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Board insulation

  • 15-10-2010 4:30pm
    Registered Users Posts: 4,425 ✭✭✭

    Just wondering can someone tell me whats the best way to use board insulation in an attic roof between the joists. I have large 8 by 4 sheets, do I cut them with a stanley knife or with a saw and should I put them up in long sheets between the joists or short? Whats the best way to prevent gaps between them also?
    Thanks in advance.

    Mod Edit: No need for product name here.


  • Registered Users Posts: 558 ✭✭✭beyondpassive

    Put an other sheet of 25 PIR board inside the rafters and tape it, its the only way to make it airtight and cold bridge free. I used to foam between board and rafter, but the foam wouldn't adhere to the timber.