Who says that a home with cutting-edge energy efficiency has to look like an ultra-modern pod? This recently completed Wisconsin home packs so much energy tech that it makes money by selling electricity back to the grid, and it still keeps a low neighborhood profile.

Neumann Developments, the creators of the home, state the following as the goal of the project:

“Constructing an economically viable mainstream home that will produce more energy than it consumes – allowing for a dramatic reduction in greenhouse emissions and dependency on foreign oil.”

Tracking Solar Array (photo: Neumann Developments)

Two solar arrays are the heart of the property’s electricity generation. A Wattsun solar tracking array in the back yard provides 4,600 kWh of electricity annually, which is dedicated to charging an electric vehicle. Another rooftop photovoltaic setup provides 14,700 kWh yearly, which is much more than the home requires. Surplus power is sold back to the municipal grid for a substantial profit – in July, the home made $408.16 from the local energy utility.

Further energy efficiency comes from the geothermal heating/cooling system in the basement. Glycol fluid circulates through tubing buried below the foundation where the temperature is a year-round 54 degrees. The heat-exchange system provides all necessary summertime cooling, and eases heat production in the winter.

Geothermal Heat Exchange Unit (photo: Neumann Developments)

Energy Star appliances and top-notch insulation round out the home’s energy efficiency. And although the specialized solar and geothermal gear did add a substantial amount to construction expenses, the cost of the upgrades was cut in half by rebates and tax credits.

For more information, visit the Neumann Developments website.

(via Dvice)

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“Low-E” Windows Maximize Buildings’ Energy Efficiency (photo: EWC)

Low-E stands for low emissivity, and these windows are constructed to minimize heat transfer through the glass. Since windows are essentially huge holes in the walls of a building, choosing a low-E window design that’s appropriate for local climate and architecture can greatly increase a structure’s thermal efficiency, while reducing energy use and utility costs.
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Interior Of A Tankless Water Heater

Tankless water heater have been used in Europe and Asia for 50 years, and they are gaining popularity in the US. Right now they represent about 8% of new sales in the US. Tankless heaters, also called on-demand, flash or instant water heaters, qualify for a $300 federal tax credit.

How efficient are tankless water heaters?

Tankless water heater are about 10%-20% more efficient than tank heaters, depending on circumstances. The problem with tanks is that heat leaks out of the tank, and the heater has to constantly reheat the water, 24 hours a day.

Tankless water heaters are available in propane (LP), natural gas, or electric models. They come in a variety of sizes for different applications, such as a whole-house water heater, a hot water source for a remote bathroom or hot tub, or as a boiler to provide hot water for a home heating system. They can also be used as a booster for dishwashers, washing machines, and a solar or wood-fired domestic hot water system.

A Woman Using A Point-Of-Use Water Heater

Some statistics: Water heating accounts for 20%-25% of an average household’s annual energy use. The American Council for an Energy-Efficient Economy determined that total cost for a tankless water heaters is less than for standard water heaters over a 13-year period. The U.S. Department of Energy site states that you can save up to 30% of the energy you currently use with a tank heater. But the American Council for an Energy-Efficient Economy says to expect only a 10%-15% reduction in water heating energy used.

Gas-powered tankless water heaters are the most efficient, but are the most difficult to install and require venting.

Electric tankless water heaters are somewhat more efficient than tank electric heaters (about 8% more efficient), but are generally less efficient than gas-heated tank water heaters. Since electric tankless heaters are less powerful, their flow rates are generally limited to 1-3 GPM. Point-of-use electric heaters (see the WaiWela mini heaters below) are great for a remote faucet or bathroom where usage is minimal and the flow rate is small.

However, when comparing water heaters, a number of factors have to be weighed: the cost of installation, how hot you like your water, the number of people in your household, and the cost of gas and electricity in your area.

Let’s quickly review the advantages and disadvantages of tankless water heaters:

Advantages:

• Uses less energy (eliminates heat loss in tanks and through pipes)
• Continuous hot water (hot water doesn’t run out)
• Long life-span (20 years versus 13 for a tank heater)
• Compact size

Disadvantages:

• Some tankless heaters have difficulty coping with large households
• More expensive than tank water heaters
• Owners may wait longer for hot water to arrive at a faucet (depending on installation)

With tankless water heaters, there is a short delay between the time when the water begins flowing and when the heater’s flow detector activates the heating elements or gas burner. In the case of continuous use applications (showers, baths, washing machine) this is not an issue. However, for intermittent use applications (for example when a hot water faucet is turned on and off repeatedly) this can result in periods of hot water, then some small amount of cold water as the heater activates, followed quickly by hot water again.

Installing a tankless system comes at an increased cost, particularly in retrofit applications. They tend to be particularly expensive in areas such as the US where they are not dominant, compared to the established tank design. If a storage water heater is being replaced with a tankless one, the size of the electrical wiring or gas pipeline may have to be increased to handle the load and the existing vent pipe may have to be replaced, possibly adding expense to the retrofit installation.

Here is a round-up of the best tankless water heaters:

Takagi T-K3 Tankless Water Heater

Takagi heaters were the first tankless water heaters available in North America, and they’ve been manufactured in Japan since 1946. Their current indoor model, the Takagi Flash T-K3  delivers 258 gallons per hour of hot water every hour.

