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Fundamentals of Sustainable Dwellings
By Avi Friedman ISLAND PRESS
Copyright © 2012 Avi Friedman
All rights reserved.
ISBN: 978-1-61091-211-2
CHAPTER 1
Principles of Sustainable Dwellings
The limits of our environment, and how we have pushed those limits, are perhaps more apparent today than they ever have been. A growing awareness of the finite nature of energy and other resources has led more people to think of sustainability as a plus. The desire for environmental sustainability, along with today's economic climate, has homeowners looking for alternatives to large, expensive, and expensive-to- maintain dwellings. Prior to introducing key components below, this chapter deals with overarching issues. Causes of global and local trends are discussed, sustainability principles illustrated, various resources categorized, and certification methods listed.
GLOBAL AND LOCAL TRENDS
New design practices have emerged in reaction to local and global trends. Understanding these trends is vital to the selection of appropriate strategies and solutions. Some of the most acute issues affecting the built residential environment, and principles to help in addressing them, are elaborated in the sections that follow.
Population Growth and Energy Consumption
In 2007, the Intergovernmental Panel on Climate Change (IPCC) published a report that addressed the role of humans in climate change. Among other things, they found that "global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004" (International Energy Agency 2008). The residential sector in the developed world is known to be the third-largest contributor to greenhouse gas (GHG) emissions, preceded by the industrial and transportation sectors. In 2005, for example, the residential sector of the Organization for Economic Cooperation and Development (OECD) countries contributed 21 percent of the total direct and indirect carbon dioxide emissions, totaling 23.1 gigatons (21 gigatonnes), as shown in figure 1.1 (International Energy Agency 2008).
Demand for energy is also growing rapidly. Between 1990 and 2005, consumption in OECD countries increased by 23 percent and electricity use by 54 percent (International Energy Agency 2008). In 2008, the residential sector of the United States consumed 21,635 trillion Btu (2.2826 × 1013 kJ), a staggering growth from the 14,930 trillion Btu (1.5751 × 1013 kJ) consumed in 1973 (US EIA 2009). Although efforts are being put forth to increase efficiency in energy creation, delivery, and use, it has become abundantly clear that further steps will have to be taken to encourage residential concepts that conserve natural resources and energy.
The global energy consumption increase can be attributed to several factors, including population growth and expanding home size. The US population grew by 30 percent to reach 300 million in 2005, up from 228 million in 1980 (US DOE 2009). The increase led to growth in the number of families and individuals seeking a shelter, which expanded the number of homes and, consequently, energy demand. In addition, the average household size shrank. There are simply more single-occupancy homes and apartments consuming energy. The number of households grew by 40 percent between 1980 and 2005, rising to 113 million from 80 million, which is significantly greater than the 30 percent population increase for the same period (US DOE 2009) (fig. 1.2). The average size of a North American home also grew along with the population and number of households. Increasing home size is regarded as the leading factor affecting the need for space heating, the largest energy consumer in the residential sector, as shown in figure 1.3.
Another rapidly growing energy consumer is household appliances. Because of their growing use, they are considered the second-largest household consumer, surpassing water heating. From 1990 to 2005 the energy consumption of appliances grew by 57 percent because of an increased number of large appliances per household and a variety of new smaller ones, as illustrated in figure 1.4 (International Energy Agency 2008). The use of Energy Star–certified appliances helped lower consumption, yet these savings were offset by the introduction of new gadgets such as high-energy-consuming LCD flat-screen TVs.
Wood-Frame Construction
Energy consumption is not the only environmental concern related to the development of homes and communities. Ubiquitous low-rise single-family wood-frame construction consumes a large amount of solid sawn lumber and therefore puts an increasing strain on forests and the environment. This dwelling type is addressed in this book since it constitutes some 65 percent of all residences built in North America. An acre (0.4 hectares) of forest is consumed to manufacture lumber for the construction of a single 1,700 sq ft (153 m2) dwelling (Nebraska Energy Office 2006). Since approximately 2 million new wood-frame homes are constructed annually, 2 million acres (0.8 million hectares) of deforestation takes place each year in the United States and Canada alone (US DOE 2009). Also, 27 million homes are retrofitted each year. While renovation consumes less lumber than building a new home, it still greatly contributes to extensive use of lumber. Additionally, the construction of a 2,000 sq ft (180 m2) house will produce 8,000 lb (3.6 tonnes) of waste during construction alone. Of this waste, 25 percent is solid sawn lumber while 15 percent is other manufactured wood products. Furthermore, if demolition is required for the very same house, the amount of waste increases to 127 tons (115 tonnes) per home (US DOE 2009; US EPA 1997).
