Overview

Buildings are one of the most important elements of human societies, and the question of building sustainability is the key question in the context of development and lifestyle of any civilization. Buildings are recognized as the main energy-consuming systems and as one of the high performing greenhouse gas emitters. Furthermore, because people in Western society spend most of their time indoors, buildings have a strong impact on human health and well-being. Multiple issues and criteria of sustainable building design and operation are introduced in this lesson. Following the assigned readings, you will engage in forum discussion and will be asked to perform an activity focusing on the analysis of some of the metrics used in building evaluation.

Objectives

By the end of this lesson, you should be able to:

• understand the principles under sustainable building design;
• list the rating criteria for determining the environmental quality of buildings;
• apply metrics to building analysis and propose scenarios for improvement.

Reading Materials:

• Book: Green Building: Project Planning and Cost Estimating [1], RSMeans, John Wiley & Sons Inc., 2011. Selected chapters. See lesson sections for specific pages to read (See E-Reserves in Canvas).
• Web article: "The Future of Green Buildings May Be Closer than You Think [2]", Press release, Wharton University of Pennsylvania, May 06, 2013.
• Journal paper: Hakkinen, T., Helin, T., Antuna, C., Supper, S., Schiopu, N., and Nibel., S., Land Use as an Aspect of Sustainable Building, International Journal of Sustainable Land Use and Urban Planning, 1, 21-41 (2013). Selected pages.
• EPRI Report: Sustainable Water Resource Management: Vol. 2 Green Building Case Studies [3], Electric Power Research Institute, January 2010. Section 2.2.5 (pp. 2-21 to 2-27).

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

7.1 Introduction to Sustainable Building Concepts

The Horniman Museum (London, UK) - CUE building's "green features include grass roof, passive ventilation, and sustainable construction materials."

Credit: Tatinauk via Flickr [4]

High-performance building – (also termed “green building” or “sustainable building”) – is called that because of:

• the higher efficiency of using energy, water, and other resources;
• reducing waste, pollution, and environmental degradation;
• protecting occupant health and improving human productivity.

High-performance buildings are designed, built, renovated, operated in a resource-efficient manner. The main objective of the "green building" strategy is to reduce the overall impact on human health and the environment.

Why did this idea of “building green” come up?

According to US EPA statistics, buildings in the U.S. account for 39% of total energy use, 12% of the total water consumption, 68% of total electricity consumption, and 38% of the carbon dioxide emissions. Furthermore, on the average, Americans spend up to 90% of their time indoors; hence, the built environment has a significant impact on human health, productivity, and emotional state.

Based on US EPA Green Building website [5], green buildings have environmental, social, and economic benefits:

Environmental benefits:

• enhance and protect biodiversity and ecosystems
• improve air and water quality
• reduce waste streams
• conserve and restore natural resources

Economic benefits:

• reduce operating costs
• create, expand, and shape markets for green product and services
• improve occupant productivity
• optimize life-cycle economic performance

Social benefits:

• enhance occupant comfort and health
• heighten aesthetic qualities
• minimize strain on local infrastructure
• improve the overall quality of life"

What exactly makes a "green building" sustainable?

This is the list of questions to explore when assessing the building design and operation:

Siting

Use of land

Energy Efficiency

Materials

Water Management

Indoor Air Quality

Occupant Health and Comfort

7.2 Assessment Tools for Sustainable Buildings

LEED rating system was developed by the U.S. Green Building Council (USGBC) in order to promote a holistic approach to construction and to encourage green certification of buildings. Rating systems developed under LEED allow projects to earn points in a number of categories that comprise the sustainability profile of the building project. LEED certification is flexible enough to apply to various facilities: homes, schools, healthcare facilities, large public sites, and even entire neighborhoods. Currently, it is a nationally recognized certification program.

The main categories of assessment in which buildings can obtain credits are:

• Sustainable sites
• Water efficiency
• Energy and atmosphere
• Materials and resources
• Indoor environmental quality

Go to the LEED website [6] to review the LEED rating systems. Here is the link to LEED Credit Library [7], which you may want to browse to see how points are scored by various building design features. Certification through LEED is quite a sophisticated process, which requires disclosure of a large amount of data, so it would be best for us to turn to specific examples of LEED-certified projects to understand how this assessment works.