It’s capable of handling water flows ranging from 0.5 – 7.0 gallons per minute, with heating capability of 11,000 to 199,000 BTU (the widest range on the market). It’s all controlled by a computer board and sensors checking for flow, temperature and demand.

The only complaints about Takagi heater we’ve seen are the same as those about tankless water heaters in general– that it takes a while for hot water to flow, and that flow rate is reduced when inlet water is cold, or when many people are using the hot water at once.

The Takagi Mobius model is capable of producing a rate of flow approaching 10 GPM, making it ideal for central water heating. You can link up to 20 Mobius units together using one main control system. Note that with most gas-supplied demand heaters, significant input BTU is required to ensure proper and safe operation

You can find Takagi heaters at Amazon and  Low Energy Systems.

Stiebel Eltron Tankless Water Heaters

The Stiebel Eltron company was established in Germany in 1924, and they’ve been selling their quality heaters in the US since 1980.

Like Takagi’s heaters, Stiebel Eltron’s gas or propane tankless water heaters are equipped with temperature sensors that continuously monitor the incoming and outgoing water temperatures, and the temperatures can be controlled to within one degree by using the digital controls provided.

Stiebel Eltron heaters are warranted for three years, and sell for about $700-$800.

Stiebel Eltron heaters are available from Low Energy Systems and Amazon.

Paloma Tankless Water Heaters

Paloma began operation in 1911 in Japan, and they are a major gas appliance company in Japan. The Paloma Group also owns the US company Rheem.

Paloma makes large capacity heaters, which can serve large households and even small businesses. They work well in homes with low-pressure, or in homes where there no electrical power or intermittent power. For example, the Paloma 28c model is said to be able to serve “the needs of a small restaurant kitchen, a school shower facility, or a large National Guard training base”.

Paloma claims to have unique safety features built into their heaters. All of Paloma’s indoor tankless water heater models are equipped with a system to monitor and correct combustion conditions that could lead to carbon monoxide production. These models are also equipped with an Overheat Limiter Film Wrap designed to detect overheating all around the heat exchanger.

Paloma heaters are available from Low Energy Systems.

WaiWela Mini Instant Water Heaters

Waiwela heaters are made by Paloma. They are compact electric heaters which actually contain a small tank. These point-of-use heaters are usually installed under a sink. They plug into a regular 120V household electric socket, and provide instant hot water, thus saving water because you don’t wait for the hot water.

There are two models available: 2.5 gallon Waiwela, and 4 gallon Waiwela. Both are 110 VAC, UL approved, and they are warrantied for six years.

They are available from Low Energy Systems.

Solar Water Heating and Tankless Heaters

What would be the most efficient way of heating water? Using direct solar water heating, in combination with another renewable source such as wood and biomass (cleanly burnt), and biogas. Biogas can be used in a LP gas water heater, but it is not commonly available in the US.

A solar water heater can reduce your hot water heating bill by 60 to 95 percent, potentially saving hundreds of dollars a year. However, upfront and installation costs can be high, anywhere from $1,500 to $5,000, although there are federal tax credits available.

A tankless heater will also work as a backup, as long as it is designed to accept hot-water input (not all of them are).

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Note: This post has been expanded and updated for 2009!

Tankless water heaters only heat water when it is needed. About 8% to 30% of the energy consumed by a standard water heater goes to keeping the water hot while it’s not being used. New tankless systems heat the water instantly when you turn on the faucet, rather than keeping a tank full of hot water 24/7 whether you’re using it or not. Tankless heaters run on either electricity or gas, just like regular heaters. They start out at about $300 for electric and $600 for gas.

There are two main brands of whole-house electric tankless water heaters: Stiebel Eltron and Powerstar. They come in various models, which are rated on the “gallons per minute” that they deliver.

The online store Low Energy Systems has a good selection of tankless water heaters, both electric and gas-powered. You can also find tankless water heaters reviewed on Amazon–this is one of the few places you’ll find reviews from owners themselves.

See more information about water heaters and electrical savings at Ask Mr. Electricity

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Basically, sunlight strikes the wall through a window, and the Trombe Wall heats up, causing warm air to flow into a room.

Trombe walls are located on the south side of houses. Clear glass is situated three to six inches away from a mass wall (one made out of concrete, rammed earth or dense masonry). See our post on The Solar House: Free Heating for more information.

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Using stone to capture heat from the sun is metaefficient.

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Available from Amazon for $19.77

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These soapstone stoves are made by the Finish company Tulikivi. They use radiant heat to warm up your house, which is a highly desirable type of heat because it’s even and non-drying. Radiant heat passes through the air in a room, and warms all of the solid surfaces in the room that it “shines” upon. Tulikivi uses soapstone to build their radiant stoves because it holds heat very well, and releases it gradually. The stoves are also very effective at burning wood. Because the fire burns so hot, the wood is totally vaporized.

There are no ash, creosote, smoke, or charcoal byproducts left behind, only mineral content from the wood. The fumes emitted by the Tulikivi fireplaces are below the requirements of the German DIN 18891 norm (also Washington state and Colorado state), but the efficiency level is higher than stipulated. The nitrogen content of wood is approx. 0.05%. The smoke gases therefore only contain tiny quantities of nitrogen oxide. The sulfur content of wood is also minimal.

In terms of price, you’re looking at a range of $4000 to $15000. Distributors can be found on the Tulikivi web site.

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