Rocket stove driving underfloor heating?

Burra Maluca wrote:

Kathleen Sanderson wrote:I didn't see anyone addressing the fact that he said the house is in zone 9a, which should only need minimal heat.  It should have far more of the year in need of cooling, in fact.  It's fine to play with something labor-intensive and failure-prone like under-floor heating if you really want to mess with it 'just because,' but in your climate, honestly, I wouldn't.  

If I was building a house in that climate, and planning to use my heat source for cooking (presumably year-round), I think I would build a sun room -- a screened porch in hot weather, but close in the screened windows with glass for the cooler parts of the year.  Attach that to the house, and put the heater/cook stove in it.  With such a small house, all you would need to do to heat the house is open the door between the two spaces when you need heat, but in summer when you absolutely don't need extra heat in the house, close the door and keep the cooking heat out in the screened porch.  In fact, unless there's a lot of cloudy weather during the coldest parts of the year, the sun room would probably provide most if not all of the heat necessary for such a small house.

I've been living in this area for 15 years already, and the climate isn't just 9a, it's also mediterranean, which means 'cool, wet winters'.  We generally get one or two six-week sessions of solid rain at some point during the winter, where we will absolutely need heat both to keep us warm and the building dry.  I've been dreaming of a rocket mass heater for so long simply because it's a perfect solution for this climate.  It's likely that a single burn of around an hour a day during wet or frosty weather will be all we need so long as there is some way to store the heat and give it out gradually over the next 24 hours. And as Austin has been dreaming of under-floor heating for years and years, we'd really like to try to combine our dreams into one functional reality.  

I totally agree about cooling in the summer, though I've never had air-conditioning and am fairly well adapted by now and have got pretty good at managing air flow to keep the temperature indoors relatively stable.  We will have gas cooking stove, designed to be swapped around so that during the heat of summer it will be in a screened porch, as you suggested, but inside the main house during the cooler months.  During the wettest, coldest periods we'll cook on or in the rocket mass heater as much as possible.  

Tim Skufca wrote:we have a ground-source heat-pump which heats our hydronic floors from a well in our in-town Missoula well. In-floor heat is very comfortable. In the summer heat we circulate well temperature water through the floors to keep the space comfortable, which is very important if the Missoula air quality gets bad from forest fires. Closing the windows and running 55 degree water through the floors is an effective way to hold off those awful smokey periods.

ALSO: what is not talked about with Rocket Mass Heaters/Stoves is the necessity to be there at all times. There is no way to take off for a few days, or else everything freezes. I have the mind-set of embracing technology and install solar panels that power the electrically sourced hot water.

Scott Weinberg wrote:  If you don't trust a relief valve, then put in two of them.
The odds of a double failure at the very same time, is well.................. pretty darn hard to calculate.

Burra Maluca wrote:I totally agree about cooling in the summer, though I've never had air-conditioning and am fairly well adapted by now and have got pretty good at managing air flow to keep the temperature indoors relatively stable.  

Tim Skufca wrote:what is not talked about with Rocket Mass Heaters/Stoves is the necessity to be there at all times. There is no way to take off for a few days, or else everything freezes. I have the mind-set of embracing technology and install solar panels that power the electrically sourced hot water.

[b wrote:paul wheaton[/b]]

Scott Weinberg wrote:  If you don't trust a relief valve, then put in two of them.
The odds of a double failure at the very same time, is well.................. pretty darn hard to calculate.

In areas that they tend to gum up in a couple of years, it would seem that in five years of use, the odds of both of them being gummed up seems to be about 100%.


yes, I had completely forgot those areas of the world where there are NO protected water heating systems. With everyone sitting on time bombs... to bad for them....

]

Walker stoves are designed to put heat out the top fast, and slowly out the sides, so they are great when installed roughly in the center of a space (as a kitchen island for example).
I've seen Lasse Holmes put a small bench on to capture waste heat from the exhaust on its way to the chimney - but you have to be careful how much heat you capture in this location, as the chimney needs heat to function (and these stoves definitely need a decent chimney to burn clean and draft well). --Erica W

Julie Reed wrote:“One mistake a lot of people make is in adding antifreeze. Not only is it toxic and expensive to buy, it automatically makes your system 10% less effecient.”

