Dave Hanson

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since Feb 24, 2013
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Recent posts by Dave Hanson


First, one of your questions is easy. Any time you heat water in containers you must have expansion tanks and pressure relief valves for safety. Not expensive. Now, on to the bigger, and harder questions:

Basically just think of the two major factors in heating. 1. the source of the energy and 2. the delivery system. Under floor heating, rmh, masonry heaters, massive walls, are all mass heaters where we deliver heat energy to a thermal mass that then radiates it back to us over time. Every piece of the system we choose will have positives and negatives so the choice we make depends on a bunch of factors about the site, the building, our age and physical ability, personality etc. We try to put all the pieces of the puzzle together to create the best system for us. This is before we even approach the questions of environmental issues.

The delivery system I like best is in floor. It is efficient, quiet, clean. Sometimes you forget you have a heating system. As I said, the bad part is cost. Another negative, for some people is the floor itself. In floor heat works best in a concrete or gypcrete floor. There are systems of transfer plates that can be attached under wood floors but they are not as efficient. A stained, concrete floor, cut to look like huge tiles is a popular floor these days and in floor heat works great in that. You ask if there is a way to reduce the cost. I think a hydronic system would work in an insulated adobe floor, but I have never done that. In a very small home you might be able to heat the water with something less than a high tech boiler. You would probably sacrifice some efficiency but that would be compensated for by the small size of the area. Pump it with a low voltage pv system. Heat the water with a homemade coil on some kind of firebox. I grew up in a home where the only hot water was heated with the kitchen wood-fired cook stove, so........

Radiators, either old fashioned cast iron, or modern steel are less costly and also good systems, with the advantage of being more accessible and repairable if there is a problem.

In my current home I have a masonry wood heater. Quite similar in many ways to a rmh. Efficient and burns clean. A very old way of heating in N. Europe.

And lastly, the massive wall or floor that collects solar energy on the right site in the right climate is wonderful.

Okay. Now energy source. Aside from the passive solar energy that heats a mass, which then radiates heat to us, all of the systems require that we actively bring energy from "fuel." Wood. Oil. Propane. Natural Gas. You can buy a boiler that uses any of these and some can switch from oil to wood if needed. The CO2 emission issue, sequestration of carbon, footprint, air quality, etc etc are well known problems and too complex to discuss here. It would be wonderful if all of us had the perfect climate and site where we could use only solar energy to heat our homes. The energy source we choose is impacted by budget, location, size of house, personality, etc., so it is difficult if not impossible to answer your question. About all I can do is rank my choices.

1. Passive solar with a mass wall or floor seems like the best we can do but it has the downside of using concrete, or the extreme labor cost of stone or masonry, and some real restrictions on design and size of house. Depending upon the quality of the solar exposure I would back up this with the most convenient thing I could get, knowing I would rarely use it. Electricity. Propane. Gas. Oil. Wood.
2. Hydronic floor. Needs fuel, none of which is perfect. High cost.
3. Radiators. ditto Can be included in a remodel.
Note: Hydronic systems need a pump but fortunately they are small and can be integrated into a pv system. The can also be powered with a battery backup for grid failures.
4. A masonry heater. High cost. Wood only.
5. RMH low cost. Wood only. Probably the cobb "bench" for mass which is a questionable design feature. Maybe in floor. Tiny wood. Temperamental but hard to beat on a cost basis.
6. High quality cast iron wood stove. Steep heating curve, and I've never seen one that doesn't stream pollutants off the door when you open it to add wood. If you have asthma, stay away from these things.
7. Steel wood stove. Steeper heating curve. Same problem with effluents.
8. Open fireplace. (Often an actual energy loser. Radiates for awhile and then sucks warm air out of your house!) Actually a terrible choice. I know there are fireplace advocates out there, but I think they are full of hot air they didn't get from the fireplace.

I have sort of gravitated into the wood world with this list but it should be mentioned that there are many many other options. We can put electric heating elements almost anywhere. The floor. The walls. The ceiling. All invisible. Electricity is an overall inefficient way to heat things but if your costs are low enough per kwh these systems can look pretty good. Here, where I live in NW WA electric heat in a well-built house competes quite well with wood, unless you have your own free wood. Also, when the grid goes down you have no heat. There are all kinds of gas or oil heaters of course and then there's the pellet stove which requires electricity, etc. etc.

It is ironic that you are asking me these questions because I am currently planning two houses, both for us. One is in the city and the other is in the forest. The city house will have a radiant floor, or if we buy an existing house, we'll retrofit it for radiators. We'll use natural gas to fuel the boiler ( yes, I know about fracking ) and also get domestic hot water. We'll build (or buy) small and concentrate on the structure's insulation and air infiltration control. We will have a cast iron wood stove, just for the aesthetic of the evening fire I love. I've been cutting and splitting wood for decades and I'm getting tired. In the forest, we'll build even smaller and heat with an attempt at passive solar backed up with cast iron wood heater. We'll also have a pv system, probably 12 volt, out there.

