I have been working on house plans lately it is very tricky finding something that is just right. So many considerations, one story? two stories? one and a half? balancing the trade offs between foundation and roof costs and ease of construction/heating. Should we build all at once or in stages? How many square feet do we need? How many can we afford?
The most recent question is whether to build in the round or not. Round is efficient, round is elegant, round is difficult to plan out. We are thinking maybe two round units connected, one with living area, one with bedrooms. This would allow us to build one smaller structure quickly, move in, then build the other. It would involve sleeping in the living room for a bit but that wouldn’t be the end of the world.
Previously I have shied away from building in the round because the floor plans are tricky and most things you put in a house aren’t round. But we have both always liked the look of a round house and if we are going to build our own house we should probably take advantage of the opportunity to have something really neat. Likely we will change our minds again but for now we are thinking round and I think Becky can be blamed, all her talk of yurts has me thinking outside the box.
We had concluded that a sufficiently beefy PV solar system to keep up with our cloudy winters would be prohibitively expensive, costing twice as much or more than hooking up to the grid. However, it rankled to spend $11,000+ just for the privilege of paying a power company for each kwh after that. Especially considering that it will likely be more than 11 grand by the time we get around to building with the rapidly increasing price of copper.
So I looked at the feasibility of solar again and it actually appears it may be doable. I used this site to calculate the minimum amount of power we would use on a winter day and arrived at a 100 kwh/month figure. I didn’t really look at it very closely or I would have seen that by not using a dishwasher on cloudy days and washing by hand instead we could cut that by half! Half! So rather than requiring a 2000 kw system we only would require a 1000 kw system. The cost of a smaller system is only slightly more than the cost of hook up to the grid. Hopefully it might even be comparable or less by the time we get around to building. PV should come down in price as the technology is developed and electricity is unlikely to drop in price and may even raise steeply if the government stops subsidizing hydro-electric.
It will take a bit more research into our actual building site (bottom of a valley) and the solar potential as well as costs of maintaining the system but a grid free house might actually be possible.
Passive solar heating is one of the most efficient uses of the sun’s energy possible. Once the building is designed it requires little to no energy input and the heat it produces is basically free. In traditional passive solar homes the sun heats a thermal mass during the day and the radiates nice even heat throughout the night. In places like the American south and midwest this works great but in areas like the beautiful pacific northwest what do you on days when the sun doesn’t shine (and it frequently doesn’t)? In situations like this Annualized Geo-Solar (AGS) design is a good bet.
Basically heat from the abundant summer sunshine is stored in a large thermal mass. Original Passive Annual Heat Storage (PAHS) designs involved either an underground home or a home with a green (dirt) roof. Don Stephens developed the AGS technique to apply passive solar heating to areas with limited winter sun without the need for earth-sheltered houses.
AGS basically involves collecting heat from an isolated source such as a solar collector or greenhouse and transferring the heat from the air to the earth under the house via ducts. The system requires (at its most basic): 1) a well insulated structure, 2) dry earth under the structure for storage, 3) an isolated solar heat collector, 4) a method of controlling when the collected heat is dispersed into the structure, 5) a radiant floor in contact with the soil.
#1 can be accomplished by superinsulating your building envelope, such as is found in a straw bale house.
#2 is accomplished by surrounding the house with a insulated water repelling apron.
#3 can be accomplished in a number of ways. Hot air can be collected from a sunspace, attic, or even under metal roofing. Dedicated solar collectors can also be built and ideally situated downhill from the structure, then the hot air will naturally siphon through ducts under the house without the need for fans.
#4 is important because you don’t want the house to begin receiving heat until approximately 6 months after you begin collecting it. One way is to deposit the heat deep enough under the structure that it takes 6 months reach the level of the floor (about 9-10′ deep). Another way is to deposit the heat under insulated floor 9-10′ from uninsulated floor and use the horizontal distance to control the when the heat begins to be released.
#5 This design obviously requires a slab type floor. The floor must be in contact with the soil underneath in order to radiate the stored heat into the house.
