Decarbonizing the Design Process
A Phase by Phase Approach for Landscape Architects 

Version 1

Low-carbon materials and high-sequestration planting design at Milton Street Park, Los Angeles. ASLA 2016 Southern California Chapter Merit Award  / Image courtesy of SWA Group, Jonnu Singleton.

                 





Authors


Alejandra Hinojosa, Affil. ASLA, LPA Design Studios

Mariana Ricker, ASLA, SWA Group

Reviewers


Chris Hardy, ASLA, PLA, Senior Associate, Sasaki

ASLA Team

Jared Green, Hon. ASLA, Senior Manager, Climate Action

Katie Riddle, ASLA, Managing Director, Programs

Pamela Conrad, ASLA, Biodiversity and Climate Action Fellow

About ASLA

Founded in 1899, the American Society of Landscape Architects (ASLA) is the professional association for landscape architects in the United States, representing more than 15,000 members. The Society’s mission is to advance landscape architecture through advocacy, communication, education, and fellowship.

About the ASLA Biodiversity and Climate Action Committee

The ASLA Biodiversity and Climate Action Committee leads the implementation of the ASLA Climate Action Plan.

The committee:

  • Provides input to ASLA leadership on strategies for communicating the role of landscape architecture in mitigating climate change and increasing and protecting biodiversity.
  • Develops and promotes programs, products, and services that provide research data and learning opportunities to practitioners.
  • Advances the adoption of climate positive design and nature-based solutions in the practice and teaching of landscape architecture.

Introduction

Decarbonizing the Design Process offers a phase-by-phase structure to decarbonize design through big ideas, strategies, and best practices. It is high-level, offering approaches that can be implemented regardless of project type, scope, and scale.

The majority of the guide is based on resources, such as:

These resources and research have been a tremendous help to our industry. They give practitioners access to information and data that we didn’t have before. But there was no guide that overlaid these strategies with the design process. The phase-by-phase approach in Decarbonizing the Design Process pulls from the SWA Guide to Decarbonize Design, developed as part of a firm fellowship project by Mariana Ricker, with close collaboration by Alejandra Hinojosa, in a previous role.

Though not covered in Decarbonizing the Design Process, it is also critical to measure greenhouse gas emissions of our projects. Tracking emissions is the only way to measure our industry’s progress towards the ASLA Climate Action Plan goal of 50 percent reduction by 2030 and zero emissions by 2040.

This carbon accounting process is achieved by conducting a life cycle assessment (LCA). There are a number of landscape calculators and tools available. Steps to incorporate these into the design process are discussed in the ASLA Biodiversity & Climate Action 101 Webinar: Decarbonizing Design: Best Practices and Strategies by Design Phase by Mariana Ricker, ASLA, SWA; Andrew Wickham, ASLA, LPA Design Studios, and Marieke Lacasse, FASLA, GGLO.

How to Navigate the Guide

The graphic overview and guide structure is intended to assist the reader with document wayfinding and orientation. You can read this guide from start to finish or navigate directly to the specific phase in which your project is currently.

Guide Overview

Project phase organization of Decarbonizing the Design Process.

At a high level, early design phases are the most important time to set decarbonization goals. The design work that follows should:

  • Prioritize strategic, low-carbon decisions
  • Follow through with those decisions during construction documentation
  • Successfully deliver a low-carbon project

The strategies outlined in the guide assume “typical” design phases and project structure. Depending on project scope or contract, there may be more, less, or alternative opportunities for decarbonization led by the landscape architects. Opportunities will vary depending on whether the project is public or private, a competition or design build project.

Guide Structure 

Each section is organized by the project phases listed in the Outline. Within these project phases, recommendations are organized in the following hierarchy:

BIG IDEAS provide a simple umbrella approach to decarbonizing design practices.

  • STRATEGIES are action items that contribute to the big idea
  • Best Practices; Resources; Examples; and Tools to execute each strategy
  • Design Tips

The Role of Landscape Architects

As practitioners and professionals, our decisions matter. We influence project goals and set priorities that guide design decisions and define the look, shape, and feel of our built environment. Currently, the built environment we help create is responsible for a staggering 42 percent of all global greenhouse gas emissions (Architecture 2030).

Considering trade-offs and understanding co-benefits is at the core of what we do to balance a multitude of project priorities. Adding a lens of decarbonization to our decision-making process will only improve the outcomes of our design work.

