SOLAR TODAY

By Ken Haggard

Completed in 2006, Congregation Beth David Synagogue in San Luis Obispo, Calif., is a passive solar building using direct-gain
heating, night-vent cooling, daylighting, natural ventilation, integrated photovoltaics and straw bale construction.
Photo courtesy of SLOSG

Passive solar design is generally considered to be a technological endeavor. Designing a building that will largely heat, cool, vent, light and power itself requires technical knowledge. However, passive applications also have aesthetic, social and cultural dimensions that are often less recognized. A brief look at the cultural dimension explains why.

The scientific/
industrial era, from which we are evolving, is based on linear processes, analysis by isolating parts and economies of large scale. This makes it hard to perceive approaches like passive design that are, in contrast, based on cyclic processes, synergetic wholes and economies of miniaturization. The industrial culture’s emphasis on reductionism is also why so much importance is placed on energy production and so little upon appropriate energy use. Problems that result from the isolation of production from use of energy were pointed out by Amory Lovins in his groundbreaking 1979 book, Soft Energy Paths. However, due to social inertia, we’ve neglected this truth. We’ve become more efficient on the production aspect (what Lovins called the hard path) while becoming massively wasteful on the use aspect (the soft path). Resolving this schizophrenia between production and use at the building scale is what passive solar is all about. One could think of it as a hybrid approach, where production and use are directly related to each other at the building scale. Here, the user can become part of the process rather than just the inhabitant of a sealed box. User awareness of energy production and use is necessary to our cultural transition from a scientific/industrial era to an information/sustainable era.

Functions Designed Together
The rebirth of passive solar design occurred during the oil embargo of 1973, imposed by members of the Organization of Petroleum Exporting Countries. At the time the emphasis was on space heating. Cooling was assumed to be harder to accomplish passively, except by visionaries such as Harold Hay, who insisted both could be done with passive design using thermal mass and moveable insulation. It took several years of intense effort, funded during the Carter administration, to overcome our reductionist bias and arrive at what now seems obvious: that heating, cooling, ventilation, daylighting and electric power can be provided in an integrated fashion through passive design of buildings. I include photovoltaic power because it fits the classic definition of passive design, which is:

1. The use of on-site energy;
2. Reliance on natural energy flows with a minimum of moving parts;
3. Energy production and use as an integral part of building design.

If multiple energy and thermal functions are designed together, very high effectiveness can be achieved in a variety of climates. Passive solar design has reached the level of sophistication needed to build zero-energy-consuming buildings and even to build net-energy-producing buildings.

Two Basic Principles
To reach this level, two basic principles must be recognized. First, the building utilizing passive design must be an energy-conserving building. However, achieving this necessary prerequisite does not necessarily make a passive building. This distinction is very important. The first principle, therefore, is: Passive design takes the next step beyond energy conservation to include on-site energy production.

In California we have what is considered the nation’s most stringent energy code for buildings. Yet, this section of Title 24 is largely an energy-conserving code. It doesn’t give credit for some very basic passive design elements like night-vent cooling, thermal mass walls or integrated photovoltaic panels. Architects in California can’t just rely on the Title 24 calculations to do a good passive building. A passive building can beat Title 24 standards by 40 to 80 percent.

To illustrate what can happen if these definitions are not understood, I will describe a local situation in San Luis Obispo. Regulations were proposed that would increase the height limit of buildings in the downtown area, while requiring Title 24 to be exceeded by 15 percent in order to move toward the American Institute of Architect’s (AIA) 2030 climate stabilization challenge. The local Chamber of Commerce (usually quite progressive), along with the local newspaper, proved uninformed on the technical issues and resisted the plan. Even many architects, all members of the AIA, attacked this regulation as draconian, claiming that Title 24 was the most stringent in the nation and that beating it would create a severe economic hardship. In the resulting brouhaha discussions never progressed beyond Title 24 as an issue, so passive design potentials and the associated cost savings were never addressed.

To avoid this type of confusion, the distinction must be made that passive buildings are energy-producing as well as energy-conserving buildings. Providing natural lighting from an optimally designed aperture in the center of a building is energy production, just as much as is burning coal to import energy for artificial lighting, except that the former is healthier, more aesthetically acceptable and doesn't incur line losses. The only downside for the passive approach is that one must design creatively for variation in available sunlight and come up with ways to distribute it. We also need to educate building occupants that they don’t necessarily need to flip the switch to have good lighting. Passive design should be the architect’s great opportunity, not something to fear.

The second basic principle is that energy functions must relate to the metabolic characteristics of the building as much as to the local climate. A biological metaphor is helpful in realizing this. A hummingbird’s metabolism is different from that of a whale. Their metabolisms are massively different because of the differences in size and shape. The same is true of buildings. Small buildings, like hummingbirds, are skin-dominated and large buildings, like whales, are internal-load-dominated.
• Skin-dominated buildings tend to have high but balanced heating and cooling needs and natural lighting is relatively easy.
• Internal-load-dominated buildings tend to heat themselves due to heat from occupants and equipment, but are more difficult to cool, vent and daylight. Also, large buildings present aesthetic, social and cultural issues, like the relation to surroundings and the degree of user isolation.

