Best type of insulation to use

mark2003

We are just starting to build a two storey house,we are trying to decide what insulation to use on the external walls,either insulation boards on the external walls inside the house or put a 6'' cavity and pump foam into it.We are trying to achieve the best airtightness as possible.We are putting down Geothermal heating and HVR system,Just want to know basically whats the best insulation i could put into the house.Thanks

MicktheMan

mark2003 wrote: »

We are just starting to build a two storey house,we are trying to decide what insulation to use on the external walls,either insulation boards on the external walls in the house or put a 6'' cavity and pump foam into it.Thanks

Mark,
need more info here. What are you trying to achieve? Have you considered a soild wall with external insulation? What's your ventilation strategy? What's your airtightness target?

sinnerboy

What is your construction professional advising ?

frag4

Do you not mean bonded bead?

I think the foam is not cerified yet and is more expenivise.

jonnyj

I would pump the 6" cavity with silver bead insulation and then line the inside with a dryliner board. I would also do an air tightness test and put in mechanical ventilation with heat recovery.

Ive heard that sometimes render on the external insulation can crack easily and this can cost alot to repair.

PCPL

EWI render generally cracks if the reinforcing mesh isnt doubled up around stress points e.g corners around window cills, also if Eps is being used it must be left to cure before it is installed, otherwise its just poor workmanship which leads to cracks

trevdahead

PCPL wrote: »

EWI render generally cracks if the reinforcing mesh isnt doubled up around stress points e.g corners around window cills, also if Eps is being used it must be left to cure before it is installed, otherwise its just poor workmanship which leads to cracks

please tell how ewi render cracks around cills.why does it crack
ive done plenty of external jobs over the last few yrs and have never seen this

Duffer2

trevdahead wrote: »

please tell how ewi render cracks around cills.why does it crack
ive done plenty of external jobs over the last few yrs and have never seen this

I'd assume he means round the reveals if it's not properly applied ie. mesh and beadings where appropriate.

I've worked on some very large scale external render over insulation applications and can assure you the system works just fine as long as it's all correctly applied. Just make sure you engage a competent firm to do the work (and that the system is IAB rated, complete con job that the IAB scheme is but that's another issue).

trevdahead

Duffer2 wrote: »

I'd assume he means round the reveals if it's not properly applied ie. mesh and beadings where appropriate.
still dont see how cracks could appear there are no stress point
I've worked on some very large scale external render over insulation applications and can assure you the system works just fine as long as it's all correctly applied. Just make sure you engage a competent firm to do the work (and that the system is IAB rated, complete con job that the IAB scheme is but that's another issue).

still dont see how cracks could appear there are no stress point
agree with you 100% on the compentacy and on the iab