Kitchen counter as mass?

We are planning how to implement the RMH in our reno design... My thought is to make the kitchen peninsula (which will also house the sink and hence, plumbing) our thermal mass instead of a bench concept... Has anyone tried this? What are some considerations we may not have considered? Obviously it will decrease available cupboard space but I think we can build in some nooks with the cob.

I have been planning to do something similar. After a bit of research, I modified things. I would like a batch box rocket feeding a double bell. The double bell would be the bar top dividing the kitchen from the living room. Bells are much more efficient at storing heat than mass with piping through it. This will allow two fires per day, without needing to fiddle with tending a traditional rocket, while providing radiant heat all day long.

Either option, bell or mass, with have considerable weight (possibly 6000+ lbs). You will need to plan for that. Other details will depend on the size of rocket, location in the kitchen, materials to be use, etc. You should be able to make it happen though.

Thanks, I wasn't expecting to have a reply so quickly. We have considered a Russian Masonry stove instead of RMH but now leaning toward the RMH for simplicity. Though we like the viewing door idea...

Hi Katie; A kitchen counter , what a great idea ! You might try making your mass with a (blank spot) at the feed tube , where you could retrofit the glass from an oven door to view the fire. I would recommend building without any glass to begin with to make sure of its performance and then add your window later. Another idea might be to place a round mirror (like they use in stores) on the ceiling where you are looking down the feed tube as well as reflecting light around the room, then you could check your fire from across the room !

That design is floating around here somewhere. It will work, but you have some design issues to deal with because of riser heights and feed tube safety. Weight is a definite issue to consider.

Amos Burkey wrote:I have been planning to do something similar. After a bit of research, I modified things. I would like a batch box rocket feeding a double bell. The double bell would be the bar top dividing the kitchen from the living room. Bells are much more efficient at storing heat than mass with piping through it. This will allow two fires per day, without needing to fiddle with tending a traditional rocket, while providing radiant heat all day long.

Either option, bell or mass, with have considerable weight (possibly 6000+ lbs). You will need to plan for that. Other details will depend on the size of rocket, location in the kitchen, materials to be use, etc. You should be able to make it happen though.

Amos, I am curious as to how you concluded that bells are more efficient at storing heat. Seems to me that given an equal mass and an equal surface contact between the mass and the hot bell or ductwork, they should have the same performance. What am I missing?

Peter Ellis wrote:Seems to me that given an equal mass and an equal surface contact between the mass and the hot bell or ductwork, they should have the same performance. What am I missing?

What you are missing is stratifying. In a channel based system all the gases of whatever temperature will follow the same path through the stove. In a bell on the other hand, the hotter gases will raise to the top and the colder gases will be pushed down where the exit is located. This effect will happen because of gravity, hotter gases are lighter by nature. The way to extract heat is completely different because of that.

https://www.flickr.com/photos/onyone/5550465744/sizes/l/in/photostream/

http://www.navitron.org.uk/forum/index.php?PHPSESSID=7a2ff600ddaf5f3222fe2fda658cd15e&topic=16393.msg186492#msg186492

http://www.inspirationgreen.com/assets/images/Blog-Building/Rocket%20Heater/rocket%20mass%20heater%20belgium.jpg

Another advantage of a bell: it is the best system in the low friction department, head and shoulders above a channelled gas path.

Thanks everyone for the replies. Antoine, that is the picture that gave me the idea in the first place, but hubby wants the actual fire to be of the masonry style.. Personally, I just want heat! As for the length and anticipated complications... It wouldnt be any different than a bench concept except taller. Of course the kitchen pipes will need to be insulated from the heat but I anticipate access doors for repairs, etc. The entire length will be about 8ft, I'm thinking tubing going out 8ft elbowing upwards instead of sideways and back to the outside wall before rising through the ceiling and out. Like the one done in the greenhouse on YouTube, of course i will have mine cobbed completely to the exit point. Thoughts? Given the complexity of building a masonry stove I personally think the fire should be in the counter but worry about its proximity to the outer wall. Putting it on the far end of the counter would require a 3rd 8ft run to exit, that seems it would be too long given what I've read.
Any input is welcome.

Also worth noting is that our house is built on a cliff beside the ocean with a crawl space underneath, so we will need to brace for weight... Any ideas on how to calculate the weight of this counter?

Katie Cabana wrote:Also worth noting is that our house is built on a cliff beside the ocean with a crawl space underneath, so we will need to brace for weight... Any ideas on how to calculate the weight of this counter?

Yep, it's not too hard, but depending on the shape, it can take time.

In a nutshell, it's L*W*H*density.

That's length x width x height to find the volume of your countertop. If it's a single rectangular shape, you're done.

To invent some numbers, it's 100" long x 24" wide x 4" deep. That makes 100*24*4= 9,600 cubic inches.

Let's say it's a more complicated shape, maybe an L. You'll divide it into rectangles and calculate them separately.
To invent numbers again, the top leg of the L is 36" long x 24" wide x 6" deep. 36x24x6= 5,184 cubic inches.
The side leg of the L is 80" long x 24" wide x 4" deep. 80x24x4= 7,680 cubic inches.

Your imaginary L-shaped countertop is made of (5,184 + 7,680 =) 12,864 cubic inches of material.

How much does that weigh? Well, you google 'density of concrete', or 'density of granite', or 'density of compacted earth', or whatever you're going to use.

Concrete, for example, weighs around 0.0868 lbs per cubic inch. So how many inches? 12,864 cubic inches. 12,864 x .0868 = 1,116.6 Your imaginary L-shaped countertop will weigh about 1,116.6 pounds.


That's it! LxWxH to find the volume, then volume x density to find the weight.



Good luck!

Thanks Mike, I searched for a density for cob but have been unable to find anything... Wonder if anyone might know or atleast know where to find it.

Katie, you might just want to go with the density of concrete for your calculations and then you are bound to slightly overbuild your system. When it comes to supporting weight it is always best to err on the side of overbuilding especially in renovations.

The nice thing about your idea is that your rocket mass is in the middle of your room rather than along a wall, which I've seen with most RSMH's in a bench. The bonus of this is that you are not radiating outside through a wall, all of the heat radiates into the room. If you insulate your floor well (around your beefed up bracing), then even more heat is kept to radiate within the room instead of downwards.

thomas rubino wrote: You might try making your mass with a (blank spot) at the feed tube , where you could retrofit the glass from an oven door to view the fire. I would recommend building without any glass to begin with to make sure of its performance and then add your window later. Another idea might be to place a round mirror (like they use in stores) on the ceiling where you are looking down the feed tube as well as reflecting light around

I really like the idea of using the curved mirror, Thomas. I also like the idea of the oven glass to view the fire, but I'm wondering how this might effect the insulative qualities of the feed tube/burn chamber. I've seen this in a design on Youtube as well, and it seemed to work but I have reservations about it. I was also wondering about cleaning the glass on the fire side of it. I've had to do this with woodstove glass before, and you would have to design in a proper access to do the cleaning... yes? Any ideas?

Roberto; I suspect that the glass would have a detrimental effect on performance. As far as cleaning the glass ,access would be straight down the feed tube and relatively easy. What i don't know is if the glass could handle the temps generated at the bottom of the feed tube . I'm sure that it would be smoky dirty all the time and only have a vague flickering view of flames as well. I think the mirror is the answer to enjoying the fire. An open feed tube with a roaring dragon will throw an orange glow with dancing shadows as well or better than a smoky glass would anyway ! Add a round mirror so you can see from across the room, sit back and enjoy the view !

As I suspected. Thanks Thomas.