Len Ovens

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since Aug 26, 2010
Vancouver Island
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Recent posts by Len Ovens

Shawn Klassen-Koop wrote:Interesting. I'm wondering, would a stratification chamber bench for inside a house be heavier or lighter than a pebble-style bench?



Mass is mass... but, there are a number of other factors that affect things. I don't think comparing to a pebble bench is the best comparison. While a pebble bench is better than a sand bench, I think it is less good than a cob or brick bench.

So the factors that matter are:
  • how much of the generated heat the mass soaks up.
  • how thick the mass is, as this determines the surface temperature
  • How well the mass conducts heat, this affects both of the above
  • how well the mass is insulated
  • how well the room is insulated
  • how well the room contents absorb the heat


  • However, a stratification chamber does not in and of itself indicate what kind of mass there is. So it would be possible to use one with gravel as a mass. In both the long pipe and the stratification chamber heat collectors, it matters how well the mass absorbs the heat from the flue gas. Then, once the heat has been transferred to the mass the next question is how fast does it travel through the mass. This determines how fast it will heat and how long it will hold it's heat. It also determines what the outside surface temperature will be. In general we want this temperature to be  as low as it can be and still be useful. There are two reasons for this. First is not getting burned by just touching the mass. The second is that hotter surfaces will radiate through walls and windows faster than a lower surface temperature. And of course, the hotter the surface is the faster the heat is used up and the sooner new fuel will need to be burned. The disadvantage to the cooler (but still hot) surface is that it does take longer to heat the living space initially but that is really a heating management problem that can be managed and has been managed for years where high mass heaters are common. (the RMH over comes this to an extent with the exposed barrel for quick heat).

    The whole area of room contents and construction are a whole different topic. Any radiating heat source like you mass will radiate right through a window. It may even depend on what is outside the window (a white fence might reflect heat back into the home for example, while a sky view may allow the heat to escape to space) Massive objects in the room can absorb and re-release that heat later. Even the colour of the walls may affect things. Insulation in itself is not always the answer. In the mass heater world, the idea is not to heat the air in the room, but the objects and people instead.

    In all the area of heating and how it works really is not well understood. Those who build houses for a living have figured out that if they keep the air at about 21C, their customers will not complain about it feeling cold and the building codes seem to have encapsulated that. However, what the long term healthiest way of both being comfortable and having good air to breath (air tight, one air exchange per hour is not it in my opinion) while not spending an armload of cash or sweat for fuel... is a long way from solved. I think the RMH or other masonry heater is a good start as a heating appliance but to find out the rest will take more research (AKA trial and error). I don't think I can say with any hope of being right that we know how to build good houses. I do think there have been accidental house builds that have turned out well but why they have turn out well is not understood in full. Two people build similar house, one is happy the other not so much. Some of that is what each finds comfortable, but some of it is the many small details that are different from one to the other that anyone examining the houses would not find. Anyway, I am babbling on...
    6 days ago

    Grant Holle wrote:

    Len Ovens wrote:

    Grant Holle wrote:Didn't know where to put this idea, and this thread seems as good as any.

    Would it be possible to take Walker's half barrel design and turn it into a pit roast alternative?



    tilt the barrel slightly down towards the door as the bottom may collect water from your cooking and the flue gas as it will take longer for the mass around the chamber to warm up if it is warming up the food mass as well.



    I really appreciate your advice and design modifications.


    No problem.

    One thing I did think of when I was reading this, The door to the barrel should not be in a gully. When you open it to unload (maybe for loading too), this chamber will not have any breathable air in it. it will rather be filled with mostly water and CO2. Even though they may be quite warm, the CO2 may still be heavier than the surrounding air and not rise. having the land tilt away downwards and allowing a short time for the gas inside to be replaced with breathable air would be a good idea. Being able to deal with the food remotely would be better.

    I suppose going farther, if you have a chamber with unknown air quality, you should put a lock on it when not in use for cooking. You do not want a child to decide it is a great place to explore. Normal RMH do not have this problem as there are no man doors in them, so you are treading new territory with something like this underground and open-able.

