Green Building Forum - Build tight ventilate right Tue, 19 Dec 2023 05:51:49 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258434#Comment_258434 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258434#Comment_258434 Fri, 26 May 2017 17:41:55 +0100 Ed Davies Posted By: djhgoodevans already explained that the test pressure isn't especially connected to anything at all. In fact the results stated at a test pressure of 50 Pa are actually calculated by regression from results measured at a range of pressures. It's just a standard value for tests.Of course. But if we want to get to some notion of what values we should be aiming at then it makes sense to try to work out how it relates to real-life performance.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258438#Comment_258438 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258438#Comment_258438 Fri, 26 May 2017 20:07:36 +0100 goodevans
I have just realised that the losses due to stack affect approximately increase with the square of temperature difference (increase pressure with temp and lower air temp infiltration).

As usual we have to guess given the present research available.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258445#Comment_258445 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258445#Comment_258445 Fri, 26 May 2017 22:40:07 +0100 djh Posted By: fostertomis a bungalow with walk-height loft, or a v skimpy flat roof 2 storey. 2 storey with loft more like 7m, so 14C - not just deep winter. A 2-storey maisonette above shop say with GrdFl entrance would be 9m, 11C.
And you've neglected that the infiltration is not all at the exact bottom and top of the building, but is instead probably distributed rather randomly up the elevations.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258446#Comment_258446 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258446#Comment_258446 Fri, 26 May 2017 22:42:10 +0100 djh Posted By: Ed Davies
Posted By: djhgoodevans already explained that the test pressure isn't especially connected to anything at all. In fact the results stated at a test pressure of 50 Pa are actually calculated by regression from results measured at a range of pressures. It's just a standard value for tests.
Of course. But if we want to get to some notion of what values we should be aiming at then it makes sense to try to work out how it relates to real-life performance.
Yes, but just trying to causally associate one magnitude with another is crazy.

I expect the whole of this issue is dealt with at length in refereed papers, some good and some poor, so there's very little point in trying to reinvent the wheel.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258449#Comment_258449 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258449#Comment_258449 Sat, 27 May 2017 08:34:20 +0100 tony Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258456#Comment_258456 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258456#Comment_258456 Sat, 27 May 2017 19:56:20 +0100 dimengineer
Just something to think about]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258467#Comment_258467 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258467#Comment_258467 Sun, 28 May 2017 10:00:10 +0100 fostertom Posted By: djhyou've neglected that the infiltration is not all at the exact bottom and top of the building, but is instead probably distributed rather randomly up the elevationsBut still overall height strongly indicates the order-of magnitude of stack effect; and that what may be significant in mid winter for a bungalow is significant in milder weather for a 3-storey.

Though goodevans calc'd one tenth of the blower test (medium breeze) effect (informative - thanks), the point is it keeps going 24/7 rather than intermittent.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258470#Comment_258470 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258470#Comment_258470 Sun, 28 May 2017 19:41:25 +0100 goodevans
I have a sneaky feeling that it the stack effect that moves most of the moisture into roof spaces via cracks, holes etc (as opposed to permeating though plasterboard). And would explain why many condensation issues show up in the roof space. On still days this would be the dominant air flow - with no wind assisted ventilation to make matters worse as well.]]> Build tight ventilate right http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258479#Comment_258479 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15102&Focus=258479#Comment_258479 Mon, 29 May 2017 10:44:11 +0100 fostertom