Green Building Trends

Europe

Jerry Yudelson

• Publisher: Island Press
• Year: 2012
• ISBN:
  9781610911344
• Topic: Architecture
• Subtopic: Architecture General

The "green building revolution" is a worldwide movement for energy-efficient, environmentally aware architecture and design. Europe has been in the forefront of green building technology, and Green Building Trends: Europe provides an indispensable overview of these cutting edge ideas and applications.In order to write this book, well-known U.S. green building expert Jerry Yudelson interviewed a number of Europe's leading architects and engineers and visited many exemplary projects. With the help of copious photographs and illustrations, Yudelson describes some of the leading contemporary green buildings in Europe, including the new Lufthansa headquarters in Frankfurt, the Norddeutsche Landesbank in Hannover, a new school at University College London, the Beaufort Court Zero-Emissions building, the Merck Serono headquarters in Geneva, and a zero-net-energy, all-glass house in Stuttgart.In clear, jargon-free prose, Yudelson provides profiles of progress in the journey towards sustainability, describes the current regulatory and business climates, and predicts what the near future may bring. He also provides a primer on new technologies, systems, and regulatory approaches in Western Europe that can be adopted in North America, including building-integrated solar technologies, radiant heating and cooling systems, dynamic façades that provide natural ventilation, innovative methods for combining climate control and water features in larger buildings, zero-netenergy homes built like Thermos bottles, and strict government timetables for achieving zero-carbon buildings. Green Building Trends: Europe is an essential resource for anyone interested in the latest developments in this rapidly growing field.

CHAPTER 1

The PassivHaus Concept and European Residential Design

In my research for this book, I found many interesting innovations, both cultural and technical, in the European approach to green buildings. Perhaps the most interesting and potentially most meaningful in terms of its impact on energy use and climate change is the approach taken in Central Europe to building design: the Passive House (PassivHaus in German).

For a moment, suppose you were assigned to design an energy-efficient home for a client in the United States or Canada. That appears easy enough. After all, you just add more insulation, upgrade the windows, maybe use some innovative technology such as structural insulated panels or insulated concrete forms, install a more efficient heating and hot water system, upgrade the Seasonal Energy Efficiency Ratio of the air conditioner, and maybe even add a solar water heater, and you’re done. For the most part, you would save about 50 percent of the energy use of a conventional home. But now suppose your client wanted to save 90 percent, without sacrificing indoor air quality or reducing the number of windows. That would be a very difficult task, particularly without adding many solar panels for heating and hot water. Well, it turns out that the PassivHaus standard addresses exactly that 90 percent savings assignment.

European governments take far more seriously the problem of global warming than the U.S. government. But while the United States has taken some steps to lower commercial building energy use, Germans and Austrians have tackled the housing sector. Like the United States and Canada, they’re still struggling with the more important issue of what to do with the existing housing stock. This is a more critical problem because the turnover of housing stock is much lower in Europe, because of slower population growth, less workforce mobility, and a large number of historically significant buildings, which makes renovating them to be more energy efficient more challenging. The Germans and Austrians are not alone. Each of the twenty-seven countries in the European Union must adopt national standards to achieve carbon dioxide reduction goals. However, according to one expert, only four countries currently have both government and private sector programs to achieve this goal, even though the European Union’s 2002 energy directive for building performance is supposed to be fully implemented by 2010.¹

In April 2008, I attended the annual PassivHaus conference in 2008 in Nürnberg, a delightful medieval city in Bavaria of some 180,000 people, known to most Americans (if at all) only as the place where Nazi war crimes trials took place after World War II, memorialized in the well-known movie Judgment at Nuremberg.

The conference is the brainchild of Professor Wolfgang Feist, an academic impresario of residential and commercial green building who has managed over 12 years not only to popularize the PassivHaus concept but also to have it accepted by the German authorities as the national standard. Attracting more than 1,000 serious researchers, businesspeople, students, and foreign visitors, the Passivhaustagung is a great place to begin considering what we can learn from the green building movement in Europe.

WHAT’S A PASSIVHAUS?

