SMALL VS BIG: Doing the math to figure out the energy efficiency of different-sized homes

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Large Southern California homeRecently, I overheard two people arguing about the relative efficiency of an old, small, inefficient, cold climate home in the Northeast versus a newly constructed large Southern California home using energy efficient methods. At first I guessed that because of the house size, the NE home would be hard to beat out, but then I realized that I was unsure. So I decided to do some back of the envelope math.

To frame the context with some kind of starting point variables, I used a home from La Costa Life, an upscale development in California, vs a dilapidated home in the Northeast. Basically, I’m going to use the best efficiency in the new home and the worst possible in the small NE home in any instance that is unknown (which is basically all of them). I’ll be making plenty of assumptions along the way, so hold on to your seats, and know that the conclusions would likely shift with different assumptions. Based on my reading, I’ll assume that a small Northeastern home uses 50-60 per cent of its energy on heating, but has roughly half the square footage.

The best data I found was from the U.S. Energy Information Administration. Every four years they conduct the Residential Energy Consumption Survey (RECS) and compile the results into reports. There are a lot of categories, but not really enough to accurately compare the Large SoCo home and the Small Northeast home. The main issue is that it doesn’t break the energy usage into categories according to just how many homes use certain types of heating (natural gas, electric, etc). Energy usage is lumped into averages based on things like year of construction, income level, and square footage.

Although they didn’t directly answer the questions I had, they did get closer than anything else I found, and gave a few interesting generalizations:

  • The higher your income, the more energy you tend to use. People in the highest income bracket used twice as much as energy as the lowest one.
  • Houses built between 2000-2009 used more energy than any other decade on record. While they are more energy efficient, the new houses are generally larger with higher ceilings. As an example, homes built in the 2000’s are almost 70 per cent larger than those built in the 1970s with 52 per ent of the ceilings being higher than the traditional height of eight feet.
  • The larger a home is, the more likely it will have energy efficiency features.  So, it is more efficient per square foot, but uses a larger amount of energy overall. Turn that McMansion into an apartment complex and you’ll instantly be eco-friendly! Or much closer, anyways.
  • The more people in the home, the less energy per person is used.

The breakdown on household energy use

When I crunched the numbers I found that, even after accounting for the fact that people with more income use more energy, there was a sizeable difference in energy consumption between the two homes… and not the kind of difference you might assume:

Usage Per Household in Mil. of BTU

  • Large Southern California Home: 85
  • Small New England Home: 99.3
  • Same small New England home in Southern California: 68.4

Those reduced heating costs do quite a bit! The smaller house comparison from the Northeeast to Southern California used nearly 30 per cent less energy. Even the large SoCo house was still about 15 per cent more efficient than the small NE home to maintain. Note that I say to maintain, because if we’re including initial energy inputs for the houses, then the small house is going to have a bit of a buffer zone in energy usage.

However, all things being equal, it looks like the West Coast is the place to be to use less energy. To support that point, in 2005, the West Coast had the lowest emissions per capita because of its higher usage of clean energy sources. Looks like they have a win-win there.

So, if you’re going to live in a large home, move to California. It’s the best place in the U.S. to do it as ecologically as possible. Just keep in mind that a large house is still not necessarily the greenest choice: the LEED for Homes rating system, for instance, makes any three bedroom house over 1900 square feet increasingly more difficult to qualify for its certification.

Of course there are dozens of assumptions here. Passive solar homes, geothermal heating, and even insulated curtains would complicate the calculations. But it does give me food for thought, and my original assumptions were wrong in this case. It definitely underscores the importance of insulating well, as that rustic cabin in the snow with single pane windows might be using more energy than an Orange County luxury home!


Warren Howe is a freelance writer living in San Diego. He lives in a small house that he shares with roommates, so he gets the best of both worlds ecowise.

Republished with permission from sustainablog ( Image credit: La Costa Life. Used with permission.

August 18, 2012 |

THE CHIP HOUSE: A net-zero compact hyper-insulated prototype

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Try This Solar Decathlon Net-Zero Energy Home on for Size: the Chip House (via

For those sustainability designers and innovators wanting a net-zero product, take a look at the Chip House, a 2011 entry in the DoE’s Solar Decathlon, placing sixth. The CHIP House – which stands for “Compact Hyper-Insulated Prototype” – was started with the goal of creating a net-zero energy…

August 13, 2012 |

HOME PERFORMANCE DIAGNOSTICS: What to look for when inspecting a home

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Corbett Lunsford

Blower door testing

The four aspects of home performance

At the Building Performance Workshop, we always strive to distill complex concepts and practices to their most essential and basic elements. This does two things:

  • It enables the professional to keep a cool, clear head when faced with complicated challenges in the field
  • It helps frame the way you talk to your clients about your work (clients, professional or otherwise, tend to tune out when we get technical)

In the interest of keeping it simple, therefore, we’ve concentrated on defining home performance in four aspects:

  • Heat flow (which everyone thinks they understand, but few truly do)
  • Air flow and pressure (two sides of the same coin, which few people even
    attempt to grasp)
  • Moisture (it kills the house more effectively than almost anything)
  • Air quality and safety (your work’s most important results are healthy, happy clients)

This list is in increasing order of importance. You’ll notice that the two aspects which have to do with energy efficiency are at the top, which is the less important end of the list. This is why your title is better defined as a home performance expert than an energy efficiency expert. People will continue to call it “energy auditing” when you’re testing, but if you can keep reminding them that you’re doing so much more than saving energy, you make yourself more valuable.

If you ever find yourself searching for a simple definition for what a “high performance home” is, look no further than this:

In a high performance home, heat flow, air flow and pressure, moisture, and air quality are all perfectly controlled.

Control is the goal, just like with your car or your body. We all know how uncomfortable uncontrolled events in our cars or our bodies can be; a home is no different.

Inspection first

Before you whip out your tools and get to it, always remember that your most valuable tool is your own experience and your senses. There are three stages to any really valuable activity in this field:

  • Inspection
  • Diagnostics
  • Recommendations for improvement

What you see, hear, smell, and feel in the home (and taste, I suppose, but please don’t let your client see you) is often the most valuable testing you perform, and it can tell you a lot about what you expect to find in the diagnostic stage.

To apply the four aspects in your daily work of inspection, simply look at any building component through the lens of each of the aspects. For example, a gas-fired water heater:

How can I better control heat flow in this component?

  • Maximize efficiency of the heat exchanger
  • Conserve energy by carefully setting the tank thermostat
  • Ensure insulation of the storage tank
  • Ensure insulation of the distribution system

How can I better control air flow and pressure in this component?

  • Ensure adequate fresh air for the combustion process
  • Test for proper venting of the combustion gases

How can I better control moisture in this component?

  • Inspect for water leakage

How can I better control air quality around this component?

