The embodied carbon of insulation materials, which are the best choices for insulating homes

Introduction: Why carbon reduction matters in construction

As global awareness of climate change grows, the construction industry has traditionally focused on improving the thermal performance of buildings, which involves adding more construction materials to a basic built home. As the construction industry becomes more sophisticated, due in no small part to the imposition of more stringent construction codes, the focus is now more towards reducing carbon footprints of buildings.

One of the key ways to achieve this is by choosing and using lower embodied carbon insulation materials, which play a crucial role in the energy efficiency of buildings. Insulation materials are essential for maintaining comfortable indoor temperatures while reducing energy consumption, but not all insulation types are created equal when it comes to their carbon-footprint and environmental impacts.

As an article The Hierarchy of Net Zero Design by Head of Climate Action, author Will Arnold puts it,  “use less stuff!” Or, in this context, use less stuff that has lots of CO2 stuff.

Before going further, I would point out that this article - which we acknowledge is a little wordy - was inspired by having sat through a day long seminar about how to reduce the embodied carbon in high performance homes in Vancouver, BC.

During the seminar, we heard solutions proposed such as the adoption of wood foundations, and ramping up the use of natural insulation materials such as hemp or strawbale. At this suggestion, myself and some others involved in commercial construction quietly rolled our eyes at times and i vowed to write this guide as a 'too long, didn't read' version of my "how to reduce the embodied carbon in high performance homes" day! 

While the use of non-toxic natural insulation certainly has a place in home construction with regards to indoor air quality and creating healthy homes for those with chemical sensititivies, any solution that will affect global change must be scalable. There just aren't enough hemp plants, sheep or bales of recyled newsprint to use as insulation that will have any meaningful impact and help us avert a climate catastrophe.

Whether you're a construction professional or someone interested in sustainable building practices, this guide will help you make informed choices about insulation materials that contribute to a lower carbon impact and greener future. 

What is whole-life embodied carbon?

Before diving into specific insulation types, it's important to understand the concept of whole-life or lifecycle embodied carbon. This term refers to the total carbon emissions associated with a product throughout its entire lifecycle - from production to installation, use, and eventual disposal.

For construction materials, this includes:

• The emissions involved in sourcing raw materials and manufacturing
• The energy required to transport and install the materials
• Its performance in terms of energy savings over time
• How easily a material can be recycled or disposed of at the end of its life

When it comes to insulation, selecting materials with lower whole-life carbon impact is key to achieving both energy efficiency and sustainability. 

Insulation types – A comprehensive overview of whole-life embodied carbon ratings in insulation

Choosing the right insulation material involves balancing thermal performance, durability, cost, and environmental impact. Below, we break down the most common types of insulation, their characteristics, and their embodied carbon levels.

Fiberglass insulation

Fiberglass insulation is one of the most widely used options in residential and commercial construction. It’s made from spun glass fibers and comes in batt or roll form, or as loose-fill insulation. 

Embodied carbon: The production of fiberglass insulation involves significant energy consumption, contributing to its embodied carbon. The carbon emissions are primarily driven by the process of melting glass and the use of raw materials. On average, fiberglass insulation has a carbon footprint of 1.7-2.5 kg CO2e per square meter per inch of thickness.

Thermal performance: The R-value (thermal resistance) of fiberglass batts varies depending on the thickness and density of the material. Typically, it has an R-value between 2.9 and 3.8 per inch of thickness.

Note: loose fill blown in fiberglass for attic insulation has a lower R value than Batts. 

Durability and lifecycle: Fiberglass is durable and resistant to moisture, but it can degrade over time if exposed to extreme conditions. Its functional lifespan is long (if not exposed moisture), but it’s important to consider its recyclability.

Environmental impact: The production of fiberglass is energy-intensive, which contributes to its carbon footprint. However, it's a non-toxic material, and some fiberglass products are made with recycled content.

Pros and cons of fiberglass insulation:

• Pros: Affordable, fire-resistant, and widely available.
• Cons: Relatively high embodied carbon compared to other materials, and it can be irritating to skin and lungs during installation.

Cellulose insulation

Made from recycled newsprint, cellulose insulation is one of the most environmentally friendly insulatrion options on the market.