The basic concept behind the PassivHaus is quite simple. In a continental climate dominated by energy use for heating during a longer cold season, one should build a house like a thermos bottle that recovers most of the heat in the outgoing air to warm the incoming air. That’s it. It is quite simple in concept but very hard to implement in the field because it requires rigorous attention to construction detail, basically sealing up all potential outside leak points.

Look at Figure 1.1. The opposite of the thermos bottle is the coffee cup, which cools off quickly and needs reheating to stay warm, as might be the case in a typical American home.

The PassivHaus standard is quite exacting because it’s aimed at achieving an incredibly low heating energy use of 15 kilowatt-hours (of primary energy) per square meter per year. Consider that the average new home in the United States is about 2,400 square feet, or about 220 square meters. To meet the standard, you shouldn’t use more than 3,300 kilowatt-hours per year, considering both gas and electricity for heating. Now, look at your own electricity and gas bills. In the United States, in which natural gas is the dominant fuel for heating, cooking, and hot water outside the Northeast, the average annual use of natural gas in single-family homes is 800 therms, or 23,000 kilowatt-hours, seven times the PassivHaus standard, not counting electricity use, which averages nearly 12,000 kilowatt-hours.² (In California, with its mild climate, the numbers are closer to 6,000 kilowatt-hours for electricity and 460 therms [13,000 kilowatt-hours] for gas.)

FIGURE 1.1 The PassivHaus system acts like a thermos bottle that holds heat in the building without further energy needs.

Passive houses are superinsulated, walls, roof, and below, using the best windows in the world. It’s hard to beat a German window manufacturer for quality. Consider what a well-insulated window will do for you. The German design standard for windows in passive homes is that when it’s 20°F outside and 72°F inside the home, the surface temperature of the window in the room won’t be below 67°F (a 3°C difference), so your body won’t sense a cold surface when you’re in the room. You can do this only with triple-glazed windows that have no thermal bridges, or “heat freeways,” between inside and outside. Feel a standard U.S. builder-grade aluminum frame window on a cold winter night, and you’ll instantly feel a surface that’s as cold as a refrigerator, so the room is losing heat even while the double-glazed window with “low-e” coating is keeping out some of the cold. The cold surface you feel is a thermal bridge that is steadily transporting nice, expensive heat from inside the house to the outside.

What gives the PassivHaus its importance is a strong commitment by the German central government to reduce the entire country’s carbon dioxide emissions significantly by the year 2020. There’s no way to do this without the PassivHaus being adopted on a massive scale. Consider that all of Germany lies at the latitude of Canada and that heating energy use can represent more than 80 percent of all energy use for heating, cooling, and hot water in the home. You can see why the Germans (and the Swiss and Austrians also, by the way) focus on improving residential design and energy performance.

What’s the goal of the PassivHaus movement in Europe? To reduce energy use in residential homes and apartments (considering only heating energy use) by 95 percent of today’s average home, which uses about 300 kilowatt-hours per square meter per year. To meet these energy targets Professor Feist and his colleagues are determined to revolutionize the way homes are built and operated.

Passive Homes, the German and Austrian Way

Most of the world’s estimated ten thousand passive houses are in Germany and Austria, where winter design temperatures are about 9°F to 16°F.³ These homes are built to standards that require approximately R-50 walls (equal to about 15 inches of fiberglass batts or 8 inches of sprayed polyurethane foam⁴) and triple-glazed U-0.14 (R-7) windows, with maximum air leakage rates of 0.6 air changes per hour. As a result, these homes have the most efficient building envelopes in the world.

In a typical PassivHaus in Central Europe there is a heating coil in the ventilation duct. Most of these heating coils circulate hot water produced by a gas-fired water heater or a heat pump water heater. So they’re not truly passive, but they certainly are low-energy.

What you should get is a home that is very comfortable, with quite low energy bills. Because Central European PassivHaus designers deliver heat mainly through ventilation ducts, heat recovery ventilators act as the key residential heating appliance. In some very cold climates of the United States, such as Minnesota and Wisconsin, there will still be a need for supplemental heat beyond that delivered through the ventilation system.