  • Again, test for proper venting of the combustion gases

I’ll include a brief rundown of the inspections that should precede the diagnostics in this book, but there’s no replacement for experience, so continue to keep your senses open whenever you’re in a building, on or off the clock.


Home Performance DiagnosticsCorbett Lunsford is technical director of Green Dream Group and author of Home Performance Diagnostics: the Guide to Advanced Testing and serves as executive director of the Illinois Association of Energy Raters & Home Performance Professionals. In addition to performing hundreds of comprehensive home performance assessments and new ENERGY STAR Home certifications in Chicago, Corbett presents at home performance conferences across the U.S.

Excerpt from Corbett Lunsford’s book Home Performance Diagnostics: the Guide to Advanced Testing, reprinted with permission (© 2012).

August 1, 2012 |

JASON F. MCLENNAN: Less bad is not good enough

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Living Building Challenge

photo courtesy Wonderlane (CC-BY)


“I believe in the 3/4-baked philosophy. People chase perfection—trying to ‘fully bake’ their ideas before they share them with the world. Too many people end up never sharing their ideas, songs, dreams, novels, and inventions. The 3/4-baked philosophy is about finding that right time to share your work—letting the community fully bake it. The more you do this, the more you put yourself out there, the more success you have.” — Jason F. McLennan

Against the century-old church next door, the modest, modern building that houses the science lab of Seattle’s private Bertschi School could seem out of place. Its metal roof glints in the daylight, a surrounding garden of native grasses rustles in the breeze, and in-ground windows offer a view of the water that flows beneath. Jason F. McLennan remembers when the owners cut the ribbon on this 1,400-square-foot addition.

Then, he recalls, the children started chanting. Not “Bertschi!” but “Liv-ing build-ing! Liv-ing build-ing!” Those elementary-schoolers knew what stood before them—a structure built to have minimal environmental impact, to exist in an almost symbiotic relationship with its surroundings, operating more like an ecosystem, less like a consumer.

McLennan has led the charge on this approach to building design and in 2006 kicked off the Living Building Challenge, a call to architects to take “green” a giant step forward.

And in winter 2011, children cheered an architectural feat. “It was humbling,” McLennan says, months later, gazing at the Bertschi building on an unseasonably cool summer morning.

The man who has been called a “change agent” in the world of sustainable architecture is in fact a humble one. Immersed in an expensive profession, promoting a cause that some might call trendy, McLennan is direct and decisive, a down-to-earth neighbour who can talk composting toilets or philosophy.

His gentle demeanour masks a hotshot in his field. McLennan, chief executive of the Cascadia Green Building Council and of the more recently formed International Living Future Institute (ILFI), wants to revamp the concept of “green,” which, he points out, still involves the consumption of non-renewable resources—just fewer of them. To be certified “living,” a building (or a park, or a street, or a remodel) must meet criteria within seven categories: site, water, energy, health, materials, equity, and beauty. “Health” includes attention to air quality, for example, while “equity” considers issues such as fair trade. Three projects, in such disparate places as Hawaii, Missouri, and New York, have achieved living status, while about 100 others, including Bertschi, are in various stages of certification; ILFI aims to have living buildings in all 50 states, each Canadian province, and every country in the world. A transformation to living buildings won’t happen overnight, McLennan said, but it’s a start.

“Each building, each project creates a ripple effect around it. It changes the way people think. When there are enough of these examples, then a sudden and large-scale shift will be possible. We can’t control the timing of major shifts in civilization, but we can increase the likelihood that a shift will occur.”

A lifelong learner

McLennan, now 38, grew up in the factory city of Sudbury, Ontario, where he planted trees as part of a community effort to clean up industrial areas. Then McLennan saw the city redeveloped into commercial sprawl; bulldozers levelled some of the very areas he and his fellow community members had worked to restore. It spurred McLennan—who as a child sketched houses, castles, and ships before progressing to drafting classes—to chart a career in architecture.

He attended the University of Oregon, which had a reputation for its progressive program, then joined the Kansas City-based firm of BNIM Architects. As he expanded his knowledge of and experience in green building, he began pushing the concept even further. McLennan’s boss at BNIM, Bob Berkebile, said the young Oregon graduate joined a team designing a green-building prototype at Montana State University. McLennan, Berkebile said, not only put in long hours on the project but sometimes stayed up until 2 or 3 a.m. peppering him with questions and engaging in broader discussions about life.

“Our talks were about trying to understand the world, trying to develop a strategy for changing the outcome of the human experiment,” Berkebile said. “Jason was then and is now a lifelong learner.”

McLennan went on to become the youngest principal at the firm and grew increasingly focused on expanding the concept of green building, incorporating the biomimicry ideas of Janine Benyus—who advocates replicating natural systems—along with the architectural strategies of Berkebile and other architects. Push beyond LEED certification—the existing gold-standard for environmental building—McLennan determined, to a design approach that doesn’t just take less but gives back.

“He’s clearly driven by an internal fire that is unique. If I had a chance to clone him, I would be all about doing it,” Berkebile said. “He is a nexus of a lot of important things in human history— the right person for the right time.”

Building as teachable moment

The Bertschi School spreads over a city block, incorporating an old church, vintage homes, and a LEED-certified academic and performance space. Around the time board members and administrators began discussing plans for the science wing, a couple of young architects attended a conference where McLennan gave a speech about living buildings. The two, Chris Hellstern and Stacy Smedley, approached McLennan afterward and pledged to complete a living building within a year. They eventually connected with Bertschi’s administration and began designing the science wing. Hellstern and Smedley donated their fees; Bertschi students provided input on some of the features. The stream that carries greywater from a cistern to the garden, visible via those underground windows? By request.

LEED and other green-building strategies had long appealed to Hellstern, but, he said, until he heard McLennan speak, he wasn’t sure how to do more. “Jason … really helped to illuminate a path to being a part of something greater than LEED work,” said Hellstern, whose firm, KMD Architects, helped form the Restorative Design Collective. That organization of architects has convinced some manufacturers to offer or switch to healthier, more environmentally friendly products. KMD is rewriting specifications to eliminate toxic materials from its projects.

The permeable concrete on the walkway, the solar panels on the roof, the indoor wall of plants for treating greywater, the structural insulated panels in the lab—every item in Bertschi’s new addition was chosen to meet living building standards and to help the students learn about natural resources. Three times a month, Bertschi administrators lead tours of the buildings—not just for prospective students, but for teachers and students from other schools, and, of course, architects.

The most popular feature on opening day—this is, remember, a school—was the composting toilet. “We had a line out the door,” said Stan Richardson, Bertschi’s director of technology and campus planning. The longest segment of any tour, Richardson added, is the discussion in the bathroom.

McLennan sees it as simply one element of the larger picture. Living buildings must consume as few resources as possible, and what they produce should be reused, be it water that would otherwise go down the drain or human waste that would be flushed into the sewer. Natural systems reuse and regenerate. “This project exemplifies integration,” McLennan explains. “In most buildings, the systems are the backdrop. There is no system in this building that is not a teachable moment. They all matter, and they all have something to offer.”