Embodied carbon: Dense packed cellulose insulation has a significantly lower embodied carbon than most other insulation types as it is made from recycled paper and produced using a minimal amount of energy. The carbon footprint of cellulose insulation ranges from 0.2 to 1.1 kg CO2e per square meter per inch of thickness. It's one of the best options for carbon-conscious projects.

Thermal performance: Cellulose has an R-value of about 3.2 to 3.8 per inch, which is slightly lower than fiberglass but still offers good insulation performance.

Durability and lifecycle: Cellulose is prone to settling over time, which can reduce its effectiveness. However, it is resistant to pests and mold when properly treated.

Environmental impact: Cellulose insulation is made from 80-85% recycled content, significantly reducing its carbon footprint. It also doesn’t release harmful gases during installation, making it safer than some other materials.

Pros and cons of cellulose insulation:

• Pros: High recycled content, low embodied carbon, biodegradable.
• Cons: Can settle over time, potentially reducing its effectiveness, which is why choosing dense packed cellulose insulation is important in wall assemblies.

Mineral wool insulation

Mineral wool, often referred to as rock wool or stone wool, is made from volcanic rock or basalt. It is fire-resistant, water-resistant, and provides excellent thermal performance.

Embodied carbon: The embodied carbon of mineral wool is comparable to fiberglass and spray foam, depending on the brand. Its carbon footprint is typically 2.5-3.8 kg CO2e per square meter per inch of thickness, largely due to the energy-intensive melting process involved in its production. However, its fire-resistant properties add value in fire-rated applications, reducing the need for additional fireproofing materials.

Thermal performance: With an R-value of around 3.7 to 4.2 per inch, mineral wool offers good thermal resistance.

Durability and lifecycle: Mineral wool is highly durable, resistant to fire, water, and pests. Its lifespan is comparable to fiberglass, though it is more expensive.

Environmental impact: The production of mineral wool has a moderate carbon footprint compared to other insulation materials. It’s made from natural, abundant materials and is fully recyclable.

Pros and cons of mineral wool insulation:

• Pros: Fire-resistant, durable, recyclable.
• Cons: Higher cost, average embodied carbon rating, less widely available than other types of insulation.

XPS rigid foam insulation panels

XPS or Extruded Polystyrene insulation is a petroleum based product. It has a high R value and works well in many applications, but these performance features come with a more significant ecological impact than other types of insulation, not to mention a typically higher price. 

Embodied carbon: XPS is one of the insulation materials with a higher embodied carbon due to the use of blowing agents like HFCs, which are potent greenhouse gases. The carbon footprint of XPS typically ranges from 3.5 to 5.0 kg CO2e per square meter per inch of thickness. However, newer XPS formulations are using lower GWP (global warming potential) blowing agents, which help reduce its environmental impact.

Thermal performance: XPS is used in foundations, walls, and roofing. It provides high R-value insulation, typically around 5 per inch.

Durability and lifecycle: XPS is somewhat moisture-resistant and has a long lifespan, but it is not as biodegradable as some other materials and may have a reducing insulation curve over the years as it off-gasses.

Carbon footprint and environmental impact: The manufacturing of XPS contributes significantly to carbon emissions, especially due to the use of HFCs as blowing agents. However, newer formulations are reducing the GWP of XPS.

Pros and cons of XPS foam insulation:

• Pros: High thermal performance, some moisture resistance.
• Cons: High embodied carbon, less recyclable, diminishing thermal performance linked to off-gassing of toxic chemicals over time, can become waterlogged in under-grade humid applications.

EPS - expanded polystyrene foam insulation

Embodied carbon: EPS foam insulation has a lower embodied carbon than XPS. The production of EPS typically results in a carbon footprint of 1.5 to 3.0 kg CO2e per square meter per inch of thickness. EPS does not use HFCs in production, making it a more eco-friendly option compared to XPS and it doesn't off-gass after the initial manufacturing process.

Thermal performance: EPS is typically used in walls, roofs, and foundations. It is a cost-effective alternative to XPS, with an R-value of between 3.6 and 4 per inch.

Durability and lifecycle: EPS is reputedly more prone to water absorption than XPS, which could compromise its effectiveness in certain climates as research supports the observation that Expanded Polystyrene (EPS) foam absorbs more water compared to Extruded Polystyrene (XPS) foam in short term testing. However, a 15-year field study in St. Paul, Minnesota, compared EPS and XPS insulation installed below-grade. The results showed that the EPS maintained 94% of its initial R-value, with a moisture content of only 4.8%, while the XPS retained just 52% of its initial R-value, with a moisture content of 18.9%... 