Auto-Centric Development
In 2005, the transportation sector contributed 26 percent of the total energy demand and 25 percent of the total direct and indirect carbon dioxide emissions of the OECD countries. A large portion of this consumption can be attributed to low-density development that requires extensive use of private cars. The US Census Bureau found that the average daily commute time to and from work in 2003 was 48.6 minutes (US Census Bureau 2009). Assuming that the vehicle is traveling at an average speed of 40 mph (64 kmh) and gets 20 mpg (8.45 km/L) of gasoline, the vehicle would travel 32.4 mi (52.1 km) daily, consuming 1.62 gallons (6.13 L) and emitting 31.69 lb (14.37 kg) of carbon dioxide per day. When a dwelling is sited within walking distance of amenities or when public transit is used, emissions are significantly reduced. In the Chicago metropolitan region, for example, households that live within a half mile of public transportation emit 43 percent less auto-related GHGs than those that reside farther away. Residents who live downtown, with the highest concentration of transit, jobs, housing, retail, and services, have 78 percent lower emissions. Furthermore, if sprawl continues to expand at the present rate, by 2030 its associated 60 percent rise of vehicle miles driven will completely negate progress made from efficient cars and low-carbon fuels (Hodges 2010).
In addition, a 2010 report by the US Department of Transportation has, upon rigorous examination of transit-related research, identified that public transportation can reduce GHGs in three principal ways: providing low-emission alternatives to driving; facilitating compact land use, which reduces the need for longer trips; and minimizing the carbon footprint of transit operations and construction (Hodges 2010).
PRINCIPLES OF SUSTAINABLE SYSTEMS
There are several perspectives on sustainability, each with its own importance to the environment, society, culture, and the economy. From an environmental perspective, for instance, every decision should be based on concerns for nature. In the private sector, meanwhile, decisions may be based on preventing the transfer of costs resulting from today's bad decisions to future generations. The author's perspective, however, is that the four fundamental aspects need to be given equal weight.
A sustainable built environment will result from overlapping these four issues, as shown in figure 1.5. The purpose of this book is to provoke and suggest new approaches to designing and building dwellings that are more sustainable and affordable.
The current, mainstream practices of dwelling design and construction need, in the author's view, to be reconsidered. The three general principles that are shown in figure 1.6 can illustrate the process. When followed, they can guide the building of sustainable homes and communities.
The Path of Least Negative Impact
Development should follow the principle of the path of least negative impact. This principle argues for the least short- and long-term damage to the environment, society, and the economy.
Self-Sustaining Process
Ideally a dwelling will be part of a self-sustaining process and will not need to draw extensively from external sources. Energy needs can, for instance, be supplied by photovoltaic panels, which can power appliances, and by solar collectors that can heat water. Additionally, if excess energy is produced, it can be used for communal needs and to power streetlights. Similarly, a self-sustaining water source can be obtained through the collection and purification of rainwater and the integration of a gray-water recycling system. This will help reduce the amount of energy used on public water purification.
Supporting Relationship
If one component of sustainability can positively affect another, then a supporting relationship will be formed. As more relationships emerge, a network will begin to develop. A dwelling that uses low-cost recycled materials, for example, not only helps the environment but becomes affordable to a wider range of consumers, leading to societal equity—a fundamental pillar of sustainability. Its "green" image may also turn out to be a marketing draw, as demonstrated in figure 1.7.
A Life-Cycle Approach
A dwelling is constantly evolving to accommodate the needs of its occupants. A dwelling that can be refurbished to extend its life is more sustainable than one that has a finite life. The home's design concept, therefore, ought to include adaptability to emerging circumstances. If a home is well built, the owner will save on maintenance and operational expenses during occupancy. These savings can be invested in new eco-friendly technologies. Additionally, the home can be designed to be adaptable to the needs of various occupants and be retrofitted rather than demolished.
RESOURCES
The proper management of resources is a key to sustainability. New eco-friendly technologies and products that rely on renewable resources are becoming common in initial construction and renovation.
Resources can be categorized in three groups: renewable, nonrenewable that can be recycled, and nonrenewable that cannot be recycled. Renewable resources are those that have the ability to replenish themselves through naturally occurring processes. Examples are water, air, and organic matter such as food and timber. Examples of renewable energy sources include tidal energy, geothermal systems, solar power, biomass, wind energy, and hydroelectric power (fig. 1.8). The natural replenishment of renewable resources may take centuries for some materials and millennia for others. Some can, however, be collected after use and recycled, which will be elaborated below.
