# Pulling a vacuum for firebox insulation.



## fitter27 (Jan 26, 2020)

Read the forum but never post. Working on another stick burner. Previously I’ve used rock wool to insulate the fire box. Worked fine but I was wondering if anyone has ever thought to pull a vacuum instead of filling with insulation? I’m a Pipefitter/welder so sealing it is not an issue and I also have access to equipment to pull a vacuum. Just wondering if anyone has tried this.


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## JJS (Jan 26, 2020)

trying to hold a static vacuum on steel is very difficult. You could attempt to seal the steel with some kind of coating but you would just be delaying the inevitable. How well you can weld is only a small fraction of the problem, steel is porous and you will lose your vacuum quickly 

I guess what I am trying to say is it’s probably gonna be way more of a pain in the ass than it’s worth


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## MikeFromTexas (Jan 26, 2020)

Heat transfer still occurs in a vacuum by means of radiation.  You could use paint or other surface applicants with low emmisivity to minimize heat loss by radiation. Of course there will be conduction heat transfer anywhere there is metal contact as well.  If you want to learn more about this look at 






						Radiation Heat Transfer - an overview | ScienceDirect Topics
					






					www.sciencedirect.com


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## mike243 (Jan 26, 2020)

I would bet it would work pretty good, you will have a port to ck the vacuum and to redo or pressurize and look for a leak, I would think something pretty heavy for the inner layer to keep the warpage down, they have been making vacuum bottles for years


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## fitter27 (Jan 27, 2020)

Thanks guys for the input. I think I might still try it since I’m just curious. If it doesn’t work I’ll drill some holes and fill it with some high temp expandable foam or something and patch the holes.


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## DoTheEyeThing (Jun 8, 2021)

fitter27 said:


> Thanks guys for the input. I think I might still try it since I’m just curious. If it doesn’t work I’ll drill some holes and fill it with some high temp expandable foam or something and patch the holes.


Did you ever try the vacuum? I was thinking the same thing - I've already got a good vacuum pump. Even if I had to pull it again before each cook that would probably be doable if the benefit was worth it.


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