Green, zero energy and energy-efficient buildings
How do you design an energy-efficient building? Learn about codes and standards, building energy terminology and design goals
- Understand distinctions between commonly cited performance-improving goals and how to leverage for setting and achieving desired project targets.
- Know about the rising bar of green building rating systems, standards and codes.
- Learn about the trajectory of green buildings and sustainability in the built environment.
Clarifying owners’ understanding of performance-improving goals establishes a unifying basis for green building project options, processes and outcomes. Sustainable thinking and building practices have evolved so rapidly that owners often struggle to assign distinctions between characterizations of “energy-efficient,” “green,” and “net zero.”
However, rather than thinking in terms of differences in establishing project goals and identifying how to meet them, a more useful approach plots such designations on a continuum that equally describes the expanding imperative to integrate systems. With this understanding, owners can better anticipate evolving user expectations and code requirements and more fully capitalize on the potential of a higher-performing building. The prevalence of specific technologies and strategies align with specific points over this spectrum, all subject to the specifics of program, scale, site and climate to succeed.
Energy: the start
The adage goes: “code represents the worst possible building that can legally be built.” Fifty years ago, that seemed perfectly sufficient when it came to energy usage. Though the oil embargo of the 1970s compelled the design industry to consider energy, there was no national policy at the time. That event started the industry on a trajectory that finds us in a much different place now.
Prompted by the sense of vulnerability that the embargo wrought, ASHRAE developed a standard for the energy-efficient design of buildings, Standard 90, published in 1975. As with many building industry standards, the intent was to create parameters that states could readily adopt as code. The U.S. began to see sporadic implementation of the standard and its periodic revisions. Responding to the rate of change in energy technologies and prices, ASHRAE initiated a cycle of triennial review and revision in 2001, renaming the code ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings. ASHRAE subsequently issued separate standards specific to low-rise residential buildings (90.2) and data centers (90.4).
Throughout its first two decades, Standard 90.1 has set a bar for energy-efficient design, continually striving to make energy improvements across all aspects of the envelope, mechanical, electrical and plumbing systems. Improving efficiency across these systems is recognized to impact various building sectors/types differently, though the standard yields portfolio-level savings and has been on a trajectory of constant improvement (see Figure 1).
With state and local entities adopting a patchwork of standard versions, applying revisions sluggishly and issuing a wide variety of exceptions at the same time as the standard’s requirements become ever steeper, the standard regularly outpaces code to varying degrees nationwide. The same has been true with the International Energy Conservation Code, the model energy code maintained by the International Code Commission.
First released in 2000 and revised every three years through a public review and consensus process, it too found sporadic adoption of revisions. Figure 2 shows the status of energy code adoption in 2018, revealing how varied commitments to Standard 90.1 and IECC and their updates have been. A relatively current accounting of state-by-state adoption can be found here.
Energy efficiency continues to be a focus of standards development, code adoption and utility incentive programs, though what was once seen as “high efficiency” — such technologies and strategies as premium pump and fan motors, variable frequency drives, variable air volume, condensing boilers, economizers, temperature setbacks and LED lighting — now register as the norm.
There is still rich opportunity for energy savings in retrofitting buildings and in new design. ASHRAE developed Advanced Energy Design Guides to support the design and operations community, releasing progressively more aggressive versions for a variety of building types. Originally targeting 30% savings beyond ASHRAE 90.1-2004, then 50%, it recently released AEDGs for zero energy design.
ASHRAE also developed Standard 100: Energy Efficiency in Existing Buildings to provide “greater guidance and a more comprehensive approach to the retrofit of existing buildings for increased energy efficiency.”
The newest ASHRAE guideline, ASHRAE Guideline 36-2018: High-Performance Sequences of Operation for HVAC Systems, provides uniform sequences of operation for heating, ventilation and air conditioning systems that are intended to: maximize the systems’ energy efficiency and performance, provide control stability and allow for real-time fault detection and diagnostics.