So you see, I struggle with these choices for us.

And out beyond all those considerations is the big picture re carbon, sustainability, etc. Everyone should have a look at an Odum Energy Analysis before they get too excited about being environmentally correct. This is why I appreciate some of the critics of each of the alternative building systems. We can be environmentally perfect in one respect and not in many others. As an example, I have a son who lives and works in Seattle. He walks to work and does not own a car. He has no intention to ever own one. Doesn't like to drive. Rides the bus. Rides his bicycle. His carbon footprint is a tiny fraction of mine. I drive a truck and burn trees to heat my home. I'm doing some good stuff ecologically, managing a forest project back into a diverse, mature, food forest( I hope), experimenting with native edibles, etc., but who knows if I will ever have the "carbon account" equal to my son who does not drive.??

Wouldn't it be great if things were simple, like they were back when I was a sophomore in college? (1954)

11 years ago
Hi Bill,

You're right, many if not most furnaces heat air and blow it into the house through ducts and a return duct takes cooler air back to the furnace. The reason it is so common is that it is a low cost system. It works, but is a terrible way to heat our bodies, which is our goal. (To be fair these systems have an advantage other than cost. The heating and cooling curve is steep, when you want it to be and they convert to air conditioning systems in hot climates quite easily. They can also act as air filters but usually just move pollutants around and around so you get to breathe them more often.)

Heat energy moves through conduction, think of that as the hot handle on your frying pan. Convection, in which warm air rises and cold air sinks, think of the warm air rising to the ceiling in your house, and radiation, think of hot lights, or a wood fire outside in freezing weather when you can feel the heat from the fire on your face. You will often hear people say that "heat rises." No, heated substances rise. Heat is a form of energy that radiates in all directions, even in the absence of air. Radiation is the most efficient way to heat our bodies. In fact, in a home heated with radiation you can set the thermostats lower and be just as comfortable as you would be with a forced air system. Radiant heat does heat objects which then heat the air next to them so the overall effect is a mixture of everything but meanwhile, your body feels the radiant heat whatever the air temperature. Another way to say this: heat can get to your skin in two ways, either as radiation or being carried by air, water, or conduction from a material.

The old style cast iron heaters were quite efficient but because there isn't much thermal mass there, the heating/cooling curve was relatively steep compared to mass heaters, which go back hundreds of years. The mass of material, stone, brick, cobb, absorb huge amounts of heat and then radiate it into the room over a long period. The heating/cooling curve is very flat. (This can be a disadvantage if the weather quickly turns warmer and your mass heater is still pouring out the heat. You can't stop it.) The air in the room does get warmer from the objects that have been warmed by radiation but we are not using the air as a medium to transfer heat.

The best system, in my opinion is the hydronic in- the- floor system. I've built many houses with these including my own and owners always love it. It combines the efficiency of using water as the transfer medium and the floor gives us a huge mass for radiation. Any energy source can be used to heat the water and most modern boilers are extremely efficient. The only disadvantage is cost. They are not cheap up front. Long term it is the only way to go.

A wood fired rocket mass heater with a hydronic loop doesn't make much sense but a rmh with an in-floor exhaust tube does but there are potential problems. Here's one: let's say you build your rmh at a level so you can exhaust it in a cobb or concrete floor. Before you do the floor over it you can test it but it is not performing in the mass you will add to it, so your test is not valid. When you build your floor on it you can only hope it will perform as it should. If it doesn't, what do you do? As a builder I hate things that are buried, that I can't see and fix. That brings us back to the old cast iron radiators with the pipes (insulated of course) running through basements or crawl spaces. Every part of the system is visible and easy to change. Again, as a builder I know that something will go wrong, someplace, where it is least expected.

Sorry to be so long-winded. I hope I answered your question. I remain fascinated by heating, air changes and moisture in houses.

11 years ago

Think insulation under the stove, not conduction. Concrete board, brick, etc. conduct. Some high density foam board will insulate your floor against the heat. Maybe 2" Maybe 4" with the brick over that. This will change the elevation of your whole assembly but your thermal mass should be insulated from the floor also. Your cob can come down over the exposed edges, or frame them with wood. Test the cob you can make with your sand and clay. If you can produce a tight, heavy, strong brick of it, it will work. Any grass straw around? Fibers will make stronger cobb. Make different recipes, dry them and see what is strongest. Sharp sand is better than smooth sand from rivers and beaches. You don't need expensive fire brick in your manifold. Good luck.
11 years ago

I'm not that wild about rocket mass heaters, having built a few of them, but if that's what you want, chop a hole in your floor, support the joists you cut, place stone, or cob, or concrete on the ground in your crawlspace high enough to build your rmh on it. Be sure to insulate that foundation before you build your stove. Now the weight of the thermal mass rests on the earth. If you build the rmh yourself pay close attention to the geometry of burn tube, riser, manifold and exhaust. This stuff is important.