As leaders and designers within our respective firms we can tackle decarbonization by:

  • Making intentional, informed, and low-carbon design decisions
  • Addressing the broader environmental impacts of our projects
  • Advocating for better practices in shaping our built environment

Our role as landscape architects is uniquely positioned to impact more than a project’s embodied carbon emissions and operational carbon emissions. We go beyond emissions reduction, and can actively promote carbon sequestration and storage throughout the lifecycle of the project. According to a study from The Nature Conservancy, “increasing carbon sequestration in plant biomass has the greatest potential to reduce net carbon emissions and slow the effects of climate change.”

Heron Elementary School protected mature trees, planted native plants, and incorporated a mix of low-carbon materials. Natomas, CA / Image courtesy of LPA Design Studios, Costea Photography


Project Kickoff

Project kickoff is a time for creative ideas and connecting with project team members. These are typically structured in a way that brings all scopes of work together to establish design intention, goals, and next steps. This is when we can begin advocating for multidisciplinary goal-setting that emphasizes decarbonization as an essential part of the overall project story and design narrative.

These points of coordination are when we can most easily establish decarbonization goals with the client and full project team. Though we want to prioritize low-carbon design strategies, these should also complement and reinforce other project priorities through co-benefits.

At kickoff, gaining alignment as a team will ensure that everyone is working from the same information and design intention as the project proceeds through the next phases.

Note: Ensure contract scope and fee is reflective of any extra hours, coordination meetings, or expertise needed as part of the decarbonization process.

“Four Common Concerns with Low-Carbon Design” / ©2024, LPA Design Studios. Diagram courtesy of LPA Design Studios Catalyst Issue 3 2024

Project Kickoff

BIG IDEA: Establish a decarbonization strategy for your project

Discuss decarbonization co-benefits and value add to the project. / Diagram courtesy of SWA Guide to Decarbonize Design.

  • STRATEGY: Discuss co-benefits and added value to the project.
  • Best Practice: Use the concept of the Triple Bottom Line as a framework for organizing complementary goals and co-benefits:
  • People: public health & well-being, building social capital
  • Planet: biodiversity, habit creation, clean water, ecosystem services
  • Prosperity: economic success, tenant/visitor attraction, net present value

  • Best Practice: Research and address any broader climate action commitments the client has. Examples include:
  • Corporate Environmental, Social, Governance (ESG) Goals
  • Firm-wide Architecture 2030 Goals
  • State/local government Climate Action Plans

  • Best Practice: Research policy requirements that can influence the project

  • STRATEGY: Confirm full team commitment to decarbonizing the design process.
  • Best Practice: Organize and conduct a sustainability charrette to define decarbonization roles and responsibilities.
  • Best Practice: Prioritize close design collaboration on decarbonization, particularly in the most impactful phases of the project.

Potential impact of designers over project life. “The potential impact of designers regarding carbon budgets of projects over the project life. The greatest potential for changing expectations is at the planning and concept phases when the design is most flexible. However, at each technical documentation phase, there is always a pull to business as usual, so planning and concept phase goal-setting studies are not sufficient without follow through.” / Diagram and caption courtesy of Sasaki’s White Paper, Designing with a Carbon Conscience V2.

Concept/Schematic Design

Many high-level, high-impact decisions that can maximize opportunity for decarbonizing project design will happen in the conceptual and schematic design phases.

At this stage, building placement, hardscape ratios, and site organization are still flexible. This is when you can advocate for design concepts that achieve project needs without sacrificing sustainability and decarbonization goals.

Find opportunities to:

  • Reuse a site’s existing materials, structures, mature planting, and natural grading
  • Design hardscape areas that are scaled appropriately to the program needs while prioritizing greenspace and diverse planting
  • Design for low impact with green infrastructure and a natural materials palette

How can you protect, preserve, and reuse existing on-site planting and materials? Always start with the lowest emissions materials possible by default. A good rule of thumb: “the more complex the fabrication of a material or product, the higher its associated carbon costs.” – Designing with a Carbon Conscience V2

“Landscape architects developed a meaningful program rooted in site history and ecology while responding to the open space needs of the neighborhood and broader community.” ASLA 2020 Professional General Design Honor Award. Naval Cemetery Landscape, Brooklyn, NY. Nelson Byrd Wolz Landscape Architects / Max Touhey  

Concept/Schematic Design

BIG IDEA: Conduct a detailed site assessment to maximize potential reuse of existing resources in design concepts

Conduct a detailed site assessment to maximize potential use of existing resources in design concepts. / Diagram courtesy of SWA Guide to Decarbonize Design.