Benchmarking of existing buildings has been driven by legislation in select cities across the country, including Seattle and New York City, leading to improved transparency about the performance of building stock. Publicly available data sets make it easier for lessors or potential buyers to understand operational costs. Having data available to owners can readily facilitate assessment and implementation of energy savings measures that may be applicable.
Beyond their communities, establishing both the political and logistical pathways for implementing benchmarking serves to provide a model and associated resources that allow other municipalities to more readily pursue and adopt similar requirements. Building energy scoring programs like EnergyStar, BuildingEQ and the Commercial Building Energy Asset Scoring Tool seek to leverage transparency and score buildings for prospective tenants and owners to be able to understand anticipated energy performance and costs. The city of San Francisco not only requires all commercial buildings to submit energy usage data annually in its Ordinance 0017-11, but also that owners will conduct energy audits every five years.
Energy and green buildings
Green buildings and sustainability in the built environment have enjoyed significant momentum and adoption in the past 10 to 15 years. The prominent mainstreaming of sustainability and fairly widespread recognition of green buildings might obscure what are in fact 30-year roots to the green building movement. With the formation of the AIA Committee on the Environment in 1989, the founding of the U.S. Green Building Council in 1993 and the “Greening of the White House” in 1993, a nascent movement began to take shape in the United States.
Across the Atlantic, the U.K.-based BREEAM rating system was launching around this same time. Its first version, launched in 1990, assessed new office buildings. Energy was a major focus of these and other early green efforts — so much so that the USGBC emphasized energy in the title of its LEED rating system.
Launched in 1998, the first version of LEED not only emphasized the importance of energy efficiency, but also established a broader understanding of and advocacy for environmental resource stewardship. Site, water, energy, materials and indoor environmental quality categorically gave breadth to the concerns and impacts tied to the built environment. These raised such issues as mass transit, native ecosystems, stormwater management, refrigerant impact on the ozone, global warming, material reuse, local purchasing, indoor air quality and occupant comfort.
Such breadth was an early challenge to design teams and the owners they were serving, while energy’s “head start” established a level of familiarity as well as defined metrics for assessing opportunities and their related economics. Whether for that association or the gathering focus at the time that most energy was tied to fossil fuels, energy efficiency became synonymous with green buildings to many.
There was an expectation that the greener the building, the more energy efficient it must be and critics of LEED often pointed to underwhelming — or what was seen to be deficient — energy performance. In 2008, the New Buildings Institute published a report funded by the USGBC and the U.S. Environmental Protection Agency evaluating the energy performance of LEED buildings. The report revealed that many were performing worse than anticipated (modeled) and some were even performing below code.
With green building rating systems there has long been the risk of conflating high levels of green performance with a requisite high level of energy efficiency, but the reality is that energy usage is just one of the many metrics of a broader set of values and strategies to reduce environmental impact and improve the built environment. While some owners and project designers found it easier initially to focus on energy, something more quantitative and familiar, others prioritized other metrics and categories as reflecting their values and objectives.
Thus, a “green building” becomes something not as easily compared one to another, even when a scoring rubric facilitates point tallies resulting in tiers of outcomes (i.e., LEED certified, silver, gold and platinum; 1 to 4 of Green Building Initiative’s Green Globes).
The growing recognition of this dynamic led many entities to begin specifying energy, water and other targets to ensure that the desired performance of within one or multiple categories would be reflected in the metrics (outcomes) of the green building rating systems. This effective prioritization of credits for each owner organization has been intended to reflect their values. Energy has been one of the most common examples, with many colleges and universities, certain states and the federal government setting targets to try to ensure that a high level of energy efficiency is indeed a major attribute of their own green buildings.
One advantage of this and even of the prerequisite energy performance targets of the rating systems themselves (i.e., 5%, 10% better), has been that in many cases, projects were pushed to go beyond code. Because the rating system versions were continually changing to subsequent versions of Standard 90.1, many projects were pressed to exceed what would have been code-minimum in their respective states, whether based on Standard 90.1 or IECC.
