Phenolic or EPS

[Rob55]

For EWI, I have heard people say phenolic board such as Kooltherm K5 can have problems and EPS is a cheaper and better product, is there any truth to this? Do any of the render systems approve phenolic, I know STO for example try to push the supply of their own boards which are EPS.

I have a 1980s house with wet dash, and would like to install EWI. The K5 would work well at 50mm, compared with EPS at 100mm which gives similar performance, but being that bit thicker causes a few other problems with window and soffit detailing.

Hopefully someone can provide a straight forward answer on what to go for. And whether it’s acceptable to put it direct onto the wet dash by adhesive plus mechanical fixings (Kingspan technical said it would be no problem)

 

[Plasterers1StopShop]

I would advise looking down the EPS route.

Many rumours circulating the industry regarding K5 saying it loses its efficiency within a short time - I’m unsure on the truth behind it, but would prefer to avoid it.

Also, the boards can’t be exposed to direct sunlight and rain.

 

[owls]

Nothing wrong with going over dash as long as it’s sound and your mechanical fixings are of decent length.
I don’t know whose told you phenolic is twice as effective at 50mm as opposed to 100mm eps, it’s duff information.
To get to building regs of a u value of 0.3 or thereabouts its 70mm of phenolic compared to 90mm eps.
Eps is favoured If I get the choice, easier to handle, cheaper etc, but phenolic has a better thermal value so you can go thinner if sofits etc are an issue.

 

[Gavine The First]

Were, you ,ever young ?

 

[Rob55]

Nothing wrong with going over dash as long as it’s sound and your mechanical fixings are of decent length.
I don’t know whose told you phenolic is twice as effective at 50mm as opposed to 100mm eps, it’s duff information.
To get to building regs of a u value of 0.3 or thereabouts its 70mm of phenolic compared to 90mm eps.
Eps is favoured If I get the choice, easier to handle, cheaper etc, but phenolic has a better thermal value so you can go thinner if sofits etc are an issue.

The house already has a 70mm bead filled cavity, so adding 50mm K5 will bring u value down to 0.21 which is well improved on building regs. 50mm would suit me well but I am just not sure why phenolic doesn’t always get good reviews?

 

[essexandy]

The house already has a 70mm bead filled cavity, so adding 50mm K5 will bring u value down to 0.21 which is well improved on building regs. 50mm would suit me well but I am just not sure why phenolic doesn’t always get good reviews?

I looked into this long and hard when doing my own house and decided to use graphite EPS in 90mm.

 

[owls]

The house already has a 70mm bead filled cavity, so adding 50mm K5 will bring u value down to 0.21 which is well improved on building regs. 50mm would suit me well but I am just not sure why phenolic doesn’t always get good reviews?

Ah you didn’t say you already had some insulation in your cavity.
Because it’s a pain to use, hastle when it gets wet and is more expensive that eps.