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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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    • CommentTimeMar 18th 2011 edited
    From http://www.bdonline.co.uk/5014839.article?origin=BDweeklydigest:

    "Inaccurate figures could lead to damaging and unnecessary interventions, warns SPAB

    Heat loss through vernacular materials can be up to three times lower than expected, according to new research conducted for the Society for the Protection of Ancient Buildings (SPAB).

    The standard U-value calculations used across the construction industry to assess thermal performance appear to underestimate the efficiency of traditional walls, according to Dr Caroline Rye from the University of Portsmouth.

    Her research suggests that 79% of the traditionally built walls sampled – including timber, cob, limestone, slate, and granite – actually perform better than expected.

    Jonathan Garlick, SPAB technical officer and project leader, said: “Amazingly, this research has not been carried out before in England. Accepted theoretical performance figures have long been used as a standard base measurement by professionals and homeowners when old buildings are being up-graded, altered or even assessed for Energy Performance Certificates, but are they correct? We believe that with some traditional materials our in-situ results prove that they are not. We appear to be actually underselling the thermal performance of our old buildings by not fully understanding them.

    “Energy efficiency is becoming the key issue for people working with historic buildings. If we aren’t basing our approaches on the right figures to begin with, then we could, unintentionally, be doing untold, invasive damage.”

    Here's the report:
    • CommentAuthortony
    • CommentTimeMar 18th 2011
    One of the problems is that U-values refer to steady states whereas buildings are rarely used like that.
    • CommentAuthortony
    • CommentTimeMar 18th 2011
    Another is that SPAB paid for this research, were they angling for certain results?
    • CommentTimeMar 19th 2011 edited
    Does Equation 1 in the report convert it to a steady state condition as it is is using the sum of the temperature changes divided by the sum of the heat flows for the test period.
    It is also worth looking at the magnitude of the measured and calculated U-Values, 6 had a U-Value under 1, 14 between 1 and 2 and 4 above 2. This can easily skew the results.

    Kind of research I like as it is real. Did you want some real data on old buildings on another thread, friend of mine did some work on this a few years back, not sure if he has still got it though, he was never very good at backing up his data and the university used to wipe it all in the summer.
    • CommentTimeMar 19th 2011
    So what U value do we give to a 500thick rubble stone wall lime plastered internally, with and without external lime render? Something better, I think, than you'd get by conventionally using the lamda value of solid limestone.
    • CommentAuthorseanie
    • CommentTimeMar 19th 2011
    Historic Scotland did similar research a couple of years ago. But there seems to be a tendency to interpret the results as meaning historic buildings are thermally efficient, whereas all they are is not quite as dreadful as first thought.
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