Energy codes around the world get stricter every year, architects need to prepare for various challenges ahead. The first step is to understand the key metrics needed to conduct early-stage analyses and collaborate across various teams. With buildings responsible for 39% of total carbon emissions, the design practice is evolving to bake in data-driven energy efficiency. This change is leading architects to quickly become building performance experts and create spaces that are high performance and healthy for occupants.
Here are 5 key metrics for sustainable building design that architects should consider:
1. Energy Use Intensity | EUI (kBtu/ft2/yr)
A building’s energy use intensity refers to the energy required to operate and sustain the project once it is occupied. An integrated building design can lower operating and maintenance costs and improve indoor air quality, thermal comfort, and access to daylight.
While running energy simulations one must understand the toll each design decision will take on altering the EUI. Depending on the building assembly, glazing percentages, active and passive strategies implemented, and space conditioning loads; costs can drastically spike leaving building owners and tenants paying millions more annually.
This metric is a factor of the floor area and annual energy consumption, expressed as the energy per square foot per year (kBtu/ft2/yr), more commonly known as the EUI. By calculating the EUI of a building, architects can better predict the project’s yearly utility cost. Understanding a building’s predicted EUI (pEUI), helps the design team understand the impact of each design decision.
The broad categories of EUI breakdown fall into heating, cooling, lighting, equipment, fans, pumps, and hot water.
2. Daylighting | sDA and ASE
Spatial Daylight Autonomy (sDA) describes the percent of space that receives sufficient daylight, defining all the required parameters to determine the building’s daylight performance. Research highlights access to daylight benefits the health, happiness, and productivity of building occupants.
To elaborate, sDA describes the percentage of floor area that receives at least 300 lux for at least 50% of the annual occupied hours (8 am - 6 pm) on the horizontal work plane (30” above the floor). Geometry plays a key role in ensuring equitable access to natural light, including the choice of materials and finishes used for windows, walls, floors, ceilings, and work plane.
Annual Solar Exposure (ASE) refers to the percentage of space that receives too much direct sunlight i.e., 1000 lux or more for at least 250 occupied hours per year. This amount of direct sunlight can cause glare, creating discomfort. It can even increase cooling loads due to the creation of hot spots within a floor plate.
Shading structures can have a significant influence on glare penetration, without cutting down on beneficial daylight. Shading devices include overhangs, fins, light-shelves, and site context (surrounding terrain, adjacent buildings, trees, etc.)
3. Indoor Water Use Intensity | WUI
The Water Use Intensity or WUI (gal/ft²/yr), is used to determine how much water a building will require during its years of occupation. It is important to design efficient water systems as a building’s potable water consumption constitutes a large portion of the world’s fresh water consumption. Collecting rooftop rainwater, treating wastewater, reusing greywater are all ways to reduce indoor water consumption. Site strategies that allow greater infiltration of stormwater enable water to be returned to the source, either with or without treatment.
Using fixtures that meet efficiency targets can also impact operating costs. Calculated only for indoor water use, this metric uses baseline and WaterSense values for five standard water fixtures, as specified in LEED’s Indoor Water Use Reduction category. Low and high-performance values are multiplied by the project’s square footage to produce a preliminary Water Use Intensity (WUI) and possible WUI Percent Reduction.
4. Embodied and Operational Carbon Emissions (tonne/CO2e/yr)
Embodied carbon emissions (kgCO2e) refer to the greenhouse gases (GHGs) emitted during the extraction, manufacture, transportation, assembly, replacement, and deconstruction of building materials, together with the end-of-life profile. This is the most complete boundary condition i.e., measuring from cradle to grave.
If evaluated early in the design phase, 80% of a building’s embodied carbon can be reduced. There is no chance of the world meeting the Paris Agreement without reducing embodied carbon from buildings.
Operational carbon emissions (kgCO2e) refer to the greenhouse gases (GHGs) generated annually during the operational or in-use phase of a building. This includes the use, management, and maintenance of a product or structure, along with the energy consumed to run a building’s systems. The carbon load is created by the use of energy to condition (heat/cool) and power a building. The use of highly efficient building systems and proper management can directly impact their energy consumption, reducing the carbon footprint.
5. View Quality (%)
Quality Views is a set of standards used to evaluate the effectiveness of a building’s design to provide building occupants substantial and beneficial views. Designing for quality views involves consideration of building orientation, site design, facade, and interior layout. Building occupants that can visually connect with outdoor environments while performing everyday tasks experience greater satisfaction, attentiveness, and productivity.
In healthcare facilities, views and access to nature can shorten hospital stays, reduce stress, depression, and the use of pain medication. Views to the outdoors also connect the occupants with natural environmental cues, such as diurnal changes from light to dark and the changes in light from season to season, which are important for maintaining natural circadian rhythms. Disruption of these rhythms can lead to long-term health care problems, including mental disorders.
Becoming a building performance expert not only allows architects to create beautiful high-performance buildings but also allows them to produce healthy environments for occupants. To learn more about the best practices for sustainable building design, check out cove.tool's resource center.