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May 19, 2006



I think solar thermal power is often underestimated/overlooked. Solar thermal is very cheap and could potentially power your washing machine, dish washer and dryer (besides from making warm water for the shower). These three household appliances take up a substantial part of a family's electricity consumption.

To put PVs on the roof producing electricity, only to produce heat in the above-mentioned appliances is a tremendous waste of both energy and money.

Dishwasher: 55°C (131°F)
Washing machine: 60°C (140°F)
Dryer: 60°C (140°F)

None of the temperatures above are higher than hot water produced by solar thermal. The main (only) obstacle is that hot water versions of these appliances are not available on the market, but developing them would be extremely easy!

Thermal storage is cheap, easy and efficient. A 150 gallon drum can hold the equivalent of 20 kWh with a temperature difference of 54°F (30°C) between min and max temperature. No problem at all in holding the energy from sundown to morning showers.

Greater emphasis on solar thermal in sunny regions can potentially drive the cost of ZEH further down.



Can you provide a link to the article?


Lot's of "ifs" and assumptions in that small snippet. Basically, we haven't a clue. I'd be stunned if ZEHs came anywhere near the mainstream market in 2012.


Actually, there's been prototype ZEH homes built around the country in the last 5 years but most builders have not yet incorporated the ZEH techniques learned in their mainstream home designs yet. Most of the building method changes do not depend on PV and do not cost any more, or only marginally more (for better appliances, etc.) than a "normal" house. PV, while very important, only accounts for ~35% of the efficiency gains. That means you can realise 2/3rds of the gains just from smarter building methods and efficient appliances. PV can be added as the last step, meaning you can wait for the price to come down. The real issue at this stage is educating new home buyers. If you are planning to build (or buy) a new home in the next 10 years, then look for a builder that will apply the ZEH techniques that have been learned. Look for link "Affordable Housing: Toward Zero Energy", which links document "Pettit-Affordable_Housing_ Toward_Zero_Energy.pdf" at Building Science Corporation Presentations for lots of good information.

Roderick Williams

The European PassivHaus movement has produced more than 5000 houses which have very low energy usage. See http://www.passivehouse.com/ for the details of design techniques. Their overall objective is to drive down the energy requiements of residential housing stock. So they focus on making the energy requirements of buildings (ie space heating, domestic hot water and appliances) so low they can be satisfied from renewables; and to ensure broad adoption the construction costs of low energy buildings must be competitive, ie no premium for green buildings. They do this by focusing on the building fabric, eg passive solar gain from orientation, insulation, high efficiency windows and removing other things eg central heating distribution system, reducing/eliminating heating and cooling equipment.

Regarding hot water, solar thermal is one way but is relatively expensive and quite prone to failure with the roof mounted absorbers, plumbing and pumps etc. Another, sometimes complementary, approach is to use heat pump on the exhaust air from the whole house ventilation system. ie the stale air that is being pumped out of the house has the high grade heat sucked out of it in the heat exchange to warm the incoming air and then is further cooled to heat the domestic hot water. See http://www.ise.fraunhofer.de/english/fields/field1/mb3/heating&ventilation_tech/publications/pdf/manuscript-iea-hpc-2005-buehring.pdf
There are already washing machines and dishwashers that can use hot water instead of heating it themselves. Miele products have done this for at least the last six years.


I used to think that photovoltaics would get us there, now I think that efficient construction/appliances are a better way.

If you visit "The Cost of Energy" blog you'll see an entry that details the costs associated with installing a PV system. There seems to be a large fixed cost of about $3-4/watt, consisting of the inverters, metering, labor, etc. So even if the cost of the PVs ever dropped to $1-2/watt you'd still be looking at substantial expense for the typical home load.

What I'd like to see is an analysis of what the home energy load would be if we adopted the most efficient cost-effective building practices available - superinsulated walls/ceilings, superwindows, low-energy appliances and lighting, etc. Also, how would we handle dehumidification in the parts of the country (like mine) that require it.


I like the idea of newer Zero Energy Homes, but I'm especially interested in ways to retrofit old homes to make them more energy efficient. I like living in the city and I have neither the means nor the desire to demolish my house and build a ZEH (which probably wouldn't work on my tiny lot anyway). However, I do have the desire to put a geothermal heating/cooling system in my tiny yard, and PV solar panels on my roof. Add in good insulation to reduce the necessary load and a host of simply conservation measures (turning off/unplugging devices we aren't using, replacing incadescents with CFLs, opening windows instead of running the AC) and that would hopefully make us a "zero energy home" in a 100 year old house in the ghetto. And when Plug-in hybrids become availible, it'll make us completely fossil-fuel free.


And when Plug-in hybrids become availible, it'll make us completely fossil-fuel free.