Carbon footprint and environmental impact: EPS is made without HFCs, making it a more eco-friendly option than XPS. However, it still has a carbon footprint from production and is less durable in extreme conditions.

Pros and cons of EPS foam insulation:

• Pros: Lower embodied carbon, recyclable (where available), affordable.
• Cons: Lower R-value per inch than xps, possible water absorption, some sensibility to UV

Rigid wood fiber insulation panels

Embodied carbon: Rigid wood fiber insulation panels are often marketed as eco-friendly, with a lower embodied carbon than synthetic foams like EPS and XPS. The production of wood fiber insulation generally results in a carbon footprint of around 1.0 to 2.5 kg CO2e per square meter per inch of thickness.

Wood fiber can sequester carbon, contributing to a lower carbon footprint overall. However, the full environmental impact depends on the source of the wood, how it is processed, and any additives used during manufacturing.

Thermal performance: Rigid wood fiber insulation typically provides an R-value of 3.1 to 4.0 per inch, which is competitive with both EPS and XPS. Wood fiber insulation also offers good soundproofing properties. It's frequently used in high-performance construction, especially in passive house applications. Additionally, wood fiber products are breathable, allowing for moisture regulation, which can help manage issues like condensation within walls and roofs.

Durability and lifecycle: Rigid wood fiber insulation is generally durable but may be more susceptible to moisture than synthetic options like XPS. While it is resistant to mold and decay when kept dry, prolonged exposure to water can reduce its effectiveness, especially in extreme weather conditions.

The natural fibers used in manufacturing can also be treated with water-resistant additives like paraffin wax, which can raise questions about the overall sustainability of the product, as these waxes are petroleum-based. Additionally, the risk of contamination from recycled wood fibers is a significant concern, particularly if hazardous materials like lead-based paints or formaldehyde from MDF or particleboard are present. These chemicals can leach out of the insulation and pose a health risk over time.

Carbon footprint and environmental impact: While wood fiber insulation is often advertised as a natural and sustainable product, there are environmental trade-offs. The use of recycled wood fibers diverted from landfill may reduce waste, but it can also lead to the inclusion of hazardous materials.

Furthermore, wood fiber insulation products often contain petrochemical additives, such as polymer binders and waxes, which can undermine the "eco" credentials of the material. These additives are used to improve the water resistance and durability of the product but introduce concerns about long-term environmental impact. The idea that wood fiber insulation is inherently better for the environment because it's 'natural' needs to be reconsidered in light of these added synthetic materials.

Pros and cons of rigid wood fiber insulation panels:

Pros:

• Made from renewable resources
• Can sequester carbon
• Breathable, providing good moisture regulation
• Offers competitive thermal and sound insulation properties

Cons:

• Potential contaminants from recycled wood fibers, including hazardous materials like lead and formaldehyde
• Often contains petrochemical additives like paraffin wax and polymer binders
• Higher water permeability in extreme conditions compared to synthetic foams
• Generally higher cost compared to other insulation options, such as EPS or XPS

Polyisocyanurate foam panels

Polyisocyanurate (also Polyiso or PIR) foam panels are widely used in high-performance applications, particularly in roofing systems and exterior wall assemblies, due to their excellent thermal resistance and high R-value per inch. However, while Polyiso foam is effective at standard temperatures, its thermal performance can degrade at lower temperatures, which is important to consider depending on your building’s location and climate.

Embodied carbon: Polyiso foam panels have a much higher embodied carbon than many natural insulation materials. The embodied carbon typically ranges from 3.5 to 4.5 kg CO₂e per square meter per inch of thickness. This is due to the energy-intensive process involved in manufacturing the foam, which relies on petrochemical-based materials and chemical blowing agents to create the rigid insulation. Although Polyiso provides excellent thermal performance, its production process contributes to its overall carbon footprint.

Recent advancements in polyiso production have led to a shift towards low-GWP blowing agents, which reduce its environmental impact. However, this still remains a synthetic material with a relatively high embodied carbon when compared to natural insulation materials like hemp, cellulose, or wool.

