Monday, May 21, 2007

Potty House Design

RC made a request for drawings/diagrams. I hope you'll forgive me, but I'm going to pass on that. For one thing, I don't have any already made up- and making them would be quite a lot of work. For another- I'm a little bit opposed to the idea of "recipes" for this kind of thing. I think they can stop people from thinking for themselves, and a Potty House is exactly the kind of project where you MUST do a lot of thinking- about your specific site, specific climates, and specific needs. (RC, it's not you I'm worried about- but other folks who will read this blog and get ideas. If you need evidence, you can take a look at some of the advice Colin is getting on "refrigeration" - cold milk?. Wow.)

So; I'd rather stick with design principles here. There are still a couple we haven't touched on, though most design stuff is outlined in the two previous posts basics and the one with pics, more, and Pics.

Looking at the pics, I can quickly see a couple aspects of our potty house you might well want to NOT copy- not because they don't work, but because they're pretty specific for our situation.

One is- all the glass on the south of the building. It's "frosted" glass, so you can't see through it (privacy being important to some people). It's certainly more work to install, and more expensive, than just putting in a wall. We need it here, for winter sun/heat. We're far enough north that the sun's angle changes hugely from winter to summer; RC, who lives in PR, has got very different sunlight parameters to deal with. Our Potty House is also IN the woods; under a couple big oak trees. Lots of shade in the summer- which is good for not frying anyone who needs to use it in the middle of the day- but you do need SOME solar heat gain in order to dry the pits. Finding the balance can be tricky.

For this particular building, probably 90% of our solar heat in the winter comes in through the south wall windows. Partly because of the low angle of the sun- but also because of the snow. Most of the time in winter there will be snow on the roof- plenty enough to prevent much light getting through that way. Luckily- when there is snow on the ground- we get a LOT more heat in through the south wall- from sun bouncing off the snow field. It's quite significant, and yes, I did figure on that before building.

2nd design aspect you may not want- you can see the roof is made of 2 different materials- part of it is asphalt shingle; part of it is corrugated translucent fiberglas. The junction is a pain in the neck; and prone to leaking, particularly during snow melt. We mostly wound up with it this way because I wanted the "turbine" "powered" air vent to go straight up, and out- and fitting an 18" pipe through the fiberglas would have been beyond my construction skills at the time. I find myself calling this air-duct/pipe the "stack", as in smokestack.

Other considerations about that roof- I wanted a substantial overhang over the entry door, because people have to use it in the rain; nicer to have a little cover while you negotiate the wet, slippery stones walkway, etc. So I opted for a frame roof there.

Why did I want a straight stack? Because bends in very low air-pressure ducts REALLY cut down on the air flow. And- the stack, you recall, is connected down into the pits, to pull wet stinky air out of the building. Using ambient wind- which is known to be uncertain. I really wanted to do everything I could to make the air flow easier- for example, the stack outside of the house is painted flat black- to absorb more solar heat, and heat the air in the stack further, making it "draw" better. (The paint is 20 years old; still looks black when it's wet, anyway.)

I'll toss out a general "sustainable -green" design principle here, which I have not seen formulated anywhere, but which I have come to completely believe in. If you are incorporating some feature which relies on a "passive" process- i.e.. it relies on physics or meteorology to work, not an electric motor- get the best advice you can on "how big" that passive feature should be- then build it twice that big. Three times bigger, if you can afford it.

"Passive" is great- and free. IF it works. And it's just in the nature of passive phenomena; like warm but not hot air rising up a chimney; that a LOT of the time, they WON'T work, if the least little thing goes wrong. Like a stray wind gust blowing down the stack, and stopping a slight air flow. Making passive features bigger gives the physics that's supposed to drive them much better odds of actually grabbing hold.

Ok, I expect to see that cited as "Greenpa's Aggressive Passive Design Principle" from now on.

Anyway- rather than build that complex roof, it might be easier/cheaper to just lead the stack out through a wall, and put a bend in it. It might also be smart to go with "active" design in a warm climate; like investing in a little solar powered fan, to really pull the air through and out. A little pricey, but nice; and the turbine, incidentally, does NOT pull air nearly as well as they like you to think; testing shows it works about as well as a ... hole in the roof. But it does keep the rain out.


Here is a major design concern we haven't touched on yet- bugs- and spiders- WILL get into the building, and into the stack. You need to design the stack so it's easy to clean out, once a year anyway- otherwise spider webs (and other webs) will build up in it to the point where you have no air flow; and everything will quit working.

It's not that you can't clean a stack with bends in it; but it sure is more difficult, and the bends invite webs.

Bugs. You need to build your potty house with bugs in mind- every step of the way. (And mice; etc.)

Big piles of poop attract lots of bugs/critters, and you really would rather not have them in the potty house with you.


A) Build the building TIGHT. Remember that a mouse can squeeze through a 1/8" crack; and little bugs through cracks smaller than that. Don't leave cracks- allow for shrinkage and movement- and caulk whatever you can't close.

