Geothermal Heat Pumps Washington DC
Down to Earth
Maryland homeowners Phil and Lisa Malone describe themselves as fairly average, well-traveled and pretty independent people. They're also quite savvy when it comes to energy efficiency. When the couple decided to leave city life behind and relocate to Deep Creek Lake in the rural hills of western Maryland, they built a home that is "a unique fusion of energy-efficient techniques and environmental sanity," as they put it.
By using Sun, earth and water to heat and cool the home, they drastically reduced energy costs and created a comfortable living environment. The Malones' single-story, triangular home integrates several innovative building techniques, including an earth-sheltered passive-solar design, geothermal heating and cooling, and a fresh-air system using an energy recovery ventilator (ERV).
"My original plan was to reduce the total amount of energy we needed [to live comfortably]," Phil Malone says. "To me, this was the most effective way to have a positive impact on the environment - my ultimate goal." The experiment in greenbuilding began in September 1998. Malone, an
Australian-born software designer, had just returned to his Annapolis home after three weeks at sea with an RMS Titanic Expedition, for which he provided software and electrical support for one of the expedition's deep-sea vehicles.
One day, after converting his walk-out basement into an office for his consulting firm, Malone had an epiphany. He realized the basement office stayed cool and comfortable all year round, even on the hottest days, which made him wonder if this concept could be applied on a grander scale. "My daydreaming and research led me through the apparently independent areas of earth-sheltering, passive-solar design, ground-source heat pumps and energy recovery systems," Malone says. "As a systems integrator by nature, the challenge for me was to integrate these concepts into a single design. The earth aspect ended up playing a big part."
Earth Sheltering In the course of his research, Malone happened upon a book by Malcolm Wells (a self-proclaimed "underground architect"), The Earth-Sheltered House: An Architect's Sketchbook. This and James Kachadorian's The Passive Solar House, inspired Malone's initial designs. "Wells' book is full of inspirational thoughts designed to expand your horizons," Malone explains. "It graphically illustrates a wide range of design ideas without dwelling on the technical side of things. On the other hand, Kachadorian's book is a wealth of technical information and practical data, designed to separate fact from fiction." (The Solar House: Passive Heating and Cooling, by Daniel Chiras, is another good source.)
Malone recalls that, as a child, he visited the opal-mining town of Coober Pedy in south central Australia. Many locals built their homes below ground in abandoned mines to ensure temperatures of around 68°, sheltering them from the scorching heat on the surface. This memory - and an experience with an underground house in the Virginia mountains in the late 1980s - also helped to spark his interest in earth sheltering. The basic idea is quite simple. If the temperature outside is 85°, then the 60° earth will help cool your home, Malone explains.
Conversely, if it is 10° outside, the 55° earth will help warm the home. "The only time earth sheltering isn't better than a traditional house is when the outside air temperature is in the 60- to 75-degree range. Then you just open the windows!" Malone says. The Malones' home is built into a wedge carved out of a hill and surrounded by earth on two sides. The third side faces south, so the Malones can reap the full benefits of the Sun during the winter. A few factors must be accounted for when designing an earth-sheltered home, Malone notes. The east/west orientation of the home's major axis is one of them, as it can determine how much heat your home rejects during the summer and retains during the winter. One also must consider earth expansion caused by freezing, and waterproofing the roof system. Historically, earth-sheltered designs have had a number of drawbacks.
For instance, light from a single direction can cause objects and people to appear flat and can cause glare, making lighting design difficult. There's also no natural cross-ventilation, and with no windows, the earth-sheltered area of the home can be dark and gloomy. To address these issues, Malone designed the house with a "high space" - a small second-story tower, or observatory, accessed by a spiral staircase. Part of the 250-square-foot area is open to the lower level. Windows provide natural light and ventilation, while blinds help prevent overheating in the summer. Passive Solar, Radiant Heat Homeowners not familiar with earth sheltering might assume that since the home is surrounded by earth, much like a basement, it gets uncomfortably cool in the winter months. But as Malone explains, "Earth-sheltered homes really aren't basements, just like penthouses really aren't attics."
One reason for the distinction is insulation. The Malones' home has 2 inches of foam insulation under its concrete slab floor, as well as insulated below-grade walls. The concrete slab is an integration of both passive solar and geothermal design. It acts as thermal mass, soaking up the sunlight from the south-facing windows, retaining the heat and gradually releasing it. The Malones also embedded radiant hydronic coils in the slab floor, which helps them control the indoor temperature. Water heated through geothermal exchange flows through the coils, providing radiant heat throughout the house.
