The Methodology Behind Nuuly’s Impact Model

Evaluating clothing rental as a “more sustainable” or “less impactful” fashion consumption solution has been an area of interest and uncertainty across the fashion industry, sustainable fashion advocates, academia, circular economy experts and more.

The most “sustainable” solution is to reduce fashion consumption or abstain altogether. Wearing what you already own will always be environmentally preferable to purchasing new, secondhand or renting clothing. That said, the impact intensity of clothing consumption is directly related to utilization—how often you wear what you buy or rent.

In the United States, clothing is worn about 25% as long as the global average, according to the Ellen MacArthur Foundation. Compared to 15 years ago, clothing utilization has decreased 36% worldwide, and the Ellen MacArthur Foundation notes more than half of “fast fashion” garments produced are disposed of in under a year.

At Nuuly, we understand the critical role that utilization plays in moving towards more sustainable fashion consumption while also recognizing that maximizing the utilization of our clothes requires a tradeoff: more rents = more wears = greater transportation and laundry impact. In order to understand this tradeoff better, we created a data model to quantify the carbon and water impact per wear.

Our Objectives:

• Compare the impact of renting clothing from Nuuly with purchasing clothing from a standard clothing brand
• Center on product utilization to compare results most meaningfully and accurately to the linear model
• Evaluate the environmental impact of rental fashion. This requires stepping outside of traditional methods of product life cycle assessment (LCA), which lack mechanisms for capturing the benefits of and accurately representing circular activities
• Find at what point of utilization rental becomes preferable from a carbon- and water-impact perspective

Our Hypothesis:

• Across one or more categories or styles, Nuuly clothing gets additional utilization compared to the purchased alternative, that is, a higher number wears over the lifetime of the garment
• Nuuly accrues additive carbon (kg CO2e) and water (gal) impact compared to purchased alternative through transport and laundering
• Nuuly may be environmentally preferable vs. the purchased alternative after normalizing environmental impact based on number of wears

Our Methodology:

Evaluate the lifetime carbon and water footprint of Nuuly garments, and normalize those impacts across the average number of wears

• First, we mapped out all stages and activities that these garments go through across their lifecycle, including before and after they are in Nuuly’s rental inventory

• Next, we gathered data on the carbon and water contributions from each stage across the value chain to calculate the footprint of the average garment for each category (jeans, occasion dresses, puffer jackets)

  ○ Primary and secondary data from industry and academic research, Nuuly shipping and operations data, subscriber survey data

• We engaged subscribers on the number of times they wear their rentals, via survey, in order to calculate the average wears per rent for our categories

I. Defining Our Scope:

We chose three distinct categories of clothing in the Nuuly inventory on which to focus our analysis. We avoided focusing on “the average Nuuly garment” because, frankly, it doesn’t exist.

There are so many reasons to rent from Nuuly, and so many nuances across clothing categories. We chose three to compare against each other, across both unique and common use cases.

II. Our 3 Categories and Rationale:

Jeans

For day-to-day wear; a wardrobe staple

• Jeans are the most studied garment type from a LCA perspective. This gave us a strong baseline to compare against for the purchased alternative, and robust data to use for calculating upstream impact (the pre-rental phase, e.g., raw material extraction, production and manufacturing).
• Jeans are highly rented and loved by our subscribers; we have lots of rental data
• Jeans are inherently durable in construction and have lower variance in material composition than other categories—they’re predominantly cotton based
• Jeans are a wardrobe staple. Combined with their high durability, they are assumed to have a high lifetime utilization

Occasion Dresses

For special events; more likely to be worn once

• Occasion dresses have been studied in the rental context from an impact standpoint in a few ways—they generally have been seen as an agreeable use case for rental since utilization is assumed to be lower (i.e., people want to wear a new dress for different events)
• Occasion dresses are less durable in construction and material compared to jeans, which further impedes utilization potential
• Popular use case for Nuulying

Puffer Jackets

For seasonal use; adds nuance to utilization

• Puffer jackets are durable, made to last for years and have a potentially medium to very high assumed lifetime utilization
• Puffer jacket utilization has been understudied, without a lot of available literature

III. Structuring the Model:

The data model is set up in three phases (Pre-Nuuly, Nuuly rental, Post-Nuuly) to map out the lifecycle of Nuuly garments across our categories by activity. Each activity across the garment’s lifetime contributes to its absolute carbon and water footprint.