“Energy efficiency” continues to have meaning, at least as something better than code, but the evolved expectations of many in the design community and beyond have set the target for energy savings much, much higher, such that energy efficient simply doesn’t fully connote what’s expected. That said, tangible benefits the industry has seen from energy being an integral component, if not the driver, in green building design include:
- Energy modeling tools (whole building, single zone, façade).
- Aa new vocabulary around energy usage metrics and target-setting that facilitates change and benefits other rating system categories.
- Promoting life cycle cost analysis, life cycle analysis and carbon accounting.
- Renewables positioned as tangible and practical.
- Integrated decision making for energy, heating/cooling loads, daylighting, occupant comfort.
The energy bar has risen
The constant revisions to green building rating systems, standards and codes continue to reflect that the building industry has progressed significantly in adopting aspects whose benefits initially seemed more qualitative and subjective. While these aspects of green buildings were a bit slower to gain owner buy-in and categories that were more quantitative were more readily adopted in the early days, project teams today reach deeper and deeper in all categories from where the industry was 30 years ago, with new credits and refined point relationships continually challenging design and construction professionals. In addition, broader thinking about sustainability has led to related rating system categories and credits that reflect a broadening definition and understanding of green buildings and sustainability (see Figure 3).
Energy has been the category leading by example when it comes to deepening the goals. What was once a seemingly far-off point on the Standard 90.1 energy savings trajectory — the point representing ultra-low building energy use intensity that could effectively be offset by on-site renewable energy — has come to be seen as believable, feasible and even cost-effective in many climates for numerous building types. A zero energy building, as defined by the Department of Energy, is:
This has become the common go-to goal for owners and design teams focused on meaningful energy efficiency. Projects now seek to push beyond annual zero energy performance, ideally generating more power over the course of the year than needed, seeking to be net-positive and “restorative” to our environment.
The Living Building Challenge is one rating system example driving this, now requiring 105% of anticipated energy use to be offset by renewables. Zero energy has been successfully achieved to such a degree that ASHRAE has been able to develop Zero Energy Design Guides for K-12 schools and small- to medium-sized office buildings. The state of California has been a leader in driving zero energy facilities with the California Energy Efficiency Strategic Plan, which outlines the goals for the development of ZEBs, using a slightly different terminology common in the buildings industry, zero net energy buildings. These include:
- All new residential construction will be ZNE by 2020.
- All new commercial construction will be ZNE by 2030.
- 50% of commercial buildings will be retrofit to ZNE by 2030.
- 50% of new major renovations of state buildings will be ZNE by 2025.
The 2019 California Building Standards Code (Cal. Code Regs., Title 24) code revision, which goes into effect in 2020, works to align with the plan, establishing the criteria for new residential design such that it will deliver zero net electricity. The code does not currently require all-electric design nor offsets for fossil fuel consumption.
On the commercial building side, Executive Order (EO) B-18-12 issued in 2017 and subsequent administrative guidance directs all California buildings beginning design after 2025 to be ZNE and at least 50% beginning design after 2020 to meet the goal. Subsequently, determining that the market is already capable of cost effectively delivering ZNE buildings, the state has accelerated the adoption by targeting ZNE in the requests for proposals it has issued for the past couple of years.
Though California may be leading the way in terms of energy code, there are examples of projects across the country demonstrating that zero energy is possible. The New Buildings Institute hosts an online database showing certified and emerging ZEBs. Many advocacy groups, cities and states are considering how to improve codes and/or voluntary paths toward widespread adoption of ZEBs.
The inextricable link between energy and fossil fuels throughout much of the country has been increasingly recognized by project goals seeking to be carbon neutral or carbon positive. To more effectively decarbonize in areas with cleaner grid emissions factors and rapidly expanding renewable content, some projects are now seeking to change over to electricity-based heating in lieu of natural gas or fuel oil.
Project teams are working with owners to also identify electrification strategies for such internal processes as cooking, humidification, sterilization and other intensive activities traditionally served by fossil fuel boilers. In some cases, new fossil fuel bans are aiding or even driving factors in these new considerations.