How to heat? We want something environmentally friendly yet also inexpensive, low maintenance and actually works.
Our current plan is to design a house that will get most of its heating needs from a free source, the sun. Unfortunately it is not so simply as merely putting in a lot of windows all over the house. Then you will roast when the sun is out and freeze at night (during the summer you will just roast). So the answer is to concentrate your glazing on the south side where it will receive the most sun and provide plenty of mass to store the heat and radiate at an even temperature throughout the day. You still don’t want to do this on a summer day so the answer is to provide overhangs/shading in the summer. In the summer the sun is at a higher angle so a 2 ft or so overhang (depending on window height) with stop the sun from coming in in the summer but allow the sun to enter in the winter when it is at a lower angle. The best kind of shading, shades only when the weather is warm. You can either do this with manually adjustable shading or even better plants.
We don’t want to have to incorporate large amounts of mass into our living spaces so we are planning on using a sunspace. Basically a green house attached to the south side of the house. The green house will trap the heat of the sun, as green houses do so well, in an area insulated from the actual living space. When we want the house to warm up we can open doors and windows into the sunspace letting in heat. In the summer we can keep the doors closed and additionally provided the green house with a bit of shade and open some windows for ventilation. The green house will have a high mass floor (some sort of stone), dirt planting beds and possibly additional solar mass in the form of water barrels to help mediate the temperature.
This set up should provide us anywhere from 50-70% of our heat in the winter. The
remainder of heat will be provided by a wood burning stove. I realize that wood burning isn’t at the top of the list as an ecologically friendly material but it is at the top of our list for cost effectiveness. Our site is conveniently located for the sustainable harvesting of scrub oak. So we will have a free relatively clean burning wood to use. Also, because the house will be well insulated and partially heated by other means, we shouldn’t need more than 3 cords of wood each year, probably much less.
Straw bale houses have been around in some form or another since the late 1800’s, many of the earliest buildings are still in use. A straw bale house basically consists of either 2-string or 3-string straw (not hay) bales stacked like legos. The bales are then plastered to keep moisture and pests out and provide further stability. Some houses don’t have any other structural supports beyond the bale walls but ours will have a post an beam structure as well. This will give us a roof to work under while we put the walls up. This is handy because while straw bale walls are in general very long lasting, fire resistant and sturdy moisture is the bane of their existence. You do not want your bales getting wet, it can lead to mold and possible even spontaneous combustion, obviously bad things.
Costwise straw bale houses cover a large range. Owner built houses have been made for as little as $10/sq ft while high end houses can be as much or more than $100/sq ft. Obviously we are shooting closer to the $10 end. Building codes are slowly beginning to include straw bale systems. Luckily in our area there is already one other permitted straw bale house so we don’t have the difficulty of introducing a brand new system.
Straw is highly insulating (r-values from 30 to 60 have been reported) and the plaster provides a certain amount of mass to help stabilize temperatures. Straw bales also provide excellent sound insulation and the thickness of the walls gives the house a cozy sturdy feel.
Any questions?
Filed under: To Do
We have a lot of work to do even before we start building. We need to come up with a floor plan that we like and is good enough for building permits. Oli needs to find a job, we need to sell our current house. We need to come up with somewhere to live while building, right now I think this will be our future workshop with a small bathroom, kitchenette and sleeping loft, which we will also need to build and get permits for. We need to get electricity to the site, for that we need a meter installed and likely a permit. We need a septic tank/drain field, for that we need a soil assessment and permits. We need water, for that we need a well and most likely permits. We will need to find a bank willing to loan us some money. We need to figure out where exactly the house is going to go. We need to figure out when we need to start cutting down trees.
It is a little daunting to see how much work has to be done before we even think about starting to build. Most of it will be money and skull sweat with a little bit of real sweat farther down the road. Then we must of course keep in mind the baby scheduled to arrive in July. Of course it is all complicated by being 1/4 of a mile plus from the next house, on a gravel road. Did I forget anything?
