Green Building Forum - Skylights, roof windows and clerestory skylights Tue, 19 Dec 2023 05:52:55 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234718#Comment_234718 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234718#Comment_234718 Mon, 11 Jan 2016 16:22:22 +0000 tony
U values assume steady state and an indoor and out door temperature

But skylights can radiate heat to outer space which is at absolute zero.

This heat loss dominates on any clear night.

Should heat losses from these be reassessed?]]> Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234749#Comment_234749 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234749#Comment_234749 Mon, 11 Jan 2016 21:30:57 +0000 Silky Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234750#Comment_234750 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234750#Comment_234750 Mon, 11 Jan 2016 22:05:35 +0000 Ed Davies
To weigh against the increased heat loss per m², roof windows also let in more light so a smaller area is possible.

Posted By: tonyBut skylights can radiate heat to outer space which is at absolute zero.
Well, about 2.7 K, not that that makes much difference from a building perspective.

More substantially, the effective radiant temperature of even a clear sky is a bit warmer than that though still pretty chilly at something like -30 or -40 °C. Obscure thing often referred to as the greenhouse effect. Anybody hear of it? Not that the UK winter sky is clear that often, particularly in winter when it matters, so usually it's effectively a bit warmer.

Vertical windows usually see at least a bit of sky, too.]]> Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234772#Comment_234772 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234772#Comment_234772 Tue, 12 Jan 2016 08:16:16 +0000 PeterStarck Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234785#Comment_234785 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234785#Comment_234785 Tue, 12 Jan 2016 10:16:49 +0000 dickster Skylights, roof windows and clerestory skylights http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234791#Comment_234791 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13951&Focus=234791#Comment_234791 Tue, 12 Jan 2016 11:52:52 +0000 Ed Davies Posted By: PeterStarckIf the skylight outer pane of glass is reflective or tinted how does that affect any loss by radiation if at all.Depends - the reflectivity or tint might have a lot of effect at short wavelengths (e.g, visible light and near IR) but no effect at longer thermal IR wavelengths.

I suspect it wouldn't make much difference - if there was a coat that could be put on the outside or in the outer pane that reduced the thermal IR emissivity significantly they wouldn't bother with expensive and (somewhat) delicate coatings on the internal faces.]]>