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      CommentAuthorSteamyTea
    • CommentTimeJan 11th 2018
     
    You may well have been :bigsmile:
    But it never takes me long to get on my high horse about it :bigsmile::bigsmile:
    • CommentAuthordelprado
    • CommentTimeJan 11th 2018
     
    Ive been learning nonetheless :)
    • CommentAuthorSigaldry
    • CommentTimeJan 12th 2018
     
    Timber frame constructions are typically associated with lower levels of thermal Mass, but dwellings using aircrete blockwork and minimal dense constructions also fall under this category.

    Building materials with higher thermal mass (more dense and higher heat capacity), such as concrete, brick and stone, have a greater ability to absorb daytime heat gains (reducing the cooling load and helping to avoid summer overheating), but in turn, they will release that heat during the night, which can make the internal temperature of a building more stable.

    The downside to higher thermal mass, is that it can make a dwelling less responsive to deliberate temperature changes. Dwellings with high thermal mass in the UK climate take longer to reheat once cooled down.
    A low thermal mass construction allows a dwelling to heat up more quickly, with less thermal lag – although it does then also release that heat more quickly. Good insulation levels should help to ensure that any released heat is largely retained within the dwelling’s envelope however.

    Under the SAP model for new build dwellings, slower thermal lag from a higher thermal mass construction is of less benefit when compared to better responsiveness from low thermal mass constructions; as, after initially heating up in the morning, by the time the next heating period is reached, the background temperature for both will typically have dropped to similar levels.

    From SAP modelling of two identical dwellings, with the only difference between those two dwellings, being the Thermal Mass Parameter, one medium dense, one lightweight construction, I found that the lightweight construction one achieved a better (lower Dwelling Emission Rate and had lower fuel bills).

    Higher thermal mass is generally considered to help with minimizing summer overheating, with good design (good night ventilation, correct materials in the correct places), it seems that it can be very beneficial – which is why in hotter climates it’s use is so much more prevalent. It is however, also possible for lightweight housing to provide similar thermal comfort levels in the summer, using appropriate ventilation and solar shading.

    A high thermal mass may be more beneficial in circumstances with a more constant, lower level heat demand, but as far as a modern dwelling in the UK climate, a quick heating response (from lower thermal mass) seems to be considered more beneficial.

    As to what construction is best, my personal feeling would be, one that is well insulated, easy to build (quick / achieves weather tightness fast / unlikely to be built badly), one that minimizes thermal bridging, and is air tight (combined with good heat recovery ventilation) - so probably SIPs - but that said, I do like timber frames.
    • CommentAuthorDarylP
    • CommentTimeJan 12th 2018
     
    +1 :-)
    • CommentAuthortony
    • CommentTimeJan 12th 2018
     
    -1 , too responsive = gets cold (or hot) too fast = uncomfortable
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2018
     
    Posted By: Sigaldrymore dense and higher heat capacity
    But as I explained earlier, there is the thermal conductivity to consider as well. Density and specific heat capacity are not related.
    What I think you are referring to is volumetric heat capacity.
    Posted By: SigaldryHigher thermal mass is generally considered to help with minimizing summer overheating
    Possibly, but you must be paying for it somewhere, probably a higher winter heating bill.

    The UK climate is pretty unique, tends to be mild, with a few extremes for a very short time. Most of the time is is cloudy.
    Someone put a link up to some wine storage place in France that had metre thick stone walls. They enthused about the temperature stability inside this mostly underground building.
    Was not a temperature I would want to live in, way too cold.
    To me, lots of stone, brick and concrete just means a cold house that needs heating more.

    Posted By: SigaldryAs to what construction is best, my personal feeling would be, one that is well insulated, easy to build (quick / achieves weather tightness fast / unlikely to be built badly), one that minimizes thermal bridging, and is air tight (combined with good heat recovery ventilation)
    I think that is good generic advice.
  1.  
    Posted By: SteamyTea
    Posted By: SigaldryAs to what construction is best, my personal feeling would be, one that is well insulated, easy to build (quick / achieves weather tightness fast / unlikely to be built badly), one that minimizes thermal bridging, and is air tight (combined with good heat recovery ventilation)
    I think that is good generic advice.

    Sounds like single skin blockwork with EWI to me !
    • CommentAuthortony
    • CommentTimeJan 12th 2018
     
    +1
    • CommentAuthorMike1
    • CommentTimeJan 12th 2018 edited
     
    Posted By: SigaldryA high thermal mass may be more beneficial in circumstances with a more constant, lower level heat demand, but as far as a modern dwelling in the UK climate, a quick heating response (from lower thermal mass) seems to be considered more beneficial.