    It would be less of a problem if the whole barrel was above ground if more dirt to move. Having the door at around waist height would make (un)loading a lot easier too. Also look at some of the rocket powered barrel ovens around too. It would make one's butt warming surface a bit high... but having a bed on top of the oven used to be quite popular in Russia, even 5 feet off the ground.
    2 weeks ago

    Grant Holle wrote:Didn't know where to put this idea, and this thread seems as good as any.

    Would it be possible to take Walker's half barrel design and turn it into a pit roast alternative?

    Here's what I imagine: the half barrel stratification chamber has a hinged door at the end so you can put in your meat to be roasted; the barrel is covered 8"-10" in cob and then insulated well (something like the easy-bake coffin only with plenty of mass in addition to insulation); the door at the end would then have to be covered in mass as well (could be as easy as berming earth against it). You'd of course  have thermometers in both the meat and the chamber. I'd imagine that you could heat up the mass in about 4-6 hours and the mass would stay sufficiently hot to cook the meat for twenty-plus hours. You'd start the fire around 8 pm the night before, keep it stoked until midnight, and feast the next day at around 6:00 pm. If the inside cooled too much during the night, you could always start a new fire in the morning for an hour or two.

    I thought about this after watching some friends pit-roast some pork last spring. It was labor intensive digging the hole, building the bonfire, stoking the fire every couple hours during the night, and digging out the meat the next evening. Plus we used a massive amount of wood.

    Most of the labor for this project would be on the front end--building the rmh, but that would be reusable. Aside from that, it's just a matter of berming and unberming the door and lighting and feeding the fire. Feeding the fire would actually be pleasant because you'd get nice warmth radiating  from the bell over the riser--the fire-feeder's seat would probably be the most popular. And it would use far less wood than a pit-fire.

    Any problems with this design?



    Most accurate answer is "please test this and let us know how it works" 

    I think in this case I would want to use a whole barrel to allow for enough room for food as well as flue gas. The larger size would also allow easier ingress/egress. I assume it is ok that the food is slightly smoked. Assuming the door is on one end, it may be ok for that end just to be insulated well rather than piling dirt there. Mass and insulation on top of the barrel should be more than under and side. (under and side may be ok with mass only, but top might want insulation)

    tilt the barrel slightly down towards the door as the bottom may collect water from your cooking and the flue gas as it will take longer for the mass around the chamber to warm up if it is warming up the food mass as well.

    if it doesn't work you at least have a nice outdoor heated bench to sit on in the fall... if it does work you can cook in it and still have a nice outdoor warm bench in the fall.

    Having played with stratification chamber flue gas heat extraction chambers like this, I personally feel these are much better than the long, long, long and bendy pipe solution. More heat is extracted with less flow resistance.

    cook me some traditional Pumpernickel  (cooked overnight in a cooling bread oven, but this might work too.).
    2 weeks ago

    Jay Angler wrote:I've been reading a Bill Mollison article and found this quote:
    "Effects on Snow and Meltwater

    ...

    More evidence, if only we could convince people, that a properly managed forest is part of the solution!



    research is expensive, so only people with money do research, people with money still want their money's worth and so tell the research what they should find before hand. This something I realized in doing my own research into medicine. However, it appears there is more to it than that. Once research is done, it costs much more to get that research in front of the right eyes and to have action taken on it. I would hesitate to include any governing body in that group of right eyes. It may be true that was the force behind replanting initially, but I think forestry companies realized they could end up with a patch of only the trees they wanted that way. The real job is convincing the people doing the damage that it will put money in their hands to not do that damage. Very few people think in terms as long as even five years (mostly two) yet many of these things are hundred(s) year problems.

    In the end it seems we can only manage the land we are on the best we can. We can be involved in the community in public land clean up and reclamation. We can choose to buy land that will have more effect on the local environment. I have a city plot where it seems the best I can do is to keep the weed man away and provide flowers for the bees.
    2 months ago
    Having thought about it a bit more. The question I think, is what the concern is. Just the smell or that things might be going bad, rotten or whatever.

    If the smell is the only concern, I would suggest more airflow before anything else. Code requires 1 full air exchange per hour but I think that is minimum... lab rats need 8 air exchanges per hour so 1 is just enough to keep law suits from happening not to keep healthy.

