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Opinion on summary U values

  • 17-05-2017 1:41pm
    #1
    Draper38
    Registered Users, Registered Users 2 Posts: 9 ✭


    Hi All,
    I have just received an initial quote for a new build and was looking for peoples opinions on the U values.

    House is story & 1/2 with concrete 1st floor, ATW heat pump, 300lt integral water cylinder.
    Air tightness <4m3/m2/hr - seems high to me?

    Floors (UFH) 0.16 w/m2k
    Walls 0.21 w/m2k
    Windows, doors, rooflights 1.27 w/m2k @25% of floor area - also seems high?
    Sloped sections 0.17 w/m2k
    Sidewalls 0.21 w/m2k
    Ceilings 0.15 w/m2k

    If I was to upgrade the windows/doors, remove all vents and install a MHRV system should this improve things?

    My knowledge is (very) limited so all opinions welcomed. Also I will be appointing all the necessary professionals when the time comes, just looking to increase my own knowledge and understanding of the whole thing in the meantime.
    Cheers.


Comments

  • #2
    kieran.
    Registered Users, Registered Users 2 Posts: 1,175 ✭✭✭kieran.


    Draper38 wrote: »
    Hi All,
    I have just received an initial quote for a new build and was looking for peoples opinions on the U values.

    House is story & 1/2 with concrete 1st floor, ATW heat pump, 300lt integral water cylinder.
    Air tightness <4m3/m2/hr - seems high to me?

    Floors (UFH) 0.16 w/m2kNeeds to be Min 0.15W/m²K
    Walls 0.21 w/m2k Aim lower 0.17 W/m²K would be the highest I go with
    Windows, doors, rooflights 1.27 w/m2k @25% of floor area - also seems high? Is this for Double Glazing what are the cost implications for improving to Triple Glazed vs the improvement U-value
    Sloped sections 0.17 w/m2k Needs to be Min 0.16W/m²K
    Sidewalls 0.21 w/m2k Aim lower 0.17W/m²K would be the highest I go with
    Ceilings 0.15 w/m2kif you are going with Mineral wool no reason not ot get this down to 0.13 W/m²K

    If I was to upgrade the windows/doors, remove all vents and install a MHRV system should this improve things? Some sort of controlled ventilation is essential IMHO

    My knowledge is (very) limited so all opinions welcomed. Also I will be appointing all the necessary professionals when the time comes, just looking to increase my own knowledge and understanding of the whole thing in the meantime. The quote you have received is pretty much useless, you/ your appointed agent needs to be supplying the contractors with a compliant specification for tendering purpose. You need to get the professionals on board as early as possible.
    Cheers.

    In bold


  • #3
    sydthebeat
    Subscribers Posts: 42,172 ✭✭✭✭sydthebeat


    Draper38 wrote: »
    Air tightness <4m3/m2/hr - seems high to me?

    slightly high, but air tightness is very subjective if no MHRV is proposed.

    personally i wouldnt at all consider an A2W HP in a house with UFH with no MHRV
    Draper38 wrote: »
    Floors (UFH) 0.16 w/m2k
    doesnt comply with building regulations
    UFH requires a u value of 0.15 or better
    Draper38 wrote: »
    Walls 0.21 w/m2k.

    very high.

    along with all the other u values mentioned id be very surprised if this spec is building regulation compliant.

    have you had a preliminary DEAP assessment carried out in order to check what u values and specification you need to reach to comply?

    That really is the only way your questions will be answered.

    as an addition to everyone, a builder CANNOT offer a quote (including their own specification) and be certain it would comply with minimum regulations WITHOUT a preliminary DEAP assessment being carried out.
    ......no matter how often they say, sure we did a house with this spec last week and it complied........


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