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Key points

  • The key ingredient in spray foam is isocyanates; exposure can cause asthma, sensitisation, breathing problems and skin and eye irritation.
  • Occupants must vacate the building during installation and return at a time set by the manufacturer.
  • Some manufacturers recommend 24 hours after two-component high-pressure foam before re-entry; re-entry time depends on the product formulation and other factors that affect curing.
  • Review the safety data sheet (SDS), and get ventilation and re-entry instructions for your product from the manufacturer or supplier.
Written for:OwnerContractor

Spray polyurethane foam is sprayed as a liquid that expands and hardens into a continuous insulating layer, used on roofs, walls and around openings. On roofs it can act as both thermