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Insulate and floor attic advice needed.

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  • 06-11-2018 12:09am
    #1
    emmo16
    Registered Users Posts: 52 ✭✭


    Hi all

    Just bought and moved into a 1950's home - 3 bed semi-d. I am about to tackle insulating the attic and would also like to use some of it for storage , nothing to heavy, mainly decorations and some storage boxes. The roughly space is 52sqm.
    I have read many posts on this topic but am still confused on what is the best way to go about it.

    The joist depth is 100mm and 320mm wide. The current fibre glass insulation is degraded, sparse and about 40\50mm thin in places. I will leave this in place. I intend on leaving a 50mm gap around the eaves, insulating pipes but not directly under the watertank and running the cables above the insulation, there are no down lightsers.

    I plan on laying 100mm between the joists and 200mm in the opposite direction. Is this the best way to go about it?
    B&Q have Knauf Eko Roll @ €18, Woodies has Knauf Earthwool (44c) @ €21, is there much or a difference. Is one better than the other. Would these be pre-cut, I cant tell from the site.
    Are there better options that I should look at?

    I plan on partially flooring some space up there but am unsure whats the best way to go about this. Would the loft lifters here https://www.woodies.ie/loft-lifters-box-of-12-1123325 along with loft boards do the job, they seem to get mixed reviews or would it be easier to lay a few of these insulated boards across the 100mm insulation. https://www.diy.com/departments/b-q-insulation-board-1220mm-320mm-123mm/183180_BQ.prd.

    Any tips would be appreciated or anything else people could suggest.


Comments

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    #2
    Calahonda52
    Registered Users Posts: 12,228 ✭✭✭✭Calahonda52


    1: google ventilation baffles: this is the only right way to do this work
    1a: the alternative is to seal off the soffits and fit roof vents in the slates/tiles
    2: not doing under tank is 1980's thinking: re-read the relevant posts: insulate the tank, cover it with an insulated but vented lid
    3: you wont be able to avoid ducting the cables as they disappear down at the eaves, the flexible ducting can be spilt with a scissors and fitted around the power cables, lighting cables not so critical
    4: as for the flooring, I have posted my approach to this issue many times.
    5: I would use cellulose, once you have done the prep for 1 to 4 above

    “I can’t pay my staff or mortgage with instagram likes”.



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    #3
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    Putting 100mm in parallel on top of 50mm in a 100mm space is not generally considered good practice. The 50mm is already compressed and you'll end up with 200mm of insulation in a 100mm space, or a gap over the joists, neither of which is good.

    That said, I have my doubts as to whether compressed low-density insulation is that bad for a given thickness. Obviously if you compress 200mm of insulation into 100mm it's going to insulate less than half as well as 200mm uncompressed, but is it going to be worse than 100mm of uncompressed insulation?

    If you look at the densities of insulation products they vary considerably between 10kg/m3 (loft rolls), 20-25kg/m3 (acoustic rockwool or metac) and 50kg/m3 (woodfibre). So compressing 10kg/m3 insulation so that it's 20kg/m3 still makes it less dense than acoustic rockwool or metac.


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    #4
    emmo16
    Registered Users Posts: 52 ✭✭emmo16


    Calahonda52 wrote: »
    1: google ventilation baffles: this is the only right way to do this work
    1a: the alternative is to seal off the soffits and fit roof vents in the slates/tiles
    2: not doing under tank is 1980's thinking: re-read the relevant posts: insulate the tank, cover it with an insulated but vented lid
    3: you wont be able to avoid ducting the cables as they disappear down at the eaves, the flexible ducting can be spilt with a scissors and fitted around the power cables, lighting cables not so critical
    4: as for the flooring, I have posted my approach to this issue many times.
    5: I would use cellulose, once you have done the prep for 1 to 4 above

    I will do some more research on the ventilation and look at doing under the tank. I’ll also take a look at your previous posts on flooring.
    Any idea of the cost of using cellulose over the rolled insulation mentioned above?


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    #5
    emmo16
    Registered Users Posts: 52 ✭✭emmo16


    Lumen wrote: »
    Putting 100mm in parallel on top of 50mm in a 100mm space is not generally considered good practice. The 50mm is already compressed and you'll end up with 200mm of insulation in a 100mm space, or a gap over the joists, neither of which is good.

    That said, I have my doubts as to whether compressed low-density insulation is that bad for a given thickness. Obviously if you compress 200mm of insulation into 100mm it's going to insulate less than half as well as 200mm uncompressed, but is it going to be worse than 100mm of uncompressed insulation?

    If you look at the densities of insulation products they vary considerably between 10kg/m3 (loft rolls), 20-25kg/m3 (acoustic rockwool or metac) and 50kg/m3 (woodfibre). So compressing 10kg/m3 insulation so that it's 20kg/m3 still makes it less dense than acoustic rockwool or metac.

    Would you recommend that I take up the old insulation and lay the new 100mm between the joists


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    #6
    listermint
    Registered Users Posts: 33,714 ✭✭✭✭listermint


    emmo16 wrote: »
    Would you recommend that I take up the old insulation and lay the new 100mm between the joists

    Leave old there . Add new on top


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    #7
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    emmo16 wrote: »
    Would you recommend that I take up the old insulation and lay the new 100mm between the joists
    That's what I did. Opinions differ. :)


  • Options
    #8
    Dr_Colossus
    Registered Users Posts: 3,122 ✭✭✭Dr_Colossus


    emmo16 wrote: »
    Would you recommend that I take up the old insulation and lay the new 100mm between the joists
    Lumen wrote: »
    That's what I did. Opinions differ. :)

    Nasty job, presumed you bagged it all in the attic and then brought it out through the house that way. Were you able to compress it sufficiently for it to fit in a few car loads or how did you dump it.


