What is Green Building?
I’ve been wanting to write an article for a while that is a general overview of various green building terms, energy systems, and strategies. I’ve found that as green building is becoming more popular, green jargon is seldom defined clearly for the layperson and rarely all in one place. We often assume that we know what something means, but its helpful to explore the true definition. So, here is a rather lengthy article that I’ve written that aims to demystify the popular terminology used within the green building industry. This will be published as 6 smaller articles in the EcoZone section of “The Bozone” (a local publication). -Emily Varmecky, Co-Owner of Greenovision Home Design
Green building is a rapidly growing segment of the U.S. construction industry. It is estimated that green building represented 40-48% of new non-residential construction in 2015. It is also reported that in 2015, “62% of firms building new single-family homes report that they are doing more than 15% of their projects green.” It seems that although discussions of green building are becoming more popular, green jargon is rarely defined for the layperson. My goal for this article is to demystify the popular terminology used within the green building industry. I will choose common building terms, energy systems, and strategies then define and generalize them to make them more understandable.
What is Green Building? Green building refers to both the structure and the process of construction “that are environmentally responsible and resource-efficient throughout a building’s life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition.” The goal of green building is “to reduce the overall impact of the built environment on human health and the natural environment.” There are a variety of methods that may be applied to reduce this impact which may include using water, energy, construction materials, and other resources efficiently and “reducing waste, pollution, and environmental degradation.”
For many professionals within the housing and construction industry, green building is a broad term describing the design or construction of a structure that is environmentally responsible in some manner. Building professionals can interpret environmental responsibility in a variety of different ways ranging from applying a complex method of energy-efficient design strategies into their structures to simply recycling cardboard within their business. Green washing is common in all areas of business and consumerism, including the housing industry. Green washing is a form of propaganda in which “green marketing is used to promote the perception that an organization’s products, aims, or policies are environmentally friendly.” Just because a company claims to be green, they may be interpreting green in their own manner, may be applying certain green principles on a spectrum, or may not be green at all. As I continue to explore various green building principles in this article, it is important to understand that these definitions are the ideals (principles to be aimed at), but should be critically examined when construction professionals are applying them in the field or are using the terms within their business.
Sustainable Building: The word sustainable means “able to be used without being completely used up or destroyed” and “able to last or continue for a long time.” In the construction industry, it is difficult to find a definition of sustainable building that is not synonymous with green building, but in my opinion, this term is slightly different. To me, sustainable building encompasses the utilization of renewable resources, which are “resources that can be replaced naturally and can be used again.” Sustainable energy systems within a home use energy efficiently in a manner that doesn’t use up all of the energy available and allows the home to consume energy for a long time. Fossil fuel is considered by many scientists to be a finite resource, therefore although using fossil fuels efficiently within a home or building is considered green, this usage is not necessarily sustainable. In many parts of the world, however, the sun shines consistently, providing an energy source that never runs out. Solar energy systems are therefore considered sustainable.
Sustainable construction materials can be materials that are grown and produced in methods that allow those materials to be continually produced, the usage of materials that last a long time, or the usage of materials that are reused or recycled. Fast growth pine, for example, is a building material that is grown and milled here in Montana. When responsibly harvested, a pine forest can regenerate and provide lumber for future generations without significant harm to the environment. Using locally available materials also minimizes long distance shipping, another environmentally-friendly practice.
The usage of metal construction material may be considered to be sustainable because of its durability. Although ore is a finite resource like fossil fuel, metal is long lasting and can be recycled into new materials. Metal roofing on a building can last significantly longer than asphalt shingles, which generally last 15-20 years. When asphalt shingles are spent, there are few ways to recycle or reuse them, so they usually end up as trash. However, when a metal roof is finally worn out, the metal can be recycled.
Energy-Efficient: Energy-efficient is a broad term used to describe a building or system within a building that produces and/or uses energy in a less wasteful manner. It can also be described as “using less energy to provide the same service.” A variety of strategies can be used to promote energy-efficiency that may include design methods, construction methods, materials, and technologies. Some methods may be active such as radiant floor heating or an “Energy Star” dishwasher and some strategies may be passive such as passive solar heating or well-insulated windows.
Before I explore various energy-efficient and sustainable energy systems, it is important to understand how we use energy within residential homes and other structures. In Montana, the three demands for energy within a home are: heating of your home spaces (accounting for about 49% of home energy usage), electricity for lighting, appliances, and air conditioning (36% of home energy usage), and lastly hot water for bathing, doing dishes, and laundry (16% of home energy usage). Passive solar, solar power, and passive cooling are generally considered renewable, sustainable energy production methods. Liquid solar, geothermal energy, and radiant floor heating are usually considered energy-efficient systems.
