Green Building Goals & Process
Environmental Issues & Building Design
Climate change is happening and its effects will have severe consequences for our society and environment. Reducing energy use in buildings is one of the most important ways to reduce humans’ overall environmental impact.
Ice core records from Antarctica show that changes in carbon dioxide concentrations (blue) track closely with changes in temperature (red). Carbon dioxide levels are now higher than at any time during the past 650,000 years. (CREDIT: Marian Koshland Science Museum)
Nearly unanimous scientific consensus has established that climate change is occurring as a result of human activity. Mathematical models of global climate change have linked a human-driven increase in Greenhouse Gas Emissions (GHGs) to an increase in global temperatures (especially in the past 250 years, since the industrial revolution). The primary source of this increase in GHGs has been attributed to the emissions generated by the use of fossil fuel-based energy.
Climate change has been linked to observable disturbances such as the loss of mountain glaciers and ice cover on the Earth’s polar regions, changes in the timing of the spring bud-break, and an increase in the frequency and intensity of extreme weather events such as cold waves, heat waves, large storms, hurricanes and tornadoes, floods, and droughts.
Climate scientists have theorized that human civilization is in danger of crossing a threshold or “tipping point” that could lead to more radical changes in the global climate, and that could accelerate the onset of either a new “hotter and wetter” age similar to the Earth’s environment before the appearance of human beings, or a new ice age. (Intergovernmental Panel on Climate Change, IPCC Fifth Assessment Report [AR5]).
Scientific estimates place the window of opportunity for reversing this trend in the very near term—according to some, as briefly as over the next ten years. After that, the global climate may change irreversibly, and humans will just have to adapt.
In many arenas of implementing real practical change, architects, engineers, and builders are amongst the few with the skills and resources that provide real, practical, cost-effective, and inspiring solutions for buildings.
Environmental Impacts of Buildings
Buildings account for 40% of worldwide energy use — which is much more than transportation. Furthermore, over the next 25 years, CO2 emissions from buildings are projected to grow faster than any other sector (in the USA), with emissions from commercial buildings projected to grow the fastest—1.8% a year through 2030 (USGBC).
Often, energy use in the form of electricity drives the largest environmental impacts. Where that electricity comes from determines what those impacts are. In the United States for example, where buildings account for more than 70% of electricity use, most of the electricity is generated by coal-fired electrical power plants (USGBC). Generating one megawatt hour (MWh) of electricity in the US produces
approximately 250 – 900 kg of CO2 depending on the mix of coal, nuclear, hydro and other sources of fuel (US EPA). As a reference, the average US household consumes approximately 11 MWh of electricity per year (US EIA).
These exact impacts can be quantified by lifecycle assessment (LCA), the most thorough way to determine the environmental impacts of a design. There is no perfect way to measure environmental impact. LCAs can measure greenhouse gas (units = CO2e = CO2 equivalent) to measure global warming potential, or might measure other things like human health, water, and land-use impacts. You may hear the word “embodied energy” or “embodied carbon” – this refers to the energy or greenhouse gas emissions caused throughout an object’s lifecycle. Alternatively, sometimes an overall normalized score is used to combine many kinds of impacts into a single number (i.e. Eco-Indicator 99). A good primer on LCA is here.
A 2012 LCA study found that “Specifically within commercial buildings, the use and operation phase of the material and building life cycle is so dominant that the impacts of construction, demolition/disposal, and transportation are nearly irrelevant for most traditionally constructed buildings.” (Journal of Green Building)
Total life cycle impacts by life cycle phase for a prefabricated commercial building with average California energy use, the building as built (30% of power supplied by photovoltaics), and net zero energy (100% of power supplied by photovoltaics), in units of EcoIndicator99 points.
Since 1920, the overall trend in building energy use for commercial buildings is higher energy intensity per square foot (BuildingScience.com). It is important to reverse this trend.
In the coming decades, rapid development will continue in the developing countries, while many buildings in the developed world will need to be renovated and retrofit. We need to make sure that the engineers and architects working on these buildings are equipped to make design choices that use energy effectively.
Net Zero Energy Buildings
An increasingly popular goal for green building is achieving Net Zero Energy – when your building is energy efficient and generates enough energy on-site to equal its annual energy needs.
Net zero energy buildings are highly energy-efficient and will use, over the course of a year, renewable technology to produce as much energy as they consume from the grid. This image of a photovoltaic array on the roof of the Lewis Center at Oberlin College in Oberlin, Ohio is courtesy of the National Renewable Energy Laboratory (ASHRAE)
For high performance building design, it’s most useful to measure and compare designs using absolute energy and resource metrics. These comparisons are objective, universally applicable, and apples-to-apples.