Malone loves the radiant floor. He works from home, spending most of the day in socks or barefoot. But the radiant heating system is more an essential than a luxury, as Deep Creek Lake can get upwards of 80 inches of snow annually. Geothermal Exchange Climate plays an important role when deciding what kind of HVAC system is right for a home, Malone says, adding that his home is a perfect example. "In my climate, winter temperatures are pretty much always below 45 degrees. So it's either use a fuel that is less than 100 percent efficient, or use a GSHP (ground source heat pump) that is 300 to 400 percent efficient." For Malone, the choice was easy. "No matter how you cut it, energy costs money, so the less efficient your heating system is, the more it will cost. Heat pumps can be more than 100 percent efficient because they don't generate heat - they pump it." Several devices, including air conditioners and refrigerators, use heat pumps to move heat from one place to another.
But if the differential between the inside and outside temperatures is too great, these pumps fail. For example, Malone explains that if it's 95° outside, a heat pump can cool your home to 65° fairly easily, but it can't heat your home to 65° if the outside air temperature is below zero. GSHPs work so well because they do not move heat between your home and the air, but rather between your home and the Earth. "[Ten to 12] feet beneath the surface, the Earth's temperature remains fairly constant year round, ranging from 45 degrees or so in northern latitudes to about 70 degrees in the deep South," explains Wael El-Sharif, executive director of the Geothermal Heat Pump Consortium ( http://www.geoexchange.org ). "Geo-exchange takes advantage of this constant temperature to provide extremely efficient heating and cooling." (To determine the exact constant temperature for your area, call a local well driller and ask for the groundwater temperature.) The Malones use a GSHP to provide hot water for the radiant slab as well as domestic hot water, which is stored in a conventional 75-gallon water heater.
The water that heats the slab, which is at a lower temperature than the water for domestic use, bypasses the water heater and heats the slab directly. By reversing the GSHP, the Malones can cool the slab if required. The system is so efficient that they estimate 60 percent savings on heating costs, compared with a traditional HVAC system. A key component of a geothermal exchange system is the ground loop, which basically is a series of long tubes buried in the ground either horizontally or vertically. In winter, a water solution contained in the tubes absorbs heat and delivers it from the Earth to the home via the GSHP and the radiant coils in the flooring. In summer, the process reverses, as heat inside the home is drawn away by the water solution and delivered to the Earth, where it is cooled before it returns to the home. As Malone notes, installing a ground loop can be expensive, depending on the configuration.
"If you have a large lot, you could dig a trench [to install horizontal pipes] about 6 feet deep around the [house] perimeter to keep costs low," he says, "but going vertical comes with the added expense of hiring a drilling company to install the loop." Malone continues, "My installation was a vertical loop, and is more elaborate than most. I'd estimate that [the geothermal system] cost an additional $10,000 to buy and install over a traditional boiler system." Going Green, Saving Green? Many homeowners might be dissuaded by the added cost of going green. But once the energy savings are factored in, these systems can save more money than they cost. Homeowners with geothermal systems enjoy utility bills 25 to 50 percent lower than those with conventional systems, according to the Geothermal Heat Pump Consortium.
Operating costs can run as low as $1 per day for a typical 2,000-square-foot home, El-Sharif says. Lisa Malone definitely has noticed the energy savings in her home. "Our utility bills are quite a bit less than for our previous house, which was a three-level duplex in a milder climate," she says. "Phil did a great job convincing me that passive solar and geothermal were great energy-saving ideas, so I was all for it. But I really didn't know what to expect. I get it now!" What is perhaps most interesting about this experiment in greenbuilding - apart from the seamless integration of energy-efficient systems - is that the entire design and building process has been documented by the Malones on their own website, which you can visit at http://www.ourcoolhouse.com . "I started the website before I had a design for the home," Phil Malone says. "I was determined to document my design process from start to finish.
I wanted to share the insights, the stumbles and the results, be they good or bad. I got lots of great ideas from my forum, and others have, too." The website provides a wealth of information documenting the design and building processes, including detailed explanations of earth sheltering, passive solar design, and geothermal heating and cooling. The site also includes a timeline, room guide, 3-D model and both the preliminary and final designs of the home. But what really sets the site apart is interactivity. You can monitor data from the Malones' HVAC system live over the Internet. If you have an experiment in greenbuilding you'd like to share, you can post it on the site's Designer Showcase, which Phil Malone set up "so other green-home designers can post their own sagas for all to see." In building their earth-sheltered home, Phil and Lisa Malone have broken new ground.
