Floor Insulation

Freemaster

Hi,

i am currentley at the stage of my build where i will be building up the finished floor to include insulation / underfloor / screed. i have 150mm of space , 50mm will be taken up with the floor screed. i was just wondering about the floor insulation. first of all , is it best to build up the insulation in 2 x 50mm or a straight 100mm? also, i have been looking at putting either kingspan Kooltherm K3 or kingspan TF70. the kooltherm has a better u value than the tf70 by about 10 / 15% however there is a huge difference in price. is it worth it ?

Thanks in advance

RKQ

Freemaster wrote: »

is it best to build up the insulation in 2 x 50mm or a straight 100mm? also,

IMO 2 layers of thinner board is easier to lay, as 50mm thick boards are easier to cut than 100mm thiock boards. Also I feel it is good practice to "overlap" the boards.

As regards the specification of your floor insulation, seek professional advice specific to your individual needs to ensure compliance with the Building Regulations.

You should discuss this floor specification with your Certifier. I must assume you have also dicussed this spec. with your BER Assessor?

sydthebeat

assuming you need to comply with 2008 part L regs, which you probably do, then you need to achieve a minimum u value of 0.15.

Depending on your floor area to perimeter ratio, you may only be able to achieve this by using phenolic board. You need this to be calculated. the other product is polyurethane (PU).

i would advise however, that phenolic foam was removed from use as external wall insulation because there was evidence it broke down when wet. theres a good chance it will get wet under a poured concrete screed, so id advise you to put a slipping sheet of 1000 gauge dpm over whatever insulation you choose before pouring.

clint_eastman

Hi Syd, are you sure on that u-value?

sydthebeat

clint_eastman wrote: »

Hi Syd, are you sure on that u-value?

yes,

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,19069,en.pdf

see paragraph 1.3.2.2.

clint_eastman

sydthebeat wrote: »

yes,

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,19069,en.pdf

see paragraph 1.3.2.2.

Thanks Syd, I missed the underfloor reference as it wasn't relative to my own situation, it makes sense though.
You just scared me as I thought my calculated 0.17 wasn't enough...just got a load of 100mm TF70 delivered!

homewardbound11

Hi Clint eastman.

do you mind me asking why you chose tf70 over k3 kool therm and if there was any cost differences

clint_eastman

homewardbound11 wrote: »

Hi Clint eastman.

do you mind me asking why you chose tf70 over k3 kool therm and if there was any cost differences

Sure.
It came down to costs v u-value for 140sqm on the ground floor and I chose cost.

TF70 single sheet 100mm gives me a u-value of 0.17 for approx €1700.
K3 single sheet 100mm gives 0.16 for approx €2900.
Sq meter (!) costs were €12.27 and €20.35 respectively including VAT.

The u-values acheiveable will depend on your Perimeter/Area ratio and floor make-up, so you'd really need to get a BER professional to be able to make a proper comparison for your own situation unless you're happy to estimate using your own calcs.

homewardbound11

hi clint eastman. Hope you might sort me out here. Sorry for my confusion.

I got a quote from my local supplier for k3 kooltherm 100mm today at 65 euro a sheet. I am assuming your sheets were not 8ft by 4ft. or 2.97 sq M.

I have a 150m2 sq groundfloor in my build and require 52 sheets. Worked out at 3380 euro total.

I think i might be missing something as 1700/12.35euro would be 137 boards. 140m2/137 boards would make the board area 1m2.

regards,
pat

clint_eastman

I've edited the above post now, apologies for the confusion.

The boards are 1.2m * 2.4m or approx 8ft*4ft. My sheets cost based on the square meter cost are (€12.27 x 2.88sqm) €35 and (€20.35 x 2.88sqm) €59.
Our quotes are a bit different (+€6/K3 sheet) but I'm sure this will vary around the different builder providers.