Insululating loft floor - alternatives to Kingspan K103

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Hi All.

I am just in the middle of a loft extension, the engineer specified Kingspan K103 for insulating the floor beneath the loft room.

I was wondering if there are any other alternatives out that that can be used, can Rockwool RWA45 100mm be used for example ?

Or does it have to be any PIR board ?

Thanks in advance.
 
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Your engineer is a bit of a div if he specified thermal insulation for a loft floor.

The two products you mention are completely different and for different tasks. Otherwise phone up whoever you paid, and ask them to do their job properly.
 
Surely you'd want rockwool / acoustic insulation fibre instead? Although, when I had my loft conversion done they used the insulation that was already in the loft under the floor.

something like this - http://www.acoustafoam.com/products/acoustic-insulation/
(other products available).

Existing loft roll is probably good enough though!
 
Tbh. Dont know what happened there, unless I'm.not reading well.

I will use rwa45 100mm
 
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Is the loft room going to be habitable or storage?
If habitable then some loft roll or acoustic batts to reduce noise would be good, K103 is for floors with a cold side (ground floor usually)
 
The insulation is partly for sound insulation and partly to enhance fire resistance of the floor.
Fibreglass or mineral wool quilt usually suffices (not rigid board insulation).
If using the fibreglass for improving fire resistance, it should be supported off steel netting stapled to the joist sides, not just supported off
the ceiling.
 
I am using Rockwool RW3 for floor sound / thermal insulation on the first floor and the loft floor.
 
Is the loft room going to be habitable or storage?
Which is it?
If it is habitable, it will need thermal insulation at roof level i.e. a warm roof, and acoustic insulation at loft floor level.
If it is storage, insulation at loft floor level is thermal. (unless you want to create a warm roof )
First floor insulation is acoustic.
 
Have you applied for building regulations approval ? You refer to a loft extension, do you mean a loft conversion ? Anyway it will require approval for all relevant bldg. regs matters like means of escape in case of fire , fire safety , structural stability etc as well as heat loss/thermal insulation. A Full Plans Submission to building control would cover these things as well as structural engineer's calculations.
 
Have you applied for building regulations approval ? You refer to a loft extension, do you mean a loft conversion ? Anyway it will require approval for all relevant bldg. regs matters like means of escape in case of fire , fire safety , structural stability etc as well as heat loss/thermal insulation. A Full Plans Submission to building control would cover these things as well as structural engineer's calculations.

Thanks.
I got it all sorted. submitted full plans, and they do regular site visits. Its just that i find that some engineers spec out hard to source materials, and its possible to use other alternatives as long as they are of similar properties.
 

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