  • STRATEGY: Identify opportunities to reduce, reuse, recycle, and upcycle.
  • Best Practice: Highlight inclusion of existing site elements in proposed designs.
  • Design Tip: “Reuse site concrete and asphalt as aggregate or pavers. Fallen site trees can be repurposed as furnishings, site elements, boardwalks, and interior use. Utilize boulders and stone as site elements, retaining structures, or aggregate.” (CPD)
  • STRATEGY: Coordinate grading approach with project engineers.
  • Best Practice: Conserve and protect topsoil and soil biodiversity.
  • Best Practice: Balance cut-and-fill to minimize offhaul and import.
  • STRATEGY: Protect existing natural ecosystems.
  • Best Practice: Designate areas of existing ecosystems on site to be protected and/or restored. Identify mature trees to be protected in place.
  • Design Tip: If applicable to the site program, design boardwalks or elevated walkways to avoid soil and ecosystem disturbance.

Concept/Schematic Design

BIG IDEA: Emphasize Low Impact Design (LID) strategies

  • STRATEGY: Advocate for parking and mobility solutions that promote low-carbon transportation and minimize the need for on-site parking.
  • Best Practice: Prioritize and plan for active transportation options.
  • Design Tip: “Plan for small and lightweight human- and electric-powered vehicles. Micro-mobility can improve last-mile connectivity to other forms of transit, while reducing congestion, pollution, and emissions, and improving street life and health outcomes” (CPD)
  • Best Practice: Improve connections to multi-modal transit networks.
  • Design Tip: “Connect to multi-modal transit networks, with stations at appropriate distances. For example, bus stops at frequent intervals, light rail stops at greater distances, and heavy rail stops less frequently” (CPD)
  • Design Tip: “Provide appropriate facilities such as shelters, restrooms, and safety features, including lighting at public transport stations, bus stops and bike parking areas, and shade trees where appropriate” (CPD)
  • STRATEGY: Evaluate design options for ratios of hardscape to softscape.
  • Best Practice: “Less is more, most of the time” as it relates to hardscape and carbon intensive materials (Designing with a Carbon Conscience V2)
  • Best Practice: Determine program requirements for the project, testing concept alternatives to right-size the hardscape and softscape areas to align to the intensity of program use.
  • Design Tip: “Aim for 70% planting and 30% paving” depending on project type and program. (CPD)
  • STRATEGY: Design with green infrastructure strategies in mind.
  • Best Practice: Advocate for the design of natural drainage swales and biotreatment areas to manage stormwater/wastewater in the landscape.
  • Design Tip: Follow the existing drainage patterns of the site
  • Design Tip: Irrigate minimally with passive, gravity irrigation
  • Best Practice: Use land forms to avoid retaining walls where possible.
  • Best Practice: Prioritize site shading techniques that rely on vegetation instead of architectural canopies.
  • Best Practice: Select permeable paving options for stormwater infiltration.

Concept/Schematic Design

BIG IDEA: Set a preliminary palette for low embodied carbon + high sequestration

Low-carbon landscape / Diagram © 2024 LPA Design Studios

  • STRATEGY: Prioritize a planting design with high carbon sequestration potential.
  • Best Practice: Do not suggest synthetic turf unless necessary for project programming. If the client requests it, suggest alternatives.
  • Best Practice: Minimize non-native lawn and turf that typically requires regular maintenance with gas-powered mowers and chemical fertilizer.
  • Design Tip: Depending on ecoregion, you can recommend species like native Bermuda grass as an alternative to St. Augustine.
  • Best Practice: Aim for a planting palette that is multilayered, native, dense, and diverse to promote carbon sequestration and ecosystem services.
  • Design Tip: Depending on programming, gauge client interest in designs that involve rewilding, afforestation, habitat restoration, pollinator gardens, and tiny forests.
  • STRATEGY: Research sustainable site furnishing options.
  • Best Practice: Seek out local manufacturers that have EPDs for their products or have company-wide decarbonization and sustainability goals.
  • Best Practice: To promote circularity, prioritize products made with high recycled content, are easily recyclable, or consider future disassembly.

  • STRATEGY: Select hardscape materials that have lower embodied carbon. High emissions materials should only be considered for key design elements that require a specific material to meet the design intent and program requirements.
  • Best Practice: For carbon intensive materials, consider alternatives.
  • Design Tip: “Gabions, rammed earth, mud walls, cobb, straw bale, wattle and daub, mud and stud, compressed earth blocks, adobe, air-dried bricks, earth mortar and other earth-based building materials, site boulders, reused concrete, bamboo, and bio-based materials such as live willow revetments, are low-carbon alternatives to concrete and steel.” (CPD)

Seat wall carbon impact analysis / Meg Calkins and Lizandro Marcial-Armas, NC State

Design Development

The design development phase is when decisions are refined and finalized. It’s a good time to revisit the decarbonization goals established at the beginning of the project and look for new opportunities when the carbon-smart move is also the budget-smart move.

When reaching out to vendor representatives to confirm your project materials and product selections, take the opportunity to inquire about carbon emissions through documentation, such as Environmental Product Declarations (EPDs).

