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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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    • CommentAuthorGBP-Keith
    • CommentTimeApr 13th 2017
     
    • CommentAuthortony
    • CommentTimeApr 13th 2017
     
    Sounds the answer to all ills.

    Look at the sponsors :shamed:

    I hate it in schools and offices when they have the blinds or curtains closed and the lights on -- the normal situation.

    Roof lights let in the sun which is hated by people using computers (most people in offices), blinds are quickly fitted.

    Roof lights let out a disproportionately large amount of energy compared to windows in walls as the radiate to outer space where deltaT is very large, this is not taken into account bu u value or heat loss calculations.

    Mention is made of solar overheating but it is not taken into account in the energy assessments

    Quite a bit of cherry picking going on.
    • CommentAuthorgyrogear
    • CommentTimeApr 13th 2017
     
    “The regulations define measures to avoid overheating in summer – one of which is to limit glazed areas (windows and rooflights) to limit the solar load, to limit the requirement for air conditioning.”

    Translation: the regulations state that rooflights should be limited, to reduce solar load and need for airconditioning…

    “It should be borne in mind that solar gain through glazing is just one aspect of internal gains within the building. People, artificial lighting and electrical appliances all contribute to internal gains.”

    Quite – another reason to limit rooflights !

    “Solar gains can be beneficial in the winter to offset demand for heating but can contribute to overheating in the summer. Specialist solar control glasses can be used to control solar gain but these will also reduce daylight levels and reduce winter solar gains. SAP 2012 assumes glass with a light transmission of 80% and a g-value of 0.63.”

    Translation: Rooflights will contribute to overheating in summer. Special solar glass is pretty much useless because it LIMITS winter solar gain!

    “Roof glass is bad every day of the year: in summer it causes furnace effect & uncontrolled harsh glare, and in winter it lets out precious heat. Glass breaks, and roof lights will leak : insurers must just *HATE* roof glass ! . The US DoE says that roof-angle glass and skylights should be avoided…”

    (Larry Hartwegg †) https://www.youtube.com/watch?v=lzGaLw__kdk

    gg
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 14th 2017 edited
     
    I have only had a quick scan through the document, and they mention a 'notional house'.
    I assume that this is something built to just achieve the current building regs standards.

    Taking just lighting, they use 60 luminaire lumens/circuit watt.
    I am not sure how realistic this is. LED lighting has moved on a lot in the last 5 years in both efficiency and cost. You would not fit anything else these days unless you are really stubborn, or have an eye condition that makes them painful.
    I had a quick google and found a document from Neweys that explains how to calculate the luminaire lumens/circuit watt.
    Their example shows a 'pass' i.e. over 60 luminaire lumens/circuit watt. of 88 luminaire lumens/circuit watt and I think that is for fluorescent lighting.

    I don't have any problem in incorporating roof light, or suntubes, as long as there is a real benefit.

    Edit:
    The DOE published this in 2014
    https://www1.eere.energy.gov/buildings/publications/pdfs/ssl/snapshot2014_indoor-luminaires.pdf
    Seems the we should be at about 100 luminaire lumens/circuit watt by now.
  1.  
    With solar gain now a far bigger issue than heat loss for me here in central Italy, and in a retrofit DIY situation where easy (relatively foolproof) installation is important, I wouldn't dream of fitting roof lights. I have 2 very short sunpipes in my large land locked vaulted ceiling hall and they are spectacularly successful. They also often work well enough at night to negate the need for turning on a light. As far as i can tell, they are also cheaper in terms of the amount of light they provide per £ but that needs a fair bit of assumption making to say. My only concern is longevity - no way they are going to last as long as a proper roof light as the plastic cap is getting brittle, the condensation foam stuff looks pretty poor now - replaceable......probably, but, in any event, expensive relatively.

    So (and I haven't looked at the paper) I doubt they added in the night time CO2 savings!
    •  
      CommentAuthorfostertom
    • CommentTimeApr 15th 2017 edited
     
    Posted By: GotanewlifeI have 2 very short sunpipes in my large land locked vaulted ceiling hall and they are spectacularly successful
    Only satisfactory under v bright skies - mostly disappointing in UK. Psychological perception of illumination seems to depend on seeing the sky itself directly, as well as the significant loss during multiple reflection in even the shiniest tube. But you say 'very short', so maybe ...
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 15th 2017
     
    I made some prototype sunpipes for a company in High Wycombe (you can google them).
    I was very impressed with the performance.
    Anyone that knows High Wycombe will remember the immortal line in George and Mildred.
    "It was as exciting as a wet weekend in High Wycombe".
    •  
      CommentAuthorfostertom
    • CommentTimeApr 16th 2017
     
    I used to live nr "Keynsham - K-E-Y-N-S-H-A-M - Keynsham" in the words of Horace Batchelor on Radio Luxembourg, further imortalised by Bonzo Dog DooDah Band.
    Keynsham's version of Bristolian co-originated, along with Australia (Neighbours-style) the upward inflection '?' on the end of every sentence (as in 'you know what I mean?') pioneered by my daughters at school there and now universal amongst the young.
    • CommentAuthortony
    • CommentTimeApr 16th 2017
     
    Re light tubes, I would not use them in the UK never. They are kind of acceptable in much hotter countries where you want light but not heat, here there is insufficient light and you generally need a light on with them, then there the many downsides too numerous to mention.
    • CommentAuthorgyrogear
    • CommentTimeApr 17th 2017 edited
     
    But Wycombe or Keynsham surely fade into insignificance beside the sleepy, thriving megapolis of BALHAM, where rooflights or greenhouse gases have yet to be invented...

    https://www.youtube.com/watch?v=74aK8w2910c

    gg
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