UKTC Archive

Re: Availability of sunshine

Subject: Re: Availability of sunshine
From: chris skellern
Date: Aug 01 2019 11:49:02

 "As a separate question, how many consultants doing 5837 reports present the 
shadow segments in their tree constraints reports?"
I only include segments if requested. But by default, I plot them on to 
drawings because my software does it automatically. But I hide the layer so 
it can be switched on later if required.
The problem I have with the segment is that it (very roughly) represents the 
MOTION of the shadow through a short part of the day and can be very 
Firstly, its unlikely the area of the whole segment will be shaded at the 
same time. Using the height as its radius, it assumes a 45 degree sun 
elevation which is around 10am and 4pm in June, 10.30am and 3.45pm in 
May/July,  11.30 and 2.30 in April/Aug. Shadows in between will be shorter, 
outside will be longer.Using the segments northwest to due-east radius lines 
gives times of 11.20 - 5.50pm for June 21st. But in reality, at 5.50pm the 
shadow length will be over twice the length of that shown! So the arc is a 
very, very rough guide to show where shading will occur during the summer 
months and during the middle of the day. 
You could have trees located very close to an eastern garden boundary with 
the segments making all kind of alarm calls. But in reality once past noon, 
the shadows have left the garden and are pointing westwards for the rest of 
the day. With tall trees on a western boundary, the segments may suggest that 
much of the garden is free from shade but in reality the whole garden could 
be swamped from early afternoon until sunset.
It is indeed a minefield!

Chris Skellern 
Arboriculturist  LinkedIn   

    On Thursday, 1 August 2019, 10:08:27 BST, Julian Morris 
<> wrote:  
 Does anyone have a copy of "Availability of sunshine" (CP75/75 - AP 155) by 
BRE (01-Jan-1975) that I could have a look at? It is referenced in 
BS5837:2012 (Clause 5.2.2) but was withdrawn by BRE and is not available to 
buy, even from BRE. I don't need to HAVE a copy, i would just like a flick 
through it to confirm it says what I think it says. Any help appreciated.

As a separate question, how many consultants doing 5837 reports present the 
shadow segments in their tree constraints reports? Personally I do not do it, 
I offer it as a service (or full BS8206 daylighting assesments), no-one has 
ever asked for it and no-one has ever protested that I haven't included it in 
my reports.

Julian A. Morris - Professional Tree Services  and
0778 XXX XXXX - 0141 XXX XXXX

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