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Zero Energy Design Technology Summary by Larry Hartweg

The following is a quick summary of many ZED technologies that we have comprehensively integrated into our unique holistic architecture-and-design systems engineering, for more than 25 years. This short overview is intended to “wet your scientific appetite” and motivate you to invest the time required to read on, and better understand the energy-problem-solving potential of our proven ZED solutions.

It has taken us decades to accumulate this valuable ZED knowledge. We attempt to summarize it in a concise form that is easy for intelligent people to appreciate. Albert Einstein said that if we cannot explain something to a six-year-old child we really do not understand it at all. His enlightened statement is very challenging, but we will do the best we can to help you become aware of what is now a formal set of ZED principles and practices.

This quick outline does NOT explain everything you need to know to make it happen. We are merely providing a snapshot of a 50,000-foot-high view of some of the categories of expertise required to solve our nation’s current energy problems. There is a lot of physics and math behind what has become “intuitive” ZED to us in hindsight.

We also offer classes and turnkey project consulting for architects, designers, developers, executives, investors, politicians, and potential Zero Energy Home buyers. Our 25 years of practical ZED demonstrations have shown that the remaining issues in front of us are educational and political, more than technical.

Highest Priority ZED Topics First

In most American homes, the largest impact on monthly energy bills is “changing the temperature of things.” During climatic temperature extremes, the heating and air conditioning bill is by far the most important. Heating and cooling often exceed all other energy expenses. One obvious solution is “move to Hawaii and live on a beach.”

1. If you choose to live where heating and/or cooling is important, we will first show you how to eliminate heating and cooling energy bills altogether, in the coldest AND hottest American climatic zones. During summer and winter temperature maximums, the utility bills to heat and cool a conventional home can exceed the sum total of all other utility bills put together. We will explain how to totally terminate heating and cooling bills, in a well-designed Zero Energy Home almost everywhere.

2. The second most expensive temperature changer is often the poorly designed American kitchen electric refrigerator. We’ll discuss a simple solution to eliminate refrigerator energy expense, with a solar-powered, non-electric, time-proven, off-the-shelf, hundred-year-old, cost-effective technology. Does this sound interesting to you? It should be. Very few people understand it.

3. The third expensive temperature changer is domestic hot water. We’ll discuss simple reliable solutions from the 1970’s and modern times to eliminate domestic hot water energy expense, and also how to have a year-round swimming pool with 92-degree water, when snow is on the ground nearby. I had it in my own residence in 1979. Do you enjoy a lengthy hot shower massage in the winter? Would you like a warm, comfortable, zero energy pool, swim spa, or hot tub, for year round use starting TODAY? No worries! It is easy and cost effective to do right now.

4. The fourth expensive temperature changer in a modern energy-wasting American home is the clothes dryer. An inefficient tumble clothes dryer can take an hour of expensive high-current electricity or gas to remove the water from only one load of clothes, and damage them in the process. In the winter, the money paid to heat the air for drying clothes is then exhausted outside. How dumb is that?

Great grandma knew how to use solar energy to dry clothes, long before the first utility company was ever created. Still, these crazy American’s demand their lazy-boy convenience, and they don’t like to hang their laundry in full public view, and then wait hours for it to dry. Soooo, we’ll talk about a fast INDOOR solar-powered clothes dryer that does NOT need a clothesline and pins, or hours to remove water from wet clothes.

5. Electric-and-gas cooking ranges and ovens are another source of high-rate energy consumption. The solution here is very simple, and much healthier for you anyway.

After eliminating all of the expensive temperature changers in a Zero Energy Home, then efficient pumps, fans, lighting, electronics and appliances can be discussed, with an explanation of how to make many of them cost LESS than the same equipment does today, to completely eliminate the need for the business-as-usual escalating cost of electricity from your local electric company (even if you do have electric power readily available).

With the total elimination of the need for utility company energy, you can build your dream home almost anywhere you like (which may or may not interest your lifestyle desires).

If you prefer to live in a populated community, you may be the only enviable one on your block who does NOT have to pay ever-increasing utility bills. You will then have more money to invest, or to spend on other nice things.

If we can do all of this in an attractive, comfortable, easy-to-own-and-operate home, would you be interested in becoming an intelligent, trend-breaking ZED innovator?

Does it all sound “Too Good To Be True”? Do you know anyone else who can do it all in a comprehensively integrated, esthetically beautiful, cost effective package, for LESS than you are already spending per month for your home today? How about someone who has been doing it for 25 years already? Read on, and soon you will. (Friendly Florida smiles to you, our new ZED friends.)