    If mold or other growth is a concern and the moisture content of the straw itself is high, I would want both large airflow and to remove some of the plaster skin and dry out the straw... I think. A natural render does allow moisture to pass. In any case, it is the moisture of the bales themselves and not the moisture measured outside the render. This site suggests the moisture of the bale itself should be less than 20%:
    http://thelaststraw.org/bonus-articles/moisture-and-straw-bale-walls/

    As that article points out, moisture inside the home comes from our activities and not the walls. However, the walls can absorb this moisture which again, points to ventilation.

    added later as an edit:
    the other question I should ask is if you have a concrete foundation. Concrete foundations tend to trap moisture, porous foundations such as gravel tend to be drier. (assuming in both cases that outside drainage is correct) Certainly all is not lost if your foundation is concrete it just means more ventilation would be required by the foundation to keep it dry.
    2 months ago

    Jason Klassen wrote:I built a straw bale house two years ago. I hired a consultant, plastered the walls interior and exterior, and have a large roof overhang. All that said - when it is warm, I can smell straw. I have used a moisture meter in a dozen places and the walls are hovering between 8%-12%. I found one spot that was particularly vulnerable to moisture penetration that was 14%-15% but I have patched it and it is dropping as well. And yet I smell straw. Anybody had this problem or fixed this problem?



    I don't have a solution to your problem... but your query opened up a question of my own in this regard. How bad does a more conventional stick built house smell? I am sure that because it is what I grew up in and live in now, I just don't notice the smell.

    So I am wondering:
       A) Is it bad for a straw house to smell like straw (assuming no allergy involvement)

       B) what does a healthy house smell like?

    I think with a straw house, very dry is important... except that from my experience of drying fruit and even kiln dried wood, there is such a thing as too dry. over dried apples are weak and crumbly and kiln dried wood is not as tough as air dried (ask a boat builder). So straw probably needs at least some moisture to retain it's strength. Straw (and wood) derives it's strength from fiber cells. If those cells are over dried the walls can loose their integrity.

    So perhaps someone with a straw allergy should not live in a straw house. Side note: the suits that allow people to work on the outside of the international space station, leak. Bears can smell the food inside a can. Is there any such thing as sealed.
    2 months ago
    Hmm, the wind has turned, the alien sun has gone... blue sky! Hope the fires go out soon too. Rain this weekend may help.
    2 months ago

    Roberto pokachinni wrote:

      At this point I almost feel: "let it burn" at least that way there won't be anything left to burn next year...

       The forest is WAY bigger than I think that you are imagining, Len.  This season will put a small dent in it.



    I think I should have put a smile or some indication I was not fully serious about that. Having said that, looking at the map of the area of the burn up by Prince George, it is already pretty big. Nor would I wish anyone to have to put up with the air quality we have here now and certainly don't want to extend this time for anyone. My thought is also that even in nature fires tend to not cover whole provinces, but I think that with the way we have managed them since that may no longer be the case.

    At this point, to be honest, I just want my eyes to stop itching and my throat to stop tickling. I want the light outside to be normal and not alien.
    2 months ago

    Nicole Alderman wrote:The smoke from the fires in BC has come down to us. Air quality is at 155. My neighbors are in an RV as their house is being built, and their daughter is really struggling to breath. I can't find anything about clean air shelters.
    ...


    Wow! We just came home (Comox Valley) through Naniamo and I thought Naniamo was bad. That looks worse. It kinda takes the special-ness out of the moon eclipse not too long ago as the moon is just as red now as then. All of us have stingy eyes and rough throats. The wind is supposed to change through the night and into tomorrow and send the smoke back to where it came from.  At this point I almost feel: "let it burn" at least that way there won't be anything left to burn next year...
    2 months ago

    Bryan Paul wrote:When using barrels for the stratification chamber, do they require barrel prep like removing paint, or are the temps low enough that they won't off-gas?



    In the end it is your house and you will have to breath whatever fumes it puts off. Buy a canary  and if it dies while using the barrel with paint still on.... maybe get rid of the paint.
    Personally, I would remove everything down to bare metal. Coated non-stick pans are designed to be heated and cooked in, but there are enough stories floating around of dead
    pet birds from people cooking with them that we have limited our cookware to stainless or cast iron (or even turned steel in the case of one of our woks). It is probably less work
    to remove paint first than removing the barrel later and removing the paint and reinstalling the barrel. I am sure that the paint on barrels is not of the high temperature variety
    used for exhaust pipes or even engine paint.
    4 months ago