It burns.So does PIR. Rockwool does not.

If I abandon the idea of using rockwool in my new "workshop" and
storage, and use EPS, I will have a wall structure like this:

Outside | prefab concrete|25mm EPS|50mm EPS|Visqueen|12.5mm
plasterboard|Inside

As the EPS will be covered, is that reasonable from the fire point of view?

Chris Bacon <chris.p.bacon@maildrop.cc> wrote:
> It burns.So does PIR. Rockwool does not.
>
> If I abandon the idea of using rockwool in my new "workshop" and
> storage, and use EPS, I will have a wall structure like this:
>
>
> Outside | prefab concrete|25mm EPS|50mm EPS|Visqueen|12.5mm
> plasterboard|Inside
>
> As the EPS will be covered, is that reasonable from the fire point of view?

It does burn, but AIUI any building grade material[1] is treated with fire
retardants so it only ignites once it's reached a sufficient temperature.
In other words you can't ignite it with a spark, you need a blowtorch (or a
fire of equivalent proportions).

So I'd question what's going in this building that might be sufficiently
flammable that would be hot enough to ignite the insulation? And once the
fire has reached that temperature, does it matter if the insulation catches
fire? It'll make a bigger fire for sure, but if your building is already
ablaze and everything inside is toast, does it matter that the toast is
extra crispy?

If you /are/ doing angle grinding or arc welding or whatever, I wouldn't be
having bare insulation on the inside (due to melting damage, mainly), but
some non-flammable wall coverings (eg plasterboard) should handle it. A
metal spark is very hot, but I'd have thought it hasn't a lot of energy to
transfer to the plasterboard to start an actual fire if the PB isn't going
to catch light if exposed to a source of ignition. And you'd need to get
the PB red hot before you can think about igniting the insulation behind it.

(although it might smoke well before that, which might be a consideration if
egress is difficult for occupants when a fire has started)

Theo
(IANA fire expert, DYOR)

[1] Possibly not the EPS that your TV came packaged in, which is why it's
perhaps not a good idea to 'repurpose' that.

On 23/10/2021 13:19, Chris Bacon wrote:
> It burns.So does PIR. Rockwool does not.
>
> If I abandon the idea of using rockwool in my new "workshop" and
> storage, and use EPS, I will have a wall structure like this:
>
> Outside | prefab concrete|25mm EPS|50mm EPS|Visqueen|12.5mm
> plasterboard|Inside
>
> As the EPS will be covered, is that reasonable from the fire point of view?

Yes. A fire needs fuel, air and a source of ignition.
Exclude the air and it should be fairly safe.

Since the inner and outer layers are rigid fairly inert and exclude the
air. I would say that you are OK with that choice of insulation.

If you are concerned then you could use magnesium oxychloride board
instead which is very effective as a fire barrier and how they faked the
fire certification of the dodgy products that led to the Grenfell fire.

https://www.resistant.co.uk/mgo-boards-in-action/

Popular in warehousing systems to isolate any fire in a single bay.

--
Regards,
Martin Brown

On 23/10/2021 13:19, Chris Bacon wrote:
> It burns.So does PIR. Rockwool does not.
>
> If I abandon the idea of using rockwool in my new "workshop" and
> storage, and use EPS, I will have a wall structure like this:
>
>
> Outside | prefab concrete|25mm EPS|50mm EPS|Visqueen|12.5mm
> plasterboard|Inside
>
> As the EPS will be covered, is that reasonable from the fire point of view?

The PB should give you 20 to 30 mins of fire protection. Also EPS
intended for building insulation use is often formulated with a self
extinguishing additive. So while it will burn if exposed to an
established fire, it should not assist a small fire in starting or
propagating.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On 23/10/2021 13:19, Chris Bacon wrote:
> It burns.So does PIR. Rockwool does not.
>
> If I abandon the idea of using rockwool in my new "workshop" and
> storage, and use EPS, I will have a wall structure like this:
>
>
> Outside | prefab concrete|25mm EPS|50mm EPS|Visqueen|12.5mm
> plasterboard|Inside
>
> As the EPS will be covered, is that reasonable from the fire point of view?

PIR does not burn in a 'normal' domestic fire. It just chars and smells
but does not contribute to the fire until the temperature gets up to
about 1000C. This is what happened with Grenfell because the aluminium
cladding burnt at very high temperature. So unless you are welding
on an alumnium shelled vehicle, or one with a lot of aluminium
or magnesium castings then you don't need to worry about PIR. If you
have lined the garage with PB you have 30 minutes to get out or
do some DIY fire-fighting anyway.