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General: Another point scored for thermal mass?

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  1.  
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      CommentAuthorOJ
    • CommentTimeMar 24th 2008
     
    I found a reference to this research recently in a timber building magazine, although the research itself seems to be older. The timber slant was warning of complacency within the timber industry apparently holding all the green cards. The "light" home described is timber-framed, masonry-clad, and it is suggested that it will need air-con by 2021. Do we know any more details of the insulation lay-up in the "light" home?

    http://www.concretecentre.com/main.asp?page=1399

    Incidentally, the heaviest construction had heavyweight external walls and partitions as well as precast first and loft floors.

    OJ
  2.  
    OJ,

    I read these reports a while ago, they were published for the 'Concrete Centre' (is that a clue there...?), based on research by Arups...

    ...the Concrete Centre... ie their sole aim is to promote the use of concrete..!

    http://www.sustainableconcrete.org.uk/main.asp?page=113

    However, notwithstanding, there is some compelling info on the face of it but the detailed results published in the reports show that either method can provide good thermal response depending on occupancy patterns and the expected levels of increased annual average temperatures.

    In addition the point at which air con was 'required' seemed a little early to me based on the figures used, i.e. it was 'required' after only a few days of summer overheating. Also no account was taken of targeted thermal mass design in an other wise lightweight structure or summer shading, or hybrids like low environmental/high mass techniques. Also as far as I could see the comparative analysis of LCA was based on energy rather than environmental impact, as we know the impact of concrete extends far beyond embodied energy.

    I think the masonry vs timber frame debate still rages, although recently it seems that monolithic masonry construction could achieve passive house standards more reliably, however timber frame still has many other advantages. IMHO a lot comes down to detailed design and workmanship and the what the building is trying to achieve in terms of economic and procurement as well as performance.

    Both publications still interesting and well worht registereing for.

    J

    see also http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=679&page=2#Item_12
    •  
      CommentAuthorfostertom
    • CommentTimeMar 24th 2008
     
    Good response James. Just 'going heavy' isn't enough, could actually be counterproductive if it accidentally results in e.g. redelivering yesterday's stored heat just when the today's solar input starts. Also, simply replacing a stud inner skin with 100 conc block gives a fairly puny massiveness gain; concrete floors only a little more. Really this Concrete Centre propaganda is only about avoidance of summer overheating, particularly relevant to present cheapskate school building programme etc. It says little about Passivhaus etc principles of storing heat gains to reduce fueled winter heating. Yes, thermal massiveness is increasingly the way to go, but definitely not in the simplistic way promoted in this marketing push. Don't know what Arups were thinking of - they've probably been selectively (mis)quoted.
  4.  
    Posted By: fostertomconcrete floors only a little more.


    Actually confirmed in the small print of the report, particularly once you've laid a carpet over...

    J
  5.  
    Incidentally, the thermal mass per unit volume of concrete and wood is surprisingly similar.

    When I first arrived in Canada, I was surprised to see that most new construction is timber frame and thought it looked flimsy compared to good old solid British brick+block construction. Now I'm not so sure. Wood, at least where I lived, can be source locally and uses far less energy to transform into a structure than brick+concrete. Thermal mass is only useful in climates which have a reasonable diurnal temperature change and a means of getting daytime heat inside in the firstplace without compromising insulation. In climates which are either hot all the time in summer (and cold all the time in winter), it's not so useful, particularly in the summer case where storing daytime heat is not a good plan. Where I live nighttime temperatures in summer are often in the mid 20s or higher (celcius) - far higher than most people in the UK would find tolerable for sleeping. Best to focus on airtightness and good insulation to keep the heat and cold out in the first place - if you want to bring in heat from the sun, use water as a transport mechanism or some kind of clever window system that won't let the heat in in the summer or the heat out at night in winter.

    Paul in Montreal.
    • CommentAuthortony
    • CommentTimeMar 24th 2008
     
    But there is a far smaller total mass of wood in a timber frame house than heavyweight stuff in a solid house. The wood is often thermally bridging the insulation too to some greater or lesser extent.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 24th 2008 edited
     
    What about these bespoke kit houses where each wall is a solid slab of laminated softwood 100-150 thick? Or solid 'log' construction?
    • CommentAuthortony
    • CommentTimeMar 24th 2008
     
    Cold? or wasteful of energy?
  9.  
    If we start building more timber houses in the UK, how are we going to pay for the timber because we aren't going to be growing it here are we (not for a few decades at least even if we started planting now)? We could do with some industries in the UK so people can have jobs and with finance looking a tad shaky and North Sea oil production going off a cliff I'd say we ought to building with something we have got in the UK and don't have to pay a foreign country for.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 24th 2008
     
    Cob?
    • CommentAuthorhowdytom
    • CommentTimeMar 24th 2008
     
    CommentAuthorfostertom CommentTime2 hours ago quote
    Cob?
    and straw bales on the outside ?
    tom
  12.  
    What about lime hemp blocks? I seem to recall reading you only need about a hectare of land to grow enough hemp for a house in one season. So you'd only need to set aside 250,000 hectares to meet the new build requirement for the whole country (more use than growing biomass). We've got limestone. Self sufficiency. Compressed earth blocks for the internal walls using the spoil from the footings. Does the insulating too if the walls are thick enough. Carbon sequestering, likewise with straw bales (might as well use them up if there are some going spare).

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