Calculating Carbon Advantages in Adaptive Reuse Projects: The CARE Tool

TE CH NO LO GY

Calculating Carbon Advantages in Adaptive Reuse Projects: The CARE Tool Responsible Decision-Making Designers are charged with

building – either by demolishing

significant amount of carbon

making an incalculable number

an existing structure or clearing

into the atmosphere, and as

of decisions about their projects,

an undeveloped site– or

the need for designers and

and increasingly these include

adapting an existing building

decision-makers to be aware

discussions about the carbon

to fit the needs of the client’s

of their projects’ emissions has

impacts of their designs. In

program in a strategy known as

increased, the need to reduce

making the best design decisions adaptive reuse. Each method

how much carbon a project emits

for responsible environmental

has drawbacks and advantages

in the early stages of design has

impact, it often falls to the

in various categories, but when

increased in kind1.

designer to guide the client

it comes to narrowing down

towards the best path forward.

decisions in the environmental impact category, one of the

One of the questions that

looming concerns is how much

comes up quite often when a

carbon will be released into the

project is in its fledgling state

atmosphere because of this

is whether it would be best

project. Building construction

to design a completely new

and operation release a

RALEIGH IRONWORKS

Calculating precise carbon

and discards; and operational

This investigation analyzes a

metrics is a relatively new

carbon emissions, which is

theoretical project example in

concept in the realm of building

carbon released through the day-

the CARE Tool to learn what

design, but some tools have

to-day use of the building, are

design decisions are associated

become available to aid in

both accounted for. The CARE

with measurable impacts to

this effort. The CARE (Carbon

Tool also allows designers and

carbon emissions. Testing

Avoided: Retrofit Estimator)

decision-makers to test various

various design configurations

Tool2 is one such tool. This online design options and methods

in the CARE Tool and similar

simulator uses information such

to see what effects a design

simulators can give insight into

as overall square footage (SF),

decision has on the carbon

the design factors that most

glazing-to-wall ratio, and building

metrics of the project, such as:

significantly impact the building’s

use to calculate the carbon emissions of an adaptive reuse project compared to a brand-new building.

Embodied carbon emissions, which is carbon released through the actual construction of the PACIFIC BOX & CRATE

building and the materials it uses

carbon emissions, and therefore » How much carbon will this project emit if it is built new? » How much would be saved if it was built in an existing building? » What adaptation methods would most effectively reduce the carbon emissions of this project?

help designers make informed decisions that maximize a project’s emission reduction potential.

Project Setup: Existing Building The CARE tool begins by establishing general information about the project: its location and climate information, electrical grid status, and the number of years over which the tool will model cumulative emissions. The theoretical project in this investigation is located in Charleston, South Carolina, postal code 29403. CARE is set to model emissions over the course of a fifteen-year period using the default climate and electrical grid information, which at the time of this analysis would end right around the 2040 mark.

Theoretical Project A (TPA) examines the advantages of adapting an office building for residential and retail use, which could become a common project example due to shifting retail markets. The second CARE tab asks users to input data for the existing building. TPA has a total area of 20,000 SF over the course of four floors above grade, with zero floors below grade. The structure is “steel and/or concrete,” and the window-to-wall ratio is 60%. The primary use is set to “Office,” and with no secondary use option the full floor area is given to the primary use. The use and operations of a building affect the carbon emission rate, and CARE reflects this nuance. This analysis uses the default energy use intensity (EUI) based on the information provided. Under these conditions, the existing building carbon emissions – operational emissions only, in this case, since no new construction means no embodied emissions – total 2,592 metric tons over the next fifteen years.

Project Setup: New Building CARE’s fourth tab predicts the carbon emissions of a new building. If TPA were a new-build instead of an adaptively reused building – a 20,000 SF, four-story structure used for multifamily housing and retail – it might have a reduced operational emission level compared to the existing building as it stands, but the embodied emissions involved in demolishing an existing building and constructing a new one cannot be ignored. Since the building is intended for multiple uses, the square footage of the primary use and secondary use must be established; 16,000 SF go towards multifamily, and 4,000 SF go to the secondary use of retail store. Once more, the simulation uses the default EUI, only this time there is a target goal of 10% energy use reduction from its predecessor. All new electrical equipment is installed, and 7% of the electricity is produced by off-site renewables, since according to the U.S. Energy Information Administration, 7% of South Carolina energy is produced by renewables as of 20223. The new building would most likely be constructed of steel and/or concrete, so that setting remains the same as the original building, and for the sake of the simulation, selecting all the modifiers assumes best practices for new construction (low embodied emissions concrete, responsibly sourced timber, low embodied emissions envelope, and high-performance MEP systems).

