Wed, 09 Sep 2026 17:55:54 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187924#Comment_187924 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187924#Comment_187924 Sat, 02 Nov 2013 11:47:48 +0000 chan what wold be optimum for heating season with SouthWest unobstructed aspect 3g or 2g?

As it stands we have kitchen dining and bedroom SW facing with single glassing and towards eve (12 till sunset) get massive amounts of Light/heat so worry that 3G might reduce this evening heat and loose beautiful afternoon and evening light compared to DG. We are in Northwest Ireland by coast.

Münster joinery Dg 24mm u1.3
VS
TG 36mm u1.1

I have actually ordered 3g but wonder should we change south west window to DG.
Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187927#Comment_187927 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187927#Comment_187927 Sat, 02 Nov 2013 13:17:10 +0000 tony
Make the windows slightly bigger to overcome the loss of light but this is small so only a few percent large.

You will likely need to shade the windows externally even in the winter! To prevent overheating more especially if you are properly insulated.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187930#Comment_187930 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187930#Comment_187930 Sat, 02 Nov 2013 13:36:10 +0000 chan this is a 1970s semi d with 50mm insulation in cavity probably will pump walls. window are relative large. so there is plenty light because the house backs SW over an estuary we get allot of light when sun is out also bounced off the water.
my worry is that TG will reduce the afternoon/eve solar gain compared to if we got DG.
or is the difference marginal compared to heat loss ?
IE with SW aspect is it best to get TG over DG in all situations?

windows are soft coat, low e, argon, pvc
4/12/4/12/4
thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187946#Comment_187946 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187946#Comment_187946 Sat, 02 Nov 2013 22:15:55 +0000 Nick Parsons https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187951#Comment_187951 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187951#Comment_187951 Sat, 02 Nov 2013 22:55:09 +0000 Ed Davies
From the http://www.degreedays.net/ site the HDD to 18.5 °C for Malin Head in 2012 December was 377 so an average temperature difference of 12.16 °C giving the extra loss from going from 3G 1.1 to 2G 1.3 W/m²·K of 2.43 W/m².

From PVGIS for Dungloe: input on a vertical panel facing 45° west of south for December is 28.9 kWh/m² giving an average of 38.8 W/m². I don't have any data on the transmission of those but looking at the simple Fresnel equation for the extra reflection from my calculator at http://edavies.me.uk/2008/10/fresnel/ says going from 2G to 3G drops the transmission from 85% to 78% so the loss in heat gain is 38.8 × (0.85-0.78) W/m² = 2.7 W/m².

3G will also have a bit more glass so a bit more absorption on the way through. But that effect is, I think, small and helps a bit with reducing heat loss anyway.

So, on the face of it, 2G is slightly better (by 0.27 W/m²) but the extra comfort from lack of drafts associated with 3G probably dominates anyway. Definitely not something to lose sleep over.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187980#Comment_187980 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187980#Comment_187980 Sun, 03 Nov 2013 15:01:17 +0000 chan Thats a lot of calks, so in basic terms 2g could loose 18% light heat and 3G 25% heat light.
in this % way i wonder over the heating season what the difference in heat lose being lost interior to exterior would be between 2G and 3G?
Sounds like it might come down to aesthetics and how the glass looks transparency/colour tint/ perceived effect on views and natural lighting.
wonder does anyone regret getting 3G because of how it affects views transparency increased feeling of being in a box?
sales men hear say 1 in 4 houses are getting 3G but think more and more are getting 3G, cant say i see much about except new builds.
Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187982#Comment_187982 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=187982#Comment_187982 Sun, 03 Nov 2013 15:23:01 +0000 tony
In the UK we are a good few years behind the times.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188016#Comment_188016 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188016#Comment_188016 Mon, 04 Nov 2013 09:49:35 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188033#Comment_188033 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188033#Comment_188033 Mon, 04 Nov 2013 12:40:39 +0000 chan Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188034#Comment_188034 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188034#Comment_188034 Mon, 04 Nov 2013 12:47:40 +0000 chan https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188036#Comment_188036 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188036#Comment_188036 Mon, 04 Nov 2013 13:08:44 +0000 fostertom
Needs careful custom consideration because potentially you'll get gain bigtime incl reflection off the water, great to exploit winter but the water makes it v hard to shade out overheating in summer. If the window is S, the usual big overhang won't intercept the reflected. If W, makes it even trickier - the sun will be lower but still powerful and the reflection will bounce in even better.

Cmon team, no pat answers, let's discuss this unique, real situation.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188042#Comment_188042 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188042#Comment_188042 Mon, 04 Nov 2013 14:32:35 +0000 chan Thing is I have ordered 3G with Munster but can be adjusted as they have not made them yet but I if I change them to 2G should do it today or tomorrow. Hmmm.
This is sligo]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188044#Comment_188044 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188044#Comment_188044 Mon, 04 Nov 2013 14:34:11 +0000 chan ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188046#Comment_188046 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11338&Focus=188046#Comment_188046 Mon, 04 Nov 2013 16:08:45 +0000 tony