When your design is guided by expected energy use and emissions, the true performance of the building is not filtered through any building code or green building rating system. While exceeding codes and pursuing rating systems like LEED is certainly helpful, it can sometimes obscure priorities. Because those priorities often boil down to energy effectiveness (see Environmental Impacts of Buildings), striving for Net Zero Energy is a very good design goal.
Definitions for Net Zero Energy Buildings
Net Zero Energy Buildings are highly energy-efficient buildings that will use, over the course of a year, renewable technology to produce as much energy as they consume from the grid. There are several definitions of “Net Zero” buildings – based on where you place the boundaries for the energy balance. Here’s a summary of the main definitions from NREL.
Net Zero Site Energy: A site NZEB produces at least as much renewable energy as it uses in a year, when accounted for at the site.
Net Zero Source Energy: A source NZEB produces (or purchases) at least as much renewable energy as it uses in a year, when accounted for at the source. Source energy refers to the primary energy used to extract, process, generate, and deliver the energy to the site. To calculate a building’s total source energy, imported and exported energy is multiplied by the appropriate site-to-source conversion multipliers based on the utility’s source energy type.
Net Zero Energy Costs: In a cost NZEB, the amount of money the utility pays the building owner for the renewable energy the building exports to the grid is at least equal to the amount the owner pays the utility for the energy services and energy used over the year.
Net Zero Emissions: A net zero emissions building produces (or purchases) enough emissions-free renewable energy to offset emissions from all energy used in the building annually. Carbon, nitrogen oxides, and sulfur oxides are common emissions that ZEBs offset. To calculate a building’s total emissions, imported and exported energy is multiplied by the appropriate emission multipliers based on the utility’s emissions and on-site generation emissions (if there are any).
Designing Net Zero Energy Buildings
The key to designing net zero energy buildings is first reducing energy demand as much as possible, and then choosing good energy sources. Here’s a simple “order of operations”…
1. Reduce energy loads
2. Optimize design for passive strategies
3. Optimize design of active systems
4. Recover energy
5. Generate energy on-site
6. Buy energy/carbon offsets
Along this course, you will dive into more specifics of how to do this.
Resource Use & Buildings
Buildings use energy, materials, water, and land to create the right environment for their occupants. All of these things cost money – and all of them have an environmental impact.
Material Use
Using more sustainable materials, using less material, and using materials in the right constructions can improve the environmental impacts of building construction, lifetime, and end-of-life.
Why it’s important
Materials have their own environmental impacts from extraction and production, and they also hugely affect the thermal, visual, and acoustic performance of the building. The choice of materials and building products also drives costs on projects.
Materials are also important because they create the physical space that your building occupants experience. Toxics or volatile organic compounds can negatively affect health. On the other hand, the right choice of materials can have positive emotional and human health implications.
Metrics
Embodied energy or embodied carbon can be used as a measure of the environmental impact of a material’s extraction, processing, manufacture, and distribution.
However, over the life of a building and depending on the application, other factors like thermal and structural properties can be much more important. For example, better thermal properties of the materials used in a building’s envelope can improve the energy use (as measured by Energy Use Intensity, for example).
The lifecycle of the material is another important factor. Is it recyclable or biodegradeable? Is it made from recycled material or rapidly renewable materials?
Design Strategies
Material selection is full of trade-off decisions, and effective strategies vary widely based on your goals and situation. It’s often a good strategy to re-use existing materials, source materials locally, and use recycled/recyclable materials.
Learn more about green building materials, the environmental impacts of materials, and life-cycle assessment.
Energy Systems
Energy systems produce, use, convert, and store energy for the building. In high performance buildings these systems need to be both efficient and effective.
Why it’s important
Systems for thermal and visual comfort all use energy in some form.
Energy production and use is the primary driver of greenhouse gas emissions and global warming. Energy use in buildings is also one of the biggest costs throughout the lifetime of a building.
Metrics
Being energy effective means choosing the right technologies and design strategies for your building systems. This can be measured by looking at the kilowatt hours per year, per unit area (Energy Use Intensity or EUI).
Being energy efficient means getting the most out of the systems and technologies that you’ve chosen to use. This can be measured by the coefficient of performance of the equipment.
