Green Building has been making a lot of headlines lately - it seems as if you can’t turn on the TV or read a magazine without hearing about it. You have probably heard buzz about LEED and wondered how this rating system applies to the building’s heating and cooling system.
The LEED (Leadership in Energy and Environmental Design) Green Building Rating System is a voluntary building certification program that defines high-performance green buildings, which are more environmentally responsible, healthier, and more profitable structures. LEED was created to establish a common standard of measurement for what constitutes a “green” building. LEED evaluates buildings in areas: Sustainable Sites, Water Efficiency, Energy & Atmosphere, Materials & Resources and Indoor Environmental Quality. Within these credit areas, points are available and depending on the number of points a project earns determines the level of certification the building will be rewarded. The four progressive levels of certification are Certified, Silver, Gold and Platinum.
Because the building’s mechanical system utilizes a large portion of its energy consumption and is a crucial area of the building’s I.A.Q. (Indoor Air Quality), it is a significant player in the overall LEED credit. Think of the Green mechanical System as a system that utilizes the earth’s resources in an effort to diminish fossil fuel use. Ideal systems are comprised of geothermal loops which transfer the earth’s resource into the building’s heating & cooling system. This is typically achieved by the use of either indoor water to air or indoor water to water heat pumps which utilize the geothermal loop to obtain the required heating or cooling for the facilities.
In an effort to temper the water temperature of the geothermal loop, a 96% efficient fossil utilizing boiler can be installed insuring lower cost of operation and less CO emissions. It is also crucial to consider the building’s I.A.Q. needs to regulate a healthy working/living environment. The use of ERV’s or HRV’s can be installed as an efficient means of ventilation. It is also important to maintain a clean work place during the “construction” process which enables the system to operate at its peak performance and reduce airborne contaminants. This can be achieved by sealing the ends of the ductwork daily with plastic. Also at the end of the job if necessary, the ductwork can be cleaned. Ideally it is best not to run the mechanical system during the building’s construction phase.
I.A.Q. construction cleanliness, earth utilizing heating and cooling equipment and proper building ventilation combine to help achieve a Green Building.
For more information on Green Buildings visit www.usgbc.org or click on “Contact Us” for more information.
Explanation of Geothermal Heating / Cooling
Geothermal heating is a method of heating and cooling a building. It takes advantage of the natural stable warmth stored in the earth. Normally the earth temperature is around 55 °F (13 °C) at depths of 10 ft. In climates warmer than 55 °F (13 °C), this can be used to cool a building, and in colder climates (those under 55 °F or 13 °C) it can be used for warmth. This is accomplished by one of a number of methods. A heat pump uses the extracted water or transfer fluid (such as water mixed with antifreeze) as a heat source in winter and a heat sink in summer. Some heat pumps provide heating and cooling via forced air distribution, and others through the heating and/or chilling of water for radiant type systems. Some systems are used to heat domestic hot water.
Types of geothermal systems:
Closed Loop. Loops of pipe are buried at a depth of 6 ft (2 m) and greater in the ground. Pipes are placed horizontally (buried in trenches) or buried in deep, vertically-drilled holes, often 200 ft (60 m) and greater below ground level. Water and antifreeze (or other transfer fluid) are circulated through the heat exchanger (heat pump) and back out through the loops continuously. Some closed loop systems bypass a portion of their working fluid with a thermostat to keep the source temperature stable.
Open Loop. Pipes draw water from a nearby water well or a shallow body of water. Once this water passes through the heat pump, it is released back to its source, generally as far from the intake as possible.
Geothermal heating is one of the most efficient ways to heat a building, but it can have high initial costs. If you have sufficient area, the initial cost can be minimized by using a horizontal loop system. If you have limited space, then the cost rises as you need to drill wells deep enough into the earth to take advantage of the earth’s temperature. It also has ongoing costs for the electricity to power the fluid circulation pump and the heat pump compressor. Otherwise, geothermal heating is much more efficient than air heat pumps and other supplemental electric heat used in warmer climates. It has the added benefit that it requires no burning of fossil fuels at the heating site, as opposed to systems that use natural gas or heating oil fired furnaces. But in order to achieve the most comfort, it can be paired with a natural gas heater to dramatically reduce, but not eliminate, the amount of fuel needed to heat a building.
With geothermal cooling the process essentially works in reverse. Heat is transferred from the building into the ground. Traditional air conditioning transfers heat from the indoors to the outside air which is usually hotter than the temperature the system is trying to achieve indoors. Since the ground temperature at a depth of 10 ft (3 m) is about 55 °F (13 °C) and since ground transfer is more efficient than air transfer, geothermal cooling is much more efficient. Additionally, as a byproduct of the heat exchange process, a large amount of excess heat is generated. This heat can be used to heat domestic hot water before it is dissipated into the ground.
For more information go to www.nyserda.org/programs/geothermal.