Which sealant has the lowest carbon footprint?
For companies selecting sealing, waterproofing or joint-protection materials, carbon footprint is becoming an increasingly important procurement criterion. However, comparing butyl, silicone and bitumen sealants solely by their reported kg CO₂e values can lead to misleading conclusions.
There is no universal carbon-footprint ranking that proves one chemistry is always more sustainable than another. Current Environmental Product Declarations (EPDs) provide useful product-stage examples, but they represent different formulations, densities, geographical assumptions, manufacturing systems and functions.
For a business making a material-selection or procurement decision, the relevant question is therefore not:
“Which material has the lowest carbon footprint per kilogram?”
The better question is:
“Which functionally equivalent sealing system delivers the required performance over the defined service life with the lowest life-cycle carbon impact?”
This distinction is critical for manufacturers, construction companies, architects, engineers, sustainability teams and procurement departments.
Why carbon footprint cannot be compared by material name alone
A carbon footprint is a property of a defined product system, not simply of a polymer or material family.
A joint may require:
- a thin compressed butyl tape,
- an elastomeric silicone sealant capable of accommodating movement,
- or a thick polymer-modified bituminous waterproofing layer.
These products may all contribute to sealing or waterproofing, but they are not necessarily functionally interchangeable.
The same amount of material by mass can provide very different:
- sealed joint lengths,
- layer thicknesses,
- coverage rates,
- movement capability,
- adhesion,
- durability,
- moisture protection,
- service life,
- maintenance requirements,
- replacement intervals.
This is why a lower factory-gate GWP does not automatically mean a lower carbon footprint for the completed installation.
A product with a lower impact per kilogram may require more material, additional primer, backing materials, site energy or more frequent replacement. Conversely, a product with a higher product-stage value may deliver the required performance with less installed material or a longer service life.
The business decision should therefore be based on the installed functional system, rather than the raw material category.
What do current EPD examples show?
The source material includes three model EPD examples based on EN 15804+A2. Their product-stage GWP values illustrate why comparisons must be interpreted carefully.
| Material / EPD example | Declared unit | A1–A3 GWP-total | Key caveat |
| Products based on butyl chemistry | 1 kg | 4.49 kg CO₂e | European worst-case model; density range 1.0–2.5 g/cm³ |
| Silicone-based products, group 1 | 1 kg | 5.31 kg CO₂e | European group worst-case model; density range 1.0–1.5 g/cm³ |
| Polymer-modified bituminous thick coating | 1 kg | 1.21 kg CO₂e | German worst-case model; density range 600–1400 kg/m³ |
These figures are useful as screening examples, but they should not be treated as generic emission factors for every butyl, silicone or bituminous product.
The underlying EPDs use different model assumptions, product groups, density ranges, geographical contexts and functional applications. Therefore, the values cannot by themselves establish that bitumen is always lower-carbon than silicone or butyl.
The source specifically warns against interpreting these values as a purchasing ranking.
What does this mean for procurement?
A procurement team should not select a material simply because its EPD shows the lowest kg CO₂e/kg.
Instead, the purchasing assessment should ask:
- Is the product designed for the same function?
- Is the same performance level required?
- Is the declared unit comparable?
- Are the same life-cycle modules included?
- Is the required quantity per metre, joint or square metre known?
- Are primers, backing materials and accessories included?
- Are installation losses included?
- Are service lives comparable?
- Will one system require more frequent replacement?
- Are the EPDs based on compatible PCRs, geographies and data periods?
Only after these questions have been answered does a carbon comparison become meaningful.
Functional unit matters more than kilograms
One of the most important principles in sustainable material selection is the choice of the functional unit.
A comparison based only on 1 kg of material can be technically correct but commercially misleading.
For example, imagine that:
- Product A has a lower GWP per kilogram but requires a greater installed mass.
- Product B has a higher GWP per kilogram but requires significantly less material to achieve the same sealing performance.
- Product A requires replacement sooner.
- Product B maintains performance for a longer reference period.
In such a case, the ranking can change once the assessment moves from kg of product to the actual service delivered.
For B2B procurement, more meaningful functional units can therefore relate to:
- one metre of sealed joint,
- one square metre of waterproofed surface,
- one completed connection,
- one building component over a defined reference study period,
- or another technically justified unit of service.
The source recommends converting the actual joint design into a fair comparison by considering geometry, density, coverage and realistic material loss.
How to perform a carbon comparison of sealants
- Define the required technical function
Before comparing carbon data, define what the material actually needs to do.
Depending on the application, this may include:
- water resistance,
- air sealing,
- vapour control,
- joint movement,
- compression,
- adhesion,
- chemical resistance,
- temperature resistance,
- UV exposure,
- fire requirements,
- substrate compatibility.