Design Strategies
Energy system design should be looked at as a whole system. Depending on your location, needs, and the available sources of energy, you may choose to get your energy from on-site photovoltaic and wind, grid electricity, or natural gas. If you can’t get good clean energy on your site, you may be able to purchase offsets.
Generally, the architect’s work defines the energy “demand” (their design places requirements and constraints on how the building works) and engineers define how to “supply” this energy.
Learn more about HVAC design and clean energy generation.
Water Use
Water is used inside a building for drinking, cleaning, and sanitation. It is used outside of a building for landscaping, and wastewater and runoff needs to be managed for a sustainable building site.
Why it’s important
Water is fundamental to human health and survival, and also plays a vital role in keeping ecosystems in balance. Shortages in fresh-water in some areas make water conservation even more important.
Metrics
Water is measured in terms of both quantity and quality. The flowrate of fixtures like faucets and the storage capacity of tanks and cisterns are different ways to measure quantity.
Water quality can be measured in a variety of ways, and you need different qualities for different uses. Whether the water is potable or not dictates how it can be used. Indicators like pH, dissolved organics, suspended solids, and turbidity help measure quality.
Design Strategies
Being effective with water is all about using the right kind of water for the right uses, re-using water as much as you can, and economizing use with high-efficiency fixtures as much as possible.
Capturing rainwater can be a great source of water. Also, plumbing systems that separate potable water, greywater, and blackwater can help get the most out of every drop. You can also purify the water on-site with living machines or advanced septic systems.
Learn more about water resources in buildings.
Green Building Costs
Sustainability requires a systems-based approach to design iteration. It is important to accurately account for the financial impacts of a design proposal. Also, understanding how systems thinking can be applied to cost can develop a better idea of how investment costs can be offset with Lifecycle Cost Analysis.
It is highly important not to omit the details of costs from the sustainable design conversation. Costs, translated at times as monetary economies, are the vehicle for supporting the execution of building projects. Everything has a financial value, and projects can only be realized when there is investment buy-in from stakeholders. Conducting building performance analysis is a valuable tool for filtering what design decisions can yield a more valuable economic return. Furthermore some building owners have very strict construction budgets, public elementary schools for example, that can cause the building design to remain within a firm financial budget that has been established in the pre-design phase of the project.
Costs Defined
Most often costs are associated with monetary expenses. However, there are a plethora of other qualities we can associate ”cost” with, such as environmental impact costs, resource use costs, human health costs, and time costs. When analyzing environmental impact costs the process is referred to as a Lifecycle Analysis, or Assessment (LCA).
While producing energy on site is great and reduces costs, the “math” to determine the Return on Investment (ROI) for such sustainable design features is not as straightforward as the costs required to purchase and install a product. Energy efficient technologies, and designs that reduce energy demands, are considered intelligent choices when considering investment and operation costs alone. But to truly get the full picture of a design project that decreases energy demands, a full LCCA should be considered.
Full Lifecycle Cost Analysis
- A building costs “A” to be built and can be sold or rented for “B”
- The difference between “B” and “A” is the ROI
- As a result, much of the ROI is based on real estate projections, which can change dramatically
In this scenario “A,” the investment cost, also dictates fifty percent of the equation, emphasizing the importance of the initial cost. For this reason the cost to erect a building has traditionally been the primary deciding factor in whether or not to build a particular design. For this reason, sustainable buildings may be more expensive to build, but it’s the ROI that is key.
Historically, only the initial and sale prices of a building were considered in LCCA. However, in order to consider the benefits of sustainable design, the capacity a design has to return energy must be considered in the calculation. Additionally, since the capacity of technologies to create energy is based on environmental conditions and equipment, the ROI is also much more predictable. The solar rays from the sun will not be altered by the real estate market, for example. All of this requires a new way of considering the financial cost of a building. Because there are capabilities to receive financial returns at a time period away from the initial construction of a building, “A,” LCCA must consider “C,” a variable that accounts for recurring return.
Design decisions must weigh initial cost against time period of pay back when proposing concepts to a building owner. Below is a LCCA that was conducted for a proposed photovoltaic glass panel roof in an ASHRAE student design competition.
The LCCA begins with investment cost, then charts money saved every year from energy production.
Here is another LCCA chart that uses traditional glazing that does not produce any energy.
If maintenance was accounted for in this analysis, the cost would actually be a net gain each year.
As can be observed, the PV glass pays for its self around year eighteen. In the year following the glass starts being completely profitable. Whether or not eighteen years is too long of an investment pay back is for the building owner to decide. But at least the designer related the proposed design to financial incentives and had an awareness of how economics fit into the sustainable goals of reducing energy consumption.