Well, yeah. Assuming a massive influx of renewable and nuke-power to alleviate the added pressure on the electrical grid, which still chugs along on fossil fuels.

But that doomer-style bon mot aside, I believe that the major issue with ZEH implementation into the American housing market is consumer attitude. Washington state has the advantage of a primarily "greenie" consciousness, which has substantiated a number of contracting firms and individuals who deal mainly in renewable home-building. It's that ugly economic foundation coming into light once again as both a cure and symptom of the PO problem: when you build it, and people can wrap their heads around it, it'll gain a social foothold.

Until that point, it's primarily niche. Rising energy costs will be a huge boon to the ZEH market, as it's already proving to be with the ethanol, solar and wind project slate.

But I agree with obscura that the mitigation scenario in the article is pretty unsubstantiated. If anything launches the technology into the mainstream, it'll be suffering bank accounts rather than their advantages over traditional homes and appliances. We only want what's best for the planet when we can get it at wholesale prices.

And when Plug-in hybrids become availible, it'll make us completely fossil-fuel free.
Well, yeah. Assuming a massive influx of renewable and nuke-power to alleviate the added pressure on the electrical grid, which still chugs along on fossil fuels.
Wrong.  At 200 Wh/mile, a Prius+ needs less fossil fuel (of any type) to run on electricity than to run on gasoline.  This is because the stationary generators are more efficient.

The PHEV is the only type of vehicle which can improve its emissions performance (including carbon) after it is built.


Being that your brain has proven itself to be about six thousand times more efficient than mine, EP, I'll defer to those figures happily. ;)

But without a shrewd application of solar array-powered recharging stations built into garages for these vehicles, I'd have to stand by the argument that "fossil-fuel free" is a bit of a misconception.

Though anything that uses LESS is a critical piece of the mitigation puzzle.



Thanks for that info on passivehouse.com. Reading their methodology, they've determined the point of diminishing returns for energy efficiency in home construction is 10 watts/m2. They state several times that trying to achieve a true zero-energy goal is wasted effort, that 10 watts/m2 optimizes cost and benefits. If you accept that as an energy budget, it narrows your choices on building materials, insulation, HVAC systems etc.


This effort needs a high profile contest.

A completely self-sustaining home located in Antarctica.


With batteries in cars, homes,and businesses; solar, wind, and water power will have the distributed storage needed for the grid to go to 100% renewable, combustion free, nuclear free power.

Forget that old 20% saw that even the AWEA touts.

Solar cogeneration (electricity, heat, biofuel)on rooftops, southsides of buildings, small home wind power all the way up to 2000 foot diameter, 2000 foot high, 100 megawatt wind/wave power stations will more than cover the power needed for electric transportation as well as all other uses.

The portion of home, commercial, and industrial heating and cooling not provided by solar cogeneration once converted to geothermal heat pumps will reduce electric power for those needs to a fraction of the present quantity.

Zero energy homes? Not really, they will be homes that generate more power than they use. With that power sold into the grid, providing income for those who invest in solar and wind power for their own homes and businesses.

This will also provide an unending economic growth source, based upon lower energy costs and revived manufacturing.

Roderick Williams


People tend to get hung up on extremes, eg zero energy houses. Which are possible now provided the capital costs of PV cells don't put you off. But we all know small scale renewables don't have the same economies of scale as utility generation. In the UK there are already generation companies that sell electricy from land based wind generators at the same price as non renewable power companies. There is no premium for buying renewable electricity, so this is way cheaper than fitting my own PV or whatever. Using leading edge building technology means that you just use less of this renewable generated electricity. Think negawatts.

The passivehouse approach is aimed at different problem from ZEH; reducing the energy consumption of housing by 90% and making the construction costs no more expensive than the current building approach. And as the aim is to reduce the energy use of all the building stock the lessons learnt from new builds are now being applied to renovations. See the renovations track at the recent passive house conference:


Being that your brain has proven itself to be about six thousand times more efficient than mine, EP, I'll defer to those figures happily. ;)

"But without a shrewd application of solar array-powered recharging stations built into garages for these vehicles, I'd have to stand by the argument that "fossil-fuel free" is a bit of a misconception.

Though anything that uses LESS is a critical piece of the mitigation puzzle."

Depends on where you live. In the Northwest, approximately 50% of our electricity is hydro, which of course has it's own environmental problems, but carbon is not one of them. Add in a dash of solar and a teaspoon of carbon credits, or maybe Bluesky power certificates and you are essentially carbon/fossil fuel free.



While I agree that the economies of scale don't exist for small scale consumer installation of solar PV, that is precisely the goal of some states in the US. New Jersey offers a whopping $5/watt rebate on initial cost of PV installation to homeowners. There aren't any massive utility generation incentives for solar PV in this region.