The comprehensive approach and broad scope of the LEED certification has an advantage of wide applicability. So the whole buildings of various size, location, and function can be evaluated within the same system. At the same time, sometimes you can see buildings that are very energy efficient, zero-carbon, water-conserving, and still are not LEED-certified, just because they do not cover all the multiple attributes necessary for that certification. Because of that, it is sometimes useful to apply a single metric to evaluate one specific feature or function of a building.

For example, ENERGY STAR [8] is a single-attribute rating system that only evaluates energy performance. WaterSense [9]is a single-attribute rating system for water conservation. There are a number of other systems and metrics. Some of those will be considered in the following sections under the specific attributes they relate to.

There are four principles that a good assessment system should follow - it should be:

• science-based – results and decisions must be reproducible by others using the same approach;
• transparent – the standards and scoring procedure should be open for examination;
• objective – there should be no conflict of interest in the certification body;
• progressive –the system should advance industry practices.

Here are some examples of sustainable buildings in the U.S.:

The Philip Merrill Environmental Center [10] is recognized as one of the "greenest" buildings ever constructed in the United States. When it was constructed, special consideration was given to material selection and energy use. This facility was the first building to receive a Platinum rating through the U.S. Green Building Council's LEED Rating System.

Pittsburgh's 1,500,000-square-foot David L. Lawrence Convention Center [11] was the largest "green" building in the world, when it opened in 2003. It received Platinum LEED certification in 2012.

Sota Construction Services office building [12] (Pittsburgh, PA) features a super-efficient thermal envelope using cob walls. It also has other energy-saving features: a geothermal well, radiant heat flooring, roof-mounted solar panel array, and day-lighting features. It earned a LEED Platinum rating in 2012 and received one of the highest scores by percentage of total points earned in any LEED category, making it the "greenest" building in Pennsylvania and in the top ten greenest in the world.

Sota Construction Corporate Headquarters, Pittsburgh, PA, is one of the "greenest" buildings in Pennsylvania.

Credit: Dutchrub via Wikimedia Commons [13]

The Energy Use Intensity (EUI) metric is easy to calculate if you know your building’s annual energy use. The most accurate way is to look at your energy bills. Take the total annual amount of energy used and divide it by the total floor area of the house or building:

Before using this metric in analysis, we need to understand the difference between the gross EUI and net EUI metrics and what they indicate.

The gross EUI reflects the total building’s energy demand and includes all available sources: electricity, natural gas, renewables, and delivered fuels. No matter from what sources your energy comes, the building will require a certain amount of energy for annual operation, and this is what is accounted. Thus, the gross EUI will depend on the efficiency of the building envelope, design, and purpose. At the same time gross EUI will not be dependent on the type of energy you choose, it will only depend on the characteristics of the building itself.

The Net EUI reflects the difference between the gross energy demand and on-site generation. This is the metric that can characterize a building on the net zero scale. In this case we need to define the Renewable Production Intensity (RPI), which is essentially all energy supplied by on-site renewable sources, primarily solar, in kbtu/year divided by the total floor area of the building.

In case of a grid-bound solar system, the electricity bill will reflect the net kilowatt-hours taking into account consumption and on-site generation. So the easy way to calculate the Net EUI would be just using your utility bills for purchased energy:

Net EUI = E(elec) + E(gas) / Area

To calculate EUI in kbtu/sf/year (this is how it is presented in the LEED studies), you need to convert your energy units from all sources to kbtu and present the area in square feet.

The following conversion factors can be used:

• Electricity (both grid and onsite solar): 1 kWh = 3.412 kbtu
• Natural gas: 1 therm = 100 kbtu
• Fire wood for space heating: 20,000 kbtu/cord*

*Note: energy content of fire wood would depend on the type of wood and vary. The given value is an average that can be used as first approximation.