If the building owner was only presented with the initial cost around $350,000 they might not be interested in this PV glass concept. This could cause the owner to potentially opt for the traditional glazing that could have as much as a thirty five percent reduced investment cost, but have no real capability to pay for itself. Sustainable design is not only good for the planet, but it also has sound economic rational.
Leveraging Cost in BPA
Building performance analysis makes LCCA more accessible to the design process. Through the combination of BPA methods, and BIM technologies, data is readily available for analysis. This data at any point in time can be run through LCCA of comparing investment, operation, and return.
Project Phases & Level of Development
The building process has been refined over thousands of years. While every project’s process is slightly different, projects generally progress along these major phases. It’s important to know the right type and level of information that’s needed within each phase to add the most value.
Project Phases
In the construction industry, the design process is described by the phases of pre-design, conceptual design, design development, and final design. The building life cycle process is described by the phases of construction and building operation.
Level of Detail (LOD)
In order to efficiently manage the process of working in a BIM workflow, the industry has adopted a formal language of describing the completeness of a digital model at a given point in time. This language is “Level of Development” (LOD). LOD, in the BIM world, ranges from 100 (basic/conceptual) to 500 (highly detailed/precise). It is not unusual for levels of expected development to be part of the contract documents as described by the American Institute of Architect’s Building Information Modeling Protocol.
LOD phases can be summarized as follows.
- LOD 100: Modeled elements are at a conceptual point of development. Information can be conveyed with massing forms, written narratives, and 2D symbols.
- LOD 200: Modeled elements have approximate relationships to quantities, size, location, and orientation. Some information may still be conveyed with written narratives.
- LOD 300: Modeled elements are explained in terms of specific systems, quantities, size, shape, location, and orientation.
- LOD 400: Continuation of LOD 300 with enough information added to facilitate fabrication, assembly, and installation.
- LOD 500: Modeled elements are representative of as installed conditions and can be utilized for ongoing facilities management.
LOD and Building Performance Analysis
Secondly, digital methods of BPA are dependent upon the amount of information that is digitally modeled. Therefore it becomes beneficial to comprehend what LOD a model is at, and what that means in terms of available data, so analysis methods can be associated with the digital information that is readily available. For example, a model at LOD 100 will not allow one to conduct energy modeling that is required for LEED certification, but energy modeling with a LOD 100 can identify how the building’s energy consumption can be influenced by solar radiation. For these reasons, the LOD of a model and BPA practices share a feedback loop that at times are not as linear as the steps to developing levels of detail in the BIM model. This may be best explained with the following graphic.
Level of Development and Building Performance Analysis Interaction Diagram
Pre-Design
Phase Objectives:
Identify the requirements of the project, existing conditions, and unearth any essential information that will inform the design process. Common activities include preparing a building program, conducting a site analysis, and inventorying local code requirements.
Awareness
It is important to begin to understand the potential and limitations of passive design strategies to meet thermal and visual comfort criteria. It is also important to understand the opportunities for renewable energy and to explore the role of materials selection.
Preparing for the next stages
It is also important to set sustainability goals such as achieving energy neutrality or certifying the building through a green certification program. Develop and review quantitative and qualitative goals throughout all stages. This will help to manage the team’s efforts and validate your design.
Conceptual Design
Objectives
This phase involves testing and comparing conceptual designs by iteratively changing design parameters. Initial energy use modeling can help determine building orientation, building massing, program layout, window sizes, and facade shading.
Adjusting the default energy model settings and operational devices, along with the characteristics of other structures, can help us understand the impacts on energy use, costs, comfort, and other factors in the building.
Natural light, glare, natural ventilation, shading, solar gain amplification, internal load distribution, and envelope materials are the key factors to focus on to achieve energy efficiency in this phase.
Perception
After these iterations, we will understand what parameters will work for our design to refine and we will start to refine the overall form, materials and functional layout of the building.
It is difficult to guess how the project content and architectural requirements will be met. We will examine the overall form and interior layout ideas to determine effective design parameters.
Collaboration
To create a design that is energy efficient, feasible, and profitable, it is best for the architects, engineers, owners, and construction teams to work together in this early phase.
Preparing for the next phases
Towards the end of this phase, when design decisions become more difficult to change, good collaboration can ensure that we are moving in the most promising overall direction.
Design Development
Once we base ourselves on the overall design direction, we can refine the design of the entire project by focusing more on the details of materials, space, building systems, and mechanical systems.