Get More Information in Larry Hartweg's 800 page book on

Passive Solar Heating and Cooling Techniques
"Zero Energy Design"

Location-Specific Environment Requirements

All of ZED begins with a detailed understanding of the location-specific environment including: degree-day heating and cooling requirements, solar gain potential, latitude, elevation (sea level to mountains), seasonal weather / winds / cloud cover, site-specific desirable natural views, transportation requirements, available public utilities (if any), predictable trends (costs, future development, growth potential for the family / community / business), budget, funding source goals / objectives, building codes, political challenges, material supply, and any other pertinent planning details.

The difference between your seasonal heating and cooling requirement is of particular importance, since they have a major influence on the overall solution architecture.

American homes vary widely in their location-specific energy requirements, and solar energy potential. One ZED solution does not fit all. In general, the farther from the equator, the more heating requirement and the less available solar energy, but this is not always true. Climate is also impacted by altitude, mountains / valleys, prevailing winds, humidity / cloud cover, albedo (surface reflection: white, black, green, etc.), heat index, wind chill, thermal mass, large bodies of water, oceans / lakes, cool trees versus hot concrete, urban heat sources and seasons.

One quantifiable measure about location-specific design differences is the number of “Degree Days” of Heating and Cooling Requirement for a particular location.

U.S. City Heating versus Cooling Requirements

LAT = Latitude (distance from equator)

COOL = Annual Cooling Requirement In Degree Days

HEAT = Annual Heating Requirement In Degree Days

SOLAR = Annual Average Solar Radiation Potential
(Insolation - Average Total BTU/sq.ft./day)

CITY	ST	LAT	COOL	HEAT	SOLAR
San Juan	PR	18 30	4981	0	1640
Honolulu	HI	21 18	4221	0	1630
Miami	FL	25 46	4037	205	1473
Orlando	FL	28 32	3226	733	1487
Houston	TX	29 45	2889	1433	1351
Mobile	AL	30 42	2576	1683	1385
Savannah	GA	32 05	2317	1951	1365
Jackson	MS	32 20	2320	2299	1409
Dallas	TX	32 46	2754	2290	1468
Charleston	SC	32 47	2077	2146	1345
Birmingham	AL	33 30	1928	2844	1345
Atlanta	GA	33 45	1588	3094	1345
Los Angeles	CA	34 03	614	1818	1594
Albuquerque	NM	34 05	1316	4291	1828
Memphis	TN	35 09	2029	3226	1366
Amarillo	TX	35 11	1433	4181	1659
Charlotte	NC	35 14	1595	3217	1344
Tulsa	OK	36 09	1948	3679	1373
Las Vegas	NV	36 10	2945	2601	1864
Nashville	TN	36 10	1694	3695	1270
Roanoke	VA	37 17	1030	4306	1270
Wichita	KS	37 43	1672	4685	1502
San Francisco	CA	37 47	108	3042	1553
Charleston	WV	38 21	1055	4590	1123
Saint Louis	MO	38 35	1474	4748	1327
Washington	DC	38 53	940	5009	1208
Grand Junction	CO	39 05	1139	5603	1659
Kansas City	MO	39 06	1283	5357	1340
Baltimore	MD	39 18	1107	4729	1215
Reno	NV	39 30	328	6021	1761
Denver	CO	39 45	625	6016	1568
Indianapolis	IN	39 46	974	5576	1165
Springfield	IL	39 48	1116	5557	1302
Philadelphia	PA	39 57	1103	4864	1169
Pittsburgh	PA	40 27	646	5929	1069
Newark	NJ	40 44	1022	5033	1165
Salt Lake City	UT	40 46	927	5981	1603
New York City	NY	40 47	1067	4847	1099
Omaha	NE	41 15	949	6601	1321
Cleveland	OH	41 28	612	6152	1091
Des Moines	IA	41 35	927	6709	1312
Providence	RI	41 50	531	5971	1112
Detroit	MI	42 20	742	6228	1120
Boston	MA	42 21	661	5620	1105
Sioux Falls	SD	43 33	718	7837	1290
Boise	HI	43 36	713	5832	1496
Minneapolis	MN	44 59	585	8158	1170
Fargo	ND	46 52	472	9270	1203
Seattle	WA	47 37	128	5184	1053
Chicago	IL	51 50	923	6125	1215

In Miami, there is essentially no need for heat, but cooling and humidity control are very important ZED issues. In Chicago, heating is 6.6 times more important as a ZED factor than is the less significant degree-day cooling requirement. Many Chicago homes have no air conditioner.