There seems to be a mixed message in this blog on the direction we should be heading regarding solar PV. Some believe it will eventually be inexpensive enough to install as part of new house construction. It's not clear to me that anyone can state a reasonable threshold for whether or not a home solar PV project is cost effective, given the fact that, on average, Americans move about every 5-6 years.


ZEH - impossible when you add in the embodied energy to build it.

Building Integrated Photo Voltaic (BIPV) roofing, direct DC from roof to power points, carbon nanotube ultracapicitor energy storage devices, LED lighting, efficient building envelope design, and a decent fridge would get you closer. And then just maybe the occupants might find their new home so pleasing that they might want to learn how to use those flowing electrons in even more efficient ways - demand load goes through the floor - another boost for ZEH.

Of course, a good home cooked meal would take some sort of on site combustion.

Carl from Heliotropic

We're doing ZEH production homes now in California. It's just starting, but starting strong. Home buyers appreciate the significantly lower energy bills and we've gotten good traction with the biggest builders in the country. I think it's fair to say that ZEH homes are in the mainstream now, there's a long way to go before it's standard on every house, but eventually I think it will be quite common.


I'm the lead designer on SunTile.


I think that today, with most people shocked by their rising electrical and heating costs, there is a more receptive attitude to alternative energy technologies. How many of us wouldn't want to live in a zero energy home?

Larry Hartweg ZEDmaster@ZeroEnergyDesgn.com

I think that the discussion about Zero Energy Homes being new, or that we have to wait for some future technology break through is HILARIOUS!

Jimmy Carter subsidized solar energy homes in 1978. I built my first near-zero energy home in 1979 - described in detail on ZeroEnergyDesign.com

I've designed hundreds from Canada to Australia, and many thousands have been built worldwide. Canada is trying to change their building codes to make it ILLEGAL to build a conventional home with utility bills.

America is simply a non-learning nation with decades of irrational resistance to change. People would RATHER buy a home with high utility bills, than live in a more beautiful home (see my photos) that costs LESS per square foot to build, and has NO net energy bills on an annual basis.

American's would rather have granite counter tops and big SUV's than drive electric cars that they can plug into their PV rooftop and drive 100 miles per day for free.

We knew how to do it all long ago. The information and specific cost-effective design details are readily available. What we need is a nation capable of learning. (Today, only 62% of males graduate from high school. Very few adults know how to learn anything new.)

90% of the Zero Energy Home solution is energy conservation. Only 10% is technology like photovoltaic systems. Adding PV's to a poorly-designed conventional house is a waste of money.


If you have looked into solar energy as a method for heating your home, panels are usually the first things that come up.

There are, however, other unique methods.

The Solar Heating Aspect You Have Never Heard of Before

The power of the sun is immense. The energy in one day of sunlight is more than the world needs. The problem, of course,

is how does one harness this power. Solar panels represent the obvious solution, but they have their downside. First,

they can be expensive depending upon your energy needs. Second, they do not exactly blend in with the rest of your home.

Passive solar heating represents a panel free method of harnessing the inherent energy found in the sun for heating

purposes. If you come out from a store and open the door of your car in the summer, you understand the concept of passive

solar heating. A wide variety of material absorbs sunlight and radiates the energy back into the air in the form of heat.

Passive solar heating for a home works the same way as the process which overheats your car in the parking lot.

Andreas Gerhard

my name is andreas gerhard-i am working in a german redy house factory-we are specialists in building woodframed ecology houses with alternative energys-I got a master in woodtechnik-as i stard at the rolf barkmann gmbh i made konstruktion and technical engineering-now i am sales manager in our factory-and now my question did you now about some faktory there surching for some new ideas in this things? i like amerika and i would try to work there for a few jears(or maybe longer)It would be nice if you know about some companys wich wuold be interestet-
pleas look at our homepage

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We all need to thinkabot the energy consumption we use everyday

boom trucks

I wouldnt mind living in a home with no electric bill =)


I would like to see more energy efficient house been built nationwide. I think the customers is ready now, more and more educated also.

Boom Truck

Energy efficient homes is a great idea! We all need to do apart to conserve energy and this would be a great idea and who wants an electric bill anyway?


Zero energy homes technology is more and more advanced. We're receiving more and more request for energy efficient house designs. Zero energy construction is still far away.

Philippines property

I have read your article.It was so informative.Such a good article what you have written.Thanks for sharing your information with us.

Deirdre G

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I think it is smart that we all start trying to be more energy efficient. More vehicles and homes need to run off alternate fuels and powers.


so this future is not far away as many people expecting


Excellent article. Keep it up.

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