Objectives
In this phase, we will start addressing issues and researching the details of the alternative design idea selected in the concept design phase. We will design elements such as facade details, interior space layout, lighting, and use this information to provide a more detailed energy analysis of the entire building.
Perception
We will create passive design details, optimizing space to take advantage of natural ventilation and daylight. By quantifying thermal and visual comfort, we will also gain more understanding of the active systems that need to be supplemented by the passive systems. Creating simple designs for passive systems will ensure that these systems operate in conjunction with the active systems.
Collaboration
Architects and engineers will focus more on their respective tasks during this phase – however, as always, good communication between both parties is crucial for creating effective energy solutions (EEM). The exchange of information and collaboration is supported by technologies such as BIM and integrated energy modeling. All data will be incorporated into the main design.
Preparing for the next phases
At the end of this phase, the research team will present a design proposal that may include various construction options and different system details for the investor to choose from before moving on to the detailed design step.
Final Design and Documentation
Activities
During this phase, the team will work on-site and will specify specific materials and construction products or techniques that will meet the energy model requirements. MEP engineers may design and specify the details of HVAC and lighting system operations.
Perception
We must ensure that the design is sufficiently clear to be constructed (i.e. handed over to the contractor) and that the systems are properly integrated for maximum performance.
Collaboration
The architect and engineer will be focused on their work, but the team can use BIM (Building information modeling) and integrated energy modeling to ensure tight design consistency.
Preparing for the next phase
The final version of the energy simulation and analysis will document the energy performance goals and provide a benchmark for validation during the construction phase. With this information, we will also be ready to complete much of the documentation required for green building certification systems such as LEED.
Construction
Bring the building design into physical reality, by practicing sustainable construction methods and utilizing quality control methods.
Activities
The team will design detailed drawings of all the construction components, connections, and systems so that the project can be built. The team may also use digital tools to organize, coordinate, and visualize the construction process.
Perception
We will ensure that the project is built efficiently and according to construction techniques.
Collaboration
At this stage the construction contractor will take the lead. The rest of the design team will work with them to ensure the building is built to design. Building materials are typically purchased during this stage. Often the specifications allow for replacements to be the same or better. A coordinated BIM detail model and energy model will help ensure that any replacements will actually meet the construction requirements.
Preparing for the next stage
The team may change the final detailed designs during the construction of the project to create a final “as built” energy model and BIM model for use during the operations and maintenance phase.
Operations and Maintenance
Once the building has been constructed (or the addition completed), it is prepared for use by putting the new building into operation. Providing guidelines for maintaining the building over time is also important to meet the needs of the users.
Objectives
First, we will check or operate the facility to ensure that all systems are functioning correctly and the settings match the ideas expressed in the design and energy model. Once the facility is operational, we will need to continuously monitor energy usage and thermal comfort to confirm that the facility is performing well, continuously improving operations (ongoing operation), and quickly detecting any faults and damages to equipment or control systems. Additionally, because changes often occur during the construction process, we will update the BIM model and the details of the energy model according to the final design. With the models and drawings of the buildings as constructed, along with sensors and feedback mechanisms, it can assist facility managers in maintaining the building and keeping it operating efficiently.
Perception
The operation of the facility and compliance with the building’s performance standards is almost always based on the design, construction, or the setting up of control systems that require fixes. Continuous monitoring and maintenance are very important to ensure the building continues to operate well.
Collaboration
At this stage, the building is handed over to the investor and the project management team. However, with a maintained BIM model, the work of the architects and design team can continue in order to monitor the building’s performance and make adjustments.
Preparation for the next stage
A good maintenance regime and performance adjustment can anticipate ongoing repair needs and prevent major renovations or fixes. When renovations or additions are necessary, having a good building information model and accurate record-keeping will make this process more efficient.
New vs Existing Buildings
Improving the performance of our existing building stock is incredibly important. New construction only replaces or adds a few percent per year at most to the world’s existing stock of buildings. Existing buildings can often be improved at far lower cost than would be required to raze and replace them.
According to the Intergovernmental Panel on Climate Change (IPCC), “over the whole building stock, the largest portion of carbon savings by 2030 is in retrofitting existing buildings and replacing energy using equipment” and energy savings for 50-75% can be achieved in commercial buildings who make smart use of energy efficiency measures.
The generalized process of ecodesign described on this site applies to both new construction and remodeling or retrofitting existing buildings. One of the big differences between the two is that during the Predesign phase of remodels and retrofits, the existing building structure needs to be studied in detail and will introduce a whole set of design constraints. The same design strategies will apply to both, but designers will not have as much latitude to reshape existing buildings.