Product and material feedback should be supplemented with additional research into available lower-carbon alternatives. It’s important to verify assumptions about materials, their availability, and how they compare to one another before the design becomes too locked in through permitting, pricing, etc.

Design development is also when you can begin finalizing your planting palette based on research done in schematic design and feedback from the client. Continue to demonstrate how a native and multi-layered diverse landscape can compliment the overall project design and contribute to sustainability goals, decarbonization goals, and the triple bottom line.

Concrete was salvaged from the loading dock and repurposed within a Birch grove and gabion walls. The plants are all native to the Piedmont region. ASLA 2021 Professional General Design Honor Award. Atlanta Diaries, Atlanta, Georgia. Perkins&Will / Sahar Coston-Hardy

Design Development

BIG IDEA: Talk to manufacturers about product and material emissions

  • STRATEGY: Ask product reps for Environmental Product Declarations (EPDs).

  • STRATEGY: Inquire about additional sustainability performance data for products such as site furnishing, lighting, and other items with synthetic materials.
  • Examples: Information regarding recycled content percentage, material health (VOCs), and sustainability certifications (FSC, Cradle to Cradle).

  • STRATEGY: Verify distances and mode of transportation between material sourcing, manufacturing, and the construction site. Carbon impact varies greatly depending on transportation method (rail, plane, ship, truck) and distance.
  • Resource: SITES guidelines for sourcing local products:
  • Within 50 miles – soils, compost, mulch
  • Within 50 miles – boulders, rocks, and aggregate
  • Within 250 miles – plants
  • Within 500 miles – all other materials

Verify distances and mode of transport. / Diagram courtesy of SWA Guide to Decarbonize Design. (*EPA standard values associated with transportation type.)

Design Development

BIG IDEA: Maintain the importance of low carbon design decisions to the client and project team

  • STRATEGY: Revisit co-benefits and project goals from kickoff.
  • Best Practice: Use equivalency calculators to incorporate environmental benefits of carbon savings into the design narrative and share with clients.
  • Best Practice: If the project is pursuing a sustainability certification, leverage credit overlaps and point targets to push decarbonization efforts.

  • STRATEGY: Promote selection of innovative low-carbon materials with project engineers and clients.
  • Best Practice: Introduce fill alternatives to geofoam
  • Best Practice: Introduce bio-based materials
  • Design Tip: Explore cork-based play surfacing as an alternative to rubberized pour-in-place surfacing to reduce carbon emissions and address other health concerns that come with synthetic rubber products.
  • Best Practice: Introduce procuring “low-carbon” concrete, steel, unit masonry, brick, and other materials and research local market availability.
  • Design Tip: Look for products, materials, and manufacturers that have existing product-specific EPDs or have the capacity to create them. This “on-demand” EPD generation is plausible for some concrete batch plants.

  • STRATEGY: Leverage the value engineering process to capitalize on additional carbon savings that can be made from material reduction.
  • Best Practice: Identify opportunities where hardscape reduction could result in both cost and carbon savings. This can be general area as well as assembly thickness, reinforcing, or footings.  

Design Development

BIG IDEA: Refine and finalize low carbon design decisions

Low-carbon materials palette. / Diagram courtesy of SWA Guide to Decarbonize Guide.

  • STRATEGY: Select and finalize low-carbon materials and products.
  • Best Practice: Select product and site furnishing manufacturers based on the best sustainability/carbon metrics in addition to aesthetic and function.
  • Best Practice: Make a compelling design argument for selecting sustainably-sourced, domestic hardwood for site elements.
  • Design Tip: Do not present tropical hardwoods as a material option. Instead, use species like domestically-sourced thermally modified Black Locust, Yellow Pine. or Ash. 
  • Best Practice: Use decomposed granite or other non-virgin stone aggregates as paving materials instead of concrete and asphalt where the program allows.
  • Design Tip: Plan on using a plant-based binder if feasible. 

  • STRATEGY: Minimize soil impact and subgrade construction.
  • Best Practice: Select paving and structural elements that have minimal depth requirement for sub slabs and footings.
  • Design Tip: “Sand-set pavers and minimize thicknesses of paving and base courses. Seek alternatives to slurries, concrete infrastructural encasements, and cementitious geotechnical soil reinforcement. Choose geotechnical construction methods with lower embodied energy, such as mechanically stabilized earth and geopiers, or rammed aggregate piers.” (CPD)
  • Best Practice: Avoid selecting annual species that would disturb soil through regular replanting.
  • Design Tip: “Choose self-seeding or spreading annuals and perennials.”  (CPD)

