A Comparison of the Environmental Impact of Mineral Wool Fibre and Sprayed Polyurethane Foam Insulations
By: Mike Richmond -Genyk Polyurethanes
Is it possible for a plastic to be considered environmentally beneficial? Is mineral wool a long term
solution and consistently efficient? The following comparison of medium density spray foam and mineralwool insulations highlights the environmental strengths and weaknesses of both products.
Five categories are used to compare the products – Quality Assurance, Health and Safety, Durability, Life
Cycle Valuation and Energy Efficiency. While not an exhaustive list of the categories associated with
environmental assessments, the groupings do address the most prevalent merits/issues with each
Both mineral fibre and spray foam insulation are subject to material and installation standards. CAN/ULC-S702.1 is the material performance standard for mineral wool. CAN/ULC-S702.2 is associated with the installation of fibrous materials. CAN/ULC-S705.1 is the material standard for medium density spray foam. CAN/ULC-S705.2 is the accompanying installation standard.
Significant Differences –
- CAN/ULC S702.1 encompasses all fiber products. That is, dissimilar products, from
mineral wool to cellulose, are referenced under one standard. Conversely, spray foam
products are dedicated to specific material type – S705.1 for medium density spray foam;
S712.1 for light density spray foam.
- Both material standards for spray foam have been formalized by the spray foam industry
and sanctioned by the Canadian Standards Council. There is no corresponding
agreement in the fibre standard. While written by the fibre community, the standard has
not been ratified, nor is any of the content enforceable by an oversight organization.
- CAN/ULC-S702.2 is a generalized standard that describes the installation of various types of fibrous materials and is not referenced in the National Building Code. The CAN/ULC-S705.2 standard for spray foam is referenced in the National Building Code. As such, installers are bound by the NBC to perform daily QAP procedures.
- The material and installation standards for spray foam are certified by a third-party organization. The material standard requires that products must be certified by a testing organization that is ISO 17020 accredited. The installation standard requires that the certification process requires third-party verification of classroom testing and on-site practical confirmation. The third-party organization must be ISO 17024 certified. Conversely, the fibre industry’s standards are confirmed by the manufacturing community.
Because of the stringent training and certification required by the spray foam industry, the products are consistently installed by certified professionals. The spray foam process starts with certification, requires daily testing and subjects installations to regular third- party evaluation. Thus, the quality control process is consistently applied from manufacture of the material to in-situ installation.
Mineral wool is subject to a manufacturer-only quality assurance program. There are no
third-party plant inspections. More importantly, the product is installed by anyone –
homeowners, drywall installers, masons, carpenters. Typically, because it is difficult to
work with, and an on-site irritant, the product is installed by the most junior
Health and Safety
Both spray foam and mineral wool have been subject to significant scrutiny regarding health and safety
issues. Spray foam products use MDI isocyanate in the formation of foamed plastic insulation. During
the spraying process, the MDI is atomized, and the airborne particles are considered a “sensitizer”. Thus,
workplace asthma is associated with the installation of spray foam. To a lesser degree, some other
ingredients in the spray foam materials are considered irritants to some people.
Health concerns regarding mineral wool are well documented. And despite industry efforts to adapt
countermeasures to some of the most pertinent issues, the health and safety problems persist.
Formaldehyde binders are at the centre of health concerns. Further, “concerns regarding mineral wool
are not limited to the issue of the level of carcinogenicity. Mineral wool is known to cause skin and lung
abnormalities. Inhalation can lead to pulmonary fibrosis, a chronic disease accompanied by
breathlessness that cannot be cured”(i).
- Outgassing, or chemical release, of materials after installation of both products is a well
documented concern. The outgassing occurs relatively quickly with spray foam (within
the first ninety days). Thereafter, minute amounts of gas release occur in undetectable
amounts for approximately two years.
With mineral wool, the outgassing of formaldehyde occurs during the manufacturing
process. While two manufacturers of mineral wool insulation have announced that they
will stop using binders containing formaldehyde in “at least some of their products”, no
dates were given, and, no testing data is available to support the claims(ii).
- Appropriate Personal Protection Equipment (PPE) must be worn during the installation of both spray foam and mineral wool. When the proper PPE is worn, the dangers of both products is mitigated.
Significant Differences –
- Use of appropriate PPE is stipulated in the CAN/ULC spray foam standards. As such,
wearing the correct safety equipment is mandatory. Failure to do so can result in
decertification of the installer.
As mentioned, there is no training, certification or inspection of the mineral wool
installation. The use of PPE is recommended and voluntary.
- The CAN/ULC spray foam standards dictate that the installer must protect the entire jobsite. Mandatory barriers, warning signs and ventilation are part of the daily requirements of the installer. Failure to adequately protect the jobsite can result in loss of certification. The lack of a binding installation standard for mineral wool often means that the jobsite is inadequately protected. Airborne particulate from the mineral wool is dangerous. In fact, “there is some data which suggests mineral wool slivers in the lungs may cause cancer, by slicing DNA and causing cell mutation”(iii).
