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Erica Wisner

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since Feb 10, 2009
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Erica Wisner currently moderates these forums:
Was born, raised, and turned loose on an unsuspecting world. Originally an educator, now growing into writing & publishing, fire fighting, family care teams, and mountain ecological maintenance. Prone to extended explanations. (I like to explain things so that a 5-year-old and her PhD grandparent can both enjoy and 'get it'... no offence meant if you're somewhere in between!)
Okanogan Highlands, Washington
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Recent posts by Erica Wisner

That one the dog is sleeping on, is the one set up to take 4x4 foot IBC rigid 'totes'.
4 days ago

Jeff Dible wrote:Erica, I'm considering doing something like this to heat an aquaponics system either building a 4x8 raft tank on top of it, or using the mass as one of the sides of the 4x8 tank.  The builders guide has been helpful and great for radiant room heating.  I'm trying to get that heat into water without playing the boom squish.  Do you have any insight?


One of our beta testers was doing micro aquaponics, so the pictures in the plan set show how he prepared his bench for part of his tank setup.  He built the mass to support two or three of those rigid liquid totes, so the tanks rest on tiles directly above the pipes in the mass.  (Brick walls support the paver-like tiles, the remaining mass is softer cob/sandy stuff infilled around the pipes.)  This setup is located along his greenhouse wall, where both mass and water also collect sunlight to reduce heating needs.  

Another option is to include a variation on Tim Barker's water heater on top of the barrel, to produce on-demand hot water for piping to other tanks.  That's described in Appendix 3 of the builder's guide.  
In this case, I'm imagining just a big pot of water, like a giant canning kettle with a regular (non-pressure-canner) lid, and a coil of pipe dropped into it to run pressurized domestic water through the hot-water bath.  This system allows the water directly over the heat to boil (which it likely won't, unless you work harder to insulate and trap the heat), but even if it did, minor spillage rather than boom squish.  The higher pressure in the piped water raises its boiling point slightly, so it won't boil until all the other water has evaporated, and even then, the heat transfer would be pretty limited if the coil is up off the bottom of the pot (like you get with a canning rack).  

Don't skip the pressure relief valves anyway, but Tim's system seems more owner-buildable than most other attempts I've seen.  I like the canning-pot size because you can take it apart and clean / de-scale it as needed.

How you dribble hot water into fishtanks without killing the fish is your deal - I'm guessing there's a lot of known mixing technology and thermostat controls available.  
I probably would not recirculate algae-rich water through small pipes for re-heating, however. It seems likely to cause blockages and complications with the pressure differentials, which are a necessary safety factor not just a convenience.  
You might look at a secondary heat-exchange system where you just drape some hose or pipe from the heated water lines into the tank, and don't let the waters mix.  Again, researching what kind(s) of hose or pipe can do this without killing fish is up to you.  I think fish can be sensitive to copper, and synthetic hose will often off-gas when hot.  Might be some type of Nalgene tubing, or stainless steel, could work?  

Those are my thoughts.  If you get something working to your satisfaction, I'd love to see pictures here.

4 days ago
Question: For physical sales, how does it work for delivery?  
Specifically, when the person clicks on it, are they prompted to give an address?  Allowed to make notes such as "UPS address / USPS address" or "UPS back porch please"?
How does that address / order information reach the seller?

Any chance there might be a magical "Permies Store" where you can send a case of physical items (books, DVDs, etc) and pay a fee per sale so that Permies elves magically ship those items as soon as they are ordered?
3 weeks ago
This is a Digital Marketplace thread, with premium content for sale.

The Six Quick Stove Tricks mini PDF contains 3 mini-stoves you can build for under $3 each, and another 3 stoves you can build for under $30.

We often use these stoves as breakout activities for fire science or rocket intro days; they are great fun to do with friends on a fire-safe campsite or backyard barbecue.

Please click below to purchase a copy of the 5-page printable instructions, titled "Six Quick Stick Tricks.pdf"

3 weeks ago

Cj Sloane wrote:I'm not sure if this is the right one for me. Can I scale it down to say 10 feet? Or if I keep it at 40' can I incorporate turns to cover a shorter but wider area?

I'm hoping to heat the floor of a shed/dehydrator as backup on days the sun doesn't provide enough heat.

Hello CJ,
You could certainly scale things down.
If you add more turns, you need to shorten the overall length a little bit, say 5 feet less for each additional 90 degree turn.
So you could do 4 passes of 5 to 7 feet in length, and cover an area a little larger than a king-sized bed.
Or the same space vertically, as a heated wall, with the exhaust travelling upwards.

We've helped people build oversized rocket mass heaters for lumber-drying kilns; I think you could do a small one for a dehydrator.
You might also look at the 6" rocket mass heater plans - such as the Annex 6" or Daybed 6" RMH plans.

Let me know if you've already bought these 8" plans, and I can email you a diagram and parts list for scaling things down to 6".

Erica Wisner
1 month ago
Nice project!
One of the major issues with many of the batch box rockets we've seen and helped with is getting the door right - the right air flows, the right secondary air, and the right attachment so that it stays airtight without causing the surrounding masonry to crack or crumble.  Custom doors can be $300-700, esp. with frames.  
How did you end up solving the door?

I agree with several folks posting above that a person's choice of materials, and who/how much help to hire, is a bigger factor to project cost than the specific stove design.  The house itself is also a big factor - if there's an existing slab, and an existing through-roof chimney, you save several thousand right there.
However, for most masonry heater designs, and especially for the standard methods using double skins of cementitious exterior materials, you need a lot more masonry units, and more expensive tools to cut them accurately.  These methods do drive up both the material and skills costs, though both can be worked around with scrounging and training.  Using earthen plaster as the second "skin" over brick or adobe does cut costs considerably.

