Heating

There are 4 sources of heating in Auerhaus. In order of use:

1. Wood cookstove
2. Passive solar
3. Plug-in electric radiator (backup)
4. Hard-wired floor heaters (required by code, never used)

It was only possible to use such small heat sources because of the high insulation values of SIPs (structural insulated panels). SIPs have channels in them for plumbing and electric, but I chose to wire everything inside to preserve the integrity of the insulating envelope.

By calculation the house can be kept warm with just 2000-watts of heating. It's also important to know that I prefer it on the cool side. About 70 ° F is my limit. My heating strategy is to run a fire in the morning to cook breakfast and heat the house to about 68° to 70° F. Then I let it cool to about 62° F, which is usually about dinner time. I then run a fire until bedtime at midnight. The cookstove's firebox is too small to have wood burn for more than an hour. Even so, with exterior temperatures dropping to 15° F over night, the house will lose only 10° to 15° F. For those who like it warmer more energy would be needed than described below.

>Wood Cookstove

I'm not sure how I decided on wood as the main heat source and cooking, but I love it. After a long search I ended up with a Mora from the Czech Republic. I liked it for its side venting and clean lines. I bought from a company in Nelson, British Columbia, but the seem to be out of business, and Mora doesn't appear to be making any wood-fired products anymore. No matter, my neighbors wood stove had been in near continuous use since 1911, so these do tend to last.

I burn about 1 to 2 cords a year. That's about 27-million BTU About a $390 ANNUAL heating bill if I were heating with natural gas. Most people around here burn 6 to 8 cords. At 2 tons of CO2 per ton of wood, I'm putting 3 to 4 tons of CO2 in the atmosphere annually. The per capita emission in the US is about 20 tons, but:...

• Wood is a renewable resource
• The amount of CO2 released is exactly the same if it rots on the ground or is burned
• The CO2 released is absorbed by new tree plantings (about 1/2 ton/tree). I've planted 2600 trees thus far.
• Almost zero energy used in transportation. Lots of trees nearby.

The point is to use what is local, natural, abundant.

>Passive Solar

Passive solar design is an ancient idea lost because cheap energy made it possible to control interior temperatures by force. Want a beautiful, south-facing wall of glass for the view? Just get a bigger AC unit for daytime and bigger heater at night.

There are only a few basic concepts in a passive solar house:

1. Orient the long wall to the south to maximize gain (short wall to minimize it).
2. Arrange roof, eaves and windows for more gain in winter, less in summer.
3. Arrange heat absorbing material to absorb heat in winter
4. Insulate it well.

 

The house is at about 45° latitude. I used the PV rule of thumb of +/- 15° to arrive at a 30° roof pitch. In fact the sun gets down to 20° altitude, but I didn't know that then. Here is a link to a sun angle calculator. Nonetheless it has worked out well as there is little sunlight in December and January anyway and the 30° angle gives me more full sun in spring and fall.

The photo shows sunlight falling on the concrete panels in mid-November. The panels are just cement backer board commonly used under tile in bathrooms. I've left it raw, but it could be plastered.

I used Dan Chiras's The Solar House as a guide to determine the optimal window area. His book is an excellent resource, and kept me from accidentally building a greenhouse.

Auerhaus minimizes northern exposure by putting no windows or doors there and making it only 7-feet high. I learned early on in Oregon the north side is only good for growing moss.

>Electric Heat

The house has no thermostat. Just in case I happen to be away during a deep freeze I have two DeLonghi Retro Oil-Filled Radiators. They have an anti-freeze setting, but are also sufficient to heat the whole house.

The baseboard heaters were required to meet code by having hard-wired heating capable of keeping the house at 68° unattended. The breakers for them are off.