Design professionals are also seeking to move beyond simple, annualized utility grid emissions factors toward an hourly or real-time understanding such that design and operational decisions can take carbon into account more effectively and meaningfully. Thermal energy storage and electric battery storage become tools for managing the time of grid-sourced electrical energy use and thus the carbon content of energy used. These are not energy-efficiency strategies, but they do align with the fundamental concerns of energy efficiency.
Efficient water use
Energy and efficient use of it has found a friend in water and the growing understanding of their mutual association in electric utilities and building systems. Termed the water-energy nexus, a growing body of knowledge is revealing where energy and water can be traded off. For example, an air-cooled chiller will typically be less energy efficient than a water-cooled chiller, but significant water and chemical use savings to a project exist when using the former. The value of each resource should be assigned to determine the best path forward for each project.
Attention to water lags energy by about two decades but is catching up rapidly. New standards and codes are providing a basis for increasing water efficiency and reuse for plumbing, irrigation and HVAC systems. Among these are ASHRAE 191P and IAPMO Water Efficiency Standard along with the water efficiency components of CALGreen and ASHRAE 189.1: Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings included as part of the International Green Construction Code.
The cost of water varies greatly from community to community as infrastructure profiles, scarcity, subsidies and quality vary greatly with a cost range of as much as 30-to-1. This has led to uneven pursuit of water efficiency as the payback varies so much. Cities such as San Antonio have adopted water reuse measures where cooling coil condensate must be captured from certain facilities and reused. The holistic view of water, blending site and building in conjunction with the water-energy nexus, is serving to propel towards greater savings and more aggressive targets, including net zero water.
As in the case of water, consideration of materials follows the path of energy to greater awareness and growing expectations. Much of the focus to date has been on toxicity (thoughtfully considering sourcing, manufacturing, end use implications), impact on indoor air quality and distance of manufacturing from projects (considering local/regional community economics as well as transportation’s environmental impacts).
The immediate concern of climate change has not only turned the energy conversation to carbon emissions, but also embedded (or embodied) carbon of materials is seeing newly heightened attention. The linking of the embodied and operational carbon creates a fuller picture for informed, metric-based decision making. This can be seen in the emerging focus on embodied carbon and greater accountability with the LEED v4 life cycle assessment credit.
The AIA 2030 Commitment benchmarking database update is expected to include tracking of embodied carbon. For now, the majority of the focus is on architectural and structural systems and their materials given available embodied emissions data. Eventually the embodied carbon of mechanical, electrical, plumbing and other nonstructural engineered systems will need to be accounted for and tracked.
The International Living Future Institute includes in its Living Building Challenge requirements for tracking and offsetting the embodied carbon from construction. It also now provides a Zero Carbon Certification that includes both the operational and embodied carbon for projects, establishing requirements and metrics to drive the conversation forward.
Holistic standards and rating systems are encouraging this sort of deep, integrated thinking, particularly if owners are compelled to continue to score higher marks and/or reflect their own deepening and evolving sustainability values.
A great example of this can be seen in California’s 2018 stipulated sum design competition request for proposals, for a new 383,000-square-foot California Air Resources Board testing and research facility (see Figure 4). Goals for the project represented the state of the imminent future across building performance categories: zero energy on-site, minimum of 3.5 megawatts on-site photovoltaics, minimum of 1.5 megawatt-hours of battery storage, minimum of nearly 100 electric vehicle chargers, an energy dashboard, LEED v4 Platinum and a minimum of 30 credits in CALGreen Tier 2.
Within the broader target-setting for LEED and CALGreen, credit categories and minimum point thresholds were mandated in many instances to establish more granular goals. This occurred for water, for refrigerants, for materials and for indoor environmental quality. With a mission for improving air quality internal and external to the building, CARB is leveraging holistic and integrated sustainability to ensure that its green building will reflect its values, both in quantitative and qualitative areas.