Fireproof foamy

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

NickWelford

So many tools, so little to show
Joined
6 Sep 2006
Messages
1,123
Reaction score
28
Location
South Lincolnshire. UK
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......
 
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.


Sent from my iPhone using Tapatalk
 
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?
 
Use sand and cement, get a mortar gun if you aren't handy getting mortar into little gaps with a trowel.
 
Stiffly mixed Vermiculite with Portland cement gives a good material to work with to fill larger gaps. Totally fireproof.

Phil
 
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
 
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
 
Back
Top