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Airtightness

  • 16-04-2021 1:33pm
    #1
    Registered Users Posts: 4,034 ✭✭✭


    Got an airtightness score of 1.9 during the week in my new house. Is this good for a brand new house? I had a mate of mine that build his house 3 years ago and got airtightness of 1.49. His house is a more complex design than my own. My house is a rectangular structure with hip roof, just shy of 2900sqf. His house was similar in size.

    The tester told me he found a leak in one room where the pipes and electrical wires/cat 6 wires are to be just to be aware of. I'm wondering how much of a difference that would make to over airtightness score by rectifying? I will get my builder to seal up this area in snaglist.


Comments

  • Registered Users Posts: 363 ✭✭Biker1


    Amprodude wrote: »
    Got an airtightness score of 1.9 during the week in my new house. Is this good for a brand new house? I had a mate of mine that build his house 3 years ago and got airtightness of 1.49. His house is a more complex design than my own. My house is a rectangular structure with hip roof, just shy of 2900sqf. His house was similar in size.

    The tester told me he found a leak in one room where the pipes and electrical wires/cat 6 wires are to be just to be aware of. I'm wondering how much of a difference that would make to over airtightness score by rectifying? I will get my builder to seal up this area in snaglist.

    Generally a leak like that would only register on the third or fourth decimal place thereby having little effect. You cannot compare one house with another as the main cause of differences in results comes down to attention to detail of the airtightness strategy. The majority of leakage I detect when testing occurs in the space between the ceiling and hollowcore. This is purely down to lack of knowledge on how to implement a proper airtightness strategy.
    The average test results throughout the country at present is around 2.5 so you are not doing too bad.


  • Moderators, Home & Garden Moderators Posts: 10,135 Mod ✭✭✭✭BryanF


    Biker1 wrote: »
    Generally a leak like that would only register on the third or fourth decimal place thereby having little effect. You cannot compare one house with another as the main cause of differences in results comes down to attention to detail of the airtightness strategy. The majority of leakage I detect when testing occurs in the space between the ceiling and hollowcore. This is purely down to lack of knowledge on how to implement a proper airtightness strategy.
    The average test results throughout the country at present is around 2.5 so you are not doing too bad.
    I’m not sure the average air-leakage value is worth aspiring too..
    0.6m3/hr/m2 is the minimum passive standard.


  • Registered Users Posts: 4,034 ✭✭✭Amprodude


    BryanF wrote: »
    I’m not sure the average air-leakage value is worth aspiring too..
    0.6m3/hr/m2 is the minimum passive standard.

    What would you be expecting a new build house to be reaching that's not passive?


  • Moderators, Home & Garden Moderators Posts: 10,135 Mod ✭✭✭✭BryanF


    1m3/hr/m2


  • Registered Users Posts: 363 ✭✭Biker1


    BryanF wrote: »
    I’m not sure the average air-leakage value is worth aspiring too..
    0.6m3/hr/m2 is the minimum passive standard.

    I personally would accept nothing other than the passive house standard as I know it is achievable. However the reality is this is rarely achieved. In 12 years of testing only one house has achieved an 0.5ACH with everything else ranging from 1.4 to 5.0m3/hr/m2.


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  • Registered Users Posts: 4,034 ✭✭✭Amprodude


    BryanF wrote: »
    1m3/hr/m2

    Highly unlikely with some of the standards of building workmanship in this country.


  • Registered Users Posts: 4,034 ✭✭✭Amprodude


    Biker1 wrote: »
    I personally would accept nothing other than the passive house standard as I know it is achievable. However the reality is this is rarely achieved. In 12 years of testing only one house has achieved an 0.5ACH with everything else ranging from 1.4 to 5.0m3/hr/m2.


    What are your houses you tested in 2020 to 2021 ranging from?


  • Registered Users Posts: 363 ✭✭Biker1


    Amprodude wrote: »
    What are your houses you tested in 2020 to 2021 ranging from?

    1.5-2.5


  • Registered Users Posts: 3,724 ✭✭✭Metric Tensor


    Great info Biker. Would love to hear more stats and common issues you come across.

    The HC one is interesting. I'm an advocate or wrapping the ends of the slabs and also using solid ends but some air tightness contractors I've worked with disagree totally and get quite good results by other means.

    Where I see a lot of fall down is the wall plaster suspended ceiling interface but surprisingly doesn't always cause major issues with results.


  • Registered Users Posts: 348 ✭✭Moggaman


    Great info Biker. Would love to hear more stats and common issues you come across.

    The HC one is interesting. I'm an advocate or wrapping the ends of the slabs and also using solid ends but some air tightness contractors I've worked with disagree totally and get quite good results by other means.

    Where I see a lot of fall down is the wall plaster suspended ceiling interface but surprisingly doesn't always cause major issues with results.

    Where a wideslab sits on the inner leaf , I understand the wrapping of the slab is required. Where the slab is parallel to the inner leaf, can you stick an airtight membrane to the block adjacent to the slab before they are dropped in and plaster into it with wall plaster after?...
    Or plaster from the top of the slab down to ceiling level before slab gets dropped in?
    Thanks


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  • Registered Users Posts: 363 ✭✭Biker1


    Moggaman wrote: »
    Where a wideslab sits on the inner leaf , I understand the wrapping of the slab is required. Where the slab is parallel to the inner leaf, can you stick an airtight membrane to the block adjacent to the slab before they are dropped in and plaster into it with wall plaster after?...
    Or plaster from the top of the slab down to ceiling level before slab gets dropped in?
    Thanks

    Fill between the slabs and blocks with wet mortar.


  • Registered Users Posts: 348 ✭✭Moggaman


    Biker1 wrote: »
    Fill between the slabs and blocks with wet mortar.

    A slurry type mix?


  • Registered Users Posts: 63 ✭✭barrystealover


    Could I ask what type of air tightness detail should one expect around the internal distribution board(aka consumer unit or fuse board). The wires from my fuse board go into up along the wall(in trunking) and into the ceiling of the utility room. The utility has a single storey pitched roof which I was told was insulated. I have no access into this utility roof to prove if insulated with rockwool. The rest of the house is a 2 storey and the attic does have rockwool.

    I can feel a breeze coming down through the trunking and when I open up the trunking that covers the cable going into the ceiling I see that a section of the ceiling has been been cut of no airtightness tape or otherwise was used? This breeze is more than likely coming from the vents in the soffits.

    What should have been done and would you have a suggestion to retrofit it?

    Attached, find airtightness results cut from report.




  • Registered Users Posts: 63 ✭✭barrystealover


    Could anyone shed any information regarding my above query?



  • Registered Users Posts: 2,820 ✭✭✭MicktheMan


    What should have been done probably should have been detailed at design stage and would generally have been part of an overall service cavity solution but that ship has sailed now and your are left with how best to proceed from here.

    To address what you have found I would get attic fibre (earthwool) and fill / stuff the hole/gap (where the bunch of cables come through the ceiling) with small pieces of earthwool at a time and keep at it until a pretty good seal (compressed earthwool) is achieved at this point. This will not be 100% but is a reasonable solution. (btw, don't use expanding foam!).



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