Ԫ Build By Design :: Geothermal HVAC (part 4)

Geothermal HVAC—The Best Thing You Can Do For Clients

Specifications—Considerations

Sizing

Some national surveys have determined that well over half of all HVAC contractors do not size heating and cooling systems correctly.1 That refers to conventional systems that they have been installing for years. Small wonder, then that we have serious concerns about how well contractors might perform given a new product and a technology they aren't used to. And yet, proper sizing is one of the most important factors in proper system performance.

The most common sizing mistake is over-sizing. This not only makes the new system cost more to install, but also forces it to operate inefficiently, break down more often, and cost more to operate. Oversized heating equipment also often creates uncomfortable and large temperature swings in the house. Oversized air conditioners (and heat pumps) do not run long enough to dehumidify the air, which results in the "clammy" feeling and unhealthy mold growth in many air-conditioned houses.2

Determining the correct size isn't easy. It's not just a matter of calculating the volume of air that you need to cool. The climate, style of your home, number of windows, amount of insulation, weather stripping and shade as well as other variables all effect the size of the unit needed.3

Fortunately, with EarthLinked® geothermal systems neither you nor the HVAC contractor will be sizing the system without support. Not only are we experienced at integrating these systems and installing them, but we've been intimately involved in the installation and evaluation after the fact. We have software that helps us factor in all the variables for the most effective solution possible. We know what works, and we'll help you ensure your client's satisfaction.

Compliance and Green Building

Geothermal heating and air conditioning has caught the interest of every "green" rating organization extant. It is worth noting those we think are going to be most significant in helping to establish the value of geothermal space conditioning technology. By properly considering and complying with green building standards you will not only ensure that your client's project performs as expected, but you will add value to the home because of the certification. In fact, the project certification has many benefits to your clients at little or no cost to you.

The U.S. Green Builing Council provides certification of a building through it's LEED certification program. LEED is a third-party certification program and the nationally accepted benchmark for the design, construction and operation of high performance green buildings. LEED gives building owners and operators the tools they need to have an immediate and measurable impact on their buildings' performance. LEED promotes a whole-building approach to sustainability by recognizing performance in five key areas of human and environmental health: sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality.4

The California Energy Commission establishes regulations for a Home Energy Rating System to certify home energy rating services in California. These regulations provide guidance on making evaluation of residential projects more consistent, and in our mind provides an interesting opportunity to establish geothermal heating and air conditioning for the home as a primary resource for a highly efficient environmental rating.5

The Green Globes system is a revolutionary building environmental design and management tool. It delivers an online assessment protocol, rating system and guidance for green building design, operation and management. It is interactive, flexible and affordable, and provides market recognition of a building's environmental attributes through third-party verification.6

Build It Green is a non-profit membership organization whose mission is to promote healthy, energy- and resource-efficient building practices in California.7 Build it Green employs its own guidelines for evaluating green building methodology, and its members contributed to the LEED standards referenced above.

We mention these organizations and standards because we think they will be key in helping to establish the value—in terms of environmental benefits, ongoing savings, and marketability—of this technology to your clients. We hope to participate in field verification and diagnostic testing in future installations. By doing so we hope to increase the perceived value of your guidance and the value of your client's home while collecting data that helps us better educate your future clients on the benefits and performance of our systems.

Certified buildings using DX geothermal heating and cooling systems will enjoy:

  • Lower operating costs and increased asset value.
  • Reduce waste sent to landfills.
  • Lower energy use.
  • Healthier and safer environment for occupants.
  • Reduced harmful greenhouse gas emissions.
  • Tax rebates, zoning allowances and other incentives in hundreds of cities.

...and will demonstrate an owner's commitment to environmental stewardship and social responsibility.

Heat Loss

The best way to make your client's geothermal installation work as efficiently as possible is, of course, to minimize heat loss or gain through proper sealing of the structure. It may seem unnecessary, but we feel we need to mention that we recommend as part of any new design or retrofit a thorough review of the building's envelope performance and insulation.

Site Considerations

Every site is unique, and the manifold and earth-loop fields should never be casually placed. We are available for consultation as part of our service on every installation.

Manifold Location

The good news about EarthLinked® Geothermal systems is that we have the smallest manifold footprint in the industry. Basically, if you have the space to park a car, you can install an EarthLinked® system.

However, it is important to integrate the manifold location into the overall plan so that in the unlikely event maintenance is required down the road, it is accessible without too much trouble. You as the architect or designer can probably determine the optimum manifold location with just a little guidance.

You will have to work with two possibly conflicting considerations, however. The manifold must be located within about 100 feet of the heat pump for maximum efficiency; closer is better. And, the manifold must be located on top of the earth loop field, whose location may be dictated by site characteristics. (See below.)

And the obvious considerations that are nonetheless worth stating:

For access considerations, of course, the manifold should not be located beneath a structure.

The earth loop field cannot extend beyond the lot lines. You will read below about your earth (ground) loop configuration options. The site characteristics will dictate which option you choose, but the good news is that you have options to fit pretty much any situation.

Finally, the earth loop field must be located away from septic systems or any other soil that is unusually acidic for any reason, to avoid excessive corrosion of the copper piping.

Ground Loop Heat Exchanger

The ground loop location and design are critical mostly because it would be expensive to alter after installation. So your expertise in this arena is critical; you have to get it right the first time.

You have three options for orientation of the ground loops. All three are equally effective if the site characteristics support them; you simply need to match the installation specification to the needs of the site and client.

Vertical

Vertical closed loops are preferred in many situations. For example, most large commercial, industrial or institutional installations use vertical loops because the land area required for horizontal loops would be prohibitive. Vertical loops are also used to minimize the disturbance to existing landscaping.

For vertical closed loop systems, a loop is installed in a hole drilled 50 to 100 feet deep. Because conditions in the ground may vary greatly, loop lengths can range from 50 to 100 feet, sized to optimize heat exchange.

Horizontal Trenches or Pits

Horizontal closed loop installations are generally most cost-effective for small installations, particularly for new construction where sufficient land area is available. These installations involve burying pipe in trenches or pits according to the manufacturer's rather extensive specifications.

Diagonal

Diagonal closed loop installations are in many cases the best of both worlds. It minimizes disturbance to existing landscaping because it has a smaller manifold footprint than a vertical loop installation, yet it has a similar sub-surface loop field footprint.


What is Geothermal Heating and Cooling? <--Previous :: Next Page--> Summary



1 Bob Vila, "Sizing Residential Heating and Air Conditioning," n.d.,
http://www.bobvila.com/HowTo_Library/Sizing_Residential_Heating_and_Air_Conditioning_Systems-Air_Conditioning-A1967.html, (16 September 2008)
2 Ibid.
3 Gary Foreman, "A New Air Conditioner?," n.d.,
http://www.thefrugallife.com/air_conditioner.html, (18 September 2008)
4 U.S Green Building Council, "Project Certification," n.d.,
http://www.usgbc.org/DisplayPage.aspx?CMSPageID=64 (16 September 2008)
5 The California Energy Commission, "Home Energy Rating System (HERS) Program," n.d.,
http://www.energy.ca.gov/HERS/, (16 September 2008)
6 Green Globes, "The Practical Building Rating System," n.d.,
http://www.greenglobes.com/, (18 September 2008)
7 Build it Green, "Who We Are," n.d.,
http://www.builditgreen.org, (18 September 2008)


© Build By Design, 2008