Less bad is not good enough

The living-building philosophy stretches the green-building concept, which, McLennan points out, still relies on using fossil fuels, unhealthy building materials, and the labour of people who are treated unfairly. Moving towards a living building process, then, is about more than just construction; it’s about a fundamental shift in attitudes, culture, and economics. But while it is easy to push living building among architects and environmentally conscious communities, McLennan acknowledges the obstacles, particularly the political ones, in society at large. Not to mention the additional, upfront costs of living-building materials, or the difficulties in finding the appropriate local sources—though he hastens to point out that the long-term savings, such as in utility costs and the broader conservation of resources, make up for that. Fighting climate change, habitat loss, pervasive toxins, and social injustice, he believes, are worth the undertaking.

“You can’t help but feel a great deal of despair and a great deal of concern for humanity and other species. But if you’re really paying attention, you can’t help but be made optimistic by some of the intelligent work all around the world,” he said. “Complex human beings can be optimistic and hit with despair at the same time. You have to sit with your pain and be smiling.”

McLennan and his wife, Tracy, try to adapt the principles of living buildings into raising a family of four children—“living” as lifestyle, if you will. They shop consignment, choose minimal packaging, participate in a CSA. His briefcase is worn and scuffed—a look that, in a child’s stuffed animal, would be called “loved.” He drives a Prius, but because he lives on Bainbridge Island, Wash., he can walk to the ferry and ride the bus around Seattle. He lives in a 1970s house, which he improves, as finances allow, to living building standards. But McLennan is no environmental saint. Although he does as much as he can via email and by phone, he flies to presentations of his work—sometimes that’s the only effective way to get the word out, he says. “I’m not perfect,” he explains, nor is the living-building movement asking people to be. What it does instead, he says, is urge people to change.

“The world of green building is a world that is a little less bad, but that’s no longer adequate,” McLennan explains. “All planetary systems are in decline. It’s time to examine the whole paradigm. It’s no longer good enough to be a little less bad. We have to be a lot more restorative.

“That’s why we have to get to work. You have to persevere.”


Kim Eckart wrote this article for The YES! Breakthrough 15, the Winter 2012 issue of YES! Magazine. Kim is a Seattle-based writer. Article licensed under a Creative Commons BY-NC-SA license.

July 25, 2012 |

HOME PERFORMANCE TESTING: Q&A with home performance pro Corbett Lunsford

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House - Home performance testing

Corbett Lunsford has performed hundreds of comprehensive home performance assessments as technical director of Green Dream Group and has also written Home Performance Diagnostics: the Guide to Advanced Testing. In this Q&A he answers some common questions about home performance testing and offers some great tips for testers.

How do you define home performance testing?

Home performance testing is the basis for all control over comfort, durability, air quality, and energy efficiency. If you can’t measure home performance, you can’t achieve it, or even define it.

Why do you believe performance testing is so important to a home’s sustainability?

Here’s the secret: there is NOTHING in a building that can be hidden from performance testing. So nobody ever has to guess about whether the house was built well or not. All it takes is performance testing! If you could know FOR A FACT that your home is perfect, wouldn’t you want to? There’s so much marketing noise and unfounded opinions surrounding “sustainability,” especially for homes, that we must start requiring actual measurable data before sinking thousands of dollars into “solutions” that simply will not work. Home performance diagnostics is the only way to scientifically pinpoint opportunities for improvement, and then verify that the work was done correctly.

Is home performance testing within the grasp of a typical green builder or is it too specialized?

Performance testing is definitely a specialization—we are the radiologists of the building industry. If you do it every day, you can be very good and get terrific results. If you only drag the blower door out once every few months when you win a new renovation project, you’ll pull your hair out. Also, many of these tests are potentially hazardous to the home, the occupants and the professional, so you should just find someone who knows what they’re doing and outsource it.

Is this a dangerous occupation?

Interestingly, the answer is yes, but not because of gas leaks. You may be amazed, but in Chicago we find gas leaks in around 40 per cent of our clients’ homes. Our clients are more mindful than the average homeowner, so you can imagine what percentage you’d find in average homes! Explosion aside, you do have to deal with carbon monoxide (CO), which is deadly, and the potential for disturbing asbestos, but the REAL danger is that this occupation requires deep thinking. Deep thinking is not a trademark perk in the building industry, where most professionals are underpaid and overworked. So giving your chess-playing, system-thinking brain the space it needs to draw accurate conclusions from the array of home performance testing is paramount. If you stop thinking, then yes, you will need to rely on your professional liability insurance, which is not terribly costly…until after you actually use it.

What are the most cost-effective ways to improve a home’s performance?

1. Air Sealing (inexpensive, installed only once)

2. Insulation (inexpensive, installed only once, defeated by air leakage)

3. Mechanical Systems (expensive, maintenance required, replacement required, defeated by air leakage and insulation issues)

In your experience, what are the best performance tests?

The number one all-time test is the blower door. And while the blower door is running, you have a gigantic opportunity to run a number of nested tests: infrared thermography, zonal pressures, pressure panning, chemical fog, etc.

The main two components of the home are the envelope (which we just tested), and the HVAC system (which has its own tests): HVAC testing, including measured capacity (it’s generally not what’s on the label), carbon monoxide emissions, airflows and leakages, temperature rise/drop, static pressures, gas leaks, etc.

What quality control methods do you recommend for testers?

Calibrating equipment is essential, of course, but you really develop a nose for quality with experience. Once you know what an erroneous reading acts like, you can identify it in the field, and make it right. This is why mentorship is so important—if we have a bunch of lone wolves running around poking homes with tools, it doesn’t make for a healthy home performance industry. The first thing I did when I started my company was find two or three more experienced professionals and hire them to mentor me.

Home performance testing can get complicated. Do you have any recommendation on how testers can best explain the results to their clients?

Oh boy, Kiva, this is the right question. There is a ton of research showing that homeowners are not convinced by energy savings or home performance test results alone, and I have hundreds of homeowners’ worth of research that shows that they are actively repelled by technical mumbo-jumbo. Your client does not want to know how the X-ray works. They want to know if you can fix what hurts.

The answer is YES, you can cure their pain, by refining your reports package to get the client education part exactly right. Crafting the message is the central issue in our industry.

What are the most effective tools you’ve come across for home performance testing?

You know, it’s kind of funny, but the tools that get me super excited are generally fans, pressure meters and barriers, thermometers, and basic Newtonian-physics stuff. Infrared cameras are definitely sexy, and it’s important to have one (to show your clients beautiful pictures-very convincing). Interestingly, I’m not too excited about tools that do a hundred different things, which is a trend lately, because it can easily confuse the user about what they’re testing and why. Also, I don’t like to put all my eggs in one basket—something always breaks down at the opportune moment.

What role do you see performance testing playing in the future of green building?