Not only did they set out to design and build a home that was energy efficient, environmentally friendly and specified to their needs, but they also managed to document the process in a fun and interesting way. The end result is a home that maximizes comfort and truly is down to earth. "This project was a real learning experience for me," Phil Malone says. "I enjoyed the process a lot, so much so that I'm thinking of doing it again. We already have the land. Everyone should have a hobby, right?" Trevor McNally is based in Austin, Texas.
Geothermal's New Twist
Four years ago, at a time when fuel prices were relatively low and Detroit was kicking out more SUVs than sedans, Del Leese sensed a looming energy crisis. When he and his family constructed their new home in Mechanicsburg, Pa., he made the decision to install a geothermal heating and cooling system. Now, while many of his neighbors are experiencing record-high electric and gas utility bills, Leese and his family are enjoying record savings.
After months of research, which entailed comparing water-sourced and direct-exchange (DX) geothermal systems, and interviewing installing contractors, Leese settled on an EarthLinked direct-exchange heating and cooling system. The type of system he chose one that's at the cutting edge of heat-pump technology is offered by only two firms, ECR Technologies Inc. of Lakeland, Fla., and American GeoThermal DX of Murfreesboro, Tenn. Both companies separated themselves from the pack by developing higher-efficiency DX geothermal technology.
Last year, Leese paid only $650 (about $55 per month) for heat, air conditioning and hot water in his 3,200-square-foot home, compared to the average of $220 per month his neighbors paid for these services in homes of about the same size. A quick calculation reveals that Leese is saving more than 70 percent on utility expenses. It's typical of what he's seen during the last three years.
Our previous home had electric baseboard heat and window air-conditioning units, Leese says. It was terribly inefficient and rather uncomfortable at that. Today, the comfort is seamless and smooth year-round, and the system is entirely reliable. We're delighted with the geothermal system.
Leese adds, We decided before moving in that we would separately monitor the system's energy use. For four years now, we've seen how it gives us four to five units of energy for every unit of electricity it consumes.
Manufactured by ECR Technologies, the Leeses EarthLinked system taps the earth's abundant energy in the most efficient means possible, through direct contact with the earth. It harvests heat directly from the earth, which maintains a constant temperature of about 52° F in central Pennsylvania. This provides a much more favorable source for heating and cooling than the constantly varying ambient air temperature, upon which air-source heat pumps rely.
Jody Hoffman of Hoffman Mechanical installed the 3-1/2-ton (42,000-BTU), 14-loop DX system for the Leese home by drilling 14 2.5-inch-diameter holes at 45° angles to depths of 50 feet. From the variety of loop configurations available for a DX system, Hoffman and Leese chose the diagonal method, which disturbs the least amount of earth. For homes where ground space is limited, and especially for existing homes with mature landscaping, this configuration is ideal because all of the small-diameter drilling takes place from a shallow 6-square-foot pit, with drill holes radiating outward and down at an angle from the base of the pit.
Most geothermal systems operate at ranges of 250 percent to 350 percent efficiency, says Hoffman, who has installed many types of geothermal heating and cooling systems during more than 20 years in business. That means the systems supply up to three-and-a-half units of heat for every unit of electrical energy required to operate them. With the variety of options available for installation of the earth field, and with the highest operational system efficiencies up into the 400 percent range, conservatively, DX is a great choice for many homes or buildings.
While some geothermal systems rely on plastic piping to transfer water and antifreeze through a plastic loop and an intermediate heat exchanger, DX technology circulates a refrigerant through highly conductive copper earth loops that are inserted into boreholes of 50- or 100-foot depth, then embedded in a protective thermal grout that enables direct transfer of energy with the earth.
While Leese opted for a DX system, water-source geothermal systems are also viable for residential use. Only a small amount of electricity is needed to power geo systems, says Bruce Ritchey, president and CEO of Fort Wayne, Ind.-based WaterFurnace, a leading manufacturer of water-source geothermal systems. The rest of the process uses the free, clean and renewable energy that's trapped just below the earth's surface.
A closed-loop system uses a continuous loop of buried plastic tubing as a heat exchanger. The tubing is connected to the indoor heat pump to form a sealed underground loop through which an antifreeze solution is circulated. Unlike an open-loop system that consumes water from a well, a closed-loop system recirculates its heat-transferring solution in the pressurized pipe. Many closed loops are trenched horizontally in yards adjacent to the home.