Nonrenewable resources that cannot be recycled include all fossil fuels, such as coal, oil, and natural gas, which are not replenished by nature over a millennium. In 1993, Buchholz suggested that the quantity of fossil fuels used annually would take nature a million years to replenish. Moreover, when fossil fuels are used, they are burned and cannot be collected for recycling, creating significant pollution.
Nonrenewable resources that can be recycled are all pure metals and metal alloys (e.g., aluminum, steel, copper) and petroleum-based products such as plastics.
CERTIFICATIONS OF SUSTAINABLE PRACTICES
In recent decades, governments, construction associations, and nongovernmental organizations around the world have set standards for sustainable building practices. Green building movements are thriving in many countries, with significant effect on education and construction practices. Innovative approaches to residential design, such as passive and net-zero homes, are recasting the way design is conceived, with the intention to reduce to minimum the environmental footprint of dwellings. In addition to national building codes, which established minimum requirements for energy performance, the new standards address other criteria for a higher level of efficiency. In recent decades agencies and rating systems have been established to foster greater environmental awareness and streamline evaluation criteria. Some of the more established ones are BREEAM (originally from building research establishment environmental assessment method) in the United Kingdom, the HQE (Haute Qualité Environnementale) standard in France, and Green Star from the Green Building Council in Australia. Other notable institutions include the Passivhaus Institut in Germany and the World Green Building Council, which is a union of national councils.
The US Green Building Council (USGBC) is the nation's leader in the promotion of environmental responsibility. The agency established the Leadership in Energy and Environmental Design (LEED) Green Building Rating System, which became a nationally accepted benchmark for the design, construction, and operation of high-performance green buildings. The method has also been extended to Canada. It includes ratings for new construction, existing buildings, interiors, and schools, as well as homes and neighborhoods, which will be outlined below. The LEED standard is divided into several categories with prerequisites and additional credits. Points are accumulated for each satisfied requirement, and certification is given once a minimum specified number of points are acquired. Depending on how many points the building is awarded, it can be considered LEED platinum, gold, silver, or certified.
LEED for Homes
The LEED for Homes (LEED-H) standard initially focused on construction of new single-family homes but eventually expanded to include low-rise multifamily housing. Both types of housing are addressed in this book. Categories and credits were adapted to the residential sphere and are similar to those for LEED for New Construction. They concern construction, design, and site aspects specific to the house (USGBC 2007).
The location and linkages category recommends that the home be sited in a community that fulfills requirements similar to those of a LEED neighborhood. The location should be served by existing or adjacent infrastructure, developments should be compact and efficient, and the community should be equipped with services such as banks, convenience stores, post offices, pharmacies, and schools, to encourage walking.
The goal of the sustainable sites category is to encourage responsible site development that minimizes ecological impacts as well as the effects on the environment as a whole. Landscape features that reduce the need for irrigation and synthetic chemicals should be used, and paved areas such as sidewalks, driveways, and patios can be shaded with trees and shrubs. To reduce unnecessary consumption of potable water, rainwater collection and gray-water reuse are recommended. Where irrigation is necessary, highly efficient systems are a must. In terms of indoor water use, low-flow faucets and showerheads are recommended, as are dual-flush toilets.
For desired indoor air quality, LEED-H recommends the use of the Energy Star Indoor Air Package, which includes ventilation systems, source control, and air removal. Other equivalent systems may also be used to regulate indoor humidity levels, air distribution, and air filtering. The USGBC also offers recommendations for local exhaust systems for kitchens and bathrooms.
The materials and resources section of LEED-H recommends the use of recycled and local materials and "environmentally friendly" products. It goes a step further by providing guidelines for appropriate sizing of homes. Based on the number of bedrooms, usually a good indicator of the number of residents in a home, square-footage recommendations are provided for the home's floor area.
In the energy and atmosphere section, once again the Energy Star package is recommended. The house should be well insulated, with efficient windows, minimal air leakage from ducts, highly efficient space heating and cooling, and an efficient water heating and distribution system. Outdoor lighting fixtures should have motion sensors to minimize use, and indoor lighting, as well as appliances, should be highly efficient. Installing renewable energy sources such as wind generators and photovoltaic panels is encouraged, and points are allocated for each 10 percent of annual electrical load met by the system. Finally, homeowners should receive a user manual and a 60-minute walk- through of their new home to provide them with the necessary information for proper operation. For the design of a green home to be effective, its features must be used correctly and efficiently.
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Excerpted from Fundamentals of Sustainable Dwellings by Avi Friedman. Copyright © 2012 Avi Friedman. Excerpted by permission of ISLAND PRESS.
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