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Energy Assessment: Will this new build need any additional heating?

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  1.  
    • CommentAuthorbigrightear
    • CommentTimeJun 13th 2008 edited
     
    A four-storey 230m2 house built on a steep slope so that it appears to be a
    single-storey building from the north-facing top road and a four-storey
    one from the south-facing bottom road.

    The walls are constructed from Polarwall ICF with a U-value of 0.14.

    The windows are by Nor-Dan of Norway. They are double-glazed, argon-filled
    and have a U-value of 1.4 for the whole window. Glazing represents
    approximately 15% of the external surface area of the building. Around 90%
    of the windows are south-facing.

    The roof is constructed with Structural Insulated Panels which have a
    U-value of 2.0. However, a further 150mm of Rockwool loft insulation has been placed in the attic floor.

    The ground floor has 100mm of Kingspan insulation beneath a concrete screed.

    The airtightness of other Polarwall houses is typically rated at 2m3/hr/m2@50pa.

    The house is fitted with a whole-house ventilation system, with heat
    recovery, supplied by Allergy Plus. The heat recovery unit includes a 1kW
    heater to boost the temperature of the incoming air. No other heating
    >system is currently provided. Will I need one?
    • CommentAuthortony
    • CommentTimeJun 13th 2008
     
    No, but you might be better without the insulation on the inside if the concrete.

    You may have problems with overheating due to too much solar gain and not enough internal thermal mass to mitigate it.

    The air leakage wants to be less than one.

    Could you use the thermal mass and insulating properties of the ground behind the house?
  3.  
    Hope the roof u value is 0.2, not 2.0! But then I always was a pedantic....proof-reader.
    •  
      CommentAuthornigel
    • CommentTimeJun 13th 2008
     
    I think you will have a peak heating load of 4-5Kw.

    It might be that on a sunny winters day you wont need it but you will need it on a dull cold day.
    • CommentAuthortony
    • CommentTimeJun 13th 2008
     
    Unless heat can be stored in the thermal mass in and behind the building to even out the internal temperatures.
    • CommentAuthorsipman
    • CommentTimeJun 14th 2008
     
    BIGRIGHTEAR

    I think the house will peform well, provided the quoted u values and air tightness are achived

    If it were my house I would be tempted to fit a wood burner to one of the lower floors, to add some additional instant heat on cold days, would only need to burn for a short period of time

    also look at using the ventilation system to move some of the heat that will be trapped in the roof space down to the lower floors

    sipman
  7.  
    Thanks everyone for your comments and apologies for the delay in replying. Tony - there is a thermal mass behind the bottom two storeys of the building, but the wall of the building that butts against it is of Polarwall with a u-value of 0.14. Shame I didn't know about the green building forum before we started building, as we didn't think of this. However, the Allergy Plus ventilation system offers a cooling option if it turns out we need it. Sipman and Nigel - yes, we think we'll need some additional heating on the coldest days, so we'll monitor the situation through next winter and report back.
    Many thanks,
    bigrightear
    • CommentAuthorGBP-Keith
    • CommentTimeJun 22nd 2008
     
    Please refrain from shouting on the forum.
    • CommentAuthorRobinB
    • CommentTimeFeb 17th 2010
     
    If by chance you still visit the GBF, bigrightear, I'd love to know how you've got on with you heating (or lack of it). I just can't make my mind up whether to have UFH.
    best wishes
    RobinB

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