Homes That Use Thermal Inertia to Maintain Comfortable Temperatures

[one...two...tree 2,762]

Enertia homes marry the concepts of geothermal and passive solar heating/cooling into what amounts to a highly energy efficient hybrid system. Pictured: a two-story "Equinox" model.

Dear EarthTalk: I recently saw a reference to "Enertia houses" that require little in the way of external sources for heating or cooling. Do you have any information on this housing design?

—Alan Marshfield, via e-mail

Enertia is a brand name for homes designed and sold in kits by North Carolina-based Enertia Building Systems (EBS). The idea essentially marries the concepts of geothermal and passive solar heating/cooling into what amounts to a highly energy efficient hybrid system. Architectural inventor Michael Sykes coined the term "Enertia" in the 1980s to describe the innovative homes he was designing that would store solar and geothermal energy and make use of it for most if not all heating and cooling needs.

Under such a system, solid wood walls replace siding, framing, insulation and paneling, while an air flow channel—or "envelope"—runs around the building inside the walls, creating what Sykes terms a miniature biosphere. Inside the envelope, solar heated air circulates, pumping and boosting geothermal energy from beneath the house and storing it within the wood mass of the walls, where it is doled out gradually.

By harnessing the properties of thermal inertia—the ability of materials to store heat and give it off slowly—an "Enertia" house maintains a relatively fixed and comfortable temperature throughout the warmer day (when solar heat is collected and stored) and cooler night (when the wood walls give off heat to keep things toasty as the mercury dips).

The heart of the system is a south-facing sun space within the envelope that is dominated by windows and which therefore soaks up lots of solar energy, filling the house's wood walls with thermal energy that in turn radiates into the primary living space. The entire house functions like an electric heat pump—moving warm and cool air around to accommodate the comfort needs of the occupants. It works even throughout the seasonal changes of the year—with minimal to no fossil fuels consumed or pollution generated.

In one Enertia house in North Carolina, the only power bill the owners typically pay is $35/month for electricity. They also have a back-up in-floor radiant heating system powered by natural gas for long cloudy stretches or unusually cold weather. Gas bills for heat typically total $150 for the year, meaning the owners' total annual outlay for heating, cooling and electricity is less than $600—some $1,000 less than traditional homes in the same zip code are paying, according to data from the U.S. Department of Energy.

EBS markets several different designs for its Enertia houses, but all share the basic premise of primary interior living space heated and cooled by air channeled in from a south-facing "buffer zone" envelope and from below grade. Smaller houses in the line top out at about 2,000 square feet over two floors of living space, while larger ones encompass some 4,000 square feet of living space over three floors. Depending on the model, you could spend anywhere from $66,000 to $292,000 for a complete plan and building materials kit. The rest—including the selection and cost of the land and the labor to build the house—is up to you.

CONTACTS: Enertia Building Systems, www.enertia.com.

[HAL 9000 96]

Awesome! So the cost could be cheaper than regular construction homes? Wow!

(The economic part is the part that MOST readers will focus on... not the scientific or energy part of it. I toured a home here in Chicago built from scratch that actually puts energy into the grid, and thusly earns the owner money from the power utility. How cool is that?)

[one...two...tree 2,762]

Awesome! So the cost could be cheaper than regular construction homes? Wow!

(The economic part is the part that MOST readers will focus on... not the scientific or energy part of it. I toured a home here in Chicago built from scratch that actually puts energy into the grid, and thusly earns the owner money from the power utility. How cool is that?)

I'm telling ya...this is going to be the next economic boom, but one that will surpass both the dot com and the housing booms because the ramifications are so dynamic - job creation while reducing our dependency on fossil fuels.

[NickD 203]

Maybe down south, but certainly not in Wisconsin, especially at this time of the year. Sun rises at 7:30 AM and sets at 4:30 PM and at noon, only about 30* above the horizon. Our option is to dig a hole at least 15 feet below the ground where even in subzero temperatures, the ambient still holds at 55*F requiring only a 15*F rise to stay comfortable. But sure not building homes like that, those story book homes with an extensive surface area to interior volume are very popular. During the last energy crisis, the dome home because somewhat popular, but quickly died when that crisis was over.

Yet another disaster are these argon filled windows, with the extreme temperature changes resulting in constant thermal cycling of expansion and contraction, no seal will hold indefinitely. And while you can save a couple of bucks on your heating costs, have to spend a huge fortune to replace them. So where is the gain?

Not really keeping close track on solar cell technology, but recently, it cost more in fossil fuel energy in what the are capable of producing, biggest savings will come from the tax breaks especially for corporations. But not really anything being accomplished for the environment. The nickel used in Ni-Cad batteries for hybrid cars is causing extremely expensive to clean up pollution. It's difficult to get accurate data even with ethanol based fuels, government likes to lie about the actual cost of production, but does have more advantage in increasing the revenue in the state than the overall good of the world.