A silicone sealant designed for high-movement joints should not automatically be compared with a butyl tape designed primarily as a compressed barrier.
Likewise, a thick bituminous waterproofing coating may perform a fundamentally different function from a narrow sealant bead.
The first procurement filter should therefore always be technical fitness.
Carbon footprint should be assessed among products that can genuinely perform the required function.
- Calculate the actual installed quantity
Once the function is defined, calculate how much material is actually needed.
The assessment should consider:
- joint dimensions,
- bead geometry,
- layer thickness,
- product density,
- coverage,
- application losses,
- packaging,
- backing materials,
- primers,
- cleaners,
- cartridges,
- liners,
- heating or other installation energy.
This is particularly important because two products with similar GWP values per kilogram can have substantially different impacts per metre of finished joint.
A nominal bead or tape thickness should not be assumed to represent an equivalent dry functional layer.
- Align EPD boundaries and methodologies
EPDs are valuable tools for sustainable procurement, but they need to be interpreted correctly.
Before comparing two declarations, check:
- programme operator,
- applicable Product Category Rules (PCR),
- issue date,
- validity date,
- declared product,
- geographical scope,
- data period,
- background database,
- allocation rules,
- cut-off rules,
- life-cycle modules,
- impact assessment method.
A cradle-to-gate result is not automatically comparable with a cradle-to-gate with options or cradle-to-grave result.
Likewise, values from different methodological versions or incompatible PCRs should not simply be placed into a procurement spreadsheet and ranked from lowest to highest.
The source stresses that EPD modules and system boundaries must be aligned before values are added together.
Why service life can change the carbon result
Product-stage emissions are only one part of the sustainability equation.
For many construction and industrial applications, durability and replacement frequency can materially influence the life-cycle result.
Suppose two sealing systems provide the same initial function:
- System A requires replacement after a shorter period.
- System B has a technically demonstrated longer service life.
Over a 30- or 50-year reference study period, System A may require additional:
- product,
- transport,
- labour,
- surface preparation,
- access,
- removal,
- waste treatment,
- installation energy.
These additional interventions can change the overall carbon balance.
However, a longer claimed service life should never be used as an unsupported sustainability claim. It needs appropriate technical evidence and must be modelled consistently for all candidates.
The source recommends using a common reference study period and including replacement, removal and preparation where relevant.
EPD does not mean “environmentally better”
An Environmental Product Declaration is an important source of environmental information, but it should not be interpreted as a certification that a product is inherently more sustainable than another product.
An EPD communicates environmental performance according to a defined methodology and set of assumptions.
It does not automatically answer:
“Which product should we buy?”
That decision also depends on:
- technical performance,
- durability,
- material efficiency,
- installation requirements,
- compatibility,
- maintenance,
- replacement,
- end of life,
- project-specific conditions.
The source explicitly notes that an EPD reports its model transparently but does not certify that one product is environmentally preferable to another.
Butyl vs silicone vs bitumen: what should businesses compare?
Butyl sealants
Butyl-based products can be highly relevant where the application requires reliable sealing, adhesion or barrier performance. For procurement, the key question is not simply the carbon footprint of the butyl chemistry but the amount of product required to achieve the specified function.
The current model EPD example in the source reports 4.49 kg CO₂e per kg for the A1–A3 product stage. This is a modelled value and should not be treated as a universal emission factor for all butyl products.
Silicone sealants
Silicone systems are commonly selected where elasticity, movement accommodation, weather resistance or other demanding performance characteristics are required.
The source’s silicone group model reports 5.31 kg CO₂e per kg at A1–A3.
Again, this does not mean that every silicone product has this carbon footprint or that silicone is necessarily the higher-impact solution in a real installation. The required quantity, durability and application must be included in the comparison.
Bituminous systems
The source includes a model EPD for a polymer-modified bituminous thick coating with an A1–A3 value of 1.21 kg CO₂e per kg.
However, this product has a different density range, geographical modelling basis and functional application. It therefore cannot be treated as a direct substitute for a butyl tape or silicone joint sealant simply because its mass-based GWP is lower.
This is an important lesson for sustainable procurement:
A lower kg CO₂e/kg value does not automatically identify the lowest-carbon solution for the project.
Five-step checklist for sustainable sealant procurement
- Define equivalent service
Freeze the:
- joint function,
- substrates,
- exposure,
- movement,
- acceptance criteria,
- reference study period.
- Quantify the installed system
Calculate:
- actual geometry,
- density,
- material quantity,
- application losses,
- primer,
- backing,
- packaging,
- process energy,
- accessories.
- Align environmental evidence
Check:
- PCR,
- declared unit,
- modules,
- geography,
- data age,
- allocation,
- database,
- impact assessment method.