Performance testing is not just central to green building—it is the future of ALL building. Here in Illinois, our building code is actually requiring performance testing (blower door and duct leakage) starting January 1st, and so will everyone else’s, eventually! Once people realize that it’s possible to get scientific proof that any home building or home improvement job was effective, they will stop paying for a worthless product.  Everyone can be in control of their homes!

In this video Lunsford explains the technical aspects of home performance testing:


by Kiva Bottero

July 24, 2012 |

MODULAR HOMES: Modular and sustainable—myth or reality?

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Modular homeFor more than a hundred years, modular has been touted as the next big thing in home building. But neither companies as practical as Sears Roebuck, which offered a house in a box in 1908, nor architects as visionary as Frank Lloyd Wright, who introduced a line of prefabricated houses three year later, have been able to make a promising idea an everyday American reality.

The gathering green revolution may change that.

According to the U.S. Census Bureau, modular construction accounted for about five per cent of all new homes built in 2010.

Those numbers appear poised to grow, with companies emphasizing sustainability starting up even amid the worst housing market since the Great Depression and others finding new markets for modular homes in cities, which have been less “friendly” towards modular construction than suburban and rural communities.

Modular advocates believe that housing built in a factory, trucked to a building site and its modules lifted into place by a crane not only makes economic sense, it makes environmental sense, too. They note that modular housing—often referred to as prefabricated or factory- built housing—is inherently more sustainable than site-built housing.

Almost nothing used in modular construction facility goes to waste. Unused strips of sheetrock are typically saved to reinforce the seams of walls. Lumber left over from creating wall studs and floor joists is re-cut for other purposes. The smallest pieces of wood, copper and vinyl are recycled. One company even gives its sawdust to a local farmer for animal bedding.

“There has been a very positive change in the last 15 years in using less wood in homes generally,” said Sami Yassa, director of the National Resources Defense Council’s forest initiative and the author of the 1998 book Efficient Wood Use in Residential Construction: A Practical Guide to Saving Wood, Money, and Forests. And modular construction has contributed to that change.”

Modular’s frugal use of resources, coupled with the economies of replication and the efficiency of constructing homes in a factory specially designed for that purpose, results in homes that cost 5 to 20 per cent less than comparable “stick-built” homes, according to Dave Boniello, vice president of marketing and development at Simplex Homes, which has been building modular homes in their Scranton, Pennsylvania, factory for 40 years.

Many startup modular companies, as well as established companies like Simplex, count on these savings to offset the higher cost of energy-saving and water-conserving technologies, or of integrating energy-producing technologies like solar panels into their homes.

It is money well spent. According to the U.S. Energy Efficiency Administration, in 2009 U.S. homes were responsible for 22 per cent of the nation’s energy use and 18 per cent of the nation’s greenhouse gas emissions.

Modular home builders have several other advantages when it comes to building green, including having highly specialized trades people on staff, according to Tim Key, senior editor of Modular Today, an independent website covering the modular industry.

“For instance, most green builders prefer to use spray foam insulation because it seals and insulates at the same time,” says Key. “But a local builder may not be able to find an experienced installer, while a modular factory has an experienced spray installer working every day.”

Key also points out that modular home builders have a dedicated sales staff that is knowledgeable about the wide variety of available sustainability features like bamboo flooring, low-flow faucets and energy-efficient heating and cooling units that modular builders typically offer.

“Builders often split their time between building and selling,” he says, “while modular companies have time to learn about new green options and to explain to customers why these options are smart choices.”

Blu Homes

Founded in 2007, Blu Homes exemplifies the trend in modular housing to build green. Based in Waltham, Massachusetts, the company produces six prefabricated models, and in its short history, has already built or has orders for more than 60 homes.

The company has aimed its homes at the wide spectrum of middle-class buyers: the homes range from $95,000 to more than $500,000, excluding the cost of a lot and foundation.

A big attraction for buyers at either end, according to Maura McCarthy, a co-founder of the company, is the ability to buy “an energy-efficient and eco-friendly home.”

The homes are built to LEED Silver standards set by the U.S. Green Building Council, a nonprofit group that has established a broad and stringent set of sustainability requirements in building.

McCarthy estimates that a Blu Home’s energy and operating costs are half that of a comparably sized existing home. Like other green modular builders, Blu Homes emphasizes the “tightness” of its “precision-built” structures, which improves energy efficiency and indoor air quality.

Blu Home architects and engineers also site homes on their lots to take advantage of passive heating, cooling, lighting and ventilation. And they build in features like sunshades, enhancing comfort in a manner that uses little or no energy.

They also study climate data from where a home is to be located, especially in areas with heavy snow loads or high winds, to ensure its structural integrity, as well as resource efficiency.

This data is analyzed by a sophisticated engineering program that “measures the performance of the home” so that the owners know before the first wall is framed what their monthly electric bill or their yearly oil bill is likely to run.

The modular home industry also tends to build smaller. This is often touted as a green advantage. It is also a logistical imperative. Most modular homes are trucked in pieces to their installation site on a flatbed that measures eight-and-a-half feet wide. (By definition, two or more units are joined at the construction site to form a modular home)

Blu Homes has figured out a way to work around the constraints of the highway by using steel framing, which can unfold a structure 20 feet wide and 15 feet high.

Still the emphasis at Blu Homes and most modular home builders are on achieving sustainability partly through a smaller footprint.

“The steel frame allows us to create open floor plans that maximize living space,” says McCarthy. “Our homes feel much larger than they are.”

ZETA Communities

San Francisco-based ZETA (Zero-Energy Technology and Architecture) Communities has taken the Blu Home emphasis on creating small spaces that feel much bigger to another level.

The company is awaiting permits to build 23 studio apartments in downtown San Francisco. The units will be about 330 square feet in size. The four-story project will be near net zero and built to LEED Platinum standards—the highest standard set by the U.S. Green Building Council.

“With smart design techniques, you can build in light and air and even furniture,” said Shilpa Sankaran, who cofounded the company in 2008, “so that residents will enjoy the comforts of living in a space associated with a larger footprint.”

ZETA’s birth would seem ill-timed. But, as the stock market crashed and the housing bubble burst, Sankaran saw opportunity in adversity.

“To bring sustainable housing to the mass market requires eliminating the price premium for green housing,” she explains. “To make a scalable difference, this kind of housing has to be financially attractive to lots of buyer, not just the wealthy, in the current marketplace.”

ZETA has already built the first 8 homes of a planned 22-home community in Stockton, California. The 1269-square foot, 3-bedroom, 2-bath homes sell for $160,000.

With solar arrays, efficient lighting and high levels of insulation, each home will be net zero, generating as much electricity as they use and saving homeowners $2,000 annually in utility bills.

ZETA has also used its factory to build school buildings. “With budgets tight, school districts often turn to portable buildings to meet the needs of expanding student populations,” said Sankaran, “but these structures often use pretty toxic materials and have poor light and air. We want to provide a better product at a great price point.”