It is not necessarily a mistake, depending on where you live. In the far north where it may get to -40, a system that was shut down for whatever reason (power outage, etc) for an extended period would be subject to freezing, especially if you had a garage floor involved that may be a less well insulated space. There are two main types of glycol common to heating and cooling use: Propylene glycol (PG), and ethylene glycol (EG). Propylene glycol is considered non-toxic.
The other consideration is if you are using just water, you may need to add a conditioning agent from time to time if you have ‘hard’ water. Reason being, you are not constantly running fresh water through the system, so the minerals never get flushed out. The pex will be fine but metal components are subject to corrosion. Or you could just flush the system annually.

One other ‘plus’ of a heated floor- you get a warmer space with less heat input. Because you are introducing heat at the lowest point of the living area, a lower setting is perceived as being warmer than the same setting if you had radiators or forced air. And since your body is warmed from the feet up, you may be quite comfortable in a house with the air temperature at 60-65 degrees instead of 70.

Julie Reed wrote:

Aside from calling it toxic, you are mostly correct in saying it’s unneeded, but it really depends on your location and potential for extended power outages. To those of us north of, say, latitude 50, it’s cheap peace of mind.

Julie Reed wrote:“Flowing water does not freeze.”

Actually that’s a fallacy. At a certain point, if it stays cold enough, it will (I saw it happen to a boiler in northern NY in less than 24 hrs). But yes, for a couple days the circulation would probably save you.

“Just do the math on antifreeze, not only do you save not having to buy the expensive stuff, but it is 10% less efficient. In about a month's time, I will have saved enough money to buy a small generator that could power my circulating pumps...or a few deep cycle batteries. Even if you use wood as a heating fuel, why have to gather 10% more of it every year just for antifreeze?”

If a 10% loss of efficiency over 1 month equaled the value of $1000 for a decent generator or decent batteries/inverter system, that would be a very large system. That would mean your cost to heat was $10k per month.
To me, a 10% efficiency loss, coupled with the $500 it costs (one time) to add enough for a 2000 sf house (typically the largest home most people would have), is more than a fair trade off to not have to worry about maintaining batteries or a generator, or having to hope the generator starts, or having to fuel the generator for a week...
And since infloor heat is probably the most efficient way to warm a building (aside from passive solar), you’ve already gained far more than 10% over any other systems anyway. So it’s a net balance at minimum.

Aside from calling it toxic, you are mostly correct in saying it’s unneeded, but it really depends on your location and potential for extended power outages. To those of us north of, say, latitude 50, it’s cheap peace of mind.

Hans Quistorff wrote:

Walker stoves are designed to put heat out the top fast, and slowly out the sides, so they are great when installed roughly in the center of a space (as a kitchen island for example).
I've seen Lasse Holmes put a small bench on to capture waste heat from the exhaust on its way to the chimney - but you have to be careful how much heat you capture in this location, as the chimney needs heat to function (and these stoves definitely need a decent chimney to burn clean and draft well). --Erica W

Aircrete method for making inexpensive high drafting chimney.  

Erica Wisner wrote:
Walker stoves are designed to put heat out the top fast, and slowly out the sides, so they are great when installed roughly in the center of a space (as a kitchen island for example).
I've seen Lasse Holmes put a small bench on to capture waste heat from the exhaust on its way to the chimney - but you have to be careful how much heat you capture in this location, as the chimney needs heat to function (and these stoves definitely need a decent chimney to burn clean and draft well).

Yours,
Erica W

Austin Shackles wrote:Build the tank so the sum CSA of the fire tubes is a bit more than the nominal rocket size, it shouldn't restrict the exhaust too much.  

Austin Shackles wrote:wonder if I can use it to heat a water tank and use that warm water to supply more-or-less conventional underfloor heating.  The advantage I see in this is that I could also heat that tank from a solar pane

Austin Shackles wrote:There's another possibly-relevant point to the anti-freeze argument - at the same time as lowering the freezing point it also raises the boiling point.  I think that's part of why they use it in solar water heating systems.  The solar system we had in Wales was pressurised (in the solar loop) *and* had antifreeze, and so far as I know it never boiled.

That was of course a closed system; it circulated through the panels on the roof and through one coil in a 2-coil domestic HW tank.  And, so far as I know, it had a PRV but that never was invoked in the UK.

Satamax Antone wrote:Austin, to further push for a real mass heater. Have you ever been near one?  I love the heat from those. Ok, the floor is not evenly hot all around. But it can be for several meters around it, if built with insulation underneath.