This new building would emit 1,380 metric tons of carbon over the course of fifteen years; however, it would also include embodied emissions of 762 metric tons cradle to grave due to the new construction. This puts the grand total at 2,142 metric tons of carbon over the fifteen-year period.

Project Setup: Adaptive Reuse Building After establishing the original building characteristics and what a new building with the desired function and characteristics would be, the impact of design decisions for adapting the existing building becomes much clearer. Under CARE’s third tab, the building characteristics, use, and operational energy and emissions remain the same – 20,000 SF with no addition, four floors, a change of use with 16,000 SF of multifamily and 4,000 SF of retail, default EUI with a 10% target reduction in energy use, and 7% of energy by renewables. The Embodied Emissions section of the tool provides the most useful insight to what design decisions can have the most impact on the overall emission count.

This section has five parts: Structural System Reuse; Envelope Reuse; Interior Reuse; Mechanical, Electrical, Plumbing Systems Reuse; and Modifiers, which have been used previously under the New Building tab. The reused building assessment tests are conducted with the modifiers turned on to assume best building practices, much like the new building assessment. Assuming there are no changes to any other parts of the building, changing each section by itself informs users what variable has the biggest impact on carbon emissions, and then bringing together all the design decisions made based on this knowledge and other relevant information gives a fair estimate of how the adaptively reused building emissions compare to what a new build’s emissions would be.

Structural Systems Assuming the existing building does not change at all beyond its use and the previously established operational emissions parameters, TPA’s total emissions would be 1,380 metric tons of carbon in 15 years’ time. However, neglecting to take additional changes into account does not make for a feasible way to move the theoretical building forward – an office floor plan and a multifamily residential floor plan are not quite the same, after all – thus certain design factors must change, beginning with the structural system.

If TPA has a structural system that must be completely replaced, but no additional changes to the building are made, the cumulative carbon emissions increase from 1,380 metric tons to 1,958 metric tons, which is a delta 41.88%. If the structural system also needs a lateral upgrade due to its proximity to earthquake or hurricane zones, that number jumps even higher to 2,028 metric tons of carbon, a delta of 46.96%.

Based on this test, the structural system clearly plays a significant role in the amount of embodied carbon a building contains. If TPA has a structural system that is fairly intact – maybe some reinforcing here and there, maybe a new stair or elevator is cut in the floor and needs to be framed around – leading to only a 25% removal of existing structure with lateral upgrades, the total emission count drop back down to 1,594 metric tons, which is only a 15.51% delta.

38TH STREET SCHOOL APARTMENTS

Envelope Reuse Emissions due to building envelope changes can be examined after setting the structural changes back to zero. Once again, CARE reflects the worst-case scenario – while the building does not otherwise change, this test assumes all TPA’s exterior wall assemblies must be replaced and re-insulated, all the windows must be replaced, and the roof must be replaced and re-insulated. Despite its redundancy, checking “insulate walls” ensures the worst possible impact reflects in the test. The total carbon emissions increase from 1,380 metric tons to 1,444 metric tons, a delta of 4.6%. Compared to the impact of demolishing and replacing the entire structural system, this impact is rather light. When it comes to carbon emissions, however, every bit counts.

The most significant impact on this figure for TPA comes from replacing the windows; when the windows are all replaced but the walls and roof remain untouched, the emissions total 1,422 metric tons (change of 3.04%). If only the exterior walls are replaced, with no change to the existing windows or roof, the emissions total 1,400 metric tons, and if the roofing is replaced and everything else is left alone, the emissions come to 1,386 metric tons. Exterior wall replacement and roof replacement lead to changes of 1.45% and 0.43%, respectively. Unfortunately, replacing windows is one of the more common changes to an adaptively reused building envelope, since windows have gotten more efficient as their technology has developed and more efficient windows help reduce building energy use. While this design decision is extremely likely in an adaptive reuse project, the carbon emission impact is significantly lighter than other potential changes, so the benefits are more likely to outweigh the costs. If TPA ends up replacing all the existing windows, but the exterior walls receive only a “medium” level of repair (such as repairing all the building masonry) and a “minor” level of restoration GRACE CHURCH ANDERSON CAMPUS

of the roof, the total emissions for TPA would come to 1,424 metric tons. That is a 3.19% change from an untouched building envelope.