B) Build everything so it can be CLEANED. No matter how tight you make it; bugs/critters WILL get in (just not so freely). They'll come in the door, with you; even mice, who will sneak in past your feet at night. (Really.) So just keep muttering "I didn't want to be the only species on the planet, anyway.", and put things together so they can also be taken apart and cleaned out from time to time.

For example- the stack not only needs to be opened and "swept" once a year- I also put in an insect screen, to keep flies from just zooming down into the pits. The screen gets dirty/webby much faster than the stack as a whole; so make life easier on yourself and design it for easy access.

Now. Here we get into a difficult area for me. I have to confess something.

I didn't INTEND to tell you all a fib- but I did. I just forgot. My "green practices" list brags "no pesticides; EVER..." My confession- I do use some "fly spray" in the outhouse; probably about 5 times a year. Flies love poop. They will get in. You have to do something about them, or you'll got completely crazy. Ick. And while I'm confessing- we do use some of the same fly spray in the greenhouse, to control fungus gnats, which are lethal for us. The spray we use we buy at the farm store- it's designed and sold to control flies in "the milk room" and around dairy cows; pyrethrin based stuff.

I'd rather not use it- but so far it's the only realistic solution. If you're going to have a composting toilet, you've got to control flies. A couple of sprays of pyrethrin down into the pit when they appear inside usually stops them for a good month. It's not easy for them to get in; due to construction- but it will happen if people insist on opening doors.

Which gets us to the last point for today- the windows do NOT open- any of them. You DO need some ventilation options, however. No matter how well you balance things, you'll find yourself with days when it's just darn hot inside, and you wish it weren't. I made our windows unopenable mostly to simplify construction- and it also makes it easier to make the building fly-tight. And it's better for SEEING , and easier to clean- you don't have big insect screen areas constantly in front of your glass, and getting dirty. What we have instead are two screened "portholes" right up in the peak of the building, under the eaves. A much better place for ventilation, since that's where the hot air goes, and glass would be pointless, since nobody is tall enough to see out right there. The portholes have hinged wooden shutters that work from the inside; so if it's too hot, or two chilly, you can just reach up and change the amount of heat that's escaping or being retained in the main room.

We'll have a summing up post next; then on to the next subject. What have I left out?


Anonymous said...


Thank you so much for your guidance! You were dead on when you said: " My guess is it just seems too huge. I'll bet if you can get Comp to do it just for a week- the idea will start to sink in."

I think Companion felt pushed. When I backed off he relaxed and he just now suggested we try a 'root cellar ' like the one pictured here: Any thoughts? We have the perfect site on our property. Again: thank you so much for the great advice!

Anonymous said...


I was so excited, I neglected to write in the appropriate thread, sorry. I will be more mindful next time.

Greenpa said...

New- no worries- actually it's kind of appropriate here anyway. Though I haven't mentioned it yet anyhwere, we do have a root cellar- quite a big one, built as a 'stand alone', away from the house. It certainly works; even works well; but it DOES require knowledge and attention to get the most out of it. Sounds like a whole new topic... Over the years, I've used 3 different root cellaring places- and one I made up; where we used the bottom of the pond as a root cellar for a while....... We'll get to it. First thing for you to know; what's the average annual soil temperature where you live?- about 3 feet down. That's the temp you hope to capture and maintain.

Greenpa said...

And that pic looks more like a bomb shelter than a root cellar! yike. We do use ours for a tornado shelter, too-

Anonymous said...

Thanks for the info Mr. G, but may I suggest fly attractant hanging tent type traps hung one below in the tank and one above in the glassed area?
I see these at open air restaurants here and will look for the name.
You can actually make your own out of those sticky mouse traps.

Greenpa said...

RC- I neglected to mention all the things I'd tried before resorting to pyrethrin (the post was already getting long). I'm VERY opposed to pesticides; for the simple reason that all life shares far more basic chemistry than people realize; and what is toxic to one organism IS GOING to be toxic to others, manufacturers' claims notwithstanding.

I tried everything "non-toxic" I could find or think of, including parasitic wasps. Wood ash, sprinkled heavily on top of each event- sticky traps of several kinds, from oldfashioned "flypaper" strips to homemade; burial with compost; and lastly diatomaceous earth, sprinkled heavily on top. And specially built "fly-exits" to let flys get OUT of the THWASPCO, but not in- inverted cone type things.

Everything works - a little. Most of those alternatives MIGHT be satisfactory for some folks. One of the major factors that tipped me onto pyrethrin was - guests. I had a very important guest coming- and a big fly infestation at the moment. It was just really yucky , and rationalizing that I'd only do it this once, I bought dairy spray at the farm store.

Flies are very sensitive to the pyrethrin- they disappeared. To my surprise, they stayed GONE for a long time. With all the other alternatives, there are always some flies to put up with, and the population waxes and wanes. With the spray, they really went away, totally, and stayed gone until a new population got established from flies sneaking in open doors. (Ah- another design feature I forgot- the door has a SPRING on it to close it and hold it closed. Surprising how many people just loaf through doors, even though they know they are supposed to move quickly.)