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    #9
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    Dr_Colossus wrote: »
    Nasty job, presumed you bagged it all in the attic and then brought it out through the house that way. Were you able to compress it sufficiently for it to fit in a few car loads or how did you dump it.
    Massive skip. Didn't cost me much extra as I was doing a general clear out.

    I didn't bag it in the attic, I just suited up, dropped it loose through the hatch and dragged it through the house. Quick vacuum round the house and in the attic and it was all clean. The whole job took a couple of hours.

    Ot4I9rz.jpg


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    #10
    listermint
    Registered Users Posts: 33,714 ✭✭✭✭listermint


    Waste of money though as your actually throwing out insulation depth.

    For no reason.

    Be different if you were converting the space at the time. Other than that its needless


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    #11
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    listermint wrote: »
    For no reason.
    It's not for no reason. The fibreglass made the attic mildly hazardous to work in. I have electrics all over the place up there, a total rats nest of wiring, which needed re-doing (and will need further work in future). The earthwool is not exactly pleasant but it's loads better.

    What cost? A couple of hundred euros and a couple of hours work.


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    #12
    listermint
    Registered Users Posts: 33,714 ✭✭✭✭listermint


    Lumen wrote: »
    It's not for no reason. The fibreglass made the attic mildly hazardous to work in. I have electrics all over the place up there, a total rats nest of wiring, which needed re-doing (and will need further work in future). The earthwool is not exactly pleasant but it's loads better.

    What cost? A couple of hundred euros and a couple of hours work.

    My attic is the same, im in it all the time. I wear a hoodie, not that hazardous tbf.

    Cost - well that skip was about 500-600 Euro i assume so fairly significant :)


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    #13
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    listermint wrote: »
    My attic is the same, im in it all the time. I wear a hoodie, not that hazardous tbf.

    Cost - well that skip was about 500-600 Euro i assume so fairly significant :)

    €355 on special, and the insulation only took up the top third, the rest was from other projects.

    The new insulation I put in was 100 + 200 at right angles. I'd have still needed the 100 anyway because the fibreglass was in such poor shape.

    So it cost me €120 or nothing, depending on how you look at it. :D


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    #14
    enfant terrible
    Registered Users Posts: 4,560 ✭✭✭enfant terrible


    Where would one source ventilation baffles?


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    #15
    emmo16
    Registered Users Posts: 52 ✭✭emmo16


    Would anyone know if there is much difference between the insulation mentioned in the op and which would be best between the loft lifters and insulation boards?


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    #16
    Lumen
    Registered Users Posts: 31,017 ✭✭✭✭Lumen


    emmo16 wrote: »
    Would anyone know if there is much difference between the insulation mentioned in the op and which would be best between the loft lifters and insulation boards?
    No, same. Higher density insulation is used for acoustic insulation or to friction-fit between studs or rafters, but in this case the boards are being supported by the loft legs/lifters/whatever so the low density quilt insulation just sits undisturbed underneath.

    You can alternatively use high density PIR insulation directly over the joists and under the boards, then you don't need the lifters. Or just buy boards which have that insulation pre-glued to the underside. Upside is more headroom. Downside is cost, probably.


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    #17
    RaPpSodIq
    Registered Users Posts: 9 ✭RaPpSodIq


    emmo16 wrote: »
    Hi all

    Just bought and moved into a 1950's home - 3 bed semi-d. I am about to tackle insulating the attic and would also like to use some of it for storage , nothing to heavy, mainly decorations and some storage boxes. The roughly space is 52sqm.
    I have read many posts on this topic but am still confused on what is the best way to go about it.

    The joist depth is 100mm and 320mm wide. The current fibre glass insulation is degraded, sparse and about 40\50mm thin in places. I will leave this in place. I intend on leaving a 50mm gap around the eaves, insulating pipes but not directly under the watertank and running the cables above the insulation, there are no down lightsers.

    I plan on laying 100mm between the joists and 200mm in the opposite direction. Is this the best way to go about it?
    B&Q have Knauf Eko Roll @ €18, Woodies has Knauf Earthwool (44c) @ €21, is there much or a difference. Is one better than the other. Would these be pre-cut, I cant tell from the site.
    Are there better options that I should look at?

    I plan on partially flooring some space up there but am unsure whats the best way to go about this. Would the loft lifters here https://www.woodies.ie/loft-lifters-box-of-12-1123325 along with loft boards do the job, they seem to get mixed reviews or would it be easier to lay a few of these insulated boards across the 100mm insulation. https://www.diy.com/departments/b-q-insulation-board-1220mm-320mm-123mm/183180_BQ.prd.

    Any tips would be appreciated or anything else people could suggest.

    Hi,

    I know that is a very old post, but the prices of LoftLifters in Woodies are too expensive. I`ve found cheaper on www.thermshop.com/Loft-Lifters-p/ll.htm. Maybe this would help.

    Cheers


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