I like furniture that is light, adjustable and portable, so the cobb/bench/thermal mass doesn't interest me. You might want to consider placing your rmh at an elevation that allows the thermal mass to be even with/part of your floor. If you do that you should get the exhaust pipe immediately outside when it exits the mass. And be sure to insulate the mass anyplace it is not in the heated space.

Somebody wrote here that a hydronic system would require changing hot liquid to warm air. No. You want the hydronic system to heat a radiator. It radiates, just like your rmh. Moving air is a bad way to move heat energy.

Good luck

11 years ago

You have an interesting and challenging site. If I was in your shoes I would buy a day from a consultant on site, that is if you can find one. Sometimes an expert can save us from big mistakes and save us from wasted time, energy and money. If they are really good they can see things we don't think of. Of course we want to educate ourselves as much as possible as we go along but some solid, experienced, expert opinion can jump start things in the right direction. Beware of those who will offer long distance advice without seeing your site.

I'm a retired builder with experience in agriculture, alternative buildings and forestry. I believe that fundamental design is the hardest part of any project. With inadequate planning or mistakes in design the long term problems multiply and projects become a series of band-aids, never completed and never quite right. The ways this plays out in reality are sometimes painful to witness. Well-meaning people expending years of hard work and finally being exhausted by an ugly, unfinished product. Permaculture, a mixture of art and science, is supposedly finely tuned to and integrated into the ecology of any given place. Every place is a bit different than every other place. Watch out for general rules.

The problem of course is finding the consultant. Can't help you there. If you do, you'll save the fee many times over.
11 years ago

It is a start and that is all any of us have. I think one of the pieces of starting is research about what local indigenous people ate in our location. (until they were either pushed out or killed, of course) Out here it would appear that Native Americans were all out on the shore. They must have journeyed inland some, for hunting and gathering but they were primarily people living on the marine edge of the forest. There are a few native people around here who can teach a little about wild foods, but not much. Just one plant is significant however. In my more urban gardening I have evolved to relying on giant red mustard for my greens almost exclusively because it is so easy. Could be its spicy flavor makes it somewhat uninteresting to deer? I'm going to find out.

It seems to me that wild food is the place to start because it is adapted to the place. I also have no problem with introducing domestics into the forest. (sigh) So much to learn. So little time.

Some time ago I noticed something about hugelkultur and just passed it by. Now I have looked into it more and realize that it may have important meaning for our forest project. We have huge trashpiles, left from the clearcut, that are small areas of several thousand square feet where there is still a lot of light and not much growing. With an excavator I can get into those and create giant hugelkulturs where I could do some intensive planting. My deer and elk, being browsers, move as they eat and do not usually destroy plants totally. If I plant enough there will be some left for humans, especially if we also eat the deer and elk. (Strangely, they find this frightening.)

Good luck with your project. Keep in touch.
11 years ago
I'd be interested in hearing from anyone who is attempting a food forest in a place similar to mine. I manage a family forest of 116 acres on the Olympic Peninsula in NW Washington. I live in this forest part of each year. Our goals for the forest are educational for our descendants, recreational for all of us now, and financial. (if any logging ever takes place it will be selective and sustainable....never a clearcut) I have a degree in Ag. and was a Biology teacher many years ago.

I've read Crawford and much of it is interesting, however our forest is alive with bears, deer and elk. Fencing is out of the question, so whatever we do has to be self-sustaining, self-protecting, self-regulating. Natural!! We can do some things around the edges such as thinning for species that can survive and spread. At 77 years of age I will never see the results of what I do now but I can envision where it might go if I start the right thing. I began by asking for help from (highly paid) and well-known permaculture "experts" who either because they were too busy or because they had no idea about how to approach it, were not interested in it, and gave me one really stupid suggestion which I will not relate here.

The forest was re-planted to Doug Fir by a timber company, post clearcut, in 2000, so it is at a very young age and nearly impenetrable. I cleared about an acre just to plant a set of native edible shrubs/berries and it looks like I got about a 50% survival rate, which is a success, but the animals will get more interested in them as they mature. I'm hoping birds will carry seed to other "edges" of light. The bears will kill a percentage of the young firs over time which may be okay, since this is a Hemlock Spruce climax forest which is where it will end up in time. Ironically, when it is more mature there will be less light for the edible stuff and whatever I do now will be confined to edges which naturally occur only with blowdown or fire. We do have small groves of young Red Alder which are probably our best areas to approach some form of ag. (I've begun some Shitake culture on Alder stumps. No results yet.) The climax species however will attempt to move in and will succeed if left unattended.

