Material to use to fill gaps around very hot pipes?

[John2016]

Hello,

I have gaps in my ceiling, where the central heating pipes feed to the boiler.

When the extractor fan is on, we can feel the air coming back through the pipes. In the winter we can also feel the cold, what can I use to cover the gaps in the pipes which is safe to use on these hot pipes?


I have attached a picture of the gap.

Thank you.

 

[John D v2.0]

More importantly I think you need to check that the fan is actually venting outside with no leaks to inside, it sounds like it's venting into the void. If it's supposed to be venting humid air outside then it can cause condensation in the void.
Regarding the gaps I'd probably squirt in some excpanding foam or stuff insulating wool if the appearance isn't important and I had some around. But if it's on show you'd probably want some collars and caulk https://www.screwfix.com/c/heating-plumbing/pipe-covers/cat831640

 

[John2016]

More importantly I think you need to check that the fan is actually venting outside with no leaks to inside, it sounds like it's venting into the void. If it's supposed to be venting humid air outside then it can cause condensation in the void.
Regarding the gaps I'd probably squirt in some excpanding foam or stuff insulating wool if the appearance isn't important and I had some around. But if it's on show you'd probably want some collars and caulk https://www.screwfix.com/c/heating-plumbing/pipe-covers/cat831640

Hi John,

The extractor fan is for a hood in the kitchen, do you still recommend I check? I checked last night with a smoke pellet and saw the smoke come out from the outside vent. But some was returning via the gaps.

Is the expanding forma and insulating wool fire resistant, the pipe go direct to the boiler and therefore are extremely hot.

 

[JohnD]

You're talking about pipes containing hot water?

Hot water is not hot enough to start a fire.

Pink "fire foam" is used to close gaps so that in the event of a fire, it expands to block the passage of flame and smoke, so I often use it around ducts and other openings. Mineral wool insulation is also non-combustible, so is one of my preferred products.

But even ordinary pipe insulation is sufficient with hot water pipes.

It sounds like the duct from your extractor is damaged or very badly fitted. Look at that first. Does it go straight through the wall?

 

[John D v2.0]

yes you still need to check as any ventilation should go outside 100%. Could just be the joint with the terminal is not securely sealed, or could be damage to the duct. It's common that the terminal is very restrictive, so the pressure in the duct could easily cause a leak.
Regarding the foam/wool, either would be able to withstand 80c or whatever the pipes are. The wool would last better under heat though.