Floor Insulation Moisture protection

Brave Harvey

Can anyone tell me what they think of rigid polyurethane foam for floor insulation. I think I heard somewhere in this forum before that this type of insulation is susceptible to ingress of water rendering the thermal insulating properties of this insulation useless. Are the Rigid polyurethane foam insulations an expensive option?? What are the most recommended types of insulation for floors (150mm ground supported concrete slab on insulation on DPM on blinding on hardcore floor make up)and the resistance of moisture. What are the most cost effective to meet Part L?? Any help on these issues would be greatly appreciated.

sydthebeat

how would water get into it if its laid on a DPM / Radon membrane

Brave Harvey

The site in question may be wetter than average, to futureproof against in the event of any possible penetrations to the membrane. Can condensation be a factor in the floor?? I read a previous thread that brushed upon this and has left me wondering and your perfectly right that the DPM should cover this.

sydthebeat

Brave Harvey wrote: »

The site in question may be wetter than average, to futureproof against in the event of any possible penetrations to the membrane. Can condensation be a factor in the floor?? I read a previous thread that brushed upon this and has left me wondering and your perfectly right that the DPM should cover this.

if your water table is up to DPM level youll have a lot more issues than just wet insulation

built the floor level high enough so as to negate this.

the only issue i have with foil backed insulation is the wet cement reacts with the foil, so a light gauge plastic should be placed over the insulation before pouring of the floor.

Brave Harvey

the only issue i have with foil backed insulation is the wet cement reacts with the foil, so a light gauge plastic should be placed over the insulation before pouring of the floor.

Yeah thats the one, there is actually a Separation layer specified in manufacturer's details between the insulation and the concretre. Thanks.

sydthebeat

Brave Harvey wrote: »

Yeah thats the one, there is actually a Separation layer specified in manufacturer's details between the insulation and the concretre. Thanks.

what manufacturer? under floor heating?

blast06

sydthebeat wrote: »

if your water table is up to DPM level youll have a lot more issues than just wet insulation

built the floor level high enough so as to negate this.

the only issue i have with foil backed insulation is the wet cement reacts with the foil, so a light gauge plastic should be placed over the insulation before pouring of the floor.

Thanks to board.ie (not sure if it was a previous comment from yourself Syd) i put a sheet of polythene over 160mm (2 x 80mm) floor insulation.... a good call ! and not too expensive - i paid ~€150 for the polythene plus ~half a day for a guy to lay it.

BarneyMc

I'm at a stage where my architect is specing such details. What's the best/cost effective way of dealing with floor insulation, i.e. what material to use and what thickness?

sydthebeat

BarneyMc wrote: »

I'm at a stage where my architect is specing such details. What's the best/cost effective way of dealing with floor insulation, i.e. what material to use and what thickness?

your Preliminary DEAP (BER) assessment will have to specify this for you. You simply CANNOT deal with these issues in isolation as you are asking.

BarneyMc

sydthebeat wrote: »

your Preliminary DEAP (BER) assessment will have to specify this for you. You simply CANNOT deal with these issues in isolation as you are asking.

Yes fair point syd, just wanted to get an idea of what others are doing.

sydthebeat

BarneyMc wrote: »

Yes fair point syd, just wanted to get an idea of what others are doing.

but what others have top do is specific to them

If you were to say to us, guys, my Prelim BER says i need to reach a minimum u value of 0.13 whats the most cost effective way to reach this in a standard build... then we could offer an answer.

but we dont know :
1. how much height you have to play with
2. what u value you need to reach
3. what your perimeter to area ratio is
4. what your heating system is
etc

then we could start to offer solutions

Brave Harvey

Yeah hey, just got Provisional Deap, and it specifies a U-value for the insulation of 0.15. Anyone got an idea of what the best most suitable insulation for to satisfy this u value, no height restrictions, beneath a 150mm floating slab type floor. No under floor heating. The ground floor area is 125sq.m. How do you calculate the perimeter to area ratio, do you calculate for each room?? Perimeter in metres to area in metre squared?

BarneyMc

sydthebeat wrote: »

but what others have top do is specific to them

If you were to say to us, guys, my Prelim BER says i need to reach a minimum u value of 0.13 whats the most cost effective way to reach this in a standard build... then we could offer an answer.

but we dont know :
1. how much height you have to play with
2. what u value you need to reach
3. what your perimeter to area ratio is
4. what your heating system is
etc

then we could start to offer solutions

Thanks Syd, just working with my Arch on this at the moment so could be back later with more info.