Fireproof foamy

[NickWelford]

Hi experts. I'm shortly moving into an old place that has a huge draught coming in around the gas boiler flue. Is there any heatproof foam I can use to seal the big gaps, or should I look for fibreglass padding?
I'm sure someone here will have the answers......

 

[Wuffles]

It'll be twin walled (the flue) and will only be carrying gasses you don't want in the house, won't get that hot.


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[Wuffles]

What size gap out of curiosity?


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[MMUK]

You can get fire rated expanding foam, about £7 a can from Toolstation. It's pink :mrgreen:

 

[NickWelford]

The gap is about 2 inches all round. I looked at pink fire rated foam, but wondered if that was just fire retardant, in the event of fire or high temperatures does it just melt and not burn?

 

[Wuffles]

Use sand and cement, get a mortar gun if you aren't handy getting mortar into little gaps with a trowel.

 

[Woody2Shoes]

I'd use rockwool firmly packed into the large gaps. On the outside I'd protect the rockwool from vermin with a bit of strongish mortar and between the flue pipe and the mortar I'd run a bead of high temp. sealant to cope with differential thermal expansion. e.g http://www.screwfix.com/p/mapei-mapefle ... 00ml/25153 or perhaps just http://www.screwfix.com/p/geocel-trade- ... 10ml/66373

Cheers, W2S

 

[Sheptonphil]

Stiffly mixed Vermiculite with Portland cement gives a good material to work with to fill larger gaps. Totally fireproof.

Phil

 

[sunnybob]

Take a look at the outside terminal. Unless its VERY old, it should be a balanced flue heater and have an inner and outer tube as wuffles said. if so, then hot exhaust gas is in the middle, and the cold intake air is around the outside, You would be able to put your hand on the flue while the boiler is working. No special heat proofing required.
If it is very old and the boiler flame is not room slealed, and flue goes through the wall and then quite a way upwards, then you would need heat protection

 

[Woody2Shoes]

I think that regardless of how hot the outside of the flue pipe is expected to get (under normal or fault conditions), you have an interface between two different materials and you need to allow for differential thermal movement. Some kind of flexible bead to seal the interface would be a wise move. Cheers, W2S

 

[Droogs]

What you need is expanding intumescent fire rated foam such as below:
http://www.sealmaster.co.uk/structural/ ... e-foam.php

I have nowt to do with the company but have used their product before