It should be noted, though, that within a certain month during the year, the net-zero condition may or may not be achieved. For example, in winter higher energy demand for heating may not be matched by seasonally decreased solar generation. At the same time, extra energy generated over the summer months would be fed to the grid and can be used to offset the winter deficit.

Weather-normalized EUI

What if we have two buildings of similar size located in different climate zones? One – in Minnesota and the other – in California. The first building has EUI of 28 and the second has EUI of 20. Would it be fair to say that the second building is more energy efficient?

As the matter of fact the first building may require more energy through the year not because of its inefficiency, but due to much higher heating load. After all it is placed in much more severe environment and has to withstand much more drastic temperature gradients, especially in the winter time.

To provide a fair comparison of the buildings in this case, we can use weather-normalized EUI. This is the metric that takes into account the weather, specifically heating and cooling needs, which can be expressed as heating degree days (HDD) and cooling degree days (CDD).

If you never heard of heating and cooling degree days [14], please check out this link. Those are common measures used to estimate the heating and cooling capacities needed for a building. Degree days indicate for how many days the outside temperature stays below or above the reference point of 65 F (this is the standard temperature by convention!). Degree days can be counted for any time period – a day, a month, or a year. Let me give you a short example.  

Let us come back to the case of two houses placed in different climate zones. We are going to compare data for those two locations in the table:

From this calculation, we see that the house in California in fact spends more energy per degree day than one in Minnesota to keep the temperature at the comfort level. So the ultimate conclusion is that the building envelope of the first house is more energy efficient.

The above-discussed metrics for house energy efficiency will be included in your lesson activity, so you will have a chance to apply those to your own residence and compare it to others.

7.4 Sustainable Building Materials

Refer to the following reading source to learn about the sustainable choices in building materials and some criteria of their selection.

As you can perceive from this reading, one of the overarching objectives here is to select materials that have high degrees of renewability, reusability, and durability and at the same time have low environmental impact and low embodied energy.

How would you guide your selection? The principles of selection of alternatives discussed in Lesson 4 of this course apply here as well. The process may involve lifecycle analysis for some of the materials and also multi-criteria analysis to ensure the highest feasibility and lowest impact.

Adobe bricks are a good example of low-impact construction materials in the areas where resources are limited. They also enable recycling of other process by-products. For example, the left image demonstrates production of bricks that utilize sugar-case by-products and rubble in a disaster relief zone.

Credit: IDVMedia [16] / Raul Hernandez Gonzalez [17] (via Flickr)

Sometimes, it is not easy to make a definite conclusion about the sustainability of particular materials. The question of sustainability requires wider thinking, which not only describes the material nature, environmental properties, and possible impacts. Sustainability also assumes identifying the specific fate of that material in a particular locale.

For example, if we consider refractory (fired) bricks as a common construction material, would those be a sustainable choice for construction? It really depends on a wider view on material lifecycle. Bricks are produced from extracted earth materials (such as clay) by firing in a furnace. Energy is needed to heat that furnace. In one case, if we burn coal to fire furnace to make bricks, it does not look like a sustainable production. Coal is a fossil fuel (non-renewable), and burning creates significant carbon emission, so this makes brick production apparently not a sustainable choice. But can that furnace be heated using a renewable energy source? For instance, can we use an electric furnace with electricity produced via solar power generation? Without going deeper into the feasibility of that choice, we can immediately see an opportunity to make this process sustainable. On the other end of the story, if the building gets demolished, where do the bricks go? If they contribute to deconstruction waste and are hauled to the dump, non-sustainable practice results. But if there is a plan of responsible demolishing, and if we know that those bricks will be separated from other waste, shipped to the processing facility around the corner, crushed, and re-used as new bricks or as coverage for the jogging trail in the town park, we have a much better feeling about it.

The routes defining the material fate should be outlined at the planning stage, and appropriate system analysis should help with that; and further, the material lifecycle should be regulated according to that plan. That said, sustainability is not so much about materials, but more about design and managing strategy. Also, the sustainability system usually has wider boundaries than the building itself, so sustainable buildings cannot be assessed apart from their infrastructure.

Lifecycle Building

Lifecycle building is known as design for disassembly and design for deconstruction. This innovative approach encourages creating buildings that provide resources for future buildings.