Which leads me to a question. In all of the comments about forest gardens I don't see mention of what the succession really is. Left to its own devices any land will proceed to some ecological climax over time. Why aren't forest gardeners and permaculture people discussing this as the template within which they must intervene? If they don't, it seems to me they are just temporary farmers like my more urban home where I grow veggies, fruits and chickens. (the hawks and coyotes in our forest would love it if I raised chickens there!) I could go on here but for now is there anyone out there who is attempting a food forest in a coniferous climax forest area of a size large enough for predators and mature enough to approach mature forest light, or the absence thereof?


11 years ago

I don't disagree with much of what you are saying but I think some of it is ideologically driven, and not completely accurate. Yes, the equipment for baling straw, was the same as that for baling hay, but you somehow connect hay, pasturage and straw, advocate not even producing straw, which would mean nobody would produce dense, commonly eaten grains, and even advocate for winter pasturing which would, in many places remove the animal industry. Would that it was all that simple. ( I should note that we should eradicate industrial meat production for many reasons, but that is not going to happen either.)

First, the plowing back of straw in many grain producing areas is difficult. Straw is cellulose and in the semi-arid grain producing regions (where most of it is grown) plowing back straw will upset the carbon/nitrogen cycle. In other words, the volume of straw is too great. To make it even more complicated, are you sure that the sequestration of straw (carbon) from shipping it for home construction isn't more beneficial from a C02 perspective than attempting to compost it locally.? In the walls of a house it is locked up for a long time. In small unit, diversified agriculture there wouldn't be enough grain grown to produce the volumes of straw that become a problem but much of the world would feel a disastrous absence of grains.

Humans have grown hay (not straw) for winter forage for their animals for hundreds of years, with very good reason. They couldn't keep healthy animals without it in many climatic areas. To suggest otherwise is simply not correct.

I admire your attitude about using local products and agree that they are often cheap, but "easy?" That is debatable. Building with rammed earth, earth blocks, stone, granite, or anything else has its place, but it is not easy. Well, walls are easier than anything else in a building. Over and over I've seen people get excited about the walls they are planning to build without a clue about how to cover the building with a good roof. I actually went to a workshop a few years ago that was supposed to be about cobb but turned out to be about strawbales and the leader did not have a clue about how to put a roof on the little building we did.

Too much ideology, not enough science. Every building product has its pros and cons. And by the way, materials do drive design to some degree. Massive materials tend to favor big buildings. I visited one of the most beautiful rammed earth houses I have ever seen. Every wall, inside and out was so beautifully striated in earth colors, it was like walking through a painting. Beautiful home. So beautifully integrated into the landscape it felt like it belonged there. About 5000 feet. 2.5 million bucks. All local materials. except for the glass.

If you are in an earthquake zone,as many of us are, I hope you are not going to build unreinforced. If you reinforce your earth, or block, or stone, or whatever, how do you reconcile the cement and steel? It is never as simple as we would hope. Good luck with your project.
11 years ago

I'm completely new to this forum but I have many objections to strawbale houses. I've been building houses for 50 years, mostly stick framed, low end to very high end, but also some strawbales. First, the embodied energy issue is part of it, and straw is not a waste product. In a small unit, diversified agriculture, there are many uses for straw right at the place it is produced, and of course there is the question about whether it should be produced in the first place. From the environmental perspective alone, I can make a case for building with trees, rather than straw. Forest practices have not done as much damage as agriculture. But there's more. Most people do not realize that when they have their house framed, roof on, windows and doors in, they have spent around 25% of the total cost of the building. Yes, if you can get good bales (something that is harder and harder to do), keep them bone dry and get them up and covered and do it all correctly you may have cheaper walls and if so, you've saved around 5% on the cost of your house for the same heated space. Of course if you build with code approval you'll need a post and beam structure which will raise the cost well above the cost of traditional stick framing, unless you happen to be building in one of the rare places that allows load bearing strawbale walls.

There is something inherently beautiful about thick walls, nicely plastered. There are also some real design drawbacks. That extra 3 feet of straw wall has to be covered and supported but you don't get to live in it.

When comparisons are made between stick framed and strawbale houses, they are usually between oranges and apples. If you make hard nosed, critical comparisons, costing all aspects of the project, include embodied energy, long term energy savings with high R value walls, the same plumbing, wiring, heating, finishes, heated space, labor, etc. etc., straw will lose every time. (The cost of plastering alone will cause bales to lose.) This doesn't mean one shouldn't build with bales, it just means we should be clear about what it costs, in comparison with other methods.

There's a lot of political correctness driving opinion in the alternative building world. There are some good reasons for code officials and the opinions of people who make their living in the industry. Yes, residential architecture in America is awful. Yes, there are some horribly shoddy building practices. But, studs and plywood have some important efficiencies and are better, in my opinion, than most alternatives, under most conditions.
11 years ago