ZETA’s holistic approach to the question of sustainability in building also considers location. The company focuses on building for urban infill sites, like the studio apartment complex in downtown San Francisco, close to public transportation and master plan communities.

“You can have an incredibly efficient building, but if it’s located far away from services and jobs, you end up contributing to CO2 in a different way,” notes Sankaran.

Despite the depressed housing market, both Blu Homes and ZETA Communities are expanding, seeking additional capital and looking to deliver homes beyond their initial marketplaces. ZETA, for instance, is exploring opening another factory in the Pacific Northwest, Colorado or Los Angeles.

Simplex Homes

Long before Al Gore’s “An Inconvenient Truth” literally brought the global warming problem home, Simplex and many other companies in the modular industry embraced certain green building principles as a practical matter.

“One advantage of building a house in a factory is that you are forced to think the whole house through before you build,” according to William Zoeller, an architect specializing in green residential design at the consulting firm Steven Winter Associates in Connecticut. “This doesn’t always happen with a stick-built house.”

The result, adds Zoeller, is a home with right-sized heating and cooling units, the right windows and the right levels of insulation for resource conservation.

Today, modular companies like Simplex Homes have evolved to offer highly energy efficient homes with a range of sustainable features, including solar hot water and solar electric. In fact, this company developed the solar energy product line to the point where it made sense to create a business that installs solar on homes constructed by other builders.

Like a car manufacturer, Simplex has also introduced engineering advances in its high-end products first, before making those advances standard on all models.

For instance, to build its first home that met the requirements for an Energy Star 5+ rating, the Environment Protection Agency’s highest rating, Simplex experimented with caulking the joint between the wall frames of its homes and the floor and ceiling plates to create a tighter air seal. In blower door tests, used to determine how air tight a building is, the seals greatly reduced air leakage, according to Boniello, so Simplex began to employ the inexpensive energy-saving technique in all its homes.

More recently, says Boniello, Simplex created “a unique wall system” using double-studded walls and mineral wool made out of glass and other recycled products for six new residential units in the Center City section of Philadelphia.  The walls achieved insulation values nearly twice as high as the city’s building code required—at only a modest additional cost.

The developers of the project, known as Bancroft Green and marketed as the only multi-family sustainable development in Center City, have highlighted the walls in their application for LEED Platinum designation.

The six residential units–with two or three bedrooms, roof top gardens and Energy Star appliances–were priced from the low- to mid- $500,000s. Boniello estimates that modular building techniques—“90 per cent of the construction was completed in the factory”—reduced construction costs by at least 10 per cent.

Building in a factory also greatly reduced construction time. The units were trucked to Philadelphia and set on foundations in December 2010. Less than three months later, the first buyers were moving in.

Although less than two per cent of all new home construction in cities is modular according to the U.S. Census, Bancroft Green has opened a new market for Simplex. The Bancroft developer is discussing a new city project with the company, while another Philadelphia developer has contracted with Simplex to construct a four-unit project in the city.

Modular and sustainable: myth or reality?

While most housing and environment experts agree modular construction could provide environmental benefits, as well as economic ones, they caution that not all modular construction is particularly green.

Green advocates suggest that those in the market for a green home look carefully at what comes “standard” with their modular home.

“The problem is that modular homes don’t have to incorporate these greener designs,” wrote Maryruth Belsy Priebe, who blogs for YellowBlue Designs, a Canadian company that sells stock green home designs by North American architects.

Priebe notes that some modular home companies tout a long list of available energy-saving and sustainable features on their websites, but fail to incorporate most of the features in all their homes. “In other words,” she writes, “green building features are not foundational to modular home designs.”

As the editor of a website dedicated to modular housing, Key admits his bias when it comes to the industry. But he is also quick to add that the determining factor for a green home is the design, materials and workmanship that went into the construction–whether the home was built in a factory or onsite.

With a controlled environment and experienced workers who specialize in green construction techniques, adds Zoeller, factory-built housing has the potential, often unrealized, to deliver consistently higher quality.

“I’ve seen crappy modular homes,” he explains, “and I’ve seen crappy stick-built homes.”

Still, the National Resource Defense Council’s Yassa said, “Modular has an important role to play in helping the environment. There are lots of efficiencies, and any time you create efficiencies, whether you use less wood or build a tighter home, you’re helping the environment.”


Brian Kell is a freelance environmental writer. In his “day job,” he is director of communications for the American Thoracic Society, an international medical society of lung doctors that advocates for clean air and for recognizing the health consequences of global warming. Comments about this article can be sent to

Reprinted with permission from Living Green Magazine.


July 18, 2012 |

COMPRESSED EARTH BLOCKS: Interview with Advanced Earthen Construction Technologies’ Lawrence Jetter


Compressed earth block building

Earth. The abundant resource is locally accessible almost everywhere on Earth. The ease of transportation alone makes it a fine green building material, but its benefits are much more than just that. It’s non-toxic, has a high thermal mass, low embodied energy and is disaster-resistant. It’s an ideal green building material, yet it isn’t used much in the West because of the high cost of labour needed to build with it. But with mechanization, suddenly labour costs are no longer the issue they were with handmade adobes. Green Building Canada spoke with Lawrence Jetter, President of Advanced Earthen Construction Technologies (AECT), a Texas-based compressed earth block machine manufacturer, about compressed earth blocks (CEB) and how economically feasible it is to build with them.

What are compressed earth blocks?

Machine-produced adobes. You use them, lay them and do everything you do with traditional adobes, but it’s so much faster and more economical. You can build a bunch of houses in the time it takes to build one house.

What do you think of stabilized earth blocks?

Stabilized compressed earth blocks will have lime, cement or fly-ash in them, making them stronger, but what people don’t realize, according to University of Texas, it takes 20 inches thickness of cement stabilized block to give you the same heating and cooling efficiency you get out of 10 inches of pure dirt. The reason for that is because cement has a crystal growth inside. When it’s curing, it makes a crystal and that crystal becomes a conductor of heat and cold just like a copper wire conducting electricity whereas with lime you don’t have that problem. Plus, lime also does not cure from water the way cement does. Lime cures in co2. If you want to talk about green building, by using lime in your blocks you’re actually scrubbing the air just like a tree would do. You’re consuming co2. A lot of people don’t realize that 60 per cent of the co2 produced in the world today is produced in the manufacture and use of cement. Cement gases off for 17, 18, 20 years. As long as it’s getting harder it’s taking water and turning it to co2 in the crystal growth process.

How do the building costs compare, per sq. ft. if I were to build a standard home with conventional building materials or that same home with compressed earth blocks?

Here in the U.S., if we build a small rectangular home you can do it for about 90 per cent of what it costs to build a brick-and-stick home. But what happens with adobe is that people start thinking about arches and all that kind of stuff. Suddenly their plain little home becomes a custom home. We’ve done homes that were $76 a sq. ft. all the way up to $300 a sq. ft. depending on the amenities they put into their homes.