These numbers are very important for location-specific ZED decisions. As we said: One Zero Energy Home design does NOT fit all. Miami houses SHOULD look and perform much different than Chicago houses.

It is interesting that the maximum and minimum AVERAGE annual solar gain potential for all of the above cities does not vary by a large amount (1053 to 1864 BTU/sq.ft./day) like heating and cooling degree days do (0 to 9270 heating and 108 to 4981 cooling). Many different solar energy technologies can be used to intelligently reduce or eliminate the need for an external non-renewable energy source. Conservation is our first ZED objective.

Some solar gain is available almost everywhere, but it is not the same amount every day. The less solar gain that is available, the more important energy conservation issues become. Imagine what has to be done for ZED space station system engineering. Activities have to be designed around available energy supply.

What about a Moon colony during the dark of the Moon? Our Moon does not rotate like the Earth. The Moon is sometimes in the shade of the Earth. With no atmosphere, the Moon’s location-specific temperature variations are far more severe than on Earth.

All of these problems are solvable with ZED Systems Engineering. A Zero Energy Home should comfortably accommodate all of the predictable extremes for a particular location.

No worries! We already know how it is done. We’ve been doing it successfully for many decades. We just need to apply what we learned long ago in outer space, down here on the good old Mother Earth, and make it popular, pervasive, comfortable and cost effective.

Get More Information in Larry Hartweg's 800 page book on

Passive Solar Heating and Cooling Techniques
"Zero Energy Design"

One Story, or Two

Single-story versus multiple-story is a ZED issue of taste, energy, comfort, esthetics, and economics. Two-story houses have roughly half of the footing, roof and real estate footprint, but they need a staircase, or elevator expense. Putting residential stairs in a greenhouse is one of the lower-cost alternatives we have used many times. In a tall office building, most of the floor space can be taken up with elevator shafts. This has always been a silly “diseconomy of scale,” in my opinion. Locate your company where real estate costs less, and let most of your employees telecommute!

An open interior staircase or atrium area can create thermal problems (not a problem in a solar greenhouse). Warm air rises, making the upstairs interior uncomfortably hotter than downstairs, all year long. In the winter, an open space must be heated from the top down. Forced convection fans can bring warm air down, for a price, but turbulent air can feel too cool in the winter.

An open two-story interior area will always be uncomfortable either upstairs or downstairs. An open loft area is a particular problem.

Separate temperature zones and stairway doors are often required, which can add even more expense and design complexity. Very few architects know how to design desirable convection airflow loops into the interior of a structure. It requires a lot of experience and some scientific knowledge about laminar versus turbulent airflow. We have been doing it very successfully in Zero Energy Homes for over 25 years with impressive success.

A two-story north wall can lose a lot of heat through turbulent “wind chill” during a cold windy northern night – hence the popular Salt Box design of colonial America days with a two-story south side and only one story on the north. The Salt Box shape is still useful wherever the winter heating requirement is significant (but the Salt Box shape is not required in all Zero Energy Homes).

1980’s Low Cost / sq.ft. Duplex – Low North Wind Buffer, High South Solarium
Could have a shared solar-heated indoor swimming pool or other amenities

Creative artistic architects (with little if any energy training) leave thermal comfort up to the poorly trained air conditioning contractors, who then leave the long-term energy bill consequences up to naive homebuyers, who then suffer unnecessarily for as long as they live there. To reduce escalating high energy bills, residents must lower their comfort level standards – NOT SO in a well-designed Zero Energy Home.

Extreme Cost-Effective Energy Conservation

To eliminate the need for conventional heating and air conditioning bills altogether, we must greatly reduce the need for space heating and cooling in the first place. This is an “opportunity rich” (long overdue) situation; since today’s traditional American homes are soooo very poorly designed and constructed as major energy wasters. Simple improvements can reduce heating and cooling costs by more than 60%. Judicious use of the best ZED whole-house systems engineering can eliminate heating and cooling bils in a wide variety of U.S. climatic zones.

Shape, Size, Appearance, and Orientation

As with traditional architecture, the exterior façade of a Zero Energy Home or Commercial Building can take many artistic architectural styles and esthetics, to meet the appearance goals of the prospective new homeowner, but in general, ZED tries to minimize exterior surface area to reduce unnecessary heat gain and loss year round.