We have built bell- and J-style masonry heaters with adobe; and perlite-clay or perlite-straw-clay materials in lieue of brick fireboxes.  They definitely wear faster, but for a mild climate where you don't mind annual repairs rather than just annual inspections, they can work.  I would tend to look for some harder-wearing split firebrick for the base of the firebox, or some kind of heat-tolerant ceramic tile; repeated repairs get old.  

1 month ago

Don't buy in Madrid, summers are too hot and winters cold, it is more continental than mediterranean. Valencia and Alicante are fantastic, the people are lovely, and it is not cold in the winter. The South of Spain has cheaper land. I am originally from Spain and I am considering buying a small plot for playing gardener in the South of the province of Valencia . I heard there are permaculture expats in Spain, land is cheap and eroded, the weather is great. Marseille and the French Meriderranan surprised me because its humidity, I did not like it in the summer. If you want really cheap land and relatively near to the coast consider the province of Albacete between Madrid and Valencia in Spain. Here is my favorite city in valencia some real-estate.

For land in Spain, check and

Thanks for posting about your experience with the region.  It sounds lovely.

The link to the blog post about Elche seems to be broken.
I found a Wikipedia post about the same place:
and I think this link will get you to the original blog post:

2 months ago
Hello Greg, and welcome to the forums!

Watching the fire is definitely one of the pleasures of heating with wood.

However we (and the building inspectors) don't like to see two combustion set-ups connected to one flue.  
Although as you say, it sounds fairly straightforward to toggle between them, there is a nonzero probability that at some point either exhaust will leak back down the unused fork of the chimney, or the toggle will be set wrong when lighting the operational stove, or someone will try to light both at once.  It is not logically possible for the chimney to be the right size for each stove, as well as the right size if both of them are operating together, and any of these situations could cause exhaust to backdraft into the room in the wrong conditions.  
Since the rocket mass heater's exhaust will often be relatively cool, in a joined exhaust it could potentially get chilled and fall back down, re-entering the room through the wood stove.  And it's clean enough that it could be invisible and hard to detect, aside from a slight smoky smell.  But not quite clean enough to be healthy indoor breathing air. The times the RMH exhaust is most likely to have lower heat are during a cold start, or when the stove is not running full on, and those are also the points in the burn cycle where there is a higher chance of CO and other incomplete combustion products/poisons in the exhaust.

Other ways you could do the flame-viewing thing:

- Get a rack of candles (Ianto's suggestion)

- Have a separate stove or fireplace with a separate chimney.  Through-roof kits for chimneys are commonly available, much more so than custom-cut ceramic glass.

- Place a reflective metal panel or convex mirror above the feed, to reflect the flickering light into the room

- Place a comfortable chair near the feed, or build the bench and firebox in such a way that the feed is easily observed from a comfortable spot on the heated bench, to allow the lady of the house to sit and gaze into its hidden depths

- Consider a more technically challenging, but equally clean burning, batch-box style firebox, and get a custom door made with ceramic glass that can withstand the (slightly less intense and more evenly distributed) heat of the initial-stage batch fire.  You won't be able to see the double-rams-head vortex in the secondary burn chamber, but not many ever do.

- Consider a small, careful window of ceramic glass in the coolest point in the feed, maybe 9" by 9" replacing a couple of bricks in the feed of the J-style firebox.  Maybe double pane, to reduce the heat shock on each individual pane.  You will need to do some careful detailing, bedding the glass with fiberglass gasket, or getting it set in a steel frame with tabs and gasket to be inset into the brickwork.  
The insulation matters least on the short end of the J, most around the heat riser; a small window at the first corner of the J could be done without compromising the heater's operation too much.  Matt Walker did a few stoves with windows in various places, and the ceramic glass holds up well.  Workmanship is key to making it work, rather than have a leaky firebox.

- One of our local boilermakers wants to try ceramic glass directly above the heat riser, in place of the barrel top.  I don't know how well it will hold up to the asymmetrical heat source blasting its center, but the light show on the ceiling could be phenomenal.  This is an "at your own risk" suggestion as I do not yet know of a successful prototype that has tried it.

I might suggest searching the forums using the "search" button near the upper right, and entering "rocket" and "watch the fire."  
Or do a similar Google search that will let you put those quotes around "see the fire", like this: (copy and paste what's below into a Google search bar)
rocket heater ("see the fire" OR "see the flames" OR "watch the fire")

You may find more recent projects with flame-viewing windows that I haven't spotted yet, and you can also ask them about how clean the thing is burning as a result.  Get them to inspect the stovepipe and get it on camera, or something.

Erica W

2 months ago
This thread was my "something beautiful" tonight between work and sleep.
Thanks for sharing.
2 months ago
Did get the design worked out, eventually, but didn't get to try installing it.

If boat shopping, the biggest feature to look for is hull insulation, or the possibility of adding it.  
If your fresh water tanks are isolated from the sea water temperature on the other side of the hull, you have an isolated mass, and lot of options to warm that mass up, whether or not you install additional mass.  (If you have multiple fresh water tanks and can keep some of them cool and algae-and-scale free for drinking, even better.)  

If your living space has only a conductive skin between it and the briny deeps, you are now plugged into the largest thermal mass on Earth.  But Mother Nature controls the thermostat, and laughs at your puny efforts to warm the sea.
4 months ago