Now, you can go out and use particle board and siding and build one cheaper than the earth block, but in 10 years it’s going to be a piece of junk. The cost of owning an earth block home is so much less. One homeowner here had a 3000 sq. ft. house with an electrical bill of $320 to $340 a month in the summertime. His new earthen home is 5700 sq. ft. and it’s $100 to $145 in the summertime because earth blocks are so much more efficient.

The block cost varied on one of the houses we built from 49 cents a block to another that was $1.05 a block. That was just the cost of the block itself. It varied that much because of the costs of trucking the soil in. For the 49 cent block we were able to mine the soil off his property. In fact, he used the soil twice. We took the soil and made the blocks with it and then we screened out a rock that was about 1.5 to 2 inches in diameter. He took those rocks, because we had a pretty high percentage of them, and laid them down and put ¾ base on it and then laid his tile on top of that for a road bed.

Why is the earth so much different ?

It’s not the difference here, it’s how they had to truck the soil. Here in San Antonio I took the soil off the property and made the blocks. Up in Austin we had to truck it 30 miles because where he was building there is no dirt. He’s got about an inch of top soil and the rest is rock

In general in the U.S., how much do people pay for soil?

I bought some soil over here that was a waste material for a dollar a yard and they loaded it and it cost me about $100 for an 18-yard dump. I bought waste material. In other words they took the top soil off and sold it to the landscapers. They have 3 to 6 feet of this stuff that’s in the way to keep them from getting to the caliche base that we use for the highways and roadways that they want to sell to the county and the state. Since this stuff was in the way, they loaded it for a dollar a yard—cost—just to get rid of it. But a lot of times you’re going to pay $10, $12, $14 a yard for some of that soil. That’s why I tell people to go to the dirt pit to find a soil that they can’t sell and don’t tell them what you’re going to do with it. That way you can buy it at a pretty reasonable price. You tell them what you’re going to do with it, the price suddenly goes up.

Normally, anywhere in the U.S. we can beat brick and stick by four or five per cent if we stay with conventional building and don’t get into the exotic stuff.

There’s so many benefits and if you can do it for even cheaper, why doesn’t everyone build with earth?

Because no one knows how to do it. I am in the machine manufacturing business, but actually I get into the education business. The architect and engineers don’t know a damn thing about this. They don’t. And it’s not their fault, they weren’t taught. That’s why I’m so happy that the University of Colorado has a machine and they’re teaching it. Texas A&M this year will graduate their tenth or eleventh class. The University of Oklahoma, Dr. Graham also has a machine.

A lot of builders choose to build with earth by hand. How can you compare the costs between handmade adobes given typical labour costs and using your machine?

The soil costs are going to be basically the same because you’ll need approximately the same amount of soil. The difference with handmade adobes is that you need a particular soil. With CEB you can use anything that’s got at least 10 per cent clay in it all the way up to 100 per cent clay. That opens up a wider range of soil, so you can use cheaper soils, which cuts your costs. Building blocks by hand is going to be a lot more labour intensive and slower. You can’t get the number of blocks you need to build a number of structures in a hurry.

Now, if a person’s going to build one house then it’s not cost effective to buy a machine. Because a person is going to build his own house and has years of time, you can’t beat his price.

When you buy adobes in the marketplace, the handmade adobes are not any cheaper than CEB blocks. Sometimes the machine blocks are about 25 per cent cheaper because people can produce more blocks, faster, without all the labour costs.

In some countries the labour costs are not that great, but in the U.S. labour costs would be cost-prohibitive. You couldn’t afford it.

One of the things about traditional blocks is that you need to use thick mud when you lay them. It’s a whole lot harder to lay those blocks because they’re so rough. With machine-produced blocks we can use a thin slurry. You can go from the slab to the barn beam in the first day. If you’re going to build with traditional adobes you can only do three courses and you’ve got to let the mortar cure and you’re going to have some settling because they’re using ¾ to ½-inch mortar. When using this thin slurry, which has the texture of a cheap milkshake, you pour it on, set the block in it and it gets sucked together, creating a monolithic wall, which makes it work a whole lot better in earthquakes. So there’s a lot of factors that enter into this other than the cost of production.

What does an average block sell for in the U.S.?

I hear anywhere from $0.85 to $1.25 depending on the location. If there’s an abundance and no shipping then it goes pretty good. But if there’s an abundance of blocks and it goes a long distance then you’ve got a problem.

How does CEB compare to rammed earth?

There’s a whole lot of resemblance between CEB using thin slurry and rammed earth. I really like rammed earth. I think it’s a great way to build, it’s just so damn expensive. You can do it with CEB for about half of what rammed earth will cost you.

image CC-BY-SA

July 18, 2012 |

SOLAR SEASONAL STORAGE: Q&A with Doug McClenahan of NRCan

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Drake Landing Solar Community

Moon over Okotoks at the Drake Landing Solar Community (photo courtesy JMacPherson – CC-BY)

Space heating accounts for 29 per cent of personal greenhouse gas emissions in Canada, second only to passenger road transportation. Other northern countries also face the space heating challenge when trying to attain environmental sustainability.

Doug McClenahan of Natural Resources Canada, used his decades of experience working with solar and other clean technologies to initiate the Drake Landing Solar Community, a master planned neighbourhood of 52 homes just outside Calgary, Alberta. The community is the first of its kind to use high fraction borehole thermal energy storage (BTES), a technology that stores solar power in the ground to save it for winter space heating use. Despite sub-zero temperatures, Drake Landing’s heating system delivers 90 per cent of every home’s space heating needs throughout the year using solar energy.

Drake Landing took home an Energy Globe award in 2011 for the successful performance of its innovative solar seasonal storage system. Kiva Bottero spoke with McClenahan about the project and future implementations of this technology.

Solar Seasonal Storage System (BTES) at Drake Landing

Borehole thermal energy storage (BTES) field at the Drake Landing Solar Community (photo courtesy daveeza CC-BY-SA)












How does your BTES technology work?

The concept is fairly simple. It collects solar energy during the summertime and stores it in the soil through a system of boreholes, which is just like a giant heat exchanger in the ground to get the heat into the soil. We then recover that heat when we need it, such as when there isn’t a lot of solar radiation in the winter and there’s a lot of heat load.

Can this technology warm homes throughout the cold Canadian winter?

It’s designed to provide an average of approximately 92 per cent of the heat demand from solar. It takes a number of years to build up to that steady state performance. So now that we’re in year five, we’re just approaching that right now. Last year we were 86 per cent solar fraction. The year before that we were 80 per cent. So we hope this year, unless it’s a really strange weather year, to be up around 90 per cent.

After December 21st we get more and more daylight hours and by February we can even get days when the system can be recharged a little bit. Then by March and April, you’re home free.

