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My house is in the foothills northwest of Denver at about 9,000 feet. It's on an old mining claim called the Boulder Valley Lode that was worked manually beginning in the 1870s for about 30 years. A patent was issued for the mine in 1904 and signed by President Teddy Roosevelt. It appears that they didn't use any heavy equipment, and they didn't do any ore processing, but there were several mine pits that I had to examine to see if they would cause problems. I ended up having to move the house to a spot that gets less solar heating. Another impact was that I could not use some desireable Universal Design features, such as having the floor of the entire structure on the same level.
Lesson: Research property that has been used for mining activities (which can be almost anywhere in the West, including low-elevation flatlands). The county courthouse usually keeps such records, and the U.S. Bureau of Land Management (BLM) has extensive archives of mining records.
My site is about 15 degrees colder than the Denver area, both summer and winter. The summer temperatures do not get much above 65 degrees, and the winter temperatures get down to about 10 degrees below zero. The ground temperature is about 42 degrees. The degree-day value is about 9,300. The site can be windy, with gusts of more than 100 mph nearly every year. Snow sets in about mid-October, and is generally gone by the first of May.
Lesson: The climate record is often available from the U.S. National Climatic Data Center. A good starting point is http://www.ncdc.noaa.gov/oa/mpp/freedata.html/ . But in my case, there have been no official weather stations in the area, so I used a short-term record from the nearby Caribou Ranch, which was a center for the recording industry for several years.
The house is about a quarter mile from the county road. During the summer there is no problem driving to the house. But during the winter, the road often gets buried with windblown snow. My solution so far has been to have a neighbor plow the road occasionally, or to leave the car by the county road and walk.
The site has great views. Out the dining area window, I see Long's Peak, soaring to 14,255 feet about 15 miles away. Out the bedroom window, I look down on the lights of Denver 35 miles away. From east of the house, I can look down the length of Lefthand Canyon to where it opens out onto the plains of eastern Colorado and the horizon some 60 miles away on a clear day. I see a lot of gorgeous sunrises.
The healthy house concept was not well known locally at the time. I found one builder who understood it, and had experience building in this climate, so I hired him.
Since local building suppliers didn't understand that chemicals in building products can be a health problem, we decided to build with standard available materials on the outside, such as engineered lumber, oriented strand board (OSB), and commercial trusses, and seal off the interior from the toxic building materials. This approach has worked out well.
The climate dictated a well-insulated house. The architect selected by the builder originally used just my general zip code for design data, and specified insulation for a location that is 2,000 feet lower, and much warmer. After correcting that error, she specified insulation of:
The house is built on a slab-on-grade with a simple open-space design. There is no basement or crawl space.
I selected "tuned" windows made by Accent Windows®; http://www.accentwindows.com/, that use materials that provide the best insulation and solar gain for the specific orientation of the window. For the south side, the R-value is 3, and the Solar Heating Gain Coefficient (SHGC) is 70%. For the other windows, the R-value is 9, and there was no need to consider SHGC since there is little direct sun. Standard windows typically have an R-value of about 2 and an SHGC of about 30%.
I also installed cellular honeycomb double cell shades with an R-value of about 5, made by Kensington®, on the inside of all windows. Even on the coldest days, I can sit under a window and not have a cold draft rolling down on me.
Within the walls, I used cellulose insulation, with a borate treatment for insect control. On the inside of the walls and ceiling, I used 6-mil sheet plastic. We decided it was OK to put the plastic on the inside, since we expected there would be no condensation problems with the relatively low temperatures and humidity. The drywall, Gold Bond®, by National Gypsum, that went over the plastic was sealed with a hypoallergenic "mud" (Sheetrock(®) Lightweight Setting-type Joint compound), which was painted with a thick, low-VOC paint made by Diamond Vogel®.
Careful construction techniques were used throughout to ensure a very tight house. Subsequent testing after construction showed very low infiltration of 0.07 Air Changes per Hour (ACH). Subsequent testing three years later reported an infiltration of 0.15 ACH.
To provide enough fresh air when the windows are closed, I installed Fresh 80® manually-operated 5-inch vents by Therma-Stor Products® in both the east and west walls. No back-flow Heartland® vents were installed on the fan and dryer vents. These units are available from Positive Energy Conservation Products; http://www.positive-energy.com/
For radon protection, I used a plastic radon barrier sheet between the insulation and the sand under the floor, a collection hood and a 4-inch PVC exhaust pipe extended through the roof, and a PV powered exhaust fan mounted on top of the exhaust pipe (which was needed after post-construction testing showed that radon levels were too high without the fan).