Thermal performance and temperature sensitivity: Polyiso foam insulation is highly regarded for its high R-value, which is typically stated to be around 6.5 to 7.0 per inch at standard temperatures (around 75°F or 24°C), but that is manufacturer testing under optimum conditions, and it is a bit misleading.

As temperatures drop, the thermal resistance of polyiso decreases significantly, especially below 25°F (-4°C). In cold climates, the R-value can decrease by as much as 20% to 30%, meaning Polyiso's effectiveness is reduced as it gets colder. This characteristic makes polyiso less reliable as a long-term solution in cold climates, where consistent thermal resistance is necessary to maintain energy efficiency.

As a result, the functional long-term R value of polyiso is considered to be about R 5.6. For this reason,  polyurethane-based foams such as EPS are often preferred in extremely cold environments due to their ability to maintain their thermal performance under lower temperatures.

Durability and lifecycle: Polyiso panels are known for their durability and moisture resistance, which makes them a popular choice for roofing systems. The panels are also rigid, making them resistant to compression and deformation over time. However, polyiso is not biodegradable and doesn’t offer the same end-of-life benefits as natural fiber rigid  insulation like wood fibre or cellulose. At the end of its life, Polyiso generally ends up in landfills, where it can take a long time to break down.

Environmental impact: Polyiso foam's environmental impact is driven largely by the chemical processes used in its manufacture. Although it offers excellent thermal performance, its higher embodied carbon means it is less sustainable compared to natural insulations. Additionally, the chemical blowing agents used in polyiso production can contribute to high global warming potential (GWP), though lower-GWP alternatives are gradually being introduced by some manufacturers.

Pros and cons of polyiso insulation:

Pros:

• High R-value per inch, providing excellent thermal performance in standard conditions
• Durable, moisture-resistant, and highly effective for roof insulation
• Long-term performance with minimal maintenance

Cons:

• Thermal performance diminishes significantly at lower temperatures
• High embodied carbon compared to natural insulation options
• Petrochemical-based production and chemical blowing agents contribute to environmental impact
• Not biodegradable; can contribute to landfill waste at the end of life

Spray foam insulation

Spray foam insulation is typically used in walls, attics, and foundations. It is a highly insulating, and appears to be an effective solution for sealing gaps and creating an airtight barrier, providing it has been installed correctly. There are however, a number of hidden dangers and problems with spray foam that become apparent over time.

In both the UK and Australia, where spray foam was used in huge quantities for retrofit home insulation, many mortgage companies are now refusing to finance homes containing spray foam because of moisture related problems like wood rot and the expense of removing spray foam.

We expect to see North America following suit, so this combined with the fact that spray foam contains numerous toxic chemicals in it's ingredient list, leads us to put it at the bottom of our insulation pile.

Embodied carbon: Spray foam, particularly closed-cell spray foam, has a relatively high embodied carbon rating due to the production of chemicals like polyurethane and the use of blowing agents. The carbon footprint of spray foam insulation is typically 2-6 kg CO2e per square meter depending on the type and thickness [source needed].

Traditional formulations use HFCs (hydrofluorocarbons), which have a high global warming potential (GWP). Newer formulations with HFOs (hydrofluoroolefins) or CO2-based blowing agents are helping to reduce these emissions [source needed].

Thermal performance: It has one of the highest R-values of any insulation material, typically around 6.5 to 7 per inch. This high thermal resistance makes it appear ideal for energy-efficient buildings.

Durability and lifecycle: Spray foam has a long lifespan and is resistant to moisture, mold, and mildew although this depends on whether it is closed cell or open cell spray foam. It can also degrade if exposed to UV light, and there is also potential for it to shrink over time, so we have to put a question mark next to it's air sealing qualities.

Environmental impact: Traditional spray foam uses hydrofluorocarbons (HFCs) as blowing agents, which have a high global warming potential (GWP). However, newer formulations use more eco-friendly blowing agents which reduces the impact.

Our main gripe with spray foam are the negative implications for human health as well as enviromental impact. The final destination of spray foamed walls is unquestionably a landfill after use as it cannot be reused, nor can wood covered in spray foam be recycled.

Health risks of spray foam insulation

Professional spray foam installers risk developing chronic respiratory conditions and chemical sensitization from regular exposure to isocyanates. This sensitization can make individuals permanently more reactive to common irritants like dust and pollen, even without direct SPF contact.