Pyrethrin allegedly has no "residual" effect, and the legally listed "reentry" time for a dairy parlor just sprayed is likely to be two hours; very short by pesticide standards, indicating a low measured response from humans. I spray down into the pit; and on a sunny day when the ventilation system is working- so the excess spray goes out the stack; very little remains inside the room, which we stay out of for 6 hours, letting the sun and wind clean it out.

I'd be delighted to hear of some other way- but at this point, the pyrethrin spray seems to be the most workable response- for me.

The other ways were both slow to work; and often messy- and I do worry about the effects of diatomaceous earth- people who work in that industry have a high level of lung disease- which the industry says has nothing to do with them, of course. We've heard that one before.

Anonymous said...

Greenpa "First thing for you to know; what's the average annual soil temperature where you live?- about 3 feet down."

We planned to measure but find that to get to our 'perfect site' we must now traverse what has become a vernal pool. We would have to interupt some very amorous frogs. (You can not believe the racket these little beings make, car alarms sound pale in comparison to our city ears).

Companion thought the photo best represented his plan to use our site's topography. Scared me at first too!

We are now looking for other spots to place a root cellar. More later....

Anonymous said...


Full disclosure: Until today, I had never heard of a 'vernal pool' or knew what topography was.

Anonymous said...

Greenpa, as dull and boring as the pesticide story may be to others, I find the situation to be very educational and will try the pyrethrin in the future. Have any info about the least toxic means of dealing with vicious ants? We have them in the ornamental farm and at the luxury villas we plant at. We have some mighty powerful and large heavy formic acid injectors. Those babies are like yellow jackets.
What to do? Sometimes they are hidden under the lawn at the villas or under the saran at the farm, hard to find the nests. Advice or experience?

Greenpa said...

New- I HAVE a pond, with 7 species of frogs. They really are deafening up close; huge fun for the uninitiated. They're priceless bug eaters too- I wouldn't want to disturb a good pool.

RC- I've used boric acid for ants, effectively. It's an old use; one that's currently being challenged in some quarters (you can google it) - possibly because some boric acid might have been contaminated with arsenic, and possibly because some people started just tossing it around all over. One chemical source lists it as less toxic to mammals than table salt when ingested. Hm.

In any case- buy some pure boric acid (often available from the pharmacy- sold to be used as.. EYE WASH and wound antiseptic) and mix it with powdered sugar- you can probably find a recipe somewhere. Put that out where the ants will find it; they'll pick it up and take it back to the nest. If your ants don't like your sugar, try something else they do like.

A similar trick I've heard of for RODENTS, which always seemed too cruel to me- was to mix Plaster of Paris with sugar. It hardens in the gut; causing terminal constipation. I'm not as worried about the feelings of the ants, for some reason. Haven't really tried that one.

Anonymous said...

OK, I will try the Boric Acid thingie.
When I lived in NYC, I used that for roaches, it works fine.
Most of my insect removal is done with phosphate, MPede or similar.
I have plenty of frogs, toads, bats and birds for most of the insects, but ants and yellowjackets need some extra discouragement. We'll skip over the giant centipede for today, we don't want to scare anyone.
Just tell me. will the Boric affect the reptiles, bats and birds?
The anoles and iguanas eat the ants and so do the toads, but they don't eat enough of them!

Greenpa said...

RC - the THEORY is that most of the ants will stay in the nest to die, and predators like the anoles will see very few of them.

But it would be worth while checking that out with some other folks there. Veterinarians have to answer questions like that fairly often, and may have some real information- otherwise, I'd go to the Forest Service research station there, and ask some of the people who work on the herps. Somebody will know- I know there are some VERY good people there.

Anonymous said...

I will be asking the herp and ornitho people of the Fish and Wildlife what they recommend. Here where I am, we have some very complicated toxicity issues related to massive amounts of Navy ordnance imbedded in the soil and being gathered and blown up constantly {the wind blows it toward us} and the miniscule boric acid use will certainly amuse the FWS and EPA functionaries.
I had hair tests done in 2001 and 2002, and the testing company notified my doctor that they were very alarmed. Imagine how I felt!
I also have some very involved soil questions for you or anyone else you might recommend. Any chance of one day having an email?
I will be growing vegetables by the fall {again} and am working on a mix that is organic, that I can make with good old dirt from the ground, compost, and maybe water holding polymer. I am also now experimenting with having termites work for me, feeding them culled brush and branches and soy ink periodicals, maybe also cardboard, and using the result as part of the soil mix. This is in place of using a chipper and long period composting of the paper and cardboard. I need to know more about termite residue, termite nest composition, trace toxins in cardboard and paper and toxicity, if any, of slowly decomposing polymer. The termites are very efficient workers, multip;lying rapidly to create more workers, ripping into that lignin like there is no tomorrow. They'll eat a large oak chest in a night {imported stuff here}, they eat mesquite, they will go for anything with a hint of lignin. They work day and night and travel around in little tunnels. They are very large and known here as the "super Pollila",
the super termite. They are the subterranean variety. They require no petroleum products in order to function, are very renewable, silent, and if well fed, easy to control except for occasional mating flights, and they are free and plentiful.
If I can't use the termite mix for organic goods, I will use it for the ornamental farm.