October 2009
By Andrea Fox, Ms. Green Quick Fixes SM
Green Building III: Energy and Alternatives
The Green Building Basics series covers several aspects of low-impact building and retrofitting — including project siting, materials and insulation, roofs, foundations, walls and more.
Green building is about weighing a multitude of factors and using resource-conscious materials and approaches when possible to reduce a home's environmental impact, make it last longer and be more cost-effective.
However, no discussion of green building could be complete without highlighting smart energy strategies and examining green alternatives.
A lower-cost, lower-impact climate-controlled home depends largely on windows and doors, outdoor vegetation, solar energy manipulation and alternative energy choices.
The following tips can eliminate or supplement your upcoming — and albeit costly — conventional fuel needs. The season is changing, and the coldest season is a growing blip on the horizon.
Windows and doors: Costly holes in insulated walls
Windows are needed for ventilation and solar entry. However, the older and thinner the windows are, the more they lose heat in winter.
Today's manufactured windows feature double and triple panes filled with gases and have high thermal-efficiency value (R-factor).
However, high R-factor windows reduce the amount of solar heat a window is able to collect, and in this they are a double-edged sword. The more solar energy, the less fossil fuel is needed to keep comfortable.
In the northern hemisphere, the south-facing windows are the best source of passive solar energy — capturing and using the sun's energy without the use of mechanical systems. The east- and west-facing windows capture limited light in winter months, and then heat in summer.
If upgrading windows, limit the R-factor of south-facing windows. Well-sealed, air-filled, double-pane glass will reduce heat loss and ensure solar energy collection.
Consider double- and triple-pane glasses with gases (such as Argon) for north-, east- and west-facing windows.
Casements and awning styles open widest, providing great ventilation in summer months.
Install flashing and seals in all door and window jams.
Without proper weatherproofing, doors and windows really do negate the power of wall insulation. Your heat will fly right out a single pane, drafty window with poor or no weatherproofing. The same is true for transoms, sidelights and glass panels in exterior doors.
If you are not replacing windows, you can still lower your monthly expenses:
- Use a compass to figure out which directions your windows face.
- Buy or make curtains or insulated shutters.
- Cover windows that do not collect much solar heat during the cold months. Lighter-colored material allows some daylight in.
- Cover windows, including the south-facing, at night to retain heat. In late summer, they'll keep rooms from overheating in late afternoon.
- Check seals and weatherproof any spaces or holes. Hardware stores have plastic and other materials that work. Also, grain-filled cloth "snakes" close out drafts from the bottom of doors and work well on window sills.
Passive solar collection is ignited by the use of thermal materials, such as concrete, adobe, cob, bonded wood chips and brick, which absorb heat during the day and then release heat at night when temperatures go down. They also absorb heat from interior air in summer.
Another option is water, contained in plastic or metal tubing, embedded into walls (roofs systems are called "thermal ponds"). They also passively release heat via convection, but they work quickly.
The Arizona Solar Center and other Web sites have more information on passive solar systems.
Vegetation around your home can help with summer cooling expenses and can buffer cold winds in the winter.
Plant deciduous trees, which work well in the Northeast, to shade south- and west-facing windows in the summer. They also provide evaporative cooling that makes the ambient air temperature cooler. They die back in the winter to allow solar energy in.
Trellises with seasonal plants that die back in winter also work well for shading.
A roof and its overhang block energy from the summer sun. Since the sun's path is higher in the summer than winter, it's easy to measure where windows should be placed to capture solar energy in winter when the sun's rays are lower and how far roof overhangs should jut out for optimum summer blockage. Note: Overhangs should be longer in warmer climates.
Consider awnings (some are retractable) that block strong summer rays.
Plant evergreen trees in the path of prevailing winds (which are site-specific) to keep the chill at bay.
Install a roof vent (cooling tower) to release hot air and pull in cooler air from north-facing windows. An attic with a fan can act the same way.
Regardless of your politics, fossil fuel combustion creates air pollution and damages the atmosphere. Alternative systems that harness the sun and use wind or water power drive fuel consumption down.
Solar panels, or photovoltaics, convert sunlight to electricity. Running through is liquid glycol (hazardous to public health if leached). Once heated, the panels' exchanger coils distribute energy, such as for heating water.
Called active solar collection, these systems convert and distribute solar energy. They are exceptional for heating water and energy-carrying liquids.
Hydronic floor heating works with mounted solar panels and can heat your home. Energy is transferred to tubes that carry heated liquid to an interior storage tank, which then feeds embedded radiant floor systems.There are other types of solar systems that heat water, interior air, swimming pools, etc., and provide energy for lights, electronics, laundry, cooking and more. Consult a professional when considering one of these systems.
Wind energy, which uses turbines attached to poles and connected to alternators that generate electricity, works well for lights and electronics. More complicated to install, such systems require a significant amount of site data. But they may be well worth it. According to the Massachusetts Department of Energy Resources, Beverly High School's lone wind turbine produces 10kw per year of electricity. Together with the school's solar panels, the city is saving more than $10,500 per year on energy costs.
Hydroenergy works the same as wind systems, but a water source with enough vertical fall (called "head") and flow to turn the turbine must be available.
A good backup for alternative energy is a wood stove. Clean-burning stoves use renewable wood as fuel, and can be cozy on grey days. Also, consider switching to a tankless water heater that uses fuel only when needed to heat water, rather than burning it all day long as with conventional water heaters.
For information on industry standards for green building, see the National Association of Home Builders model guidelines.
To learn more about greener community planning and reducing urban sprawl, check out the Massachusetts Smart Growth Tool Kit.