  • STRATEGY: Design and finalize a carbon-smart planting palette.
  • Best Practice: First, restore any existing native ecologies found on site. If none are present, create conditions for new ones to thrive.
  • Design Tip: If native to your project ecoregion, explore afforestation or establishing mangroves, wetlands, or prairie grasslands.
  • Best Practice: Select species based on what can be procured locally to avoid transportation emissions associated with tree-tagging travel and shipping plant material from nursery to site. This is particularly critical for large site trees.
  • Best Practice: If programming requires lawn, select species and cultivars that are native or adapted to the site. Specify seed or hydroseed rather than sod.
  • Design Tip: “Maintain healthy, actively growing perennial turfgrass. Avoid tilling or renovating turf under 30 years of age, as turf sequesters more carbon in the first 30 years of its life, on average.”  (CPD)
  • Best Practice: Design and plan for a low-maintenance landscape.
  • Design Tip: “Allow the landscape and species composition to evolve over time, improving resilience and reducing maintenance and replacement emissions. Avoid hedges and planting designs that rely on regular trimming or pruning. Choose plants that need only occasional (once or twice-yearly) pruning or mowing. Give larger shrubs space to grow to full size, and underplant with self-spreading annuals and perennials.” (CPD)
  • Best Practice: Design a diverse planting palette with high carbon sequestration and storage potential.
  • Design Tip: “Multi-layered planting above and below ground, with plants of different heights, forms and root structures, results in complex, adaptive, healthy ecologies that can maximize sequestration, resilience, and biodiversity.”(CPD)
  • Design Tip: “Plant a mix of, large, and fast-growing native and adaptive trees, shrubs and plants. Include both annual and perennial plants, with a larger proportion of perennials. Select species with longer growing seasons to maximize sequestration potential. Avoid plants that are too aggressive or competitive.” (CPD)
  • Design Tip: “Use tree plant spacing that exists in natural forests rather than typical plant spacing guidelines. Using techniques such as the Miyawaki Method, up to 57 trees can be planted in an area the size of a parking spot!” (CPD)

Sample planting design for a “Carbon Garden.” / © 2024 LPA Design Studios

Construction Documents 

Some landscape architects may ask:is it too late to incorporate decarbonization strategies on a project that is already in construction documents? The answer is no.

Sometimes, small adjustments to a detail can reduce the carbon emissions of a material assembly in a big way, especially if those materials represent a large portion of the design. The process of reviewing construction documents for carbon optimization is known as “greenlining.”

Detail-level greenlining should be coordinated across the entire project team in order to ensure that geotechnical, civil, and structural requirements are still met.

In addition to project details, there are also many opportunities within the project specifications for further decarbonization. The AEC industry is increasingly seeing federal, state, and local legislation that focuses on decarbonization efforts by requiring projects to include documentation verifying low-carbon material procurement through EPD submittals and global warming potential (GWP) limits in kilograms of carbon dioxide equivalent (kgCO2e).

 “Native plants and site boulders unearthed during construction anchor arroyo soils in place and reintroduce local character and ecology to the campus.” ASLA 2023 Professional General Design Honor Award. The University of Texas at El Paso, El Paso,Texas. Ten Eyck Landscape Architects / Adam Barbe.

Construction Documents

BIG IDEA: Coordinate with the team to decarbonize details 

  • STRATEGY: Avoid over-engineering and minimize the complexity of your assemblies.
  • Best Practice: Right-size carbon-intensive forms such as concrete or metal seat walls, stairs, large signage elements, and retaining walls.
  • Best Practice: Optimize reinforcing design with project engineers to align to requirements for the final intended level of use.

  • STRATEGY: Confirm use of innovative low-carbon technologies with the team.
  • Best Practice: Use Glass Fiber Reinforced Concrete (GFRC), fiberglass dowels, geotextile fibers in concrete mix designs (see more below under big idea: greenline specifications).
  • Best Practice: Explore fill alternatives to geofoam.

  • STRATEGY: Discuss what will be needed for local procurement.
  • Best Practice: Use EC3 tool to compare low-carbon material options.

