Flooring loft - keep insulation?

santiagobravo

Hi All,

Going to floor my loft with B&Q loft panels but not sure about the insulation. I currently have insulation up to the top of the joists. Should i remove all of the insulation before putting the boards down? Or get a new insulation of less thickness?

I have read a few posts about loft flooring but could not really decide.

Thanks

S.

Kiran

If it's up to the top of the joists then you should put the loft boards on top. That being said, that sounds like you are short on insulation? Current reccomended depth is 270mm. I would imagine you have 100mm? Its worthwhile topping up, it does make a difference.

ormus

you only remove the insulation if youre making a room in the loft. then you have insulate the actual roof.
for just loft boarding out, keep the insulation.

santiagobravo

thanks for your reply.

i'll be laying the loft panels on the joists meaning that any additional insulation will be compressed. will this still provide sufficient insulation?

Kiran

What depth insulation do you have at the moment? If its only coming up to the joists then Im imagining 100mm approx?? This should be 270mm. This depth of insulation presents a problem with boarding lofts (multiple posts on here re boarding full depth insualted lofts). You can obviously not compress 270 down to 100mm without losing the insulating properties.

Compressing insulation does effect its perfomance but its not a straight forward compressed = bad. If you are only loosing a few mm and you are placing boards, which would provide further insulation, above it you will probably end up with similar insulating properties

santiagobravo

just checked, its about 100mm

so should i just board over the existing insulation or top up and compress?

Kiran

You will be doing minimal compresion if theres 100mm there so for simplicity you might as well go for it. It's worth then considering somthing like the knauf insulation boards which can be layed directly on top of the boarding to increase your insulation up to the levels required by Part L of Building Regs.

HTH

santiagobravo

ok, some good info there

thanks

ormus

one option:
you could increase the insulation, by fixing say 2x2 on top of the joists, then boarding out.

ic

In my loft, my insulation was in two layers, 100mm between the joists, then a top of 170mm on top of the joists. I removed the 170mm from the area I was boarding and used it to double up in other areas. I then boarded over the top of knauff board.

jaywhoopee

I bought a load of the Knauff Space Board (very expensive - around £25 for 4 boards, but it was 2 for 1 in Focus at the time) intending to lay it in the center of the loft and just use regular insulation under the eaves (leaving it unboarded), but have done almost the reverse!

In the center I've laid 4"x2" perpendicular to the joists and used a mixture of 100mm and 170mm insulation between those (some of the existing 100mm was rather compressed, hence the 170 over the top).
Opinion is divided on using extra timber in this way - some say it helps spread the load across several joists, others that it just adds extra weight for little benefit. I particularly like it as no matter which way you want to run a cable/pipe you can run it down the side of a timber.

Under the eaves I've doubled up the space board to avoid difficulties fixing the 4x2.
Each board is about 50mm thick and two layers of the space board are equivalent to 170mm of regular insulation. Since the loft has 4 inch timber running the length of it (part of the roof frame), this allows me to board the whole loft continuously.

As with many polystyrenes the Knauff board should be kept away from electrical flex as it will damage the flexibility of the electrical insulation.