- Model the complete life cycle
Where relevant, include:
- transport,
- installation,
- maintenance,
- replacement,
- removal,
- surface preparation,
- waste,
- end-of-life scenarios.
- Perform sensitivity analysis
Test whether the procurement decision changes when assumptions about:
- dosage,
- service life,
- transport,
- electricity mix,
- installation,
- waste,
- end of life
are changed.
This five-step approach follows the comparison framework established in the source material.
What procurement teams should request from suppliers
For a credible B2B sustainability assessment, suppliers should be asked to provide current, product-specific evidence wherever available.
A procurement package can include:
- current product-specific EPD,
- technical data sheet (TDS),
- safety data sheet (SDS),
- coverage or consumption calculation,
- durability evidence,
- recommended application conditions,
- change-control information,
- relevant certifications and test reports.
Sector-level or group EPDs can be useful for initial screening, but they should not automatically be treated as evidence for the carbon footprint of a specific commercial product.
This is especially important when a company is preparing:
- ESG documentation,
- tender submissions,
- environmental declarations,
- embodied-carbon calculations,
- green building documentation,
- customer sustainability questionnaires,
- Scope 3 assessments,
- product comparisons.
Carbon footprint is only one procurement criterion
A carbon-only procurement strategy can create unintended technical or environmental risks.
Material selection may also need to consider:
- durability,
- resource consumption,
- water-related impacts,
- VOC requirements,
- chemical safety,
- compatibility,
- reparability,
- maintenance,
- fire performance,
- regulatory requirements.
The source therefore cautions that carbon should not override technical fitness or other relevant environmental indicators.
For business buyers, the most robust strategy is to establish minimum technical requirements first, followed by a transparent environmental comparison among compliant products.
Common mistakes when comparing sealant carbon footprints
Mistake 1: Ranking materials by kg CO₂e/kg
This ignores how much material is actually required.
Mistake 2: Treating an EPD as a universal emission factor
An EPD describes a defined product system and methodology.
Mistake 3: Comparing different functions
A waterproofing coating, compressed tape and elastic joint sealant may not provide the same service.
Mistake 4: Ignoring replacement
A lower initial footprint can be offset by additional replacement cycles.
Mistake 5: Mixing EPD boundaries
Cradle-to-gate and cradle-to-grave results cannot simply be combined as though they were equivalent.
Mistake 6: Making generic marketing claims
Statements such as “low-carbon silicone,” “greenest sealant” or “bitumen has the lowest carbon footprint” require evidence based on an appropriate comparison.
The source specifically recommends avoiding universal rankings and precise carbon-saving claims unless the exact product systems and functions have been compared consistently.
FAQ: Carbon footprint of butyl, silicone and bitumen
Which has the lowest carbon footprint: butyl, silicone or bitumen?
There is no universal winner. The appropriate comparison is between functionally equivalent installed systems using aligned product data, life-cycle modules, service lives and scenarios.
Is silicone always higher-carbon than butyl?
No. A model EPD may show different product-stage values, but the result for an actual project depends on formulation, quantity, application, durability and life-cycle assumptions.
Is bitumen automatically the most sustainable option?
No. The model example in the source has a lower A1–A3 value per kilogram, but it represents a different product type, function, density range and geographical model. It cannot establish a universal ranking.
Can I compare two EPDs directly?
Only when their PCRs, declared units, impact assessment method, system boundaries and relevant functions are sufficiently aligned.
Is factory-gate GWP sufficient for procurement?
No. Installed quantity, installation, maintenance, replacement and end of life may materially influence the total result.
Does longer sealant life reduce carbon footprint?
Potentially, because fewer replacements may be required. However, service-life claims must be supported by evidence and assessed over the same reference period.
Sustainable sealant procurement: the B2B approach
For professional buyers, sustainability should be treated as a performance-based procurement issue, not simply as a material-label comparison.
The strongest purchasing methodology is:
Technical function → Installed quantity → Product-specific environmental data → Service life → Life-cycle modelling → Sensitivity analysis → Documented procurement decision
This approach helps companies avoid false sustainability comparisons while creating an auditable basis for material selection.
For manufacturers and suppliers, it also provides a stronger foundation for communicating environmental performance to customers without making unsupported carbon claims.
Request a functionally equivalent carbon assessment
If your company is comparing butyl, silicone or bituminous sealing systems, the most useful starting point is the actual application rather than the material name.
Prepare:
- joint or component drawings,
- required performance criteria,
- estimated installed quantities,
- application method,
- expected service life,
- candidate product EPDs,
- technical documentation.
The comparison can then be structured around the same functional unit, reference study period and life-cycle methodology.
The objective should not be to identify the “greenest” chemistry in general. It should be to identify the technically suitable solution with the best documented environmental performance for the specific application.