It did make sense for me to install an closed combustion high efficiency furnace, the immediate advantage is that burnt gas smell left our home, and no matter how well these furnaces were vented, could not get rid of that. Plus it was burning the oxygen in our home that we also could use. To my surprise, our gas bill also dropped from $1.27 a therm to 82 cents. Still high since natural gas is a domestic product, but it's price is determined by OPEC. And we have a known 4,000 year supply of it here. And with the tax refund, it was cheaper for me to buy a high efficiency furnace than a conventional one. So not only efficiency has to be considered, but the cost of the fuel, and what the government gives back. It certainly would not be wise for me to install a $25,000 geothermal system and only get $1,500.00 of that back. Plus the maintenance of these systems is extremely expensive.

I did look into gas hot water heaters, for the supposed buck I would save each month for closed combustion units, even with the tax credit would be a loss. I did buy a Bosch on demand electric full house water heater, but haven't installed it yet. Can no longer find aluminum wire and would cost me $250.00 just for copper wire as the price is at an all time high. Waiting for it to go down a bit.

Also slowly replacing the fogged argon windows in my home, but fortunately, I only have to replace panels, not the entire window. And the only fogged up ones are the ones on the south side of my home, where that sun causes excessive thermal cycling. None of this ####### last very long. If I didn't pay off my home well in advance to the thirty year mortgage, would still by paying for the old #######, they don't even make stuff anymore that lasts as long as your mortgage.

[HAL 9000 96]

Very good post Nick.

Indeed, in northern latitudes, some adjustment of these plans would be in order.

In HS I had a teacher, I remember, with normal appliances linked to surrounding (the entire house) solar panels. These panels could swivel downwards to face at the ground when snow covered the ground. We took a field trip as a class to his place in the dead of winter and noticed how HOT the place was with this panels facing down, picking up so much light from reflected snow.

I can imagine now with improved solar panel efficiencies that if more homes hit the market with this technology, the technology would continue to create diversity in home energy options for consumers depending on market conditions, geographical location, etc.

[NickD 203]

Very good post Nick.

Indeed, in northern latitudes, some adjustment of these plans would be in order.

In HS I had a teacher, I remember, with normal appliances linked to surrounding (the entire house) solar panels. These panels could swivel downwards to face at the ground when snow covered the ground. We took a field trip as a class to his place in the dead of winter and noticed how HOT the place was with this panels facing down, picking up so much light from reflected snow.

I can imagine now with improved solar panel efficiencies that if more homes hit the market with this technology, the technology would continue to create diversity in home energy options for consumers depending on market conditions, geographical location, etc.

Another good reason I didn't install a vented gas hot water heater in my home, against our city building code to do so, can't be mounted in the basement, but would have to be mounted on the main floor, yeah, right in the middle of my dining room. Really don't know who comes up with these crazy laws, but get tired of fighting it. And when I called our building inspector a moron, he took that as a compliment.

Was some interest that was never developed in heat transmission. Since gas laws start a O* Kelvin, compressing even air generates cold outside air into nice warm air. Present refrigerant systems based on existing refrigerants lose all that capacity when the temperature approaches freezing. Amorphous simple to print solar cells can also be developed. But some of these projects are way too risky for private firms to develop that would be tantamount to developing nuclear fission in WW II. If our government takes an interest in these concepts, we stand a chance to make some drastic changes. They should also have the power to change building code laws to our benefit rather than our destruction.

[HAL 9000 96]

Very good post Nick.

Indeed, in northern latitudes, some adjustment of these plans would be in order.

In HS I had a teacher, I remember, with normal appliances linked to surrounding (the entire house) solar panels. These panels could swivel downwards to face at the ground when snow covered the ground. We took a field trip as a class to his place in the dead of winter and noticed how HOT the place was with this panels facing down, picking up so much light from reflected snow.

I can imagine now with improved solar panel efficiencies that if more homes hit the market with this technology, the technology would continue to create diversity in home energy options for consumers depending on market conditions, geographical location, etc.

Another good reason I didn't install a vented gas hot water heater in my home, against our city building code to do so, can't be mounted in the basement, but would have to be mounted on the main floor, yeah, right in the middle of my dining room. Really don't know who comes up with these crazy laws, but get tired of fighting it. And when I called our building inspector a moron, he took that as a compliment.

Was some interest that was never developed in heat transmission. Since gas laws start a O* Kelvin, compressing even air generates cold outside air into nice warm air. Present refrigerant systems based on existing refrigerants lose all that capacity when the temperature approaches freezing. Amorphous simple to print solar cells can also be developed. But some of these projects are way too risky for private firms to develop that would be tantamount to developing nuclear fission in WW II. If our government takes an interest in these concepts, we stand a chance to make some drastic changes. They should also have the power to change building code laws to our benefit rather than our destruction.

Sounds like your building inspector is on VJ.

Now I know you're in Wisconsin and all... but come one... 0 K????

I seriously think that the legislation will calm down and start making more logical sense once the naysayers learn a thing or two about rational science.