Structuring the model this way allows us to:

• Understand the relative impact of the Nuuly rental phase compared to the pre-Nuuly and post-Nuuly phases
• Understand the relative impact of various activities throughout the Nuuly rental phase (e.g., outbound shipping vs. laundry vs. inbound shipping).
• Evaluate how processes differ across categories, and how impact changes. For instance, we assume subscribers wash their rented jeans at home while occasion dresses are dry cleaned at our distribution hubs and have a different chemical usage

Pre-Nuuly Phase

Captures the environmental footprint of garment production through arrival at Nuuly DCs

Nuuly Rental Phase

Measures carbon and water impacts from all activities in one rental loop. Impacts are multiplied by the number of rental cycles.

Post-Nuuly Phase

Evaluates end-of-life impacts for garments exiting inventory, based on exit channel (e.g., in-box purchase vs. Nuuly Thrift vs. Reclectic)

IV. Calculating Lifecycle Impact

We calculated the lifecycle impact for the average Nuuly jeans, occasion dress, and puffer jacket. Each activity per lifecycle phase accrues impact in terms of carbon emissions and water usage.

The functional unit (e.g., the average pair of Nuuly jeans) utilized per category is a representation of averages derived from Nuuly rental data. For instance, to represent the average Nuuly jeans, we used the following inputs:

• Average material composition of jeans in Nuuly inventory
• Average distance traveled from distribution center to subscriber, and weighted average of ground versus air shipments
• Average number of rents for jeans before exiting inventory
• Weighted average of jeans exit distribution (i.e., % of jeans exiting via Nuuly Thrift vs. Reclectic)

For the pre- and post-Nuuly phases, we used industry benchmarks and available data from industry and academic databases. This includes the estimated number of wears garments are receiving once they leave Nuuly’s rental inventory (i.e., someone buys a pair of jeans from Reclectic, we estimate they will get X wears before being donated)

V. Calculating Impact Per Wear (Amortized Impact)

In order to calculate the impact per wear, we had to gather data on utilization. We surveyed subscribers to find out the number of wears the items in their most recent Nuuly received, and generated an average of wears per rent by category. This average includes the responses from subscribers who did not wear their items.

The wears that items receive in the Nuuly Rental Phase = avg. # of rents (for category) x avg. # of wears per rent (for category)

Average wears per rent by category:

• Jeans: 6.2
• Occasion dresses: 8.3
• Puffer jackets: 6.6

Average estimated wears from Nuuly Rental Phase:

• Jeans: 19.8
• Occasion dresses: 6.5
• Puffer jackets: 40.0

Impact per wear = lifecycle impact of garment / # of lifetime wears (wears x rents in Nuuly Rental Phase + avg estimated wears post-Nuuly)

Average estimated wears post-Nuuly by category:

• Jeans: 33.27
• Occasion dresses: 2.2
• Puffer jackets: 23.1

VI. Comparing lifecycle impact & amortized impact to purchased alternative

In order to compare our findings to the purchased alternatives, we calculated the lifecycle impact of standard/generic jeans, occasion dresses, and puffer jackets using:

• Primary + secondary data derived from published academic + industry research (e.g., LCAs, product footprint analyses)

Apparel market research + industry benchmarks to estimate the average lifetime utilization (# of wears) for the purchased alternatives.

The impact intensity (kg CO2e, gal) of purchased alternatives = the calculated lifecycle impact (kg CO2e, gal) / average estimated lifetime utilization (# of wears)

Total estimated lifetime wears (utilization comparison)