Insulate or not insulate the heat riser...

Hello all. I would like to see a healthy discussion that list reasons to insulate or not insulate the heat riser. I understand why the heat riser is traditionally insulated but I am also seeing designs where the heat riser is not insulated. Please share your experiences below!

Amos Valenti : Properly installed there is no negative to insulating your heat riser ! Big AL

Is there any reason why you would not want to insulate the heat riser? Maybe material choice? I am seeing some designs that do not use insulation and wondering why.

Amos Valenti : There is so much Dreck out there in You-Tube land that I go weeks at a time without venturing there ! A few signs of a video to
ignore, a video that starts' look what I am doing,' a single video showing a build with no follow up videos or follow up history, I also pay some
attention to comments like its ok to substitute Vermiculite for perlite (?) or other poorly thought out answers !

For me the only choice is price, probably in the next 5 years there will be something enough better than Perlite / clay slip, then I will up grade!

I will always insulate my Heat Risers, while wood is for me cheap, and I love tending my R.M.H., my Scottish nature requires me to be frugal,
and its the Permiculture way ! Hope this Helps For the Craft ! think like Fire!, flow like a gas, Don't be the Marshmallow ! PYROlogically Big AL !

Amos Valenti wrote:Is there any reason why you would not want to insulate the heat riser? Maybe material choice? I am seeing some designs that do not use insulation and wondering why.

Of course it's possible to build the heat riser out of insulating material. Like vermiculite board, ceramic blanket vacuum formed in a duct shape or the soft and light insulating fire bricks. Risers built out of metal without any insulation has to be looked at with suspicion: these stoves will work sub-optimal, almost quaranteed. Most of the time these are shown as a bare core, nothing like a barrel and a bench to slow down the gas flow. Complete systems will behave differently and has a dire need for the extra oomph of the larger temperature difference which is provided by the insulation.

In short: leaving out one of the recommended parts or introducing new ones like an extra air inlet in the lower regions of the feed tube will cause the stove to perform sub-standard. The whole thing is fairly critical, there's simply not much room for tinkering. When you do want to try to enhance it, buy a gas analizer and do the measurements, you would be surprised. To understand the merits of an analizer see this article by Crispin Pemberton-Pigott.

Peter Berg wrote:

Amos Valenti wrote:Is there any reason why you would not want to insulate the heat riser? Maybe material choice? I am seeing some designs that do not use insulation and wondering why.

Of course it's possible to build the heat riser out of insulating material. Like vermiculite board, ceramic blanket vacuum formed in a duct shape or the soft and light insulating fire bricks. Risers built out of metal without any insulation has to be looked at with suspicion: these stoves will work sub-optimal, almost quaranteed. Most of the time these are shown as a bare core, nothing like a barrel and a bench to slow down the gas flow. Complete systems will behave differently and has a dire need for the extra oomph of the larger temperature difference which is provided by the insulation.

In short: leaving out one of the recommended parts or introducing new ones like an extra air inlet in the lower regions of the feed tube will cause the stove to perform sub-standard. The whole thing is fairly critical, there's simply not much room for tinkering. When you do want to try to enhance it, buy a gas analizer and do the measurements, you would be surprised. To understand the merits of an analizer see this article by Crispin Pemberton-Pigott.

Good to hear. There is one video in where the top is taken off of a RMH and an uninsulated heat riser is shown. It makes sense now knowing that the fire bricks that were used must be the soft insulating type your referencing.

Amos Valenti wrote:Good to hear. There is one video in where the top is taken off of a RMH and an uninsulated heat riser is shown. It makes sense now knowing that the fire bricks that were used must be the soft insulating type your referencing.

That video is almost certainly the one picturing Ernie & Erica. And yes, when this riser is built out of bricks I am convinced it is the insulating kind. This video also shows a substantially wider side gap between riser and barrel as compared to the recommended values in the book.

In the interest of precision, when you refer to insulating the heat riser; do you mean the internal chimney, the external 55 gallon drum, or both?

You can do it however you like, but due to how the heat differential in the riser section drives the rest of the horizontal flue system, the ideal case is a well insulated internal chimney and an un-insulated outer barrel. It's the rapid drop in gas temps that creates the draft. So anything that permits the inner chimney from getting as hot as it can, or anything that prevents the outer barrel from functioning as an efficient radiator, will negatively impact your draft.