Saw-Tooth Roof Orientation

[Anonymous]

Can anyone confirm my understanding that a glazed saw-tooth roof should be oriented northwards to minimse overheating rather than south to mazimise winter solar gain?

[SimmondsMills]

What is the building type – domestic, commercial, etc?

Are you trying to use this vertical high level glazing to maximise well distributed daylight AND to maximise passive solar gain to displace the building's space heating requirements, or just for daylighting?

[David Olivier]

AFAIK there are now a few 100 well-daylit US schools that have copied the first ones in North Carolina 20 yrs ago which all face the vertical glass south. The term “Smart schools” and USDOE in Google should find a few sites if anyone's interested.

If it works in the hot humid summers of the USA, it's pretty viable here. It's planned to do it on a new small office building in Essex and on an educational bldg in Shropshire. It's also been done on some schools and laboratories in France described in EU publications which I have dating from the early 1990s.

David.

[Anonymous]

Thanks for the replies.

Just been looking at a planning application for an educational building in Shropshire(where m children are likley to be educated) which is presumably the one you are referring to David. It was seeing that which prompted my question?

I am not clear about the science behind having south facing unshaded vertical glazing. Clearly in the winter there will be passive gains and natural light. However is there going to be a comfort issue during the summer with both overheating and glare from the windows?

I can see how a south facing glazed elevation is beneficial but this is normally where there is an overhang or briese soleil to reduce solar gain in the summer.

Can you clarify?

[David Olivier]

Nigel

It's a small world! The web sites describing the North Carolina daylit schools (first one in 1985) describe in detail the methods used to prevent glare including either
1 vertical white metal or cloth bafffles at ceiling level to block the direct sun and admit diffused light or
2 horizontal white blinds behind the window to achieve the same goal.

Usually arranged in the mid-Atlantic USA at 37 deg N so that building users never see the direct sun – too much glare. Similar principle in Shropshire at 52 deg N although somewhat less concern over building users occasionally seeing the sun on a clear day in November, December or January.

The rationale for vertical south glass is that it produces twice as much daylight as north glazing, yields passive solar gains for heating and glare can be shaded out (as above). Sloping glass is common in the UK and is good for daylighting but overheats in summer (most orientations) and has a large heat loss in winter.

HTH

David.

[Author]

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