The North Street Side of the above home appears to have interesting
features, but if you look closely, the living space is nearly rectangular.
The south side can have a large area of passive solar collection glass,
and active solar panels for hot water, photovoltaic electricity, etc.
Motorized window quilts can help minimize heat transfer through the glass.
Pleasant landscaping shades the east and west sides of the structure.
Outside walls and roof are insulated from the summer sun’s radiant energy
with reflective radiant barriers plus an air gap. The hip roof, with hurricane
clips offers powerful resistance to windstorms. Custom-made sturdy
removable window covers can protect glass in category 4+ hurricanes.
We would prefer a bright white roof, but this light color is a reasonable
compromise. We can work with your preferences, within your budget.

More artistic architectural cut-and-jag surface area may be attractive (to some who care nothing about energy), but it certainly costs more to build, and excess exterior surface area can also increase turbulent air flow (winter wind chill and summer heat transfer), and expose more square feet of the building to annual temperature extremes than would be necessary with more intelligent ZED surface area minimization.

The simple summer and winter energy loss calculations are based on exterior surface area square footage, times the temperature difference between the outside and inside of each wall, divided by the thermal resistance factor for the wall (R factor plus other considerations for radiant heat, etc.). Obviously, if you reduce the exterior surface area, you reduce the heating and cooling energy requirement.

Esthetics and energy are sometimes mutually exclusive, UNLESS the best of ZED is applied well, which we always try to do cost effectively.

Street Appeal

The side of the house with the main entrance is the most important for esthetic visual street appeal and resale value. It is usually best when the street is on the north or south side of the home (NOT WEST). If you want privacy for your south-facing greenhouse (sunroom, solarium, conservatory) activities, then it would be best if the street is on the north side. North side street-facing windows can have insulated window treatments, to provide privacy and minimize heat loss on cold windy winter nights.

Building orientation is important for solar community land developers AND for lot buyers who want a Zero Energy Home that is not in a ZED planned community. Luckily, so few people recognize the added value of such lots that you usually do not have to pay a premium for them yet (but soon you will, and land developers will be forced to respond to increased demand, bringing well-planned ZED lot prices back down again).

Depending on local heating and cooling requirements, the overall exterior ZED shape tends to be rectangular – longer in the east/west dimension than in the north/south. This maximizes winter solar gain, and minimizes summer west wall exposure.

Reducing Undesirable Heat Flow Summer and Winter with Super Insulation

ZED spends more time engineering energy conservation and multiple types of CONDUCTION / CONVECTION / RADIATION insulation into the basic structure than any other architecture and design process used by others (who have much less experience).

We go way beyond simple conductive R-value issues, and common problems with undesirable air infiltration. We integrate effective radiant barriers (especially in the roof and west wall), zero-energy natural convection flow loops that don’t need fans or thermostats, humidity and evaporation analysis, etc. One of our most-effective insulating techniques has a conductive R-value of essentially zero (which almost no residential architects fully comprehend).

Some of the walls in a ZED home involve the use of two thermal barriers with a thermal buffer zone between them (like a solar greenhouse, or the roof / attic / ceiling). When the buffer zone is maintained at a temperature between the exterior temperature and the interior living quarters temperature, there are two small delta T’s (temperature differentials) instead of one large one, which yields a MUCH lower heat transfer than single wall construction. Lower delta T means lower heat flow – VERY IMPORTANT ZED ENERGY CONSERVATION PRINCIPLE!

When a single wall exists between the interior and exterior temperature extremes, special care is taken to minimize heat transfer by conduction, convection AND radiation. Quality control insures that cavity space insulation is neither too long (compression bends), nor too short (gaps), and that it is NOT going to settle over time, creating future problems.

Undesirable air infiltration (air leaks) are of significant ZED concern. Vapor barriers are used on at least one side of exterior walls and ceilings. (If humidity condenses and is trapped inside convective-cavity-wall insulation, it acts like a wet sponge and loses most of its conductive R-value, since water is a good thermal transfer medium). Air leaks and humidity traps are very bad for several reasons. They are commonplace in poorly-supervised conventional home construction, but avoided by ZED quality control. I demanded this in my own homes, and you should in yours, since it is frequently overlooked by many.

Post-construction air pressure tests identify systemic construction flaws that can be corrected in each individual unit BEFORE it is occupied, and in the houses built by the same workers in the future. This improves overall quality assurance now, and especially in the future. The goal is to correct construction errors before the sale is complete, and to avoid making similar errors in the future of an expanding Zero Energy Home construction business. We want to design future construction systems that minimize the opportunity to make energy-losing construction mistakes.