Construction Documents

BIG IDEA: Discuss strategies to “greenline” specifications

  • STRATEGY: Refer to the ASLA Guide Decarbonizing Specifications.
  • Best Practice: Given that Concrete (033000) is often the highest emitting landscape material, updates to this specification section should be a priority, with alterations or inclusion of the following:
  • A “low-carbon” concrete mix design
  • Allowing a hydraulic blended cement (ASTM C595)
  • Allowing supplementary cementitious materials (SCMs) - fly ash, slag, etc.
  • Allowing recycled concrete aggregate (RCA)
  • A reference to GWP (kgCO2e) limits and EPD submittals
  • Domestically sourced steel reinforcing with high recycled content
  • Allowing non-potable water use per ASTM C1602 standard.
  • Best Practice: For Stone (044000), Base Course & Aggregates (321100), and Aggregate Surfacing ( 321500), local sourcing – extraction, finishing and processing – is the most important consideration. Natural stone is recommended over stone veneer or any highly processed or finished stone options.
  • Best Practice: The emissions from Metals (057000) can be significantly reduced by specifying high recycled content minimums, sourcing domestically within the U.S., specifying natural finishes and patinas and considering sufficiency in size and quantity.
  • Best Practice: Specification of wood for all Carpentry (061000) elements should ensure a third-party verified sustainability certification of all materials. Tropical hardwoods such as Ipe should be avoided at all costs, even if they happen to have a sustainability certification.
  • Best Practice: Consider specification of regionally available Lightweight Fill (321100) like foamed glass aggregate in lieu of carbon intensive geofoam.
  • Best Practice: The carbon sequestration potential of Soils (329100) is significant. Specifications can support this through protection requirements, testing criteria, appropriate amendments, and import sourcing restrictions.
  • Best Practice: Consider specifying Asphalt (321200) as a Warm Mix Asphalt (WMA) instead of a Hot Mix Asphalt (HMA). Consider including Reclaimed Asphalt Pavement/Shingles in either mix type (RAP/S). Consult with manufacturers to confirm feasibility in certain freeze/thaw climates.



Construction Documents

BIG IDEA: Revisit local regulations for specification compliance prior to permitting

  • Best Practice: Plan in accordance with climate action regulations in place to meet code compliance and future-proof projects for any anticipated policy changes.

Consult the CLF Policy Toolkit. / Image courtesy of Carbon Leadership Forum (CLF).

Construction Administration 

Efforts to decarbonize design are put to the test when the project moves from design to construction. There are many ways in which the emissions reduction intent of low-carbon design decisions can be impacted by construction procedures.

Within a typical project structure, however, the role of the landscape architect is to:

  • Coordinate with the contractor
  • Verify design intent is being accurately depicted in the construction drawings
  • Provide recommendations to the client for how best to ensure that the built project is consistent with the design intent

Decisions related to construction means and methods are generally within the scope of the contractor. Achieving low-carbon built work therefore depends on:

  • Clear communication
  • Established expectations
  • Careful review at key construction milestones
  • Risk mitigation

This can be facilitated by engaging the contractor during the design process, and using project specification requirements to verify key decarbonization goals are met.

ASLA 2022 Professional General Design Honor Award. West Pond Living Shoreline, Brooklyn and Queens, NY. Dirtworks Landscape Architecture P.C. / Alex Zablocki

Construction Administration

BIG IDEA: Monitor construction progress and review at key milestones

Monitor construction progress and review at key milestones. / Diagram courtesy of SWA Guide to Decarbonize Design

  • STRATEGY: Set clear expectations before start of construction
  • Best Practice: Any additional submittal and mockup requirements should be clearly identified in the drawings and specifications.
  • Best Practice: Any additional reporting or submittal requirements should be reflected in the contract between the contractor and client to avoid change orders later in the process.
  • Best Practice: Expectations and procedures that require involvement by various sub-contractors should be covered in pre construction meetings.
  • Best Practice: Throughout the construction progress, landscape architects should expect that this will be a learning experience for both the contractor and themselves.

 

  • STRATEGY: Review site protection measures
  • Best Practice: Protect as much of the site as possible from construction traffic to minimize the negative impacts of soil compaction.
  • Resource: Refer to ASLA’s guide Decarbonizing Specifications for guidance on tree and vegetation protection (Division 1) and soil protection zones (329100).

  • STRATEGY: Require submittals to ensure compliance
  • Best Practice: Review EPDs and related information as required in specifications.
  • Best Practice: Verify that source locations are consistent with assumptions made during design as well as sourcing requirements in specifications.
  • Best Practice: Refer to ASLA’s guide Decarbonizing Specifications for guidance on soil testing, amendments, and import (329100).

  • STRATEGY: Use mock-ups to mitigate installation risks
  • Best Practice: For high-carbon materials like concrete, it is particularly key to ensure that the desired quality of construction is met by the mock-up in order to avoid issues later that could require large areas to be redone.
  • Best Practice: For less typical or innovative low-carbon construction techniques, such as rammed earth walls, mock-ups can be used to resolve any questions that subcontractors have if they are less familiar with the installation process.

Operations and Maintenance  

Design decisions made throughout the project process have direct impacts on the long-term maintenance and operation of a landscape.