Passive Solar: In passive solar design, the sun’s natural energy is harnessed to help heat a home. “Windows, walls, and floors designed to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer.” This process is passive because it requires no plumbing or wiring, just good design. There are different passive solar strategies, but typically, sunlight enters through the building’s south facing windows and is stored as heat within a concrete floor. The heat then emanates from the floor mass during the day and night. Passive solar heating also provides natural day lighting, which reduces the need for electric lights.
Solar Power: Solar power is the conversion of sunlight into electricity, using photovoltaics (PV) or concentrated solar power (CSP). Solar electricity can be produced at the structure location (on-site) with photovoltaic arrays or can be supplied through the grid (electricity produced off-site that is delivered to the building through power lines). Although grid-tied electricity is typically produced from fossil fuels, a small amount of commercially produced electricity is derived from the sun. “Solar energy provides four-tenths of one percent of the total energy consumed in the United States.”
Solar Water Heating (AKA Liquid Solar): Solar water heating systems use the sun’s energy to warm domestic hot water. The water is heated with solar water heating panels, which are affixed to the outside of a structure similarly to solar electric panels. “A conventional boiler or immersion heater can then be used to make the water hotter, provide hot water when solar energy is unavailable,” or store the hot water. This hot water can then be used in the kitchen, bathroom, or laundry room or can be used in a variety of different methods to help heat the building spaces.
Geothermal Energy: Geothermal energy is heat that is generated and stored within the earth that can be used to produce electricity or more commonly, be used to help heat or cool the domestic water and spaces of a building. When geothermal energy is captured on the building site, a system of water-filled pipes (closed loop or open loop) runs horizontally or vertically into the earth. The earth’s temperature stays at a consistent temperature compared to the fluctuating air temperatures throughout the seasons. The water within the pipes is preheated by the earth then is further heated by an electric-run indoor geothermal HVAC (Heating, Ventilation, and Air Conditioning) system that “compresses the heat to a higher temperature and distributes it throughout the building.” As an example, water within a geothermal well is heated to 50 degrees F. If the outdoor air temperature is 0 degrees F, the HVAC further heats to water to create a comfortable indoor temperature. If the outdoor air temperature is 100 degrees F, the 50 degree F water can be used to help cool the home.
Passive Cooling: Passive cooling is defined as “a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or nil energy consumption.” There are a variety of strategies in which this cooling method can be achieved within a building, but it usually combines energy available from the natural environment on-site with specific architectural design and building materials. With stack effect, for example, warm air naturally rises and escapes through carefully positioned high windows or openings within a building and cooler outdoor air enters the building through low openings. “The pressure difference between the outside air and the air inside the building caused by the difference in temperature between the outside air and the inside air… is the driving force for the stack effect.” This method, when implemented correctly, can effectively cool and/or ventilate a building on a non-windy day and can be designed to require no mechanical systems.
Radiant Floor Heating & Cooling: With radiant floor heating, heat is supplied directly to the floor of a building and “relies on radiant heat transfer- the delivery of heat directly from the hot surface to the people and objects in the room via infrared radiation.” Radiant heating “is more efficient than baseboard heating and usually more efficient than forced-air heating because it eliminates duct losses.” With hydronic radiant heating, the most energy-efficient floor heating system, warm water is circulated throughout the floor systems of the building through a series of tubing. This water can be heated with fossil fuel based energy systems such as gas or oil fired boilers or can be heated with on-site energy systems such as passive solar, solar power, liquid solar, and geothermal energy.
“Sun smart radiant heating,” for example, is the combination of radiant floor heating and passive solar heating. With this system, the sun’s heat that is passively collected and stored within the mass of a concrete floor is actively circulated throughout the home via the hydronic tubing. When the radiant flooring is also connected to a water heater, the radiant floor provides heat on non-passive solar (cloudy) days. When a radiant floor is connected to a geothermal well, the 50 degree F water from the geothermal system can be circulated throughout the floor on hot days to effectively cool the building.
A simple Google search will show that there are many strong and varying opinions held by green professionals. There are a variety of different sustainable and efficient energy systems that can be used within a building. There are also a variety of different green design methods, construction methods, and material choices. There is a plethora of different reports and thoughts on which strategy or method is most effective, affordable, energy-efficient, easy to build, sustainable, etc. It generally seems, however, that the specific green methods implemented into a building depend on geographic location, available resources, budget, and personal preference.