The lifecycle building initiative was catalyzed by a number of problems. According to U.S. EPA [18]:

• more of the 100 million tons of building-related construction and demolition debris are sent to landfills in the United States each year;
• construction and demolition debris comprises about 40 percent of the solid waste stream;
• reusing building components reduces the energy and greenhouse gases emissions associated with producing and transporting building materials;
• between the years 2000 and 2030, an estimated 27 percent of existing buildings will be replaced, and 50 percent of the total building stock will be constructed.

Lifecycle building approach implies easier building material recovery and reuse, thus reducing energy and resource consumption.

7.5 Energy and Use of Sun

Efficient use of energy is one of the key targets of high performance buildings. There are two main strategies pursued: (i) conservation of energy through more efficient building design and (ii) on-site power generation through energy-conversion technologies. The options for the power generation include renewable and no-emission resources, such as solar, wind, and geothermal energy, depending on the building setting preferences. A sustainable building can be still connected to the grid, but should be much less reliant on it and, in some cases, can even feed some of the extra energy produced on site back to the grid (net-zero energy building concept).

Let us start with the following chapter reading. This reading will introduce you to the main systems and energy interactions inside a building. It also contains useful terminology.

One of the ideas we can get from this reading is the importance of flexibility and tunability of design. Designing and building for variable conditions allows for significant energy savings and more efficient use of resources when it is needed. For example, one of the cornerstones of green building designs is proper ventilation. Sensitive ventilation, such as adjusting ventilation requirements based on human occupancy, is one of the sources of energy saving.

Such tunable designs require special technologies for monitoring and control. For example, Air monitoring technologies, such as sensors, "smart controls" can be of great benefit in the regulation of high occupancy spaces (conference rooms, auditoriums) in terms of total required energy. Technology is currently available that monitors the CO2 levels in the space. Occupancy sensors can be used to turn off light in occupied spaces.

Net Zero Energy Building

One of the very attractive concepts in building design is net zero energy building (NZEB). In brief, it means that energy generated by the building offsets the consumed energy by the building operation. In that case, ideally, the building does not require grid and can sustain itself. This concept is currently under development, but some successful examples of its implementation already exist. Read the following web article to get a deeper insight into this topic.

Optimizing use of the sun

Many existing homes and buildings heavily rely on oil, coal, and natural gas as fuels to heat and cool our homes. If not burning those fuels directly, we consume electricity from the grid, anyway, much of that electricity coming from the fossil fuel power plants. Those fuel resources are expensive, create pollution, and they are also being depleted rapidly. This makes attractive the strategy to adapt buildings for using the solar energy, which is an unlimited resource.

There are active and passive strategies for sun use:

Active strategies

Active strategies use solar photovoltaic (PV) panels or solar collectors to turn the solar radiation into electric energy or thermal energy. The technical principles of operation of PV and solar thermal technologies will be considered in more detail in another lesson, specially devoted to energy. Currently, many residential and commercial buildings are being evaluated for installation of active solar systems. While some are very well positioned to accommodate such on-site energy converters, others may be less suitable. Decision may be driven by such factors as: building design, shading structures, solar resource at the location of interest, building energy need compared to the system capacity, available roof or ground area for installation, and building aesthetics.   

Passive strategies

Passive strategies include features and adaptations in the building envelope and smart use of the natural solar activity. The passive approach does not imply installation of a separate solar energy conversion system, but rather utilizes features of building design. For example, a house can be oriented to minimize summer afternoon solar heat gain and to maximize winter solar heat gain. If the building is located in the Northern Hemisphere, the long sides of the house are made facing south and north while roof overhangs and landscaping are built to shade the east, south, and west sides. Alternatively, house design can take advantage of prevailing breezes during the spring, summer, and fall. Natural air movement is valuable for cross-ventilation of the house. In addition, foliage of trees and shrubs that create shade around your house helps keep the house cool, while bare branches in winter let the sunlight through to warm the house.

