Loft insulation

[JulianHJ]

My parents have a post-war semi-detatched, and the loft insulation is probably as old as the house, and about as thick as a nice duvet. I'd expect it does as good a job at keeping the heat in too. The insulation in my new-build is literally seven or eight times thicker.

I'm aware that there are grants and lots of offers on insulation out there, however the loft is for the most part boarded out and full of all kinds of junk. There's a four inch depth for the insulation to sit in (rafters are 2x4) and a twelve inch gap between each rafter.

Is there a high-performance product that would fit in that space, is it cost effective or is there another practical solution?

[mrmaggit]

Celotex RR or Kingspan TP10 or equivalent are rigid laminate boards, supplied in 2400 x 1200mm sheets, cut on site to fit between rafters. Available in loads of differen thicknesses.

Much higher insulation levels than fibreglass etc, but they are more money too.

HTH

[eps]

Does the insulation sit in the joists or rafters?

You say they are 50x100 (equivalent), if joists then you can place celotex inbetween...

100mm of Celotex will give you : 0.31 W/m2K (based on 400mm joist spacing)

(using http://www.celotex.co.uk/Other-Resources/U-value-C... )

Ideally you need to aim for 0.20 or 0.16... But it should be better than the current setup they have.

[JulianHJ]

Thanks for that.

The rafters/joists are 2x4 inches spaced 310mm apart. The current insulation sits between them.

Given that the area is approximately 47m2 (7 metres by 7 metres), what sort of cost could be expected, and are there grants towards the materials mentioned? Are they typically available at Travis Perkins, Wickes etc? My parents are both over 60, and my mother is retired.

A quick calculation reveals that I should be able to insulate the whole area with 19 or 20 2400x1200mm sheets...

TIA

Edited by JulianHJ on Thursday 6th August 12:05

[Busamav]

do a google search for " kingspan seconds "

a cheap way of purchasing insulation board .

[JulianHJ]

Busamav said:

do a google search for " kingspan seconds "

a cheap way of purchasing insulation board .

nice one, thanks!

[eps]

spacing is centre to centre btw...

there are people on fleabay selling celotex bits as well...

Edited by eps on Thursday 6th August 12:17

[JulianHJ]

eps said:

spacing is centre to centre btw...

there are people on fleabay selling celotex bits as well...

I presume you mean the gaps between the rafters? Given that the actual gap seems to be in the region of 300mm I was thinking that I'd get four 2.4 metre lengths at 300mm wide each from a board - minimum effort, so to speak...

[eps]

JulianHJ said:

eps said:

spacing is centre to centre btw...

there are people on fleabay selling celotex bits as well...

I presume you mean the gaps between the rafters? Given that the actual gap seems to be in the region of 300mm I was thinking that I'd get four 2.4 metre lengths at 300mm wide each from a board - minimum effort, so to speak...

no, not the gap, it's measured from the centre of one joist to the other, in your case they are 300 + 25 + 25 = 350.

[mrmaggit]

eps said:

JulianHJ said:

eps said:

spacing is centre to centre btw...

there are people on fleabay selling celotex bits as well...

I presume you mean the gaps between the rafters? Given that the actual gap seems to be in the region of 300mm I was thinking that I'd get four 2.4 metre lengths at 300mm wide each from a board - minimum effort, so to speak...

no, not the gap, it's measured from the centre of one joist to the other, in your case they are 300 + 25 + 25 = 350.

Yes, but the OP says the clear gap is 300mm wide, so you would get 4 x 300mm wide strips per board.

[eps]

mrmaggit said:

eps said:

JulianHJ said:

eps said:

spacing is centre to centre btw...

there are people on fleabay selling celotex bits as well...

I presume you mean the gaps between the rafters? Given that the actual gap seems to be in the region of 300mm I was thinking that I'd get four 2.4 metre lengths at 300mm wide each from a board - minimum effort, so to speak...

no, not the gap, it's measured from the centre of one joist to the other, in your case they are 300 + 25 + 25 = 350.

Yes, but the OP says the clear gap is 300mm wide, so you would get 4 x 300mm wide strips per board.

thanks for that, but we were talking joist spacing... this was to help with insulation calculations. I'm sure the OP can cut the board to fit the space he sees before him...

[mrmaggit]

Just the difference between the way the public and pros' explain things.

We're both right in what we say, but he stated gaps, not centres, no offence meant.

[eps]

No worries I was trying to tie it into the thermal calcs.

Everyone's a winner!

[mrmaggit]

Indeed they are, the wonder of PH, eh?

[JulianHJ]

Many thanks for all your replies, I now have something to go back to my parents with...

[Busamav]

JulianHJ said:

Many thanks for all your replies, I now have something to go back to my parents with...

they may even let you stay up late tonight

[JulianHJ]

Busamav said:

JulianHJ said:

Many thanks for all your replies, I now have something to go back to my parents with...

they may even let you stay up late tonight

Not sure what my wife will think about that...