condensation/vapour under the metal drains across the top of the membrane, through the tangled plastic wool.

Interesting,; where to ....the gutter?

No, just drips off the edge; not that I've ever seen any evidence of any. The gutter is on top of the roof in our case. (a formed stand-up barrier at right angles to the roof surface near the eaves)

Edit: Actually it seems more likely that small amounts of condensation would just sit on the membrane until the roof heated up and evaporated it.

I think any excess water - ice, liquid or gas - that is above the membrane is most likely to exit sideways through the plastic wool to the edge of the roof. Most likely as vapour but perhaps as liquid sometimes.

Any excess water - ice, liquid or gas - that is inside the roof structure either has to find its way up through the plywood and membrane so it is outside, or down through the panelvent, intello and plaster to the inside. The idea is that the variable vapour permeability of the intello means it is easier for vapour to escape to the inside than it is for vapour to make its way from inside up into the roof. I just hope the theory is right! But Pro Clima do warrant that it works.