The last few weeks have been a whirlwind of activity at our construction site in Moab as we enter our final month volunteering for the nonprofit group Community Rebuilds. We installed the doors, windows and interior walls and screwed up drywall for the ceiling of the straw bale home we?re building. It?s starting to look like the inside of a real house.
The master bathroom doesn?t have a window, so my wife, Julia, helped install a sun tube to illuminate the space during the day without having to switch on a light. It?s a flexible mirrored shaft capped by a plexiglass dome sticking out of the roof that directs sunlight through a hole in the ceiling of the bathroom.
The goal of Community Rebuilds is to build affordable, sustainable homes for low-income families, and the sun tube is an inexpensive design strategy for cutting the homeowners? daily energy needs once they move in. According to the organization?s founder, Emily Niehaus, limiting the owners? utility costs is a major consideration.
Another goal ? beyond that and building small ? is to wean homeowners from heavy reliance on fossil fuels, a big factor in the advance of climate change. Electricity around Moab comes from coal-fired power plants, and most of the homes are heated with natural gas.
Emily and her design team chose to build homes from straw bales partly because the material is superinsulating, resulting in drastically lower heating and air-conditioning costs. Yet she is not installing solar panels or any other electricity generation system based on renewable energy sources.
She came to that decision after meeting Jeff Tobe, a photovoltaic instructor for the Colorado-based nonprofit Solar Energy International Although he is a strong solar advocate, he convinced Emily that solar panels were not where she should put her time or her clients? money.
Mr. Tobe, a former heavy metal headbanger turned industrial engineer turned renewable energy guru, recently ran a daylong workshop for us. (Nine of us volunteers are working on the straw bale house.)
The majority of Solar Energy International?s work involves training people to design and install photovoltaic systems (known as PV) and training others how to do it. That?s where society?s focus and the money is these days, he said.
But using solar panels to make electricity is actually the last, and least important, part of making a home less dependent on fossil fuels, he said.
?You can?t go to a standard residential home and slap PV on it and think you have solved our energy problems,? Mr. Tobe said. ?We can?t make enough PV modules on planet earth to solve our energy issues if we don?t address how we use energy first.?
Heating and cooling consumes almost half the energy in a typical American home, so designing a building that naturally stays thermally comfortable is the best way to reduce energy consumption.
For Mr. Tobe, that means making sure the house is superinsulated and takes advantage of passive solar design.
Passive solar design resurrects some basic building design principles that were common throughout the world before fossil fuels made mechanically heating and cooling a home relatively easy and cheap. The idea is to use the sun?s heat to warm a building during the day and to then trap the heat inside for the night.
In the Northern Hemisphere, buildings should be oriented so their longest wall faces directly south with plenty of windows to let in the sun. The north wall should have very few windows, since it never receives direct sunlight and windows are poor insulators.
Modern window technology allows for fine-tuned calibration of a home?s glazing. Windows are rated for the insulation (U value) and how much light they let through (E value). Generally, the south wall should be glazed with windows that let in a lot of light, while the other walls should be glazed with windows that have better insulation.
The next component of passive solar design is thermal mass. Ever notice how a rock left out in the sun all day stays warm at night? That?s thermal mass in action. The rock absorbs the suns energy and releases it slowly.
In a house, heavy, thick materials like adobe, stone, brick or concrete that contain a lot of thermal mass should be placed inside the living space in the path of the direct sunlight coming in through the south windows. In our straw bale house, the six-inch-thick adobe floor and one-inch-thick earthen plaster over the straw bale walls will act as the main thermal mass.
During the day, they absorb heat, keeping the living space a little cooler. When the sun goes down and the temperature outside drops, these thermal masses radiate their heat back into the living space. As a result, the ambient temperature in the house stays relatively constant as the outside temperature rises and falls.
In the summer, keeping cool is the priority. Since the sun arcs higher in the sky, strategically placed eaves and window shadings prevent direct sunlight from passing through the windows.
The leaves of trees and shrubs planted around the house can also block out direct sun in the summer. After their leaves fall, they let rays from the winter sun pass through.
At the beginning of our build project, Mr. Tobe lent us a simple low-tech device called a Solar Pathfinder. It?s designed to figure out where to place solar panels for maximum effect, but we used it to site the house on the property for optimal passive solar performance.
The pathfinder is essentially a reflective plexiglass dome and a stack of circular black pieces of paper called sun path diagrams. The diagrams are covered with a series of white arcs delineating the path of the sun at different times of year for different latitudes.
We picked the diagram for Moab?s 38-degree northern latitude and put it under the plexiglass dome, making sure it was level and facing true south. Standing on the north side of the dome and looking down into it, we could see the reflection of the trees, red rock cliffs and neighboring buildings that obscured the sky. Using a white grease pencil, we traced the outline of those obstructions onto the diagram sitting just beneath the dome.
When we removed the dome, the pencil mark cut through the various arcs on the diagram representing the path of the sun in different months of the year. Within the area demarcating clear sky, we could see what percentage of the day?s direct sunlight would strike the house each month.
We repeated this process at several locations around the property and found the spot where the house would get the most direct winter sunlight possible and put the house there.
According to Mr. Tobe, beyond using passive solar to cut your heating and cooling bills, the other important way to reduce fossil fuel consumption is to get serious about energy efficiency.
?Efficiency is the first place to start, always,? he said. ?And if you are thinking about off-grid, you better home in on this, or you?re not gonna be able to afford going off grid.?