The discussion regarding these principles must occur at the earliest stage of design, at the programming level. Too often energy considerations are brought into the design process too late to allow integration with other concerns needed to produce a high-performance passive building.

An Evolving Design Discipline
Passive design has come a long way from the passive solar buildings of 30 years ago when the term was first coined. Some of these advancements are:

1. Achieving multiple functions. Using architectural elements to accomplish more functions has increased the effectiveness of passive design as well as reducing costs. The narrow mindset that we must do this to save energy is progressively being replaced by the realization that this is a more economical, more comfortable and more aesthetic way of building while being healthier for the planet, for our society and for ourselves.

2. Better and more diverse modeling. Since in passive design we are dealing with a complex holistic system rather than discrete parts that are easily calculated in isolation, computer simulation modeling becomes extremely important. Performance-based modeling is far superior to prescriptive-based modeling, as used under California’s Title 24 code discussed earlier. The expansion of functions served by passive design means that other models, such as computation fluid dynamics modeling for natural ventilation, are now being used in conjunction with thermal-performance models. Performance simulation and better materials are what now allow us to create high-performance passive design.

3. New materials. It’s been recognized for years that the passive solar approach to conditioning is less expensive than active solar devices. For example, in most cases it costs nothing to orient the building to the south or to provide properly shaded, operable windows for ventilation and winter gain. The biggest expense in passive design up to now has been the thermal mass needed to moderate interior temperature swings and thereby minimize expensive back-up mechanical systems. A promising new material is the nanotech phase-change additive that can be mixed into concrete or into wall panels, thus providing inexpensive but effective thermal mass. This material (Micronal micro-encapsulated wax from BASF chemicals) was used by the winning entry of this year’s Solar Decathlon in Washington, D.C. (see “Solar Decathlon Highlights,” SOLAR TODAY, January/February). For years, passive solar designers have wished for inexpensive, easily applied thermal mass. This may be the grand slam.

However, new products with great promise must be carefully evaluated and made part of the passive design process. An example of unintended consequences occurred with the advent of low-emissive glass. The new technology proved to be so efficient that one form of low-e glass (soft coat/heat rejecting) gave the capability to essentially eliminate any meaningful solar thermal gain through south-facing windows while maintaining normal lighting characteristics. Thus we could design an ideal passive building for heating with just the right orientation, thermal mass, percentage of glazing and size of overhangs. But if we installed the wrong type of low-e glazing, the building would literally fulfill the old in-house joke, “Mass, glass and freeze your a_ _!” This happened too often, because the glass companies found it easier (and cheaper) to market and inventory one type of low-e glass rather than two. The American Southwest was deemed to be an overheating area, so most companies refused to carry the other low-e glass (hard coat/heat receiving). Sales representatives pushed the heat-rejecting low-e glass and many people unknowingly installed the wrong glazing. Reductionist thinking got in the way once again! Only recently, and after much complaining by solar architects, has this unfortunate situation been addressed by the glass industry.

4. Other resource concerns. Energy and carbon costs are becoming part of passive design, with the goal of creating a greener architecture. The carbon sequestering potential of building materials is a new issue. There are also passive approaches to water and waste that promise to reduce the very high material and energy costs of our community infrastructure. Buildings located off the water grid now use rain catchment and new water-free or minimal-water plumbing fixtures. Buildings located away from the sewer grid can incorporate onsite biological waste treatment. These designs qualify as passive just as much as any reduced-energy building designed to be fully powered by an integrated photovoltaic skin.

Potentials of Passive Design
Three of the most critical problems facing us in our new century are global warming, soaring costs for post-peak fossil fuels and resource wars. These are all exacerbated by the way we use energy, and we can help to mitigate them through wide application of passive design. Recent quantification of global warming gives us some inkling of what our best strategies for carbon mitigation could be. Some of these mitigations are reactive and require big changes in behavior. Some are proactive and easier to accomplish. Passive design is part of this second approach. The AIA estimates that about 48 percent of the greenhouse gases discharged in the United States originate in buildings. If that’s the case, we’ve an obligation to design buildings in a way that can help to reduce global warming. With sustainable planning, green architecture utilizing passive design and appropriate technology, we can build our way out of these dire predicaments.

About the author: Ken Haggard is a principal architect of the San Luis Obispo Sustainability Group, founded in 1976. He was the architect, with Polly Cooper and Pliny Fisk, for the first passive solar building in California in 1972 and the first permitted straw bale building in California in 1992. He is co-author of the Passive Solar Handbook for California with Phil Niles(1980) and Fractal Architecture: Design for Sustainability with Cooper (2007), both available through Amazon.com.

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