Comparing the two water-source units, an open-loop system tends to be more efficient because it simply pulls the heat out of a steady stream of water from deep in the ground. It's not recirculated, as with a closed-loop system. But open-loop systems are prohibited in many parts of the country because of water quality and water conservation concerns.
DX and water-sourced geo systems cost about the same to install (usually several thousand dollars more than a conventional air-to-air heat pump), though with DX you'd see better operating efficiencies and possibly something akin to surgical insertion of the ground loops. The process of getting the tubing in place for a DX system is faster and less invasive to the property, making it possible to retrofit homes with mature landscaping.
Although not yet commonplace, ground-source heat pumps have been installed for more than 30 years and are recognized as the most efficient heating and cooling systems available today. Geothermal heat-pump technology offers a renewable-energy solution that's right for almost any home, says Gemma Tiller of Air Brokers HVAC in Branson, Mo. Thermal energy of sufficient temperatures anywhere in the United States and Canada is harvested from the earth and transferred into buildings by a heat pump that provides heating and cooling.
Even if you have a small patch of land, it's your best hedge against an energy crisis that creeps closer to home each day. Thermal energy is stored in the ground, ready to be used. Newer technology extracts it with greater ease, with little disruption to the surrounding landscape and at such high operating efficiencies, it makes payback on the investment faster than ever before, Tiller notes.
A ground-source unit works like a conventional heat pump to cool a home in the summer and heat it in the winter. The key difference between an air-source heat pump (which can't heat a home efficiently when outdoor temperatures dip below 30° F) and a ground-source pump is that the latter harvests the stable and renewable heat from beneath the earth's surface. The equipment transfers virtually endless thermal energy (heat) from the earth into the home during the winter months and transfers excess heat from interior spaces into the earth, where it's stored during the summer.
As a result, a ground-source unit saves energy, which reduces greenhouse-gas emissions and can cut utility bills by up to 70 percent. And very little maintenance is required. Surveys conducted by the Geothermal Heat Pump Consortium show that ground-source owners rank their systems higher in comfort than do the owners of other heating and cooling systems. Also, more than 95 percent say they would recommend ground-source systems to friends and family members.
Tiller, whose company installs all types of geo systems, prefers DX technology because the refrigerant lines are placed in direct contact with the heat source without the need to pump water through an intermediate heat exchanger. These systems are ideal for new construction and retrofit installations, with earth loops installed vertically, diagonally or horizontally.
Typically, any geothermal system provides service for up to 30 years, which is twice the life expectancy of air-source heat pumps. This is because the stable heat source helps prevent thermal stress to the compressor, the enclosed unit is out of the weather, and no fossil fuel is burned other than the electricity to operate the system.
An All-in-One System
Geothermal heat-pump systems do the work that typically requires two appliances" a furnace and an air conditioner. Many systems can provide a third function, which is to heat a home's domestic water by one of two means: through integrated full-time water preheating or through desuperheating water heating.
Integrated (on demand) water heating uses the heat-pump system to heat water any time of the year. Its initial cost is higher, but it provides operating savings all year. Because this water heating option has the full heat-pump-system capacity available to heat water, it can provide quicker recovery (going from cold to hot) than an electric-resistance water heater.
A desuperheater reclaims heat from the air-conditioning cycle to heat water. Its initial cost is lower, and savings are realized in the cooling season by transferring waste heat to your hot-water tank. Even in the heating mode, the desuperheater can provide preheating to the water heater, reducing the work required of the electric-resistance elements. A desuperheater provides free water heating throughout the summer season, and typically reduces water-heating costs by 40 percent to 60 percent, depending on the amount of cooling required.
Return on Investment
To calculate system payback with some accuracy, you must know how much per year you'll save in energy costs with a geothermal system and the difference in costs between it and the alternative heating system and central air conditioner. To calculate your return on investment (payback in number of years), divide the additional cost by the annual savings. When you install a geothermal system in a new home, the monthly savings in operating costs will generally offset the additional monthly cost in the mortgage and result in a positive monthly cash flow from the first month. That's a return on investment any homeowner can appreciate. When you factor in the environmental benefits, geothermal seems like an alternative energy source whose time has come.
Manheim, Pa.-based John Vastyan is a journalist and communications professor whose work focuses on the plumbing and mechanical, radiant heat, and geothermal industries.