The chemical hazards extend beyond installation. Improperly mixed or applied spray foam can continue off-gassing toxic substances almost indefinitely, as the chemical reaction remains incomplete. This risk depends heavily on installer expertise and integrity (as unscrupulous operators can save money by "leaning out" the mixture ratios) and equipment calibration.

Even properly installed foam releases volatile organic compounds (VOCs) and potentially formaldehyde during and after curing. These chemicals can cause headaches, nausea, and respiratory issues, with some compounds linked to cancer. Many spray foams also contain flame retardants that can accumulate in the body over time, potentially disrupting endocrine function.

To minimize risks, areas must be properly ventilated and vacant during installation and curing of spray foam. However, only skilled professionals with well-maintained equipment should attempt installation, as errors in the mixing ratio or application process can create long-term chemical exposure risks for building occupants. Given these significant health concerns and the availability of safer alternatives, we choose not to use spray foam insulation in any our projects.

Pros and cons of spray foam insulation:

• Pros: High R-value, excellent air sealing at first, long lifespan.
• Cons: High embodied carbon in traditional formulations; can release fumes during and after installation; expensive to fit, not recyclable, and removing spray foam from homes is very expensive .

Cotton, hemp, sheeps wool and other natural fiber insulation products 

Natural fiber products, such as hemp, cotton or sheep wool insulation are highly effective natural insulators known for their thermal and acoustic properties. They are made from renewable, biodegradable and sometimes recycled materials that also offer excellent moisture control and resistance to mold. In terms of sustainability, cotton, hemp and sheep's wool insulation are carbon-storing fibers, capturing and sequestering carbon during their growth, which provides a net environmental benefit over time.

Recycled cotton insulation

Cotton insulation is made from recycled cotton fibers, often sourced from discarded denim fabric or other cotton waste products, so don't be shy, bust out those bell-bottom flares from the 70's and get them down to your local recycling centre!

Cotton insulation is a renewable, biodegradable option known for its softness and flexibility, making it easy to install. It has good thermal and acoustic properties, as well as resistance to mold and mildew. It is especially valued in environments where moisture control is important, such as in basements or humid climates.

Embodied carbon: Cotton insulation has a relatively low embodied carbon compared to synthetic materials. The embodied carbon for cotton insulation typically ranges from 0.3 to 1.0 kg CO₂e per square meter per inch of thickness.

As a plant-based material, cotton stores carbon during its growth, helping offset the emissions from its production. However, cotton farming itself can have a higher environmental impact compared to other plant-based insulations due to water usage and pesticide applications. That said, the embodied carbon of cotton remains low when compared to conventional insulation products like fiberglass or foam, making it a sustainable choice overall.

Cotton insulation’s carbon storage during growth helps balance the emissions from its production process, although the overall environmental footprint may be affected by farming practices. Cotton is still considered a good low-carbon option in the context of natural insulations.

Thermal performance: Cotton insulation offers an R-value of around 3.5 per inch, which makes it similar to wool. It performs well in terms of both thermal and acoustic insulation and is especially useful for soundproofing. Cotton insulation also manages moisture effectively, helping to maintain consistent indoor temperatures, especially in climates with fluctuating humidity.

Durability and lifecycle: Cotton insulation is durable but may be more prone to compression over time compared to other natural insulations. It is biodegradable, which makes it a sustainable option at the end of its life cycle. However, if not kept dry, cotton insulation can absorb moisture, potentially leading to mold or mildew growth.

Environmental impact: Cotton insulation’s environmental impact is influenced by the energy used in processing cotton fibers and the farming practices involved. While its carbon footprint is lower than synthetic insulations, the overall environmental impact of cotton is shaped by factors like water usage and pesticide application during cultivation.

Pros and cons of recycled cotton insulation:

• Pros: Renewable, biodegradable, good thermal and acoustic performance, moisture-resistant. 
• Cons: Requires proper moisture management, may compress over time, less widely available.

Natural hemp insulation

Hemp insulation is made from the fibers of the hemp plant (Cannabis sativa), a fast-growing and low-impact crop - (and no, you can't smoke it!) Hemp is a natural insulator with excellent thermal and acoustic properties, offering a breathable material that helps regulate moisture. It’s particularly useful in homes or buildings where energy efficiency and indoor air quality are important. Hemp insulation is made from a renewable resource, and its production is more sustainable compared to many other materials.

