Joint Sealants

Photo credit: Pexels photo by Erik Mclean


Joint Sealants are popular building products that play an important role in a building’s weather-resistance and energy efficiency. Sealants are placed between two substrates, filling a gap and forming a barrier.1 Sealants differ from adhesives and caulks, which bond elements together.7


The most common sealant options include:2

  • acrylic and latex
  • polyurethane
  • silicone
  • hybrid/modified polymer

The HBN (Healthy Building Network) categorizes hybrid/modified polymer and most polyurethane sealants as dangerous for their toxic qualities.3


Dangers of Sealants

Different sealants represent different hazards as they can contain undisclosed VOCs and toxic additives.6

  • Silicone sealants are a popular choice in the building industry as they’re typically a low VOC product.2 However, they do contain silica, a filler which has associated health effects ranging from irritation to cancer.2
  • Sealant sprays like single-component polyurethane foam rank as one of the most dangerous sealants in the HBN hazard spectrum and in Building Green’s comparison of products. 2,3
    • Chemicals like isocyanates can be found in spray foam, and are known for work-related asthma from inhalation or contact exposure during construction.3 Halogenated flame retardants are also commonly found in single-component polyurethane foam and pose health concerns since they’re persistent and bioaccumulative toxicants.8
    • Isocyanates are a group of monomers used to create many types of polymers such as adhesives, foam insulation, and composite woods. Isocyanates are included in Perkins&Will Precautionary List and the International WELL Building Institute (IWBI) hazard listing as Toxic Material Reduction Feature 25.9,10
  • Two-component polyurethane sealants present double the risk because they also include plasticizers, which are developmental toxicants.3

HBN classifies polyurethane as one of the most dangerous options compared to acrylic latex materials unless it comes in the form of low-density, pre-formed, compressed polyurethane foam tape.3 However, even the better “green” sealants like hybrid/modified polymer can still contain phthalates and associated asthma and reproductive toxins.


✓ Choose caulk sealants as an alternative to spray foam sealants like polyurethane foam.3

✓ Prefer phthalate-free products if hybrid/modified polymer sealants are required.3

✓ Choose pre-formed sealants like foam sealant tape – ranked green in HBN Sealant Hazard Spectrum.3

✓ Prefer multi-purpose sealants categorized as siliconized latex sealants with low VOCs of less than 25 grams per liter.3

✓ Avoid mold and mildew-resistant products unless necessary. If used, avoid products containing arsenic-based fungicides.3

✓ Avoid accelerators which are typically two-component formulas known to contain isocyanates.6

✓ Prefer products from the Building Clean Certified product database.5