    However, the effects of global warming seem likely to significantly change the UK climate, particularly to significantly increase summer temperatures.

    For example the Government's 2012 Climate Change Risk Assessment predicts with 'high confidence' that overheating of buildings in London will occur on between 22 and 51 days each year by the 2020s. The Environmental Protection Agency advises that excess deaths occur when temperatures reach 25°C (other sources quote a figure at 24.7°C for London - the statistics vary by location).

    And Government advice (Review of the potential effects of climate change in the United Kingdom, DOE, 1996) recommends that buildings "be designed with the probable climate of 2050/59 in mind" - though I've come across scant evidence of that advice having been promoted to building designers.

    In a previous job I did some forward looking climate comparisons for London.
    Looking over the data as a whole, it suggests that what we now consider to be 'heatwave' temperatures are likely to be 'normal' summer temperatures by 2050, with considerably hotter and longer heatwaves.
    Specifically (using the IES London Temperature File of 'current' London temperatures), 'now' - around 2010, I think - there were approximately 5 days each year with temperatures between 25°C and 28°C, and a further 5 days with temperatures exceeding 28°C. And 3 contiguous days with peak temperatures over 25°C.
    By 2050 the projection indicates 18 days between 25°C and 28°C, and a further 36 days with temperatures exceeding 28°C. And 15 contiguous days with peak temperatures over 25°C.

    Since the buildings being designed now are likely to be in use far beyond 2050, much greater account should be given to such considerations.
    • CommentAuthorgyrogear
    • CommentTimeJan 12th 2018
     
    Posted By: SigaldryA high thermal mass may be more beneficial in circumstances with a more constant, lower level heat demand,


    +1

    particularly if one subscribes to the notion that a house's temperature would ideally remain constant, year-round...

    It's a bit like a motorbike throttle - wide open to get the acceleration, then once at cruising speed, ease it off to save money / petrol...

    Posted By: SteamyTeaTo me, lots of stone, brick and concrete just means a cold house that needs heating more.


    well, ST, I can assure you that it is not the case in my case, and you can come & see for yourself whenever you want !

    :smile:

    gg
    • CommentAuthorgoodevans
    • CommentTimeJan 13th 2018 edited
     
    Sorry Steamy but I think some of your figures are a bit off.

    Density of seasoned spruce is lower - around 450kg/m3, concrete a bit lower than stated as well - 2200 to 2400kg/m3 - SHC of spruce around 2300 J/kg.K as you said, concrete a bit higher at 880 J/Kg.K

    So multiplying out it means that Spruce around half the heat capacity of concrete for a given volume - in addition the insulative effect of the spruce means that it is relatively slow to heat up and extract heat from the core of the store - i.e. not ideal as thermal mass.

    The right material depends on what it's doing - as a barrier to heat - spruce is better than concrete because the insulative qualities of concrete let it down. But put a layer of ewi outside of the concrete and all is well - the little bit of heat getting past the ewi means that it take ages for the heavy concrete to increase it's temperature. As a thermal store, concrete easily beats spruce - but water easily beats concrete and most other materials by volume.

    So far as the original question is concerned. I will be going for single skin block (140mm), EWI and blockwork/dense plaster internal walls. With JJI joists as rafters, dry blown cellulose fill between the rafters for sound proofing, gap free insulation with a good combination of density, SHC and insulation values.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 13th 2018
     
    Posted By: goodevansI think some of your figures are a bit off.
    Quite possibly, as I said, I had not done an exhaustive search of all material properties.
    The main point I have been trying to make is that almost regardless of of what materials you choose, there sill be enough mass. Not as if you can make a house out of only air.
    Adding unnecessary extra mass does nothing at best, and causes winter cooling at worse.
    Get the insulation and airtightness right, then consider the affects of solar gain and you will not go far wrong.
    •  
      CommentAuthorjoe90
    • CommentTimeJan 13th 2018
     
    I am with Tony on this one, argue all you like, his house is warm, does not overheat and is very cheap to run.
    • CommentAuthorborpin
    • CommentTimeJan 13th 2018
     
    Posted By: Peter_in_Hungary
    Posted By: SteamyTea
    Posted By: SigaldryAs to what construction is best, my personal feeling would be, one that is well insulated, easy to build (quick / achieves weather tightness fast / unlikely to be built badly), one that minimizes thermal bridging, and is air tight (combined with good heat recovery ventilation)
    I think that is good generic advice.

    Sounds like single skin blockwork with EWI to me !
    Sounds like a Timber Frame with tea Cozy insulation to me!