Embodied carbon: Hemp insulation products have one of the lowest-carbon insulation materials available. The embodied carbon typically ranges from 0.3 to 1.0 kg CO₂e per square meter per inch of thickness. Hemp captures carbon during its growth, contributing to a net positive environmental impact. It requires minimal fertilizers and pesticides, making it a sustainable choice.

The carbon footprint of hemp is largely influenced by the energy and methods used during processing, but it remains significantly lower than that of synthetic insulations like fiberglass or foam. Overall, hemp insulation provides a great balance of low carbon emissions and high performance, making it an environmentally friendly choice for sustainable building projects.

Thermal performance: Hemp insulation offers an R-value of approximately 3.5 per inch, which is comparable to that of cotton and wool. It is an effective thermal insulator and also performs well in soundproofing. Hemp is breathable, allowing moisture to escape from walls and preventing the buildup of damp conditions that can compromise insulation performance.

Durability and lifecycle: Hemp insulation is durable, naturally resistant to pests, and mold-resistant. Like other plant-based insulations, it is biodegradable and can be safely composted at the end of its life. Hemp fibers tend to be robust and long-lasting, ensuring a high-performance product throughout its lifespan.

Environmental impact: Hemp insulation has a minimal environmental impact due to the hemp plant’s ability to grow quickly and without the need for harmful chemicals. It also requires little water compared to other crops like cotton. While processing the fibers does require some energy, the overall environmental impact of hemp insulation is relatively low.

Pros and cons of hemp insulation products:

• Pros: Renewable, biodegradable, low-carbon, good thermal and acoustic performance, very cool. 
• Cons: Availability may be limited depending on location, higher cost compared to synthetic alternatives.

Sheep's wool insulation

Sheep's wool insulation is a natural product made from the fleece of sheep, offering excellent thermal and acoustic properties. Wool has the unique ability to regulate moisture, helping to maintain a balanced indoor climate by absorbing and releasing moisture as needed. This moisture regulation makes it ideal for environments where maintaining a stable indoor temperature is important.

Wool insulation is also naturally fire-resistant and non-toxic, which makes it a safe, eco-friendly option for insulation. Using wool for insulation in your home is like wrapping it in a big woolly sweater - but having said that, in our experience if it ever gets damp it smells like one too!!

Embodied carbon: Wool insulation has a higher embodied carbon compared to other natural fibers like hemp or cotton. The embodied carbon for wool insulation typically ranges from 0.8 to 1.5 kg CO₂e per square meter per inch of thickness. This higher embodied carbon is primarily due to the energy involved in processing the wool and the carbon emissions from sheep farming. However, as with other natural insulations, wool captures and stores carbon during its growth, helping to offset the emissions from its production.

Despite its higher embodied carbon compared to other natural insulation products, wool insulation remains a more sustainable option compared to synthetic insulations, offering long-term environmental benefits, especially in buildings where moisture regulation and natural materials are a priority.

Thermal performance: Wool insulation has an R-value of around 3.5 per inch, which is similar to other natural fibers like cotton and hemp. It is highly effective in regulating both temperature and humidity, ensuring a stable indoor climate. Wool is particularly valued for its ability to maintain comfort in both hot and cold climates.

Durability and lifecycle: Wool is naturally durable and resistant to pests, mold, and mildew, making it a long-lasting insulation material. It is also biodegradable, allowing it to return to the environment safely at the end of its lifecycle and it is nice to handle. However, wool’s higher carbon footprint associated with sheep farming should be considered when assessing its overall environmental impact.

Environmental impact: Sheep farming does contribute to carbon emissions and land use changes, which can increase the carbon footprint of wool insulation. However, wool’s ability to regulate moisture, its fire-resistant properties, and its biodegradability make it an environmentally friendly option overall. Its environmental impact will depend on factors such as farming practices and transportation distances.

Pros and cons of sheep's wool insulation:

• Pros: Renewable, biodegradable, excellent moisture regulation, fire-resistant, good thermal and acoustic performance and easy handling. 
• Cons: Higher cost, limited availability, higher carbon footprint compared to plant-based insulations.

