Green Martha : Going green and saving greenbacks
By Steve Myrick
Published: February 11, 2010
What is the most economical thing a homeowner can do to make his castle greener and save money at the same time? What seems a simple question is actually quite complex. The many different styles of houses, construction techniques, location, geography, and budgets all influence the calculation of how to get the most bang for the buck when going green.
For some, the first thought that comes to mind is windows. But windows are the wrong place to look, according to Rob Meyers, an energy analyst for South Mountain Company.
"Windows are very far down the list, because they are very expensive to replace," Mr. Meyers said. "It's never the first thing we look at."
Instead, he looks at air sealing and insulation. Think of your house as a present, and the air and thermal barriers as tight wrapping paper. Most older homes do not have a continuous thermal barrier or air barrier (wrapping paper) around the building. There are often plenty of places where warm air can escape.
"Air can wash right over fiberglass insulation and pull heat outdoors," Mr. Meyers said. Infrared photography, which illustrates heat, and blow tests, where air pressure inside the home shows how air is escaping the barriers, can help determine the best route to cost savings. "It depends on the size and the style of the building. The more corners and more hips to a building, the more complex. Attic knee walls are notorious energy losers. Those are areas we know to hone in on."
Mr. Meyers also recommends another cost-saving measure that most people overlook. Until recently, heat loss calculations were not much more accurate than an educated guess. As a result, many homes have furnaces that are too big for the home.
"This is sort of a systemic issue with residential construction in cold weather climates," Mr. Meyers said. "It's a huge one, a really big one, and we see it a lot."
There has been a vast improvement in matching heating systems to a home's requirement in recent years, Mr. Meyers says. More accurate heat loss estimates can be made by using data loggers to record temperatures at various locations inside and outside the structure. When furnace capacity is matched closely with the requirements of the home, peak efficiency results.
David Sprague of Nelson Mechanical Design in Vineyard Haven agrees with Mr. Meyers in the belief that air source heat pumps will be a significant factor in reducing energy consumption. Widely used in Europe and Asia, air source heat pumps have come to the U.S. market only in the last two years. Some look like stretched out air conditioners, others can be disguised by ceiling installations, and some work with integrated air ducts, like a conventional hot air heating system.
"Pretty much heat pumps are it," Mr. Sprague said. "It's getting us away from fossil fuels." Integrated with an on-site wind or solar generating system, the heat pumps become even more efficient. "It's running strictly on electricity we can generate on site. We can't generate our own propane."
A heat pump works much like a refrigerator, or an air conditioner. Many heat pumps can both heat and cool. They take advantage of the changing state of liquids and gases to transfer heat.
"It's like a conveyor belt of heat," Mr. Sprague said. "You have refrigerant, which goes through a phase change. When you change phases, you have to exchange heat."
The phase change enables a very efficient use of energy. Mr. Meyers said for every unit of energy that goes in, 2.5 units come out. That is far more efficient than conventional electric resistance heating.