PassivHaus technical specifications are strictly established in Germany and Austria, and they are generally well understood by builders. The annual energy consumption for space heating must be no more than 15 kilowatt-hours per square meter. (Note that this level of energy use would equate to an annual energy use for heating of 2,800 kilowatt-hours—about 100 therms—in a 2,000–square-foot house, pretty low by American standards in cold climates.)

For an entire residence, the PassivHaus standard specifies that the maximum annual energy budget for all purposes (including space heat, domestic hot water, lighting, appliances, and all other electrical loads) must be no more than 120 kilowatt-hours per square meter (11 kilowatt-hours per square foot, or about 760 therms per year for a 2,000–square-foot house in the United States). Although this is a small energy budget, it is not zero energy by any means. If you want a net-zero-energy house, you’ll have to supply the balance with solar thermal and photovoltaic panels for both heating and hot water. In a mild climate without a significant air-conditioning need, these systems would be quite affordable in most parts of the United States and Canada, taking into account energy prices along with current local, federal, and utility subsidies.⁵

The Innovator, Wolfgang Feist

Unlike many academics, Professor Feist emphasizes the practical nature of the PassivHaus standard and its usefulness in North America.⁶ He says 15 kilowatt-hours per square meter (1.4 kilowatt-hours per square foot) is not arbitrary but a good benchmark.

The definition of a PassivHaus doesn’t need any [particular] number. As long as you build a house in a way that you can use the heat-recovery ventilation system—a system that you need anyway for indoor air requirements—to provide the heat and cooling, it can be considered a PassivHaus. Since you need a house to be tight, you need a supply of fresh air. If you need that anyhow, the idea is to do everything else—the heating and cooling and dehumidification—with the ventilation system. To do that, the peak load for heating and cooling has to be quite low, including appliances.

Delivering heating by methods other than through the ventilation system has adverse impacts, according to Feist. For example, direct electrical heating is inexpensive to install, but the primary energy use (for electric power production) is extremely high, so he thinks that’s not a good idea, in most cases. Woodstoves are okay with him, but a good one is quite expensive, so you should use just one stove. If you do that, and you still want to have good thermal comfort all around the building, you will need quite good insulation. Because biomass is limited, if you burn biomass (e.g., in the form of wood pellets) in your house, the house should be well insulated—in the range of what is required for a PassivHaus. Keeping the heat source in the ventilation system (in the form of a hot water coil) is not necessary, but in Feist’s opinion it’s the cheapest way.

Feist believes that in many of the milder climates of the United States, low-energy houses can indeed include standard exhaust-only or supply-only ventilation systems and not use heat recovery ventilators.

If you can meet the requirements for a very low amount of additional energy, in summer and in winter, without a heat-recovery ventilator, why not? In San Francisco, for example, you don’t need a heat-recovery ventilator; just build the house with operable windows. [In colder places], I think it is important to install a heat-recovery ventilator before any other system in the house, such as a forced-air heating system.

The PassivHaus standard has very exacting requirements for window performance, specifications that would be hard to meet with standard double-pane, low-e windows that are the current U.S. definition of an energy-efficient window, with or without...

Table of contents

• About Island Press
• Title Page
• Copyright Page
• Acknowledgements
• Table of Contents
• PREFACE
• ACKNOWLEDGMENTS
• FOREWORD - Architecture and the Human Condition
• INTRODUCTION - European Green Buildings in Context
• CHAPTER 1 - The PassivHaus Concept and European Residential Design
• CHAPTER 2 - European Design Innovators
• CHAPTER 3 - European Green Buildings Today: What Do They Know That We Don’t?
• CHAPTER 4 - Green Buildings in the United Kingdom
• CHAPTER 5 - Sustainable Buildings in Germany
• CHAPTER 6 - Green Engineering in Europe
• CHAPTER 7 - Eco-Towns
• CHAPTER 8 - Green Building in the Retail Sector
• CHAPTER 9 - Looking to the Future
• CHAPTER 10 - The Challenge and Promise of Green Buildings: Lessons from Europe
• DESIGN AND DEVELOPMENT FIRMS AND PROJECTS
• NOTES
• BIBLIOGRAPHY
• INDEX
• ABOUT THE AUTHOR
• Island Press Board of Directors