From Emily Varmecky
This is part 3 of 6 articles that aims to demystify the popular jargon used within the green building industry.
Before I explore various energy-efficient and sustainable energy systems, it is important to understand how we use energy within residential homes and other structures. In Montana, the three demands for energy within a home are: heating of your home spaces (accounting for about 49% of home energy usage), electricity for lighting, appliances, and air conditioning (36% of home energy usage), and lastly hot water for bathing, doing dishes, and laundry (16% of home energy usage).
Passive solar, solar power, and passive cooling are generally considered renewable, sustainable energy production methods. Liquid solar, geothermal energy, and radiant floor heating are usually considered energy-efficient systems. In passive solar design, the sun’s natural energy is harnessed to help heat a home. “Windows, walls, and floors designed to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer.” This process is passive because it requires no plumbing or wiring, just good design. There are different passive solar strategies, but typically, sunlight enters through the building’s south facing windows and is stored as heat within a concrete floor. The heat then emanates from the floor mass during the day and night. Passive solar heating also provides natural day lighting, which reduces the need for electric lights. Solar power is the conversion of sunlight into electricity, using photovoltaics (PV) or concentrated solar power (CSP). Solar electricity can be produced at the structure location (on-site) with photovoltaic arrays or can be supplied through the grid (electricity produced off-site that is delivered to the building through power lines). Although grid-tied electricity is typproduced from fossil fuels, a small amount of commercially produced electricity is derived from the sun. “Solar energy provides four-tenths of one percent of the total energy consumed in the United States.” Solar Water Heating (AKA Liquid Solar) systems use the sun’s energy to warm domestic hot water.
The water is heated with solar water heating panels, which are affixed to the outside of a structure similarly to solar electric panels. “A conventional boiler or immersion heater can then be used to make the water hotter, provide hot water when solar energy is unavailable,” or store the hot water. This hot water can then be used in the kitchen, bathroom, or laundry room or can be used in a variety of different methods to help heat the building spaces. Geothermal energy is heat that is generated and stored within the earth that can be used to produce electricity or more commonly, be used to help heat or cool the domestic water and spaces of a building. When geothermal energy is captured on the building site, a system of water-filled pipes (closed loop or open loop) runs horizontally or vertically into the earth. The earth’s temperature stays at a consistent temperature compared to the fluctuating air temperatures throughout the seasons. The water within the pipes is preheated by the earth, then is further heated by an electric-run indoor geothermal HVAC (Heating, Ventilation, and Air Conditioning) system that “compresses the heat to a higher temperature and distributes it throughout the building.” As an example, water within a geothermal well is heated to 50 degrees F. If the outdoor air temperature is 0 degrees F, the HVAC further heats to water to create a comfortable indoor temperature. If the outdoor air temperature is 100 degrees F, the 50 degree F water can be used to help cool the home.
Emily Varmecky is co-owner of Greenovision Home Design in Bozeman.
Please visit greenovision.com/ for further information. •