Mr. Tobe recommends replacing old incandescent light bulbs with compact fluorescents and upgrading to more energy-efficient appliances. In fact, when designing off-the-grid photovoltaic systems for clients, Mr. Tobe said, he will sometimes spend part of the client?s budget on a new, more energy-efficient refrigerator.
In the end, he said, the client will need fewer solar panels because the new refrigerator requires so much less power to run. The money spent on the new fridge is less than the extra capacity would have cost.
He said he also encourages homeowners to turn down the thermostat on the hot water heater by 10 degrees and wrap the device and all hot water pipes in the house in insulation.
The other major power suck, according to Mr. Tobe, are phantom loads. These are the myriad of electronic devices that consume small amounts of power even when they are off. The main culprits are home entertainment equipment like television sets and stereos and on any device that has a power converter, that little box on the end of its power cord where you plug it into the wall, like cellphone and laptop chargers.
For example, Mr Tobe said, an average DVD player uses about 20 watt hours of power to play a two-hour movie. But the other 22 hours of the day, when it is doing nothing, it still burns through 44 watt hours of power, more than twice what it took to actually do its job.
The cheap and easy fix, Mr. Tobe said, is to buy surge protectors, plug your electronics into them, and switch them off when not in use.
After passive solar design and super-insulation and making a home energy-efficient, ?it?s still not time for solar electric,? he said.
The next most cost-effective way to reduce fossil fuels is installing either solar hot water, solar air systems or both.
Solar hot water systems pump water through a tightly wound series of black pipes installed in a glass box on the roof facing south. The sun heats up the water in the tubes and then the heated water is stored in an insulated tank that feeds the shower, sinks, etc. Often a gas- or electric-powered boiler is necessary to add a boost of heat to the tank when the sun?s energy is not quite enough.
Similarly, solar hot air systems use the sun to heat up air in a box mounted on the outside of the house and then blow it inside. When a thermostat kicks the system on, fans suck cool air out of the house through a metal heat collector that can be anything from a stack of beer cans to intricately baffled duct work.
The air heats up in the metal collector and shoots out of vents into the house. Here?s a unit recommended by Mr. Tobe.
Using photovoltaic cells to heat water or air is a bad idea, Mr. Tobe said. Electricity is an inefficient way to create heat. The sun?s energy should be harnessed directly as heat when that is the end goal, not converted from light to electricity and then to heat.
After considering all these other ways to cut fossil fuel use, then it?s time to think about photovoltaic solar panels, Mr. Tobe said. Although the price has dropped steadily in recent years, they?re not cheap. While emphasizing that the needs of every household are different, he used PVWatts, a Web site run by the Department of Energy?s National Renewable Energy Laboratory, to show us how to estimate the cost of the photovoltaic needs for a typical energy-efficient home near Moab whose owner wanted to generate all the electrical power it used.
The result was a three-kilowatt photovoltaic array tied into the grid with a DC-to-AC inverter that would cost roughly $15,000 to buy and have installed. Grid-tied photovoltaic costs $5 to $9 per watt, Mr Tobe said. Compared with the price of electricity in Utah these days, the system has about a 50-year payback on the financial investment, excluding any rebates or tax incentives.
That seems like a pretty high premium to pay, but Mr. Tobe argues that the reason to consider solar power in the first place is that the environmental consequences of burning cheap coal are not factored into our energy bills, and the financial bottom line should not be the motivation for going solar.
Many of his potential clients considering solar panels have disposable income, he said, and his job is to convince them it was a more important investment in their children?s future than, say, the new fishing boat they?ve been eyeing.
What is more, the 50-year payback for solar panels is based on the assumption that the price of electricity stays low. In Utah, it averages 7 cents per kilowatt-hour and in New York State, about double that. But fossil fuels are nonrenewable.
Environmental advocates warn that just as the price of oil will creep up as the world burns through what it has in coming years, coal and natural gas will gradually become scarcer. Solar power, on the other hand, will always be free.
Of course, for budget-conscious builders like Emily, none of this matters if there is no capital to invest in solar in the first place. That?s why Mr. Tobe dissuaded her from investing in photovoltaic electricity for the Community Rebuilds homes.
The only reason to consider solar panels before undertaking the other energy-efficiency measures is if the government or utility companies are offering great rebates that might not be around forever, Mr. Tobe said. He directed us to the database of state incentives for renewables and efficiency, a Web site maintained by the North Carolina Solar Center.
My wife and I are planning to build a home on land that her family owns outside Woodstock, N.Y. I checked out the government incentives that would be available to us.
First off, any incentives only apply to renewable energy systems plugged into the electrical grid. Going off the grid may sound more hard-core and resilient, but it costs significantly more to install, and you get no support from the government, Mr. Tobe said.
The federal government provides a 30 percent tax credit for solar panels, solar hot water systems, wind turbines and a few other clean energy technologies. In New York State, we can get a 25 percent tax credit worth up to $5,000 for solar panels, solar hot water or solar air heating systems..
On top of that, we would be eligible for $1.50 in cash back per watt of photovoltaic capacity installed, up to 40 percent of the cost of the system after the tax rebate.
I don?t know what my electricity needs will be. But if I use Mr. Tobe?s typical three-kilowatt photovoltaic system as a baseline, according to Solar-estimate.org, I would pay around $18,000 for it to be installed in New York. ?But I would get back around $12,000 from state and local incentives.
Around $6,000 for decades of free, clean power is starting to sound more appealing.
However enticing these incentives seem, we will revisit the state of our home construction budget after we?ve spent our resources on the less sexy stuff that Mr. Tobe suggests.
Source: http://green.blogs.nytimes.com/2012/11/08/first-things-first-an-efficient-abode/?partner=rss&emc=rss
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