Both spray foam and mineral wool experience outgassing during and after installation of
the product. Similarly, both industries have made significant advancements regarding
the risk associated with outgassing. As a requirement of the CAN/ULC-S705.1 material
standard, every certified spray foam material must undergo a Human Health Risk
Assessment. For use in an inhabited structure, the HHRA provides guidelines as to the
adequate time before occupancy. The risk from any emissions is typically gone within
the first few hoursiv. For additional safety, the CAN/ULC-S705.2 installation standard
requires contractors to instruct residents not to return for occupation for twenty-four
hours. Further, new advancements in the spray foam materials have established zero
VOC tolerances (GreenGuard Gold Certified).
Although there is no binding material standard for mineral wool, and thus, no way to
verify the statements, manufacturers have assured the public that the use of
formaldehyde has been discontinued in selected fibre products. The majority of VOC emissions are burned off during the manufacturing process, the outgassing risk to
inhabitants of homes insulated with mineral fibre is negligible. Some mineral wool
products have also achieved GreenGuard Certification.
Spray foam, and all plastic insulations, typically grade superior than fibre products when analyzing
durability. Moisture resistance, rigidity, and adhesion to substrate equate to a product that performs
efficiently, longer. However, recent advancements to mineral wool insulation have made significant
- Spray foam and mineral wool are both resistant to moisture absorption. Each product
has hydrophobic properties, and thus, at least theoretically, resist mould growth.
Further, if water is absorbed by both products, once dried, the materials retain their
- Once cured, spray foam maintains the initial performance properties for the life of the
structure. The material will not sag or settle. Likewise, the higher density mineral wool
products are resistant to compaction and settlement.
Significant Differences –
- The advertised thermal resistance properties of spray foam remain unchanged with time.
The CAN/ULC-S705.1 material standard requires manufacturers to post the Long Term
Thermal Resistance. The LTTR value is calculated by estimating the loss of gas and is
representative of the thermal resistance after five years. Because spray foam is
manufactured ‘in-situ’, the advertised thermal resistance is the installed property.
Mineral wool advertises the thermal resistance of the material as tested in a laboratory
prior to manufacture, shipping and installation. Transportation and installation are
known to reduce the effectiveness of mineral wool.
- Environmental factors such as wind have a negative impact on all insulations. However,
the reduction in thermal resistance due to wind load is significantly less for spray foam
than that of mineral fibre. The U.S. Department of Energy studies cite air infiltration in
buildings as responsible for 40% of the energy loss in homes. Given that spray foam is
an integral air barrier material that exceeds the physical properties of most stand-alone
air barrier materials (i.e. house wrap, bitumen membranes), the effects of wind pressure
is not a detriment to thermal resistance.
- Closed-cell spray polyurethane foam is the only Class 5 flood damage-resistant insulation,
as rated by FEMA. FEMA defines a flood damage-resistant material as any building
product capable of withstanding direct and prolonged (72 hours or longer) contact with
floodwaters without sustaining significant damage. While mineral wool is water resistant,
sustained exposure to water, and subsequent saturation, renders the product unusable.
- Closed-cell spray polyurethane foam adds structural strength to roof and wall assemblies.
Factory Mutual Global measured medium density spray foam’s adhesion to concrete at
over 990psf of uplift pressure; and over 220psf of resistance to metal deck assemblies.
The National Association of Home Builders (NAHB) Research Centre concluded “during a
design racking event such as a hurricane, there would be less permanent deformation of
the wall elements and possibly less damage to a structure that was braced with SPF-filled
walls”. Further, NAHB research demonstrated that spray foam “doubled the maximum
average racking load of a plywood-clad wall assembly at 16” spacing and was 2.2 times
the racking load at 24” spacing”.(v)
Note: more recent research demonstrates that “applying a medium density spray foam fillet along wood roof member can increase the wind uplift capacity of 1⁄2” thick OSB roof sheathing panels by more than two times the uplift capacity of the control panel fastened using only nails. The results also showed
that a continuous 3” layer of medium density spray foam can increase the wind uplift capacity by as much as three times that of the control roof panel.”(vi)
The mineral wool used today is more rigid, more hydrophobic and higher in thermal
resistance than any other currently available fibre insulation. However, when compared
to plastic insulation in general, and spray foam specifically, in terms of durability, the
advantage goes to plastic insulations.
Based on research, the installation of spray foam results in significant structural benefits
and reduced building damage for impact and high winds. Spray foam performs
consistently for the life of the building. Finally, unlike other insulations, spray foam is not
negatively impacted by environmental factors like wind, cold and flooding.
Severe Weather Performance Comparison