Next in this article, I will discuss a few different green building strategies as well as green certifications. It should be noted that (along the lines of green washing) just because a green professional is certified to implement a certain strategy, it doesn’t necessarily mean that they are more qualified than a green professional who isn’t certified. For example, even if a building is not LEED Certified, it still may have been designed and built to provide environmental benefits and may have similar features as a LEED building. After researching “Not So Big House,” I discovered that designers and builders can easily become a “Not So Big House” registered professional after paying an annual fee. Of course, there are many building professionals that practice the design and construction of quality, smaller homes, but are not registered with “Not So Big House.” With training, it is also possible to be a certified Passive House or Green Building professional (among many other green building related certifications).
High Performance Walls and Roofs: Since 49% of home energy usage in Montana is for the heating of home spaces, reducing the total amount of heat required within a home is a common energy-efficiency approach. One of the best ways to use less heat is to prevent heat created in the building from leaving the building. This is done by constructing the walls and roofs to be well-sealed and insulated. There are many different design and construction methods as well as material choices for creating “better thermal barriers and fewer air leaks,” but this is usually done by creating an envelope that has a high R-value (or insulation value). This structure can then be fitted with conventional fossil fuel-run heating systems or with sustainable, energy-efficient systems. Either way, the building is still requiring less heat than if it had less insulation.
A high performance building envelope not only prevents heat loss in the colder months, it also prevents heat gain in the hotter moths. This helps promote energy-efficiency within the building during all seasons. It is very important to incorporate a ventilation system into a building that has low air leakage to prevent moisture build-up. Just as heat cannot escape this type of building, water vapor (present in all buildings) also cannot escape. Energy-efficient ventilators that limit heat loss and gain are available.
A blower door test is one method that energy professionals use to help determine a home’s airtightness. The results of a blower door test are measured as ACH units (air exchanges per hour). As a reference, “older homes, like living in a ‘barn’” have a 10-20 ACH. “Average new homes with some air sealing, but no verification and little attention to detail” have a 7-10 ACH. An ACH of 3 or lower is achievable for new homes and is recommended by most green professionals.
Passive House: A Passive House is a super-insulated and extremely tightly sealed home that achieves its energy-efficiency by keeping heat within the home, rather than letting it escape and producing new heat (and vice-versa in the hotter months). Passive House requires a blower door result of 0.6 ACH, a difficult standard to achieve. There are many different Passive House strategies; some rely more on active technologies for heat production, heat recovery, and air circulation and others incorporate passive solar heating and passive cooling design strategies. The Passive House Institute of the U.S. (PHIUS) offers Passive House certification, however, it is possible to work with green designers and builders who are skilled in various Passive House strategies, but have chosen not to purchase certification.
Smaller Home: According to the 2013 U.S. Census, the average newly constructed single-family American house is 2,598 square feet, hitting a new square footage record. As of 2014, “smaller homes, of 1,400 square-feet and less, [represent] 4% of homes built” and “extremely large houses, 4,000 square feet and up… account for more than 9% of new homes.” “Houses that are a little smaller but still verging on mansion territory, those between 3,000 and 4,000 square feet, made up 21.7% of new homes in 2013.”
Not to be confused with “Tiny Houses,” smaller homes are moderately-sized homes that use less of the construction budget on square-footage and instead focus that money on quality design, quality materials, and/or energy-efficiency strategies. Smaller homes typically consume less energy and use fewer construction materials than larger homes and therefore are generally more energy-efficient and green by default. “The U.S. Energy Information Administration says homes of 2,000 to 2,500 square feet use an average 102.3 million BTUs of fuel yearly — 13% less than homes that are 1,000 square feet larger.” Terms similar to smaller house may include simplified home, down-sized home, or “Not So Big House.”
LEED Certified: LEED (Leadership in Energy and Environmental Design) certification is a rating system for the design and construction of green buildings that is managed by the U.S. Green Building Council, a private non-profit organization. The owner, designer, or contractor of a building can pay a fee to have their structure approved by the organization and achieve levels of certification ranging from “LEED Certified” to “LEED Platinum.” LEED buildings are designed and built to provide environmental and economic benefits and requirements may include the use of recycled materials, energy efficiency, renewable energy, water conservation, etc. Additionally, building professionals themselves can choose to become LEED Certified after paying a fee and taking an exam.
Energy-Star: Energy Star is an EPA (Environmental Protection Agency) rating program for energy-efficient consumer products such as computers, electronics, appliances, lighting, heating and cooling systems, and new homes. Products with the Energy Star label “generally use 20–30% less energy than required by federal standards.” A product can be Energy Star Certified after meeting energy efficiency standards and having it tested by a licensed professional (testing is paid for by the manufacturer of the product).