Our ideas about what we wanted in our home evolved during about twenty years of camping on our future building site in the Texas Hill Country. When we were ready to begin the actual design process, we had already decided on many of the "green" building concepts and techniques that we wanted in our future home. At this point, we were fortunate to find our architect, Matt Bachardy, who shared our philosophy about home design. This page describes many of the concepts used in our home.

Passive solar design is a common-sense approach to home design based on working with the environment rather than trying to "conquer" it. The following principles were relatively easy and cost-effective to incorporate. Somewhat different approaches would be needed for other climates.

Site considerations: The main living areas and windows of a passive solar house should face as close to due South as possible. Our lot forced us to face south-southeast which still works quite well because our prevailing wind is from the southeast, and a hill protects us from the north wind in the winter. Happily, this orientation provides good views for nearly every room in the house.

Foliage: Deciduous trees and shrubs play an important role, shading the house from the hot summer sun, while allowing the sun to warm the house in the winter. Grasses and other ground covers reduce reflected heat during the summer. Evergreen trees and shrubs on the hill behind the house help to shield it from north winds during the winter.

Roof overhangs are designed so that they block the summer sun but allow the winter sun to shine in. During hot summer days, the interior of our house is relatively cool until early afternoon. During the winter, the warmth of the morning sun is delightful. These benefits would be further enhanced if we were facing due south.

Natural ventilation is maximized with operable windows, screens and other design features that allow cooling breezes to pass through the house.

• Nearly every room has cross-ventilation.
• Our dog-run (or dog-trot) is Matt's contemporary interpretation of a feature found in early Texas ranch houses. During the hot summer months, breezes through the dog-run are magnified by warm air rising and exiting through the high windows on the downwind side, drawing air through our screened deck and other rooms of the house.
• Awning windows can be kept open for good ventilation even when it rains, and they let us enjoy the sound of the rain.

Natural lighting provided by careful window placement is both pleasing and energy conserving, especially during the warmer months when days are longer.

Reflective exterior surfaces: In warm climates like Texas, light colors and reflective surfaces reduce heat gain. Our light-colored limestone walls, shiny Galvalume siding and roof, reflective sheathing and Low-E window coatings help to keep our house cool in the summer, which is much more of a concern here than heat during the winter. The opposite (heat-absorbing exterior surfaces) would be desirable in a cold climate.

Thermal mass: The stone and concrete in the walls and floors of our house absorb heat from the sun during the daylight hours, and release it slowly at night. This has a moderating effect on indoor temperature swings. During the summer this definitely helps to cool the house during the day. During the winter it helps to keep the house warmer at night, although we haven't found the warming effect to be as beneficial as the cooling effect during warm months.

Water is an even more efficient thermal mass than concrete or stone, and the river (in our subjective judgment) seems to help moderate summer temperatures.

House size

One of the most obvious ways to increase energy efficiency and reduce impact on the environment is simply to build a smaller house. The planning of our home was greatly influenced by the books and articles written by Sarah Susanka advocating "The Not So Big House," a home that favors the quality of its space over its quantity. According to Susanka, "The Not So Big House isn't just a small house. Rather, it's a smaller house, filled with special details and designed to accommodate the lifestyles of its occupants."

For our house, the number and size of rooms were determined by our lifestyle and activities, rather than by traditions like formal living and dining rooms. This approach enabled us to afford quality construction and features that we will enjoy for years, not to mention lower utility and maintenance costs. We use every room in the house, most on a daily basis.

Our house is not small - we have 2318 square feet of conditioned space - but most importantly, it's sized just right for us. Interestingly, it is slightly smaller than the average American house built in 2003 according to the National Association of Homebuilders. It's encouraging that in a recent NAB survey, over 63% of potential new-home buyers indicated that they would prefer a smaller house with more amenities over a larger house with fewer amenities.

Other energy-efficient measures

Well-insulated walls: lower and main floor walls constructed of insulated concrete; upper floor walls with fiberglass insulation and reflective sheathing.

Well-insulated roof: manufactured I-beam rafters with 6" thick foam panels designed to provide a 2" air space under foil-faced reflective decking.

Low-E, double-glazed, steel-clad wood windows and doors make the best of our compromise between energy efficiency and having a lot of windows so that we can really enjoy our surroundings - the main reason we wanted to live here.

Zoned heating and cooling: three high efficiency (SEER-12) heat pumps.

High efficiency wood-burning stove: much more heat and much less pollution than a fireplace, while letting us enjoy the aesthetics of a wood fire.

Ceiling fans in every room except baths and closets, provide cooling breezes during the warm months. Reversing the direction that the blades rotate helps to provide even, efficient heat during the cold months.

Energy- and water-efficient appliances: choices based largely on Energy Star® and other ratings provide long-term savings and minimize environmental impact. This is especially true of our high efficiency front-loading clothes washer.

Energy-efficient lighting: today's long-lived compact fluorescent bulbs provide a very pleasing light quality while reducing energy consumption and heat emission.

Other measures to reduce environmental impact:

Rainwater collection system helps to conserve our ground water and reduce soil erosion and runoff into the river, while providing a reliable source for better tasting, softer water. Conserving water resources is becoming increasingly important in the more arid states like Texas where current water supplies are inadequate to sustain the anticipated population increases.

Electricity generated from 100% renewable energy sources now available from our local electric company (PEC).

Pervious driveway: Unlike impervious concrete or asphalt, our StoneyCrete™ driveway allows water to reach tree roots and reduces rainwater run-off and resulting soil erosion.

Environmentally sustainable, low maintenance, long-lasting materials: Examples include stained concrete, linoleum and cork floors; concrete countertops; IPÊ decks; native stone and Galvalume siding; Galvalume roof; steel structural framing including Spaceframe.

Landscaping with native plants, reducing demand for water, fertilizer and insecticides.

About active solar and wind technologies...

We evaluated wind and active solar technologies for generating electricity and heating water, and found that neither would not be cost-effective for our particular site at this time. The design and construction of our house should allow us to use these technologies if they become more economical and/or efficient in the future.

Compromises...

We are the first to admit that our home is not as "green" as it could be. Some compromises were neccessitated by budget constraints. Sometimes we made deliberate decisions to favor being able to enjoy our environment over energy efficiency. Other times it just seemed too overwhelmingly complicated to get the information we needed and/or to find someone knowledgeable about how to do the work. Sometimes we were met with passive resistence to doing something different from the way it's always been done.

We learned a lot during the building of our house, and are continuing to learn as we live in it during the various seasons.

Related links

• Austin Energy Green Building Program
  Including fact sheets on variety of green topics, and links to other relevant organizations
  
  
• Energy Star®
  product ratings and other information from government-backed program to help businesses and individuals protect the environment through superior energy efficiency
  
  
• Green Affordable Housing Coalition
  San Francisco Bay Area coalition of private-sector and public-sector professionals dedicated to providing education and outreach programs promoting green building
  
  
• Greenguru.org
  Wimberley site with excellent information and links related to sustainable living and green issues in our area
  
  
• Passive Solar Design (DOE)
  Good information with links to relevant subjects and an excellent Passive Solar Design Technology Fact Sheet (PDF 233 KB)
  
  
• Passive Solar Design (California Energy Commission)
  Provides easy to understand explanations of passive solar design principles that can work for any home
  
  
• Passive Solar Design (Sustainable Building Sourcebook)
  From the Austin Green Building Program, providing detailed information about passive solar design