My neighbour has given me 4 sheets of 50mm PIR board for free. Not being one to refuse a freeby I bit his hand off. Current plan is to fit it between the ceiling joists in my attic. House is a 2002 build with a part boarded out attic done by the builder. I was a bit suprised to find no insulation under the boarded out section, so my plan of attic attack is to put this insulting board under the boarding, then stick the rest of it under the fibreglass atop my lads bedroom - its the coldest room in the house and because why not! I think in the fullness of time the boarding needs raising and even more insulation under it as it is just chipboard screwed to the 3x2 joists. But some is better than none and it gets the 8x4 PIR boards out of the lounge. It needs a bit of a rejig and sorting out as i found that the fibreglass has been blocking the ventilation anyway, so ill ensure the venting is sorted out at the same time. Any reasons why i cant do this or it is a bad idea?