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The art of the possible"All great truths begin as blasphemies." "Words are plentiful, deeds are precious." "Why should I care about posterity? What's posterity ever done
for me?" Some miles east of Salida on Route 50 as it winds along the Arkansas River, you pass through a wide spot in the road called Coaldale. About a mile above the river, nestled in pinon pines up against the foothills of the Sangre de Cristo Range, lies a year-old custom home built by Tierra Concrete Homes for Janet and Scott Engel. It's a beaut. Most notably - at least for the purposes of this column - that home recently earned the highest score (97) awarded by E-StarTM Colorado during its last five years of home energy ratings issued. This score could earn an EPA award for energy performance when those winners are announced next month. What does a 97 mean? It means the home is 75 percent more efficient than a home built to the 2003 International Energy Conservation Code. It means having a very sound design, paying attention to key details, and building for clients who care. THE CLIENTSWhile living in Littleton, the En-gels began research for their future energy-efficient, semi-retirement home about five years ago. A number of their friends lived in passive solar homes built with straw bale and earth-sheltered systems. The Engels considered those systems and a number of others. After hearing Judy Fosdick with Pueblo-based Tierra Concrete Homes speak at a building seminar, they started seriously considering concrete construction. While they kept researching and refining their design for several years, they eventually selected Tierra Concrete Homes as their builder. Final design and materials se-lection began in January 2003. Fosdick broke ground in May and the Engels moved in last December. EFFICIENT SHELLThe key to the shell's extraordinary efficiency is its concrete wall system. Walls are poured on flat ground around the building site. They get formed around the perimeter and insulated with 3 inches of polyisocyanurate foam; after running conduit and placing boxes to meet all electrical needs, concrete is poured, the walls cure for seven days, and then they're craned into place. The result: an incredibly strong, durable, quiet and airtight wall that provides R-24 insulation. The low-e windows selected include an R-2.75 insulation factor. Windows are "tuned" by orientation; south-facing windows with higher solar heat-gain coefficients (SHGC) transmit more sunlight, while east-and west-facing windows with a lower SHGC block more sunlight for better summertime comfort. The rest of the insulation package includes R-38 ceiling insulation plus R-10 extruded polystyrene foam around the slab edge. Since the slab floor is heated directly by both the sun and an in-floor radiant system, Fosdick installed R-10 foam beneath the entire slab. Blower door testing conducted by Kent Shelman (Colorado Realty Reports) during his energy rating showed the home leaked only 0.15 air-changes per hour-roughly three times tighter than the average new home today. PASSIVE SOLAROnce you start with a well-insulated, tight building shell, you need five basic features in a passive solar home: good building orientation, good solar access, sufficient south-facing windows, sufficient heat-storage material (concrete, brick, etc.), and climate-specific overhangs designed to limit summertime solar heat gain through south-facing windows. Like most classic passive solar residences, this home's long axis runs east-west to facilitate solar access into most living spaces. Unfortunately, the site slopes slightly uphill to the south and comes with a small hill to the southeast, so solar access is not quite optimum. Yet 440 feet of south-facing windows provides all the space heat the Engels need during sunny winter days and evenings. One hundred and fifty tons of concrete in the slab floors and most interior partition walls store a significant amount of excess solar heat energy captured during the day for evening comfort. A 20-inch overhang prevents unwanted solar gains during the summer while leaving the windows unblocked during the winter. (Note to production builder skeptics: while it's unusual to orient sub-divisions such that either a majority or all homes can be passive solar, it certainly isn't impossible. During the early 1980s, three Denver-area subdivisions were laid out with every home designed for passive solar. Several builders in New Mexico, Tucson, Ariz., and Davis, Calif., have achieved similar layouts, dating from the 1970s through the present day. In Loveland. Colo., Aspen Homes of Colorado plans to build a passive solar subdivision in 2005. And no, you don't have to: A) sacrifice building lots to achieve good solar access or, B) lay streets out on a straight grid. The Solar Village in Davis has moderately curving streets and apparently sells at a 20 percent premium compared to adjacent non-solar sub-divisions that were similarly priced when built during the 1970s.) MECHANICAL SYSTEMS (HRV)The solar water heater includes one 4x 10-foot roof-mounted solar collector, plus a 75-gallon storage tank. A Rinnai propane-fired, direct-vent, on demand unit provides backup water heating. Another Rinnai unit heats water for circulation through the floor when the home needs backup space heating in any or all of the four-zone in-floor system. All homes need some type of fresh air system. The Engels opted for a heat-recovery ventilator (HRV). An HRV upgrade costs substantially more than other ventilation options, especially in a home like this one with no ductwork used for heating and cooling. On the other hand, the modest energy savings from heat recovery add up more in homes heated with propane and located in colder climates. Appliances in the home all meet EPA's Energy Star standards. THE RESULTSThe E-Stare"' rating projects this energy-miser home will consume around $430 a year in propane for backup space and water heating - a small fraction of similar sized homes built to current energy standards in the same mountain valley. Comfort comes with the building system; the Engels report extraordinary temperature stability during the summer (no air conditioner included). Wintertime temperatures in the home's core tend to run between 68 degrees during the morning and 75 degrees mid-afternoon. But this home isn't just about efficiency and comfort. Daylight floods interior spaces year-round, especially through the high clerestory windows. The appealing sunspace/hallway along part of the home's south wall connects living room, offices and studios to the home's core kitchen and eating area. Airy vaulted spaces that step back and forth with varying finish angles in the ceiling add interest. Doors handmade by Scott Engel from bluish beetle-kill pine add a striking touch. Using colors that blend in with light-colored soil, stucco wraps the walls beneath a light-green metal roof. A direct benefit of these exterior finishes and the interior stained concrete floors is low maintenance. The 3,400-square-foot home cost around $300,000 to build, excluding land, site development and utilities. The Engels also earned some sweat equity in the home; that reduces costs and adds value.
Janet and Scott Engel relax at their energy efficient abode built by Tierra Concrete Homes. It recently earned the highest score (97) awarded by E-StarTM Colorado during its last five years of home energy ratings issued. TIERRA CONCRETE HOMESSince the mid-1990s, Judy and Frank Fosdick have built about 25 custom homes in Colorado. Recently, demand has picked up. They expect to finish five homes this year and six next, with an ultimate goal of building a dozen a year. Judy hasn't been completely pleased with the solar thermal and photovoltaic (PV) installations that have gone into some of their homes. To upgrade that area, this year they're starting a subsidiary solar installation firm - Solar Way - to handle both Tierra Concrete Home's installations as well as solar hot water and PV installations for other builders. With energy prices on a strong rising trend, solar construction firms like Tierra Concrete Homes could well experience a strong increase in demand for their services. Steve Andrews consults with builders for E-Star Colorado and writes on energy issues (sbandrews@att.net). E-Star (www.e-star.com), is a nonprofit home energy rating system that works with both new and existing homes statewide. |
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2008 Built Green Colorado
Home Builders Association of Metro Denver, 9033 E. Easter Place, Suite 200,
Centennial, CO 80112 Last Updated: 10/05/2007 |