When you get really cold days of -40 degrees Celsius do you need to use the backup gas boiler or can your system handle it?

It depends on the time of year. We can handle it early on if it was a really cold November or December. If we get -40 in January or February the boiler would likely have to come on at that point because our soil temperature would probably have reduced. Fortunately, those really cold periods don’t last that long. It’s a small percentage of time in the year that you’re at the really cold temperatures—maybe 5 per cent or something like that—even though it represents a large part of the heating load. So far this year we’ve experienced -20s and there was no problem providing 100 per cent solar heat at those temperatures.

What have residents’ reviews been like?

Excellent. All their comments have been very positive. They’re like-minded people wanting to live in a community like that. They’re very much environmentally conscious and want to bring their kids up in that environment. They have street parties and bring musicians in. They love it out there.

Is Drake Landing meeting the five tonnes per home annual decrease in greenhouse gas emissions target?

Yes. That’s based on a combination of energy efficiency plus solar contribution. And that’s the contribution at the 90 per cent solar fraction level or slightly higher at year five, year six, which is what we’re getting into right now. So, the system has been performing as expected so far.

Have any of the homes been resold yet? Do these homes have a higher resale value than conventional homes?

Yes, there have been a number resold. There’s anecdotal evidence that there is a premium. When they were sold they started out at around $230,000 each. They now sell for twice that.

I think we had about 10 families for every home on a waiting list back then. We had people moving from different parts of the country. A couple even moved from the U.S. just to live in the community. So it attracted a lot of attention and since that time I’ve had calls from a number of people wondering when the next community like this is going to be built.

When is the next community going to be built?

We’re keen on moving to the next step. For us the next step is looking at a larger scale community. Drake Landing was considered a technical demonstration. It was never considered to be economic at that scale because it’s too small. The borehole storage is quite small and the efficiency is fairly low, but we knew that we wanted to use Drake Landing as a means to verify the computer models and predicting the performance. Then we would take those models to design a much larger community.

We’re in the process of doing that now as we’re looking at a number of possible new solar communities in Alberta or even Whitehorse in the Yukon. Because of this project’s publicity a lot of communities across Canada have expressed interest for some of their new developments to introduce this new concept. A proposal came in to our department to build a larger scale one and we’ll see whether that gets accepted in the next few months.

DLSC was a project conceived by Natural Resources Canada. Most people don’t think of a government department initiating a project such as this. How did it come about?

It wasn’t something that happened on the spur of the moment. My first job was working at the University of Toronto with Prof. Frank Cooper, considered one of Canada’s pioneers in solar energy. One of the concepts that he was really interested in exploring was solar seasonal storage. I started working with him when he was on contract with the U.S. Department of Energy to model and do research in the area back in the late 70s, early 80s. And that’s where I got my inspiration and learned about the potential for this concept in Canada.

When that work wound up I eventually moved to Ottawa to manage a solar thermal research program in 1986. During that period I was always looking for an opportunity to build a project like this, having had some background already in it. However, there needed to be a number of components in place before such a project could be proposed. We needed solar companies that could supply good quality collectors, a utility that would be willing to own and operate such a system, good computer models for predicting the performance of heat in underground storage, and funding programs that would assist the project.

We did a lot of work on other applications at Natural Resources Canada to go after the low hanging fruit, but by the early 2000s we started looking into space heating and what we can do in Canada. That’s when I promoted the concept of seasonal storage.

How did you implement the project?

First we needed a developer, a builder, a utility, and a municipality. Then we put together a number of federal, provincial, and other funding partners. Since the private sector had no experience with this concept, we funded the extra costs for the solar and storage, thus removing the financial risk associated with the project.

Since we were using quite accurate simulation tools, we were able to convince them that you could displace almost all of the space heating with solar using seasonal storage. One of the first steps our team took was to do a study tour in Europe of similar projects that were at a lower solar fraction. During that tour we consolidated the main concept and design ideas. That was a great start. From there we went to the detailed design phase and then ultimately to the construction.

Why has it taken so long to implement another project?

The main thing is cost. Especially in Canada we have very low cost energy. Even when putting insulation in homes it’s hard to get a payback. Until energy prices really go up quite a bit higher than what they are, it’s going to be difficult for utilities to fund a project such as this on their own and do it as a business case.

The next step is to get the cost down by going to a larger scale project. We just finished a round of performance and cost estimations for the larger scale project and it looks like the cost can be reduced anywhere from 35 to 50 per cent compared to the original Drake Landing. But, it’s still in an area with low cost conventional natural gas. So, we’re looking at other areas in Canada where heating energy costs are higher, such as Whitehorse. They don’t have natural gas and they use oil for their heating, which is six times the cost of natural gas in Alberta.

Also, a lot of people are waiting to make sure this first system performs well. All the messages we’ve been putting out so far have been yes, everything is on track. We’re looking good for the over 90 per cent solar fraction that we said. But you can imagine that people were waiting to see that type of information come out before they look more closely at it themselves.

What does the future look like for this technology?

The country that’s really taking off in large scale solar district heating—with and without seasonal storage—right now is Denmark. The number of systems going in has just risen exponentially and it is related to the price of energy. Their taxes appear to be higher than other countries to the point where solar is competitive. So, those systems are going in without subsidy, which is interesting. All the previous systems in Sweden, in Germany, even this one in Canada required subsidies because the cost of natural gas or other heating forms were much lower. Really, Denmark is an example of what we’re going to see in the future when the price of energy increases and solar is competitive.

July 9, 2012 |

BENEFITS OF COMPRESSED EARTH BLOCKS: Interview with Dan Powell of EarthTek


Compressed earth block home (CEB)

Green Building Canada interviewed Dan Powell, owner of EarthTek, a New Mexico-based compressed earth block machine manufacturer, to get the details on some of compressed earth blocks’ (CEB) many benefits and the advantages and disadvantages of interlock blocks and horizontal and vertical presses.

What are the major benefits of compressed earth block construction?

The number one benefit of CEB is sustainability, particularly for homes. CEBs are more comfortable, cooler in the summer and warmer in the winter. They use less energy to modify the temperature when it needs to be modified. They’re extremely adaptable to nice, complex designs. They’re load bearing, so you can do whatever you want with the walls, with some limitations.

Also, they’re easily available throughout the whole world. Compressed earth blocks are made from soil, which is normally taken out of somebody’s backyard—it may not be yours, but it will be somebody close—so people can take a product and build a home out of something they mine themselves. That’s a big deal. In a third world country where people have to import everything for building materials, that’s a huge deal. You can save two-thirds of the cost of construction because you can do this.

It’s fast and inexpensive to erect a building. Overall,  I’d say that CEB is probably the simplest way to build homes and a community—worldwide, whether you‘re talking about Sudan or Mississippi.

You’re saying that CEB homes are cooler in summer and warmer in the winter. How much?