To further minimize air infiltration, perforations in single exterior walls (for plumbing, electrical wiring, etc.) are NOT allowed, or they are minimized and very carefully sealed before they are covered up. This sometimes requires clever placement of interior electrical wiring, fiber optics, and plumbing to avoid running any lines in the thermally sensitive exterior walls. Plumbing and wiring (switches and outlets) can be run in walls that are perpendicular to the exterior walls. Floor outlets can replace exterior wall electrical outlets, etc. Sometimes, pre-engineered Structural Insulated Panels (SIPs) are used to accelerate construction time, minimize framing labor, improve structural strength in windstorms, and to provide better-sealed exterior walls. We hope that ZED principles will be better integrated with SIPs in the future. One challenging issue is their lack of an effective radiant barrier + air gap.

Perforations in the top plate of interior walls are carefully sealed to minimize attic air infiltration into, and out of, the living quarters. Care is taken when ceiling elevation changes (such as 8-foot to 10-foot ceilings) to insulate the vertical wall section as well as the ceiling is insulated for conduction, convection and radiation. When there is no attic (as in vaulted cathedral ceilings), radiant barriers, air gaps, ventilation paths and super insulation are all designed in from the beginning, and verified with quality control before they are covered up with interior wall board.

Air ducts (if any) and ventilation convection-flow air paths are designed into interior spaces, so any air leaks that may occur during construction, or over time, are not lost to the outside.

Hot water tanks and hot water lines are carefully placed and insulated to minimize heat loss in the winter, and to avoid heating the house interior in the summer. The distance between hot water source(s) and the end points of hot water usage are minimized with three dimensional plumbing cluster design (shortest run and minimum plumbing possible – single or multiple stories).

Radiant barriers with adjacent air gaps are added (preferably on the outside of vertical walls), and on the bottom side of roof decks, where they will not gather dust and become less effective over time. Minimizing construction costs for this effort are of special interest.

Have you ever noticed what happens just outside a northern climate home when there is a light dusting of snow on the ground? The snow melts away from the house. This is because the concrete of your foundation is very thermally conductive, and so is the earth. You are paying energy to heat your house, which is lost all winter long to melting snow and warming the outside earth. To reduce this negative effect, we place at least one inch (more in some climates) of EXTRUDED waterproof foam insulation (NOT Styrofoam bead board which freezes and breaks up) on the outside of your home’s foundation thermal mass. The colder the climate in the winter, the more important this becomes.

When concrete walls are used, they should be insulated on the OUTSIDE, so they participate in the temperature stabilization thermal mass of the interior living quarters. Sometimes, insulated foam concrete forms are used to minimize labor and provide superior wall insulation, with no air leaks and minimum material and construction time. Concrete wall porosity, condensation, mold, mildew and other allergen prevention topics are issues that must be resolved, particularly when part of the home is earth buffered (set into a hillside) – discussed later.

Concrete roofs with earth buffering or landscaping on TOP of the home are also possibilities. A variety of options exist for greenery on any home’s roof. Integrated, living, “green roofs” are an ancient concept from man’s desire to stay cool in the summer, and to live in harmony with nature. They are “growing in popularity” as an essential part of sustainable “green architecture.”

The Hanging Gardens of Babylon with lush roof gardens are among the earliest green roof records, built around 3,000 years ago. Earth-sheltered huts dating from the Viking era were found in Ireland and Scotland. Around 1000 A.D., sod-covered roofs were used in Iceland and Scandinavia. Early 19th century settlers in Canada and the northern United States used living grass roofs. Frank Lloyd Wright promoted the benefits of roof gardens. In the 1930’s there were the Rockefeller Roof Gardens in New York, and the Derry and Tom's Garden in London (the modern Kensington Roof Gardens). Green roofs are now found around the world. They are a great match for ZED objectives of low energy consumption and harmony with nature.

Greenery on the roof provides natural evaporative cooling that is superior to simple shade. Selecting plants is a critical issue, with much to be learned from green roof project history. The elevated view while maintaining and enjoying a roof garden is often one of the best in (or on) your home. A solarium or south-glass conservatory can be on the south side of your house, or on top of a flat roof.

In hot climates, light exterior colors on Zero Energy Homes are preferred. Bright white pitched metal “galvalum” or white tile roofs are desirable (if a green roof is not used), to block the high summer sun. Even light-colored roofs are better than dark roofs - White roofs are not always required.

Radiant barriers on the bottom side of roof decking provide similar lowering of attic temperatures in the summer. Some type of green roof, or attic radiant shield, is mandatory in climates with a summer cooling requirement. At only a few cents per square foot, radiant barrier roofs also provide a small benefit in the winter, by reflecting heat loss back down toward warm ceilings.

Landscaping, trellises or shade screen are designed in to minimize western-wall-and-window solar radiation exposure. Window materials and interior window insulation are part of ZED holistic com