Go to Forum Home Building Simulation Reveal shading in PHPP

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    • #31182
      Nick Grant
      Participant

        How to enter shading from a wall or L shaped building element in PHPP.

        I know it is as a reveal but:

        1. how to allow for the fact that it is a single shading element on one side of glazing only?

        2. for the curtain walling example attached (not the actual project, for illustration only) do I need to enter the shading for each pane (there are 10 in reality) or is there an acceptable fudge?

        3. and any ideas for a fudge to allow for wall height varying? Could be full building height or a garden wall.

        I know Mark S has been looking at this.

        Thanks in anticipation

      • #36446
        Mark Siddall
        Participant

          Hi Nick,
          To my mind this is not something that has been completely resolved. I’ve looked at thermal bridging and frame dims and I’ve read papers discussing thermal bridging vs solar gains – see below – but I’ve not had the chance to undertake a first hand examination of thermal bridging vs solar gains.

          As for using PHPP and determining solar shading from reveal depths, again I’ve not looked at this in any great detail.
          At this time I have had to settle on the idea that as PHPP looks at the monthly performance it is appropriate to use the average reveal depth for each window pane. (This is the method employed in the CarbonLite Programmes PHPP training course.) From the perspective of a purist this feels wrong – you’re modelling a fudge rather than “reality” – but owning to the use of monthly data sets (averaged data) it can be argued appropriate to use the average reveal depth i.e. the averages smear out the differances.

          The use of and average reveal depth does give me some concerns about the accuracy of the over heating risk calculation (westerly sun being more problematic) but I have no real basis to justify whether or not this concern is truly justified (an errors may be down in the noise).

          I hope that the above goes someway to addressing items 1 and 2. At this time I’ve no idea about how to approach item 3.

          Last week I was approached by a student at CAT regarding a thesis that he is preparing examining window geometry, daylight, solar gain, reveal depths and thermal bridging. Sounds like a really interesting study. I directed him to th efollowing:
          Heat load day lighting study: http://www.ebd.lth.se/fileadmin/energi_byggnadsdesign/images/Publikationer/Energy-efficient_terrace_houses_in_Sweden_Maria_W.pdf
          Passive House Conference Paper “Considerations considering the suitability of thermal-bridge-free window installation in practice in old an dnew buildings” (from 2006). This paper examines thermal bridging vs solar gains.

          Cheers,
          Mark

        • #36447
          Nick Grant
          Participant

            Thanks Mark

            So to clarify, in my example you would use a reveal depth of wall length/2 (given that other reveal is almost zero)?

            Can we model 1 window and use average distance to reveal as we would for a normal multipane window in a normal wall reveal situation?

            Obviously we can ask all this at Strathclyde but I wanted to wrestle with it first.

            Re point 3 this makes a big difference as with a wall, the height soon becomes more important than the length (just playing around in sketchup).

            BTW I'm very happy with rules of thumb and fudge factors as long as it is transparent. Can always do quick sensitivity analysis by varying fudge factor and looking what difference it makes.

            Can we ever really model reality? After all people plant trees and put up trellis and pergolas.

            Cheers

            Nick

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