Polyurethane Spray Foam and Rockwool: A Comparison of Two Popular Types of Insulation Materials

Time seems to slip through the fingers like grains of sand, or minerals, if you will. As the clock ticks forward, long-established insulation materials are being replaced by new ones. Spray-applied polyurethane foam is being used ever more often for insulating homes and commercial facilities rather than traditional mineral wool.

Mineral Wool

Mineral wool, or “minwool,” is an insulating material made from long fibers of inorganic materials. It’s primarily composed of rock (gabbro-basalt and carbonate rocks) used as the raw materials to produce fiber. The process of creating mineral wool isn’t overly complex. That said, it does require specialized equipment. Broken, unusable glass and quartz sand are heated in a furnace at temperatures ranging from 1200°C to 1500°C. This creates a liquid mass which, when processed on special discs, forms fibers. The resulting material is then sprayed with resin or another type of binding agent with added polymers. It is out of these fibers, boards, mats, or shells that the insulation material is made.

Mineral wool varieties

Mineral wool comes in the following varieties, with its R-value ranging from 2.2 to 3.7. R-value is the main method of measuring how well an insulation material prevents the passage of heat, the most important factor of insulation.

• Glass wool, with an R-value of 2.2 to 3.3;
• Basalt wool, with an R-value of 3.0 to 3.3;
• Slag wool, with an R-value of 2.8 to 3.7.

Polyurethane Spray Foam

If you’re not yet aware of what spray foam is, it is a polymeric material featuring a porous structure. The gas within the pores prevents air, cold, and heat from passing through. The gas content in the foam gets as high as 80-90%, allowing the material to achieve high thermal insulation properties. Thanks to special chemical additives, the material is resistant to UV radiation as well. Typically, the foamed insulation uses a finish coating that protects it from sunlight. Polyurethane foam is created by mixing two components together – polyol and isocyanate, in specific proportions. Polyol, the resin, and isocyanate, the hardener, are manufactured separately at a factory. The foam material forms right as the mixture is being sprayed. As polyol and isocyanate exit the spray gun nozzle, they react, swelling and forming a solid insulation structure.

Varieties of spray foam

Polyurethane foam insulation comes in two main types:

• Open-cell spray foam insulation with a density of 8-20 kg/m³ and an R-value of around 3.5;
• Closed cell spray foam with an R-value of 6 or 7 with a denser structure starting at 25 kg/m³.

The open-cell variety is generally used in certain situations, such as when sound absorption is a priority or when one is attempting to insulate hard-to-reach spaces.

Head-to-Head Comparison

Here we are going to break down some of the most important characteristics between the two.

Longevity

On this count, spray foam insulation kits (1000 sq ft often being the area of application) outperforms not only mineral wool but also most other similar materials. It retains its characteristics even under extreme temperatures. The service life of polyurethane foam is estimated at 35-50 years but can last for 80 to 100 years if properly handled. The R value of spray foam is higher than those of mineral wool. Therefore, more wool will be needed for insulation. 

Despite the superior spray foam R value, mineral wool is a long-lasting material in its own right which can last over 50 years under ideal circumstances. Moreover, its sturdy composition allows it to strengthen the structure of the living space and give the walls and roof increased resistance to wind and heavy rain. 

Water Resistance

Spray foam (closed cell) is more water resistant than mineral wool. The density of spray foam is more than 30 kg/m³. Thanks to its rigid structure, the material is virtually waterproof. For mineral wool, water is a destructive factor seeing as the fibers that absorb the liquid significantly deteriorate in thermal insulation potential. Moisture leads to the material overfilling and clumping, also causing mold and mildew and cutting its insulation efficiency by up to 25%. 

When moisture gets into the mineral wool, it swells and then evaporates, causing it to significantly shrink in size and creating vulnerable spots for the cold. 

Air-Tightness and Protective Envelope

Spray insulation provides better sealing than mineral wool. When using mineral wool, gaps can remain between the wall and the insulation material, reducing its efficiency and resulting in condensation. This ushers in more problems than just energy, however. Rock wool’s shrinking leaves a space for pests to enter through the walls, such as bugs, spiders, and mice. Spray foam and its technology on the other hand tightly seal all gaps and surfaces, leaving no room for air or other types of penetration.

Thermal Efficiency

The thermal conductivity index of polyurethane foam is (0.02-0.05 W/mK), while the same figure for mineral wool is significantly worse at 0.035-0.052 W/mK. What this means is that spray foam insulation R value caused less heat to be released than in the case of mineral wool. The thermal efficiency of mineral wool is 30% lower than that of spray foam, meaning substantial energy loss. 

Fire Safety

Spray foam and mineral wool both meet fire regulations and are class A, but when choosing a material for insulation, it is worth noting that mineral wool burns at a lower temperature than any other popular insulation material, igniting at about 500 to 800 degrees Fahrenheit. Also, a significantly thinner layer of polyurethane foam is required to be applied for insulation to ensure the same degree of thermal insulation. This can provide less fuel for the fire to spread in the event that one does break out.

Installation  

Mineral wool can only be installed by trained professionals. The product also creates a lot of dust during installation, which is a breathing hazard. Both materials kick up debris and release chemicals that may be harmful, so installation always requires a mask and protective gear.

 

Attachment options for mineral wool include the use of:

• Adhesives;
• Lathing;
• Dowels and screws. This can be used as an independent attachment method or as a supplement to lathing and adhesives.

When applying spray foam insulation, there is no need for additional fasteners, as the insulation excellently adheres to any kind of surface that it’s sprayed on. The spray method significantly simplifies the process of insulating rooms and it can be applied by homeowners themselves, which can come particularly in handy in the event that cracks and openings are discovered long after the installation job is already complete.

Spray foam insulation closed cell has its hazards just like other home improvement projects. In this case, there are gasses emitted and chemicals shot out that you cannot get on your skin. We have provided an article overviewing the spray foam kit you’ll need to prepare in advance if you do decide to go ahead with a do it yourself spray foam insulation project. This includes goggles, gloves, skin coverings, and other preparations. 

 

Final Thoughts

A spray foam insulation machine has a wide range of applications including insulating garages, hangars, balconies, concrete, building walls, attics, crawl faces, pipes, tanks – the list goes on and on. For those considering professional-grade options, an insulation spray foam kit is a popular choice, however, if you want to ensure optimal efficiency you would be well advised to have a spray foam insulation company come out for you, such as Ecothermix. Our professional will come out, survey your home, and use his spray foam insulation cost calculator to provide the ballpark cost for your project.

Get in touch with us and set an appointment today.

 

 

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