The majority of the ideas and strategies discussed throughout this guide are focused on embodied carbon. However, long-term operational emissions should be a consideration  when applicable. If your client is amenable, suggest putting together a maintenance manual or assist with training for maintenance staff.

“Zones of preserved and introduced vegetation highlight stages of woodland succession across the site.” ASLA 2021 Professional General Design Honor Award. Ferrous Foundry Park, Lawrence, Massachusetts. STIMSON / Ngoc Doan 

Climate Positive Design’s Operations + Maintenance Recommendations

Operations and Maintenance

BIG IDEA: Develop sustainable landscape maintenance practices

  • STRATEGY: Encourage the use of electric maintenance equipment, especially charged by renewables.

  • STRATEGY: Minimize fertilizer and pesticides, using organic alternatives instead.

  • Best Practice: Do not use quick-release nitrogen fertilizer, which can result in nitrous oxide releases to the atmosphere, a greenhouse gas 300 times more heat-trapping than CO2.

  • Best Practice: Conduct tests to verify general soil health.
  • Best Practice: Incorporate slow-release amendments, including fertilizer only after testing soils to support healthy root systems early on, then taper to minimal fertilization.
  • Design Tip: Cease fertilization before heavy precipitation or irrigation or during warm periods.

  • Best Practice: Do not use glyphosate herbicides or other chemical herbicides and pesticides, including the neonicotinoid (neonic) class of pesticides. Chemical herbicides and pesticides devastate soil life.

  • STRATEGY: Reconsider traditional lawn maintenance techniques.

  • Best Practice: Leave grass clippings in the turf. Increase grass mowing height, which may promote deeper root development.

  • Best Practice: Avoid chemical pesticides by using Integrated Pest Management (IPM).

  • Best Practice: Include flowering forbs in turf planting to support pollinators.

  • STRATEGY: Improve lifecycle management through planting, pruning, and mulch
  • Best Practice: Keep logs and pruned woody material onsite as woody debris, perpetuating a healthy regenerative ecosystem that can cycle carbon into soil and reduce carbon release.
  • Best Practice: Compost, especially on-site compost); compost tea; probiotic inoculants;  and vermiculture build soil ecologies and capacity for carbon sequestration.
  • Design Tip: Biochar is also an excellent way to capture carbon and store it in the soil, while improving the nutrient uptake of plants.
  • Best Practice: Monitor planting and fill in gaps with seed and underplanting, to maximize carbon sequestration through photosynthesis.
  • Best Practice: Use mulch appropriate to the site. A variety of mulch material – leaf litter, wood, bark, straw – provides more nutrients that can be cycled into the soil by microbes.
  • Design Tip: Wood chip mulch decomposition releases as much as 80 percent of the stored carbon. Wood-based mulches have a lower carbon footprint than gravel mulches.
  • Design Tip: In sandy or desert environments, use local sand or rock-based mulches to avoid introducing inappropriate organic material. Retain woody debris, snags, brush piles, and leaf litter for a healthy, productive ecosystem of increased soil carbon.

Glossary

Carbon - The many names of “carbon.” The following list of terms are used somewhat interchangeably to refer to the emissions associated with climate change or global warming:

Carbon (C)

Carbon footprint

Carbon dioxide (CO2)

Carbon dioxide equivalent (CO2e or CO2eq)

Greenhouse gas (GHG) emissions

Fossil fuel emissions

Global warming potential (GWP)

Climate change (CC) potential

These terms do not share the exact same meaning. Although the term “carbon” is commonly associated with climate change, it is technically not elemental carbon that contributes to climate change, but carbon dioxide gas along with many other substances, such as nitrous oxide and methane.  

Nevertheless, “carbon” is often used as an abbreviation to refer to global warming potential (GWP), which is quantified in kilograms of CO2 equivalent (kg CO2e) (CLF)

Carbon Accounting - The process of tracking and calculating the embodied carbon of materials you select as part of your design, as well as the embodied carbon of the required material assembly for construction, and the emissions associated with transport and installation.

Depending on what software you are using, you can also calculate how much carbon your planting is sequestering and storing throughout the life cycle of your project. Some tools provide opportunities to capture emissions from maintenance.

Carbon Dioxide Equivalent (CO2e) - The carbon dioxide equivalent (CO2e) is a way to calculate GHG emissions by multiplying the amount of gas by its Global Warming Potential (GWP) (See definition below). This allows materials, such as concrete, to be measured equally on a per-unit basis to determine environmental impact. (CLF)

Carbon Footprint - The total amount of greenhouse gas emissions, primarily carbon dioxide, released directly or indirectly throughout a landscape’s life cycle. (One Click LCA)

Carbon Sequestration - The active storing of carbon from the atmosphere into vegetation or soils. (Carbon Conscience)

Carbon Stored - The mass of carbon locked up within materials, vegetation, or soils that is not readily offgassed into the atmosphere. (Carbon Conscience)

Climate Positive Design - Design that reduces emissions and increases sequestration over a project’s life span while also providing environmental, cultural, and economic co-benefits such as biodiversity, equity, and resilience. (ASLA CAP)

Embodied Carbon - Estimate of the probable carbon emissions from a material or product’s sourcing, fabrication, transport, and installation on site. (Carbon Conscience)

Environmental Product Declaration (EPD) - An EPD transparently reports objective, comparable, and third-party verified data about products and services' environmental performances from a lifecycle perspective. (EPD International) Typically these documents capture emissions from raw material extraction through manufacturing. They don’t include transportation to your construction site or emissions associated with installation. (CLF)

Global Warming Potential (GWP) - “A measure of how much energy the emission of 1 ton of a gas will absorb over a given period of time, relative to the emission of 1 ton of carbon dioxide (CO2). The larger the GWP, the more that a given gas warms the Earth compared to CO2 over that time period. The time period usually used for GWPs is 100 years. GWPs provide a common unit of measure, which allows analysts to add up emissions estimates of different gasses (e.g., to compile a national GHG inventory), and allows policymakers to compare emissions reduction opportunities across sectors and gasses.” (EPA)

Greenhouse Gasses (GHG) - Any gas in the atmosphere emitted by human activity that absorbs and re-emits heat. There are seven GHGs covered by Kyoto Protocol: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), Sulphur hexafluoride (SF6), and Nitrogen trifluoride (NF3). (One Click LCA)

Life Cycle Assessment (LCA) - Life cycle assessment (LCA) is the rapidly evolving science of illuminating environmental impacts in terms of their quality, severity, and duration. A landscape  generates environmental impacts throughout its life cycle. The various stages of a typical life cycle as defined in LCA:

  1. The production and construction stages
  2. The use stage
  3. The end-of-life stage
  4. Externalized impacts beyond the system boundary

The beginning of the life cycle is also referred to as the “cradle,” while the exit point of the manufacturing facilities is known as the “gate,” and the end of the life cycle is known as the “grave.” Thus, terms such as “cradle-to-gate” and “cradle-to-grave” are used to refer to different ranges of the life cycle. (CLF)

Net Zero - An activity that removes as much greenhouse gasses from the atmosphere as it emits. (ASLA CAP)

Operational Carbon - In contrast to embodied carbon, operational carbon refers to the greenhouse gas emissions from energy consumption. Associated with the life-cycle phase B (use stage). (CLF)

Supplementary Cementitious Materials (SCMs) - Soluble siliceous, aluminosiliceous, or calcium aluminosiliceous powders used as partial replacements of clinker in cements or as partial replacements of portland cement in concrete mixtures. (Source)

Whole Project Life Cycle Assessment (WPLCA) - “A study that calculated the environmental impacts of an entire project inclusive of a site and building impacts, materials, construction, and operations over the project’s lifespan.”  (Carbon Conscience)

Zero Emissions - An activity that releases no greenhouse gasses into the atmosphere. As opposed to net-zero emissions, which allows for offsetting of emitted carbon to reach a balance of zero, zero emissions focuses on absolute emissions. (ASLA CAP Field Guide)

Citations and Resources

  1. American Society of Landscape Architects (ASLA) Resources and Guides
  1. Climate Action Plan
  2. Collaborating with Industry Partners on Climate Action and Biodiversity
  3. Navigating Environmental Product Data
  4. Decarbonizing Specifications

  5. Biodiversity & Climate Action 101 for Landscape Architects Webinar Series

  1. External Resources
  1. Climate Positive Design Toolkit
  2. Carbon Conscience White Paper & Resources 
  3. Australian Institute of Landscape Architects (AILA) Climate Positive Design Volume 1: Action Plan of Australian Landscape Architects
  4. Architecture 2030
  5. Carbon Leadership Forum 
  6. Building Transparency
  7. SITES Certification
  8. Microsoft White Paper “Reducing Embodied Carbon in Construction”
  9. AGC Playbook on Decarbonization and Carbon Reporting in the Construction Industry 
  10. LMN Architects “Path to Zero Carbon Series”

  1. Carbon Calculators and Tools
  1. Carbon Conscience - intended use for planning and concept
  2. Pathfinder - intended for use from SD through CD
  3. EC3 Tool - intended use for CD/CA and procurement
  4. EPA Greenhouse Gas Equivalencies Calculator - intended to provide you with everyday equivalencies based on entered emissions
  5. iTree - intended to estimate carbon sequestration & storage potential of planting palette