Conclusion -What is the best practices for reducing carbon in home construction?

Choosing the right insulation material is crucial for reducing the whole-life carbon of a building and contributing to a greener future and ranks second after concrete in construction materials that need a careful choice to reduce the overall embodied carbon of homes. Low-carbon insulation materials like cellulose, hemp, and expanded polystyrene (EPS) offer significant environmental benefits over conventional materials like fiberglass and XPS foam boards.

However, every project has unique needs, and factors such as cost, durability, and thermal performance must be balanced with the embodied carbon of each material. Overall, building the homes we do now but making better choices of concrete and insulation products can lower embodied carbon by up to 80% without having to resort to drastic measures or incurring a significantly higher cost of construction.

Insulation types with the lowest embodied carbon:

Rigid and semi-rigid insulation products:

EPS (Expanded Polystyrene) stands out among rigid foam options for its low embodied carbon. With a carbon footprint ranging from 1.5 to 2.5 kg CO₂e per square meter per inch, EPS provides a solid balance between performance, cost, sustainability and lower health impact.

Hemp insulation can be found as a semi-rigid insulation material with an exceptionally low embodied carbon of 0.5 kg CO₂e per square meter per inch of thickness. Hemp's sustainability is enhanced by its natural, biodegradable nature and low-energy manufacturing process but it also carries a higher cost and a more restricted range of applications.

Loose-fill or batt-type insulation products:

Cellulose insulation is one of the best options when considering loose-fill insulation products. Made from recycled paper, cellulose offers a carbon footprint of just 0.2 to 1.1 kg CO₂e per square meter per inch of thickness, making it one of the most eco-friendly options available for buildings seeking to minimize embodied carbon and control costs, although these figures may rise when using it in dense packed applications - careful studying of different manufacturers EPD's is necessary.

Fiberglass insulation, although widely used, does have a higher embodied carbon, ranging from 1.7 to 2.5 kg CO₂e per square meter per inch. While still relatively effective, it is surpassed by cellulose and hemp in terms of reducing the carbon footprint of homes.

How to reduce a buildings carbon footprint

To significantly minimize the carbon footprint of building projects and produce an embodied carbon reduction of up to 80%, concentrate on your concrete use, both quantity and type, and the choice of insulation product by applying these important tips:

• Specify reduced carbon concrete and concrete products. Various manufacturers of both readymix and precast concrete products offer reduced carbon concrete options at low to zero price increases - it simply needs to be specified, asked for and work scheduled according to availability, along with an EPD to prove the reduced carbon rating. 
• Use the manufacturers EPD for insulation products, choose the lowest low-carbon or reduced carbon materials for insulation where possible (e.g., hemp, cellulose, EPS) and that fit with your budget.
• Incorporate alternative insulation methods like dense-packed cellulose in a perfect wall design or larsen truss or use EPS foam applied as a continuous external insulation layer.

What does EPD stand for?

An environmental product declaration, or EPD, is a document that transparently reports the environmental impact of a product or material, based on a product life-cycle assessment (LCA). The LCA evaluates the environmental effects throughout the product's lifecycle, from raw material extraction to disposal. EPDs, derived from these LCAs, can support carbon emission reduction targets by enabling comparisons of the environmental impacts of different materials and products, helping to select the most sustainable option for homes.

Architects, engineers, designers and eco-conscious homeowners are able to choose the most sustainable option for their project. Manufacturers are able to optimize the impact of their products and market their carbon transparency. 

An EPD is usually valid for five years, and is generated according to the relevant standards. Construction EPDs are based on the ISO 14040/14044, ISO 14025, EN 15804 or ISO 21930 standards. EPDs help to achieve EPD and LCA credits in certification schemes, like LEED, BREEAM, and others.

The combination of whole-life carbon analysis, thoughtful material selection, and energy-efficient building practices will be key to creating a more sustainable and resilient built environment. By focusing on rigid and semi-rigid products such as EPS and hemp, as well as loose-fill options like cellulose, construction professionals can help significantly reduce the embodied carbon of their projects and contribute to the fight against climate change.

By making thoughtful, informed decisions about insulation, you’re not just optimizing energy efficiency - you’re also investing in a greener, more sustainable future for construction.

Author: Robert J. Pierson - Ecohome Network

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