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Diminishing returns for insulation

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  • 21-03-2019 12:50pm
    #1
    Jcanty85
    Registered Users Posts: 95 ✭✭


    Hi all,

    Just wondering if anyone has ever come across a graph illustrating diminishing returns of insulation as in graphing kW/yr against R value to give an indication of when enough is enough.. We are trying to get out ducks in a row to start a self build (3000 sq ft, south facing 2 storey, large southern windows with limited north facing glass), currently trying to work out "ideal" insulation levels for floors/cavity walls. Everyone I've spoken to that has built recently is of the opinion that put in as much as possible but from my calculations the payback/savings reduces dramatically after you go over 100mm PIR.. I am just starting to try to work this out so any insights/advice any one can offer is greatly appreciated.

    Thanking you,


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    #2
    sydthebeat
    Subscribers Posts: 41,229 ✭✭✭✭sydthebeat


    Jcanty85 wrote: »
    Hi all,

    Just wondering if anyone has ever come across a graph illustrating diminishing returns of insulation as in graphing kW/yr against R value to give an indication of when enough is enough.. We are trying to get out ducks in a row to start a self build (3000 sq ft, south facing 2 storey, large southern windows with limited north facing glass), currently trying to work out "ideal" insulation levels for floors/cavity walls. Everyone I've spoken to that has built recently is of the opinion that put in as much as possible but from my calculations the payback/savings reduces dramatically after you go over 100mm PIR.. I am just starting to try to work this out so any insights/advice any one can offer is greatly appreciated.

    Thanking you,

    you need to first work out what the minimum thickness you need use are... and work back from there.

    These thicknesses will be affected by other decision such as heating system, ventilation, windows etc.... so you cant just look at insulation on its own in isolation.

    after you have a Preliminary Part L assessment carried out... you might find these questions already answered for you.


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    #3
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Check out the passive house software.


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    #4
    Jcanty85
    Registered Users Posts: 95 ✭✭Jcanty85


    BryanF wrote: »
    Check out the passive house software.

    Hi Bryan, what software in particular would you recommend?


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    #5
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Jcanty85 wrote: »
    Hi Bryan, what software in particular would you recommend?

    https://passipedia.org/planning/calculating_energy_efficiency/phpp_-_the_passive_house_planning_package


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