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Hi I have a large (c. 5.8 x 1.6m) skylight, on a low pitched roof (I'd guess c. 15 degrees). This appears to be made of two sheets of 10 or 12mm polycarbonate. I suspect it was built in around 2006/2007. The polycarbonate has since turned somewhat cloudy – so a little translucent now, rather than clear (clear would be preferable). The roof is an unusual and lightweight construction – see Since it’s a single sheet, thermal performance is terrible – there a lot of heat loss, and a lot of condensation in winter months. So it either needs to be: 1) Replaced with a glass double glazed unit (quotes seem to be c. £12k-20k), and a structural engineer would be needed to confirm whether the loft can bear the weight of a glass unit, so quite apart from the huge cost, it might not even be viable. On the plus side, this would be professionally installed, stay clear, provide decent u values, and could be done in UV control glass, etc. 2) Secondary glazed with acyrlic. I suggest with a sheet of 12mm Perspex (clear cast acrylic), either on the inside or outside, with a between the two sheets. It might make sense to replace the existing polycarbonate at the same time with new, clear sheets. Vastly cheaper (perhaps £1k-2k, including labour and materials). Thermally not quite as good as a proper double glazed unit with inert gas between the layers, but should make an appreciable different for a much lesser outlay. I’ve had a few thoughts on how this might be done by building a frame on top, or a frame underneath, but ideas would be much appreciated; also on how best to re-seal the outside of the skylight to the roof (flashband would probably work … though it seems a bit temporary!). I’m a bit concern that 2 might be a false economy in the long term. But since we may ultimately need to replace the Decra roof, I’m equally concerned that replacing this with a glass unit (1) should only really be done once the roof’s (re)done …. Step 1 of course is getting a structural engineer in, but in the meantime, thoughts welcome – as would suggestions of inexpensive glazing companies for sky lights.

We plan to have about 5 square meters of roof light. It's above our Winter Garden. (1720 by 3200) On a partially protected South West face The darkish area below the roof is an open, barn-style set of baffles. ... I'm thinking about our equinoxial gales, and the occasional hoolie. The area to the right of the glazing is meant to represent solar PV I'm wondering whether polycarbonate is the best choice? Or maybe 4 toughened glass sheets? I have no experience of polycarbonate at all. I've looked at too many videos. I'm all over the place and wonder what your experience is? Ian