    Of course what has not been discussed is floor design. Some of the negatives of a TF frame can be offset by a large thermal mass floor and UFH.
    • CommentAuthorSilky
    • CommentTimeJan 13th 2018 edited
     
    +1 on hollow clay bricks

    For example, this building is passive without any added wall insulation, it's just 2 layers of hollow clay blocks ( 38 + 38 cm ), the inner and outer skin are staggered vertically to reduce thermal bridging.

    picture of wall detail here

    https://www.bauforum.at/bauforum/atmosphaere-statt-maschine-57190

    some blurb here

    https://www.detail-online.com/article/house-without-heating-office-building-in-austria-16667/
    •  
      CommentAuthordjh
    • CommentTimeJan 13th 2018
     
    Posted By: SilkyFor example, this building is passive without any added wall insulation, it's just 2 layers of hollow clay blocks ( 38 + 38 cm ), the inner and outer skin are staggered vertically to reduce thermal bridging.

    Hmm, it's an office building and the usual problem in offices is keeping them cool rather than heating them. It's also a lot taller than a domestic dwelling so the passive ventilation has a lot more stack effect available to make it work, and much bigger than a house, which changes the balances. And of course the walls are 800 mm or so thick, which is not ideal for a house, especially to achieve only a U value of 0.14 W/m²K

    Hockerton is another example of thermally massive houses with stable temperatures.

    I'm of the "there's more than one way to skin a cat" school of thought.
    • CommentAuthormattwprice
    • CommentTimeJan 14th 2018 edited
     
    At just 140 block will monolithic block be sufficiently structurally stable for what you are intending? I’m thinking along the same lines but was more thinking of a 200 block with EWI.. what internal lining were you thinking of? If it’s dense plaster what thickness? I’m just considering chases for wiring and pipe work etc...
  2.  
    I've built Passive Houses using Aircrete, Poroton, Timber Frame with WoodFibre Board, External Insulated block on the flat , externally Insulated Timber Frame, Cavity Wall with 200mm Pumped bead, and ICF.
    Here's some of my opinions/conclusions:

    I saw no difference in their heating/overheating requirements as most required tilt/turn windows downstairs and openable windows upstairs to provide stack ventilation to satisfy the PHPP energy calculations.

    I've no problem with block houses if they're built properly but the airtightness can't be tested until the plastering is done so you usually have to accept what you get, this makes it difficult to estimate the heating requirements.

    BedZed has thermally massive walls but suffers a lot from summer overheating, when I was there last summer the thermally saturated internal walls were radiating 26 degrees, it would be easier to cool it if it was low thermal mass.

    Woodfibre-board is expensive and isn't worth the extra money spent on it compared with EPS which is equally breathable.

    Some of the Aircrete house's I built had cracks in the internal walls, widening the cavity by 10mm and using regular blocks had the same U-value but was cheaper.

    Poroton blocks are expensive, a regular hollow block with 30mm extra external insulation gave the same U-value but was much cheaper. You can't see the colour of the blocks when they're plastered.

    ICF is no quicker than block construction but more expensive, we had to add an extra 150mm external insulation to reach Passive standard.

    Houses with External Insulation can look tatty after a few years, they don't wear well.

    We produce Twin-Stud Timber Frame houses in our Irish factory so my opinion's a bit biased but I do believe we've picked the most cost effective method to build Passive Houses.
    • CommentAuthorgoodevans
    • CommentTimeJan 16th 2018 edited
     
    Posted By: mattwpriceAt just 140 block will monolithic block be sufficiently structurally stable

    I have a structural engineer for my project - And I will be using him for all the elements that the BCO will want to see independent calcs - The building guidence states 190mm minimum for single skin in my situation - but if you can find an engineer to do the necessary calcs then you can use the whatever the engineer is prepared to sign off on. I will have to have one wind brace for a 9m long gable wall that does not have an internal buttresing walls.

    I will have to have bed reinforcement every 450mm (2no 3mm flattened bars) - but the advantage of 140mm is that medium density blocks come in at just under 20kg allowing single man laying.

    In addition, because I am using the bed reinforcement and the blocks won't be subject to wide temperature flucturations (behind ewi), the engineer has stated I will not need expansion joints on my longer walls.

    Just by using 140mm blocks will pay for the cost of the engineer.

    I may be lucky in finding a 'can do' engineer.
    • CommentAuthordelprado
    • CommentTimeJan 16th 2018
     
    "Houses with External Insulation can look tatty after a few years, they don't wear well."

    Viking what is that based on? Surely if rendered properly you can't tell what is underneath?
    • CommentAuthortony
    • CommentTimeJan 16th 2018
     
    Most of Central Europe uses EWI and high tech thincoat render
  3.  
    To be fair I prefer the front of my house ie original Victorian red brick to the rear EWI render. Not sure what system they used but it does look grubby
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