Ask the Green Architect: Geothermal heating systems, green specs and sources

Ask the Green Architect: Geothermal heating systems, green specs and sources

the earth below ground maintains a consistent temperature of around 57 degrees Fahrenheit (14 C). Rather than heat the building from the freezing air outside, or cooling the building from the blistering air outside, you heat it up from this 57 degrees.

Since this geothermal temperature is much closer to our normal comfort zone, it requires much less energy to use.

Diagrams by Energy Right & Geothermal Heat Pump Consortium

The U.S. Environmental Protection Agency credits geothermal as "the most energy-efficient, environmentally friendly heating and cooling technology available."

With this warm water, you can heat both the air and the water needs for your building.

Archaeological evidence shows the first use of geothermal heating occurred more than 10,000 years ago with the settlement of Native Americans using hot springs. A source of warmth and cleansing, the spring minerals were known as a source for healing.

Our modern use of geothermal dates back to 1864 at the Hot Lake Hotel near La Grande, Oregon. By 1930, the first commercial use of geothermal energy was produced using a 1000-foot well in Boise, Idaho.

Generally speaking, geothermal systems come in two standard configurations: Vertical or Horizontal.

  • Vertical Closed Loop. The most common is the vertical system. As the name implies, loops of piping are fed several hundred feet into the earth. As you can imagine, this requires a great deal of boring. Given the depth, the ground source temperature remains consistent throughout the year. On site with expansive soils or bedrock, the vertical systems would prove to be too expensive.

  • Horizontal Closed Loop. Horizontal loops are installed in trenches only five feet below the surface. Due to this shallow installation, the ground temperature changes seasonally. While these horizontal loops are much easier to install, and work for bedrock sites, they do require significantly more surface area (approximately 2500 square feet of surface area per ton of cooling) in order to work effectively.

    There are also Surface Water systems that use a body of water adjacent to the building. These are less common as they demand specific requirements of the width and depth of the lake in order to work.

    Homeowners with geothermal units typically realize energy savings of 25% to 50% over conventional gas, oil, or heat pump systems. As a rule of thumb, a typical 2000 square foot house can be heated or cooled for as little as $1 a day.

    Since a geothermal system also produces hot water as a byproduct, these systems are up to 30% less expensive to operate than a traditional gas or electric water heater.

    A geothermal system is housed entirely indoors, thereby avoiding the strain of freezing and thawing. Since it is a closed loop system, it is practically maintenance free.

    Air Quality
    Rather than sucking in outside air, as a forced air heating system does, a geothermal system does not draw spores and pollen into the building. For people with allergies or asthma, this is a welcome change and they will notice a marked improvement in indoor air quality. And since the geothermal system does not involve combustion, no pilot light, chimney, odor, or fumes will be added to the house.

    For smaller buildings, cost is the main drawback. Drilling the holes for the vertical system can be prohibitive for single family homes. Another possible roadblock is the lack of qualified contractors who know how to properly design, install, and service these systems.

    According to our research, it is best to look for equipment certified by the Air Conditioning and Refrigeration Institute, a nonprofit organization that rates residential and small commercial systems.

    When working with any contractor, check references and verify they have installed these systems before. The contractor should determine the size of your system, the type of loop, and the fluid to be circulated in that loop.

    Remember, an energy-efficient building is more important than anything else as it reduces the size of the system needed and lowers operating costs well beyond what even the most efficient system could. That being said, be sure to have proper insulation, efficient windows and radiant barriers installed as well.

    For a list of providers in California, I would consult:

  • California Service Providers.

  • Other states can find providers here.

    Given their affordable installation cost, low operating costs, low maintenance costs and overall energy efficiency, geothermal systems are an obvious choice to consider for many building types.

    More Information
  • Geothermal Heat Pump Consortium

  • U.S. Department of Energy

  • 9 Ways to Make Your Home More Energy Efficient

    Where can I find green specifications and source products to place within these specs?

    Eric: Constructing a building takes much more than a set of blueprints. Every detail of the structure from the style of the doorknobs to the color of the switchplates must be explained in a large document called the specifications.

    Specifications are an integral but oft overlooked aspect of architecture and construction. GIven their meticulous and tedious nature, specifications are now outsourced to professional consultants, typically certified by the Construction Specifications Institute ( They are organized into CSI Master Format, a confusing but generally accepted standard of sixteen categories containing everything from site work through to finishes.

    Given the surge in popularity in green building, there are now several sources for green specifications. While these contain the basic elements in all standard specs: Definitions, Standards, Products and Installation, these green specs also contain a series of environmental considerations. These include issues to consider, qualities and recommendations related back to the environmental responsibility of that particular section.

  • MasterSpec: The industry standard specification writing tool from the American Institute of Architects also offers a section on the LEED (Leadership in Energy and Environmental Design) Green Building Rating System. This does not get into specific products, but if you already work with MasterSpec, this might be an interesting addition.

  • BuildingGreen Green Spec: Published by the good folks at Environmental Building News, the BuildingGreen Green Spec is perhaps the best source for specs and green products. Their guideline specification documents are an education in themselves on how to put together a green building. With over 2000 environmentally preferable products listed, it is an invaluable tool. You can even sort your search by the CSI division, by LEED credit or by Homebuilder category.

  • GreenSpec (UK): GreenSpec is the UK construction industry's definitive guide to sustainable construction. Inside GreenSpec you will find a wealth of information aimed at helping you to design more energy and resource efficient buildings using materials and technologies that minimise damage to people and the environment.

  • Arcat: Arcat is a free, online spec writing tool. While it does not specifically contain green specs, using it combined with some others on the list will be helpful.

  • WBDG Product Guide: The whole Building Design Guide offers an online list of specs & building products.

  • New York City Department of Design and Construction: The NTC Green Building program offers a wonderful online resource of green specs.

  • McGraw Hill GreenSource: McGraw Hill, publishers of the ubiquitous Sweets Catalogs, now offer an online directory of information on sustainable design, practice and products. While these are not specifications, it is a wonderful source of product information. The large green covered Sweets Catalogs are often criticized for their enormous consumption of paper and energy required to ship the heavy books. The company now offers the same information online.

  • US Green Building Council: The USGBC offers a great list of links and additional resources.

    Once you find a product you wish to use, the individual product manufactures can usually provide you with outline specifications to use for your own work. Remember, they want to help you specify their products.

    These books might also prove helpful:

  • Green Building Materials: A Guide to Product Selection and Specification, by Ross Spiegel, Dru Meadows

  • Green Guide to Specification: An Environmental Profiling System for Building Materials, by Jane Anderson

  • Green Building Resource Guide, by John Hermannsson

    More Information
    Construction Specifications Institute

  • Architects/ Designers/ Planners for Social Responsibility (ADPSR)

  • Federal Green Construction Guide for Specifiers


    Eric Corey Freed is principal of organicARCHITECT and teaches Sustainable Design at the Academy of Art University in San Francisco and University of California Berkeley. He is on the boards of Architects, Designers & Planners for Social Responsibility (ADPSR), Green Home Guide and West Coast Green. This article has been excerpted from his upcoming book, The Inevitable Architect: A Phase by Phase Guide to Green Building.