Interior Reuse Changes to the building interior are particularly common – nearly inevitable – when a building gets a new use, such as with TPA. The CARE tool offers three degrees of interior alterations which can be used to varying degrees throughout the analyzed building design: restored/refurbished finishes, new finishes, and rebuilding/ reconfiguration. Once again assuming the worst-case scenario, if TPA needs to be completely gutted and rebuilt for its new use 100% of the interior is reconfigured and rebuilt - the total emissions come to 1,476 metric tons of carbon, a delta of 6.96%. These metrics indicate that changes to the interior have a higher impact on embodied emissions than changes to the exterior – depending on the square footage of the building – but still significantly less impact than the structural changes. If TPA is in relatively good shape and some of the public areas of the building are salvageable with some new finishes but most of the building needs re-configuring for its new use – 5% restored finishes, 20% new finishes, and 75% rebuilt interiors, for instance – the carbon emissions would total 1,460 metric tons for a delta of 5.80%.

Mechanical, Electrical, Plumbing Systems Reuse The ability to reuse the existing mechanical, electrical, and plumbing systems ties into how new the system is and how it can work with any changes made to the interior, so this parameter and the interior reuse parameter could be somewhat linked. If all systems in TPA need to be completely replaced, the total carbon emissions increase from 1,380 metric tons with no additional building changes to 1,504 metric tons, an increase of 8.99%. Medium changes to TPA’s system, such as replacing the system equipment but keeping the system distribution, only increases the emissions by 26 metric tons (1.88% RALEIGH IRONWORKS

increase). Minor repair and refurbishments increase emissions by only 6 metric tons (0.43% increase).

ABOUT THE CONTRIBUTOR

Conclusion After examining the worst-case impact of each embodied emissions design factor and adjusting them for a more reasonable alteration to the existing building, the environmental advantage of adapting an existing building for TPA rather than building a new building becomes clear. If 25% of TPA’s structure has to be replaced and lateral support added, a medium level of exterior wall repair is called for, all windows replaced, minor repairs made to the roof, 75% of the interior reconfigured and rebuilt, 20% interior finishes replaced, 5% interior finishes restored, and a medium level of changes made to the MEP systems, the total carbon emissions come out to 1,746 metric tons in fifteen years. A new building would emit 2,412 metric tons of carbon in that same time period. With all the operational emissions metrics the same in this example, the difference between a new building and a reused building comes down to the savings in embodied emissions. The reused building emits 366 metric tons of carbon, cradle to grave, while the new building would emit 762 metric tons (see Figure 1), which is a savings of 396 metric tons of carbon.

In general, the building with the lowest embodied emissions is the one that changes the least. Knowing where you can make changes that have the least impact is an incredibly useful tool for making design

KAYLEE JACOOB

Practice Professional Kaylee Jacoob is a Practice Professional in LS3P's Charleston office. A graduate of Ball State University with a Bachelor of Science in Architecture and a Minor in Historic Preservation, Kaylee joined LS3P in 2018

FIGURE 1

and has since been integral to growing our industrial, adaptive-reuse, and mixed-use portfolios. Kaylee is passionate about historic preservation; she is a member of the Historic Charleston Foundation and the Preservation Society of Charleston.

decisions that tip the scale. If you have two designs in which one keeps most of the structure but changes the exterior envelope and interior significantly, and the one keeps the exterior envelope relatively intact but in turn most of the structure is lost, knowing how much impact saving an existing structural system has on the carbon emissions of a building becomes a significant variable in the ultimate fate of the project design. The cultural and financial impacts of reusing an

SOURCES 1. https://www.epa.gov/ghgemissions/overviewgreenhouse-gases

existing building cannot go unnoted, either,

2. https://www.caretool.org/about/

and with the arsenal of knowledge that these

3. https://www.eia.gov/state/analysis. php?sid=SC#:~:text=Solar%20energy%2C%20 hydropower%2C%20and%20biomass,state%20net%20 generation%20in%202022

environmental impact simulations and tests can provide, design remains thoughtful and purposeful.