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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    I have plans for a living room extension with south facing elevation comprising approx 50% glazing. The windows sit 450mm above floor level and finish just below the eaves.

    There is no overhang to shade these windows. Do I need shading (e.g. brise soleil) in the east of Scotland??
    • CommentAuthortony
    • CommentTimeFeb 6th 2020
     
    Probably, potentially even in winter, or hopefully in winter too, if you have sufficiently low heat losses.

    Can you run a thermal model on it?
    • CommentAuthorCerisy
    • CommentTimeFeb 6th 2020
     
    I did ensure the eaves shaded the first floor windows on our new build and included a lengthy porch on the south side to shade the larger windows from the full summer sun. Found the angle of the midday sun in mid summer online and worked from there. Felt it was very important to reduce solar gain in our heavily insulated house, but we still struggle with over-heating.
    •  
      CommentAuthordjh
    • CommentTimeFeb 6th 2020
     
    Posted By: tonyProbably, potentially even in winter, or hopefully in winter too, if you have sufficiently low heat losses.

    That's extremely unlikely.

    I would say that planning some shade that blocks/restricts summer sun whilst allowing full access to winter sun is much more likely to be the right policy. If the windows really do extend all the way up to the eaves then a brise soleil is going to be very difficult to arrange, since there needs to be some extra height to allow the winter sun in. So maybe moveable shade of some kind will be needed. Deciduous plants are often cited as a possibility but I'm not sure how well they work.
  2.  
    Architect disagrees on the need for shading but I will query this. I've yet to have a summer in the house but experience from Sept with the sun on the current large bay window suggests shading will be needed, especially with improved insulation.
    •  
      CommentAuthordjh
    • CommentTimeFeb 7th 2020
     
    Posted By: WeeBeastieArchitect disagrees on the need for shading

    Ask him/her how s/he's modelled it and what assumptions they used in the model (e.g. about opening windows or not), and look at the predictions from the model.
    • CommentAuthorbhommels
    • CommentTimeFeb 7th 2020
     
    Not sure about East Scotland, but during the heatwave we've had this summer I was very, very happy with the roof overhang the architect designed in (using PHPP) with the south facing extension, shading the 3G patio doors and large window. Extension is well insulated, so getting the solar gain wrong could have easily turned it into a summer months sauna.
  3.  
    Posted By: djh
    Posted By: WeeBeastieArchitect disagrees on the need for shading

    Ask him/her how s/he's modelled it and what assumptions they used in the model (e.g. about opening windows or not), and look at the predictions from the model.


    He has not modeled it. It turns out I rather mislead him when asking if the roof needed an 'overhang'. The eaves are already quite low and he didn't want to cut out any winter sun. He agrees that a brise soleil/shade may be needed.

    Some of the windows will be opening and there will also be rooflights in the adjacent old part of the house - to be open plan to the extension - to provide through ventilation.
    •  
      CommentAuthordjh
    • CommentTimeFeb 7th 2020 edited
     
    Posted By: WeeBeastieThe eaves are already quite low and he didn't want to cut out any winter sun. He agrees that a brise soleil/shade may be needed.

    The problem is that a brise soleil needs to be higher than the windows, so it lets in the low-angle winter sun whilst blocking the high-angle summer sun. If you haven't got any height above the window then you won't be able to use a brise soleil. You'll need to use a moveable/temporary shade that you can put in place during summer and remove during winter.

    Awnings are a possibility but watch out for high winds. External shutters are a possibility but can be a faff. There may be others, such as deciduous plants. We've got a flyscreen over a west-facing window that's in place over the summer and removed in the winter.

    edit: I'm also planning a brise soleil that's basically a pergola with a deciduous plant growing on it (a grapevine). That might work even if it was too low to be a 'proper' brise soleil. Will be built when/if I get permission from SWMBO :bigsmile:
  4.  
    Our sunroom near Aberdeen had south, west and north facing glass walls and an insulated slate roof, with 'normal' eaves overhang. It got hot enough in summer that windows needed to be opened, though not on haar days. The solar gains were welcome in winter.

    Adding insulation doesn't increase summer daytime overheating because the outside air is quite warm, even up here. Opening windows solves the overheating because the air is never really hot, except in Fife.

    Insulating the roof actually reduces the heat gains.
    • CommentAuthorgyrogear
    • CommentTimeFeb 8th 2020
     
    overhang calculator here.

    https://www.youtube.com/watch?v=LiywHmWdIHA

    You don't necessarily need free height above the window, use vertical brise-soleil slats etc.

    gg
      brise-soleil-beau-extérieur-architecture-contemporaine-originale.jpg
    •  
      CommentAuthordjh
    • CommentTimeFeb 8th 2020
     
    Posted By: gyrogearYou don't necessarily need free height above the window, use vertical brise-soleil slats etc.

    The idea in the UK, especially the northern parts, is to let all the winter sun in! A brise soleil immediately above the window doesn't allow that, especially not one with a downward extension as in your photo. Presumably taken somewhere with a warmer climate.
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