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High-performance buildings use far less energy, water, and money to run them. Building science is fundamental to high performance building design. Learn building energy fundamentals and how to apply strategies like passive heating and cooling to your projects. This will provide a strong foundation for getting the most out of building performance analysis software.
Year Published: 
2014
Software Covered: 
Revit, Ecotect, Green Building Studio
== Green Building Goals & Process ==
To design high performance buildings, you need to set concrete goals and follow a sound design process. Along the way you’ll need to optimize for both resource use and human comfort. Usually energy use is the largest environmental impact, and Net Zero Energy is an increasingly popular design goal.
=== Environmental Issues & Building Design ===
According to the scientific community, 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, source)
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 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 Fourth Assessment Report [AR4]).
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 ====
===== Quick stats =====
* Buildings account for 40% of energy use worldwide (WBCSD).
* Energy used during its lifetime causes as much as 90% of environmental impacts from buildings (Journal of Green Building).
* Building operations consume more than 2/3 of all electricity (BuildingScience.com)
* Residential and commercial buildings consume 40% of the primary energy and 71% of the total electricity in the United States. (ASHRAE)
* 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 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.
	“Lifetime energy use energy dominates traditional and even energy-efficient building life cycles, by far. In such cases, other environmental concerns are nearly always trumped by energy performance. Once a building meets all energy needs by clean power generation (whether it be on-site PV panels, PV grid power, or other equally clean renewables not analyzed in this study), then building materials and manufacturing becomes the dominant life cycle impact phase.” (Journal of Green Building)
 
Since 1920, the overall trend in building energy use for comercial 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.
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 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).
NREL
 
==== 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
Other sections of this website dive into more specifics of how to do this.
==== Links and References ====
Zero Energy Buildings: A Critical Look at the Definition
This study by NREL shows the design impacts of the definition used for ZEB and the large difference between definitions.
Getting to Net Zero
This article by NREL provides an overview of the DOE’s efforts toward realizing cost-effective net-zero energy buildings (NZEBs).
Zero Energy Buildings Database
Profiles of commercial buildings that produce as much energy as they use over the course of a year. A subset of the High Performance Buildings Database.
High Performance Buildings Database
This USDEO database collects information on the design of high performance buildings all over the world buildings around the world.
Net Zero Energy Buildings Development Agenda, USA
US Federal Agenda for Net Zero Energy, High Performance Green Buildings
Understanding Zero Energy Buildings
A paper published in the ASHRAE Journal that examines the feasibility of Net Zero Energy buildings.
Topics: 
Sustainable Design, High Performance Building Design
Industry: 
Building Design and Construction
=== Resource Use & Buildings === 
=== Green Building Costs === 
=== Project Phases & Level of Development === 
=== Occupant Comfort === 
=== New vs Existing Buildings ===
== Climate & Site Analysis ==
Site considerations include climate (sun & clouds, wind, temperature, humidity, and precipitation), the building's immediate surroundings (other buildings, trees, etc.), and location in the context of a city or other area (walkability, transit access, and other transportation for the people who use the building).
	
=== Climate Analysis ===
Climate is the first thing that architects and engineers should consider when designing a building. It dictates what passive design strategies are most suitable for the building site.
==== Temperature ====
==== Reading Temperature Charts ==== 
==== Humidity ==== 
==== Solar Position ==== 
==== Reading Sun Path Diagrams ==== 
==== Sky Conditions & Precipitation ==== 
==== Solar Radiation Metrics ==== 
==== Wind==== 
==== Wind Rose Diagrams ==== 
	
Human Thermal Comfort
Buildings are only energy-effective when their occupants are comfortable. Thermal comfort is difficult to measure because it is highly subjective. It depends on the air temperature, humidity, radiant temperature, air speeds, activity rates, and clothing levels. Learn how to use comfort concepts like Predicted Mean Vote and adaptive comfort to improve your design.
Psychrometric Charts
	
Building Site and Program
A building’s site and program will help you understand the energy loads you will need to manage, what passive design strategies are most appropriate, how make the building fit into the landscape and people’s lives.
Building Site Surroundings
Building Program and Schedule
Building Site Location
Links and References
Architectural Programming
From the Whole Building Design Guide