When working with an existing building, you’ll want to understand the energy use of the building and its thermal performance, existing equipment and controls schedules, occupancy patterns, lighting and other systems. It is often difficult to get detailed information on constructions and other things that cannot be readily observed. Tools like sensors, sub-meters, and infrared cameras can help.
Getting a good as-built model of the building is also important, and often difficult. Reality capture tools like smart cameras (GPS, level and accelerometer) and laser scanners can help capture the geometry of the building.
Occupant Comfort
Buildings are designed for people, and those people are trying to accomplish a task – whether it’s raising a family, running an office, or manufacturing a product. The building needs to keep people comfortable, efficient, healthy, and safe as they set about their task.
Green design seeks to create buildings that keep people comfortable while minimizing negative environmental impacts.
Thermal Comfort
Maintaining a person’s thermal comfort means ensuring that they don’t feel too hot or too cold. This means keeping the temperature, humidity, airflow and radiant sources within acceptable range.
Why it’s important
Creating comfortable conditions is one of the biggest uses of energy in buildings and it is also critical to the happiness and productivity of its users. Often factors such as airflow and radiant temperature are overlooked in a design, leading to higher energy use and occupancy dissatisfaction.
Metrics
To keep people comfortable you need to provide the right mixture of temperature, humidity, radiant temperature and air speed. The right level of these variables depends on what activity is occurring, how active the people are, and what they are wearing. Everyone has slightly different criteria for comfort, so comfort is often measured by the percentage of occupants who report they’re satisfied with the conditions.
Design Strategies
Some ways to keep people comfortable are to use the sun’s heat to warm them, use the wind or ceiling fans to move air when it’s too warm, and keeping surrounding surfaces the correct temperature with good insulation. HVAC equipment like boilers, fans, and heat exchangers can temper the air temperature and humidity, but surface temperatures and moving air have to be considered too.
Visual Comfort
Maintaining visual comfort means ensuring that people have enough light for their activities, the light has the right quality and balance, and people have good views.
Why it’s important
Good lighting helps create a happy and productive environment. Natural light does this much better than electric lighting. Having good views and sight-lines gives people a sense of control of their environment and provides a sense of well-being.
Metrics
Good lighting is well-distributed, is not too dim or too strong, and uses minimal energy. Lighting is often measured either by the amount of light falling on a surface (illuminance) or the amount of light reflecting off of a surface (luminance). These are objective measures, but how people experience this light is often subjective (i.e. are they comfortable?, do they experience glare?). Good visual comfort also generally means that as much of this light is natural light as possible. Humans are hard-wired to like the sun’s light and it saves energy.
Design Strategies
Daylighting design strategies like high or clerestory windows, light shelves, and well-placed skylights can help distribute sunlight inside a space. When you do need to use artificial lights, you can reduce energy use by using efficient fluorescents or LEDs, with daylighting dimming controls, effective fixtures, and good lighting design. Good controls can automatically balance natural and artificial lighting. Most lights should have occupancy sensors.
Air Quality
In addition to air that’s the right temperature and humidity for thermal comfort, it’s important that air is clean, fresh, and circulated effectively in the space.
Why it’s important
If air is too stale or is polluted, it can make people uncomfortable, unproductive, unhappy, and sick. Fresh air helps people be alert, productive, healthy, and happy.
Metrics
Fresh air requires a certain percentage of outside air circulating into spaces. Clean air requires pollutant and pathogen levels to be below certain thresholds.
Design Strategies
Air can be kept fresh with high ventilation rates, either using natural ventilation such as operable windows and skylights, or active systems such as HVAC fans and ducts. Clean air can be achieved by filtering air, by flushing spaces with fresh outside air, and by not contaminating the air with impurities from the building, such as volatile organic compounds from paints or materials.
Acoustic Comfort
Acoustic comfort means having the right level and quality of noise to use the space as intended.
Why it’s important
People are more productive and happy when they’re not distracted by noises from outside or from surrounding spaces and occupants. Acoustic comfort is especially important for schools and office buildings.
Metrics
How humans perceive sounds and loudness is a subjective measure. However, you can create a comfortable environment by controlling objective measures like decibel level (sound pressure), reverberation time, and the sound reflection and damping properties of materials.
Design Strategies
Creating barriers and sound breaks between sources of noise is important. You can optimize room shape and size to reduce echoes and reverberation. And you can use acoustic tiles on ceilings and walls to dampen the sound.