In passive system design, many physical parameters are manipulated to achieve the balance of heat distribution. There is a lot to learn in terms of how the light transmitting and absorbing surfaces are geometrically positioned, and what materials are used. You would have to turn to an architectural design course to become better educated on this topic, should you have interest. A couple of links below would give you some examples of passive solar strategies, if you are interested to learn more.

7.6 Use of Land

Land use by buildings is a significant aspect in sustainable development. We can recognize direct use (because buildings and their related infrastructure occupy a certain land area for their entire lifetime) and indirect use due to impact on land via extraction of raw materials for construction, waste disposal, etc. Both types of land use impact should be considered in environmental assessment.

Here are some key land use impacts [Hakkinen et al., 2013]:

• Soil sealing
• Soil compaction
• Change of land use
• Fragmentation
• Extraction of raw materials
• Reduction of biodiversity

Read the explanations to these impacts on pages 24-26 of the following article:

To propose strategies to improve the building design with respect to land use, those impacts need to be assessed and possibly quantified. Introduction of metrics helps compare buildings and refer them to certain standards of advanced or poor practice. Land use indicators can be either included in the LCA for buildings or be used independently.

Examine the land use metrics proposed in some European countries in Tables 2 and 3 of the above reading [Hakkinen et al., 2013].

What are strategies to create avenues for more sustainable land use by buildings? Some of those strategies are:

• urban densification;
• complexity and mixed use;
• green zoning;
• accessibility to public services and transport.

Read about them on pages 34-35 of the Hakkinen’s paper.

7.7 Indoor Air Quality

Indoor pollution consistently ranks among the top five environmental risks to public health. Because, by statistics, Americans spend up to 90% of their time indoors, the impact of building environment is increased compared to outdoor environment. Many air quality technologies need to be planned at the design stage of the building, since accumulation and removal of contaminants is largely dependent on air flow, moisture condensation patterns, and other physical properties. Physics and flow dynamics of the building need to be understood thoroughly in order to be used to the occupant benefit.

What are the main factors that can potentially make the indoor air a health problem?

Refer to the following reading source to study this question.

7.8 Building Hydrology Systems

All buildings must use water for daily operation, but statistics indicate that currently employed buildings (residential or business) use too much of it. Centralized water supply and treatment creates an impression of abundance of water resource, but is virtually inefficient in showing how much water is actually used rather than wasted. Sustainable building designs target to improve that efficiency, implementing reuse systems within them and promoting water conservation through a number of technologies and strategies.

Here are some of the features of resource-efficient building hydrology systems:

In resource-efficient buildings, plumbing fixtures that use minimum amounts or zero water represent important water conservation technologies. These technologies include:

• composting toilets, low-flow toilet (0.8 gal/flush), waterless urinals;
• low-flow shower heads (less than 2.5 gal/min);
• low-flow faucets (less than 2.5 gal/min), metered faucets.

Gray water systems allow reuse of the water coming from sinks and washing machines for toilet flushing and irrigation. Gray water can be reused directly or after cleaning with on-site sand filters.

Waste heat recovery systems can capture heat from the used gray water going down the drain and use it for heating the clean water. Heat recovery can be especially efficient in facilities with extensive hot water use (e.g., laundries, locker rooms).

Instead of trying to list all possible technologies and tactics related to sustainable water management in buildings and characterize them generally, it would be more useful to study a good example of practical implementation. Here is a report that describes a few case studies of sustainable buildings, which includes quite detailed characterization of their water management features.

Summary & Activities

This lesson overviews the key aspects of high performance buildings. The bottom line here is that different systems inside the building require specific technical knowledge, so creating a sustainable building is a collaborative, multi-expert task. All of the design and technology efforts typically target two main directions: resource use efficiency and human health. Because of the complexity of building design, assessment of buildings requires a comprehensive framework, such as LEED, which was adopted as a universal metric set in the U.S. It is not the only certification system for buildings, but is probably the most well known and widely used in assessment of public facilities and large common use buildings. While we do not go through every step of the LEED system here, we explore a few common metrics and study several examples. The design + technology collaborative thinking made a Net Zero Energy Building a reality, so this lesson also took a brief tour of that concept.