Depending on how you construct the house. The baseline we work with is a geothermal temperature of about 13 degrees C (55 F). When you have a thermal in contact with the ground and you have the roof insulated well so that you’re not overheating from the sun, in the summertime when it’s 38 degrees (100 F) outside you’re walking into a house that’s 18 or 21 degrees (65 or 70 F).

Now, it doesn’t stay that way. As soon as you open up the doors and the windows, it begins to warm up a little bit because you have the convection bringing the warm air in and it warms up the walls inside. In the evening because you have enough wall exposed the sunlight hits the wall and the heat does penetrate the blocks. And when the sun goes down then the house begins to warm up. At that time you open the windows and doors to let the cooler night air come in to cool the house down and then by morning everything is nice and cool again. The walls are still warm so the house doesn’t get any cooler than about 16 or 18 degrees (60 or 65 F).

How thick would the walls have to be to create that much of a difference in temperature?

It’s been my experience that an 8-inch or 10-inch wall doesn’t quite cut it. The block sizes that we recommend are 12-inches to start. With a 12-inch wall you really improve the energy efficiency of a house. When you go to a 24-inch wall you have no heat transference either way.

Do you know what level of earthquake and tornado compressed earth block buildings can resistant?Dan Powell of EarthTek

We don’t have any real-life experience, but we’ve seen areas in Peru where adobe structures have been around for 400 or 500 years and are still standing while modern concrete structures have collapsed.

We understand why that occurs. If the earth movement exceeds the plasticity of the wall,  it doesn’t matter whether it’s earth or plastic, it’s going to come down.

A super rigid structure made of concrete and steel could withstand great force,  but it’s extremely expensive. With CEB you have all these joints between each layer and between each block. So if the wall starts to move, you have joints in the wall where the earth blocks are doing their shimmying, but they won’t have a catastrophic failure unless the movement of a wall exceeds 45 degrees. And if it shakes that hard, you’ll probably lose the wall.

As far as a tornado is concerned, the walls are not going to go. If you tie the roof down to the foundation with the weight of the walls holding the foundation down, you’re not going to lose your roof. You may get a tornado that’s big enough to literally rip the roof apart and it still isn’t going to pull the roof off the house because the house weighs more than the force of the tornado.

Are dry stack walls less earthquake or tornado resistant?

I actually think they’re more. Understand the nature of earth blocks. Nothing sticks to dirt. Traditionally, mortar has only been used as a levelling compound. We don’t have to use mortar because we don’t need a levelling compound since the walls are precise, but if you had a bit of mortar, the density of the mortar would be different than the density of the blocks. If it were cement and the density were higher then the cement would be brittle. When the blocks started moving the mortar would break up and as soon as the mortar broke up and fell out you would have a catastrophic collapse of your wall. An earthquake study by Berkeley proved that less mortar, thicker walls and a really high-quality wire-stucco finish on the outside will make the house more earthquake resistant than any other way.

In dry stacking we can put the blocks on dry, but we don’t really care to do that. We like to moisten them so that they set a little better. But the truth is that they don’t stick. They don’t ever become monolithic.

In a tornado if you had the roof tied to the top three layers of the house it would probably pull the roof off the house and the top three layers of blocks, or at least break them loose.

But if you tied the roof to the foundation with the walls in compression between the bond beam, the ring beam and the foundation, you’re not going to lose the house or the roof because the weight of the house weighs it down.

If there was an impact in the wall,  the blocks in a pure dry stack would probably have more of a tendency to dislodge and get pushed in than one that has a slurry mix where the blocks are stuck together, but it wouldn’t take much difference in impact to get the same results.

If you wanted to completely overcome that you would have to go with rammed earth walls that have cement built into them. Rammed earth walls are an upgrade of compressed earth blocks. I’m not saying we’re the best one out there. I’m saying we’re the one that people can afford. It’ll take a guy six weeks to ram a house that I can build in five or six days.

Speed, efficiency, cost. Are there any other advantages of compressed earth block over rammed earth?

You don’t have to use cement in CEB. You don’t really have to use cement in rammed earth walls, but you use so much less compression in rammed earth that you have to use cement to make them set good.

With all the advantage of CEB why don’t more people build with earth in the West?

In the U.S., it’s because our coding and advertising systems have been geared specifically for lumber and concrete. And the lumber and concrete industries are so big that they’ve done their best to make earth block a non-player in the deal. I’m convinced that the concrete industry absolutely destroyed the earth block code in California by lobbying for changes so that people couldn’t do it and that if they did do it, it would fail by design. How I read it, the code is written in such a manner that there’s no way an earth block wall could withstand an earthquake the way the California code requires it to be built.

Traditionally, adobes were for the very poor and the very rich. For the poor because they could make their own blocks and build their own houses. For the rich because they could afford the labour to have other people build for them. The people in the middle have not been able to do that.

Homes for the lower to middle income has been another problem in the U.S. Most people today don’t have a clue about building their own homes. They have to hire someone to do it. The educational process has got to be such that there are enough people who can do it. I think it’s a numbers game—the bigger you get, the more accepted you’ll be. We’re still in the starting phase here.

What’s the advantages and disadvantages of horizontal and vertical presses?Horizontal press - Compressed earth block machine

We manufacture horizontal presses, but actually, when I talk to my clients I ask them what they want to build. In some instances a vertical press makes more sense than a horizontal press. If what they want is a traditional adobe look and they aren’t interested in speed of construction—they just want to have control of their blocks—a vertical press is a really great way to do that, especially if they want exposed blocks and they want to do half bonding or one-third bonding, they will all be uniform. Vertical presses are great for that. The blocks are not uniform in height so they require mortar joints, they don’t have to have big thick ones like the old adobes, but they still have to have a small mortar joint somewhere between a 3/8 and ½-inch mortar joint. They’re good for that.

A horizontal block press makes a block that is precise in two-dimensions, both in height and width, which is the thickness of the wall and the height of the run is the height run of the blocks. By not requiring mortar you could get in there, lick ‘em, stick ‘em and stack. If you have a guy feeding and a guy stacking, two guys can stack 1000 blocks a day. Nobody’s doing mortar two run blocks like that. We could stack a wall from the foundation to the top of the wall in a day. We don’t have to wait for drying or curing time for the mortar. So the benefit for low-end and middle-end housing is greater in a horizontal block press than a vertical block press.

What do you think of interlock blocks?

Interlock blocks are a gimmick. They’re something that people made because somebody said “Wouldn’t it be nice if we could do this?” Well it would be nice, but the fact of the matter is you don’t need them and they just make building more expensive.

You have to put cement in them to make them work. Then you’re very limited in your wall design because the interlock blocks don’t offer much fluidity. If you’re building a cookie-cutter and it was designed for interlock blocks you’ll probably get it done. I know Hydro Form is having great success in South Africa and Central Africa with interlocks. But it costs more to build a house out of interlock blocks than it does out of what I call a P.O.B, a plain old block.


photos courtesy EarthTek

July 4, 2012 |
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