After three years, I've had no obvious health problems I can blame on the house. One visitor who is very sensitive to formaldehyde said "this is the first new house I've been in I can stand!"
1) Using standard construction materials on the outside of the house and sealing off the interior worked out well;
2) "Tuned" windows are well worth the additional cost. The house is more comfortable, and the annual heating bill is about half what it would be without them;
3) It was well worth it to use low-infiltration construction techniques. A lot of heat gets lost via infiltration if it's not controlled, and the house is much more comfortable;
4) I should have installed more insulation under the floor and around the foundation. The floor has four inches of foam insulation. The foundation has two inches of foam insulation on the south side, and four inches on the north side. During windy days, there is noticeable heat loss in the floor and lower walls. The house would be more comfortable, and use less energy, with more insulation in all these areas;
5) Install a radon exhaust system.
6)Install low-voltage data cables throughout the house for telephone, doorbells, and possible computer connections. These cables are variously called "Cat5" for Category 5, datacom, local area network, or ethernet cables. They amount to a cable with four pairs of 24 AWG solid copper wire. If such wiring is not installed, there is a tendency to use the currently popular wireless devices, which are a problem for people with electromagnetic sensitivities. Some in-house data displays are poorly protected from static electricity, such as can build up even on a tile floor. Ensure that all wires in the Cat5 cables are protected with an eight-line thyristor network.
7) Take lots of photographs throughout the construction, especially of the inside studs, pipes, and wiring before the interior walls are finished off.
8) Visit the contruction site often. Or, better yet, live on the construction site. A lot of misunderstandings can be cleared up at this point.
It was cheaper to use photovoltaic (PV) power than to run a spur from the local commercial electrical system to the house site. PV-based power can now be well-engineered, straightforward, reliable and very adequate.
However, PV power does have a few unique requirements. It's best if you have some understanding of electricity; are willing to monitor and respond to how much power is being used; and can do hardware maintenance occasionally (although commercial companies are available to provide much of the needed maintenance on a regular basis).
A subtle problem for sizing an off-grid system is estimating the power needed by automatic loads, such as refrigerators, or even fans such as in a heating system. Best to allow for worst case for these items. In addition, it's expensive to provide 220-volt power from a PV system for the few appliances that need it, such as electric ovens or clothes dryers, so it's best if you're able to avoid those (see `Cooking` near the end of the article for more information).
A useful feature of my PV system from Outback Power®; http://www.outbackpower.com/ is a "search mode" that automatically turns the AC power inverter off if the house electrical load drops below a few watts. A test pulse is sent every second to see if a light is on, but otherwise the AC electrical power stays off with low-load conditions. I've had visits from two people with electrical sensitivity, and both of them felt better when I turned the AC power off.
For general safety, emergencies during mountain living, plus periods of limited sunlight, an auxiliary generator is necessary with an off-grid system like mine. I used a 5 kilowatt gasoline-powered generator during construction, and have kept it for backup power. I rarely need it. For instance, with twelve 115-watt PV panels from Evergreen Solar®; http://www.evergreensolar.com/, plus eight 6-volt, 820 Ampere-hour batteries by Surrette Battery®; http://www.surrette.com/ which are adequate for a couple no-sun days, the generator was needed for only about 2% of my power in 2007.
Questions have come up as to just how much the auxiliary generator has been used to augment the power from the PV sysytem. Here are the recent statistics -
1) Off-grid photovoltaic power is a realistic and reliable source of electrical power. This makes it economically possible to put a house in a remote, less expensive location, which may be a consideration for people with sensitivities. It can offer an additional subtle benefit to people with electrical sensitivity, since the power can be automatically turned off under low-load conditions;
2) Equipment is available to automatically run the auxiliary generator if the PV system does not have enough power;
3) Install a "power shed" to house an auxiliary generator (which likely will be propane-powered) located away from the house. The shed may also be able to house other electrical equipment such as batteries and inverters, if you're sensitive to their EMFs.
4) Install 24-volt wiring into the house. This can be very useful for using the 24-volt appliances, such as the refrigerators, freezers, compact fluorescent lamps, that are becoming available as well as enhance activating the search mode in the PV system.
5) One gets advice that "a few shadows on the PV panels don't matter." Not so!!! A shadow only some five inches across, depending on orientation, can block all power from a PV panel. While there are occasionally extenuating circumstances such as existing house structures or a favorite tree, aim to ensure that all the PV panels are completely lit by the sun at winter equinox.
