Healthy indoor air quality 

Indoor air quality has become an important consideration when building a new home.  Conventional materials such as paint, plywood, fibreglass products, and spray foam insulation release chemicals (known as Volatile Organic Compounds - VOCs) into the air as they age.  These VOCs produce a strong odor, commonly described as “new house smell”, which is immediately recognizable in conventional new homes. According to Health Canada, the high levels of VOCs found in conventionally built new homes can cause fatigue, nausea, dizziness, headaches, breathing problems, irritation of the eyes, nose and throat, and can lead to chronic health issues based on levels of exposure.  Children, seniors and pregnant people are especially at risk.  

Synthetic insulators like fiberglass and spray foam are known to off-gas VOCs that are harmful for air quality. Fiberglass insulation contains formaldehyde and fine particles that may be inhaled during installation or when disturbed. Spray foam insulation off-gasses VOCs for weeks or months after installation, significantly affecting indoor air quality.

At Elm Natural Builders, we utilize a hempcrete wall system that replaces VOC releasing insulation, plywood and paint.  Our hempcrete wall system combined with natural plaster finishes provides a chemical-free alternative made from simple natural ingredients: hemp shive, hydrated lime, water.  Cured and dried hempcrete does not off-gas any VOCs.

Hempcrete is mold-resistant 

Mold in homes is a major concern for air quality, especially in colder climates.  Mold can grow behind drywall, in ceilings and inside of conventional insulation.   Building materials like wood and concrete can trap moisture, also leading to the growth of mold. Exposure can be a health risk, especially for those who have respiratory issues.  

Hempcrete is naturally resistant to mold because of its naturally high pH levels. Mold requires a pH level of 4.5 or lower to grow, but since the pH of hempcrete is 12, it is inhospitable to mold growth.  Hempcrete is airtight, but vapour open, which means that it allows moisture to pass through its pores.  This effectively prevents the accumulation of moisture in the walls that can lead to mold. The lime binder in hempcrete is antimicrobial and antifungal, adding to the mold resistant properties of hempcrete.  Hempcrete is a safe choice for homebuilders looking to avoid the growth of mold in their new home.  

Hempcrete is fire-resistant 

Hempcrete insulation is naturally fire resistant and does not require any addition of flame retardant  chemicals that are typically applied to building materials, like spray foam insulation, foam boards, paints and glue.  Health Canada has linked the use of fire retardants to thyroid disruption, delayed mental and physical development and memory and learning problems.  

Hempcrete has passed national fire testing testing in the UK, France and more recently (2020) in the United States where it passed the ASTM E 84 test.  According to Hempitecture USA, hempcrete received a 0 on the Flamespread and Smoke Developed Index ( a scale from 0 to 450, with 0 being the highest possible rating). Lime, a key ingredient in hempcrete, is a non-combustible material that is resistant to high temperatures and has a class A1 rating for fire resistance.

Hempcrete repels insects and rodents

The hemp used in hempcrete insulation contains cannabinoids, naturally occurring compounds found in hemp plants, which may have evolved to deter pests from chewing on them.  Experiments showed that higher cannabinoid concentrations in hemp leaves led to less damage from insect larvae. Hempcrete is rodent resistant due to the naturally occurring silica content in the hemp fibres which repels rodents. The lime binder in hempcrete is extremely caustic and helps deter animals from chewing on the material. Hempcrete is made from the chipped stalk of the hemp plant which contains virtually no seeds or leaves which means it contains very little protein for pests to feed off of.  Finally, hempcrete walls are solid, they do not offer cavities or voids for nesting rodents.