The sun provides about 10-15% of my heat. The main solar features are high-solar-gain windows in the south walls, and a 4-inch concrete floor which absorbs the sun's heat during the day and releases it slowly at night.
For the remaining heat, I was able to install a smaller, less expensive heating system than normal, since a well-insulated house with low infiltration needs less heat. My sealed-combustion propane fireplace, made by Heat n Glo®; http://www.heatnglo.com/, in the living room is rated at 40,000 BTU input. At this elevation, about 20,000 BTU is available. In practice, a low-flame setting of about 8,000 BTU is very adequate for the vast majority of the time. A circulation fan in the fireplace turned out to draw so much 120 volt power that it was replaced with a 24 volt capability.
A review of the house by a professional energy consultant (see reference to Kinney's article below) estimated the heating need to be about 3.00 BTU/Degree-day/Foot squared of floor space. For the year of 2008, the heating index came out to be 1.96 BTU/DD/ft**2. And this was without any "hardship" living.
1) Design for solar heating if possible;
2) Heating system size can be significantly reduced by designing and orienting for solar gain, insulating well, and using low-infiltration construction techniques;
3) For fuel-based systems, use only sealed-combustion equipment.
A limitation of PV power is that large electrical loads, like those needed to power an electric oven, are not recommended. I installed an open-flame Hotpoint propane stove, with an exhaust fan above it, but I don't use the stove. Instead, I use a microwave oven.
Domestic hot water is provided by a Takagi®; http://www.takagi.com/ sealed combustion on-demand tankless hot water heater. This unit uses considerable 120 volt power in idle mode, so the power cord must be switched with a breaker strip, for both efficiency and to enable search mode in the PV system.
A refrigerator is installed inside the house for food management. This unit is a 24-volt powered unit by Sun Danzer®; http://www.sundanzer.com/. A freezer is installed in the garage for long-term storage of frozen food. Again, this unit is made by Sun Danzer. These units are good examples of where direct low-voltage operation of appliances pays off. Even though the refrigerator and freezer are more expensive than 120 volt units, the total PV-installed system cost is considerably lower. Plus, there is the long-term reliablility factor that the PV system inverter is not necessary for operation. Again, powering these units directly from 24 volts facilitates search mode in the PV systm.
A GE Profile® Energy Star rated washing machine was installed for laundry. A unit without electronic controls was selected for general efficiency plus it facilitates search mode operation of the PV system. A GE Profile Energy Star rated dryer was installed for drying clothes. Again, unit without electronic controls was selected for general efficiency plus it facilitates search mode operation of the PV system. But - this unit is not sealed combustion and is used sparingly with lots of house ventilation and fans running. Also, running the unit in No-Heat mode awhile after a laundry session helps.
I had to have a 300-foot well drilled. An efficient pump made by Grundfoss®; http://www.grundfoss.com/ which runs on AC or DC power and designed for PV systems, brings water into a 60-gallon tank in the house. The county tested the water, and it's good enough that I don't need to do any filtration. I use the water indoors, and for a bit of outdoor irrigation.
Lesson: Efficient, low-power, 120 volt water pumps are available. This is much better than the typical 220 volt pumps, which a neighbor says " dims his house lights every time the pump comes on."
I'll be glad to tell you more about the house, and you're welcome to make an appointment to visit.
Builder: Bighorn Builders Inc., http://www.bighornbuildersinc.com/gallery.html (then click on Sawmill House)
They received an `Energy Value Housing` award from the National Association of Home Builders for their work on my house. After the house was finished, it was evaluated and given an Energy Star rating of 95, or Five Star Plus.
The builder also received a New Millenium Builder's award presented by E-Star Colorado.
The Sawmill House was included in the local 2005 Parade of Solar Homes. Among the featured highlights were its off-grid electric power, the passive solar design, and the healthy house construction. It also was considered the third-most-efficient house constructed in Colorado during the year.
The Parade sponsors expected about a dozen people to show up, but there were over 80 visitors, asking many intelligent questions.
A detailed analysis of the house by a professional energy consultant is available on the Web site of the Boulder Green Building Guild, See below.
Window supplier, Accent Windows, http://www.accentwindows.com/ .
Basic information on efficient windows, from the Efficient Windows Collaborative, is at http://www.efficientwindows.org/ . For basic information on windows and daylighting, from the federal government, see http://windows.lbl.gov/ .
estiltner AT sccs DOT com
Additional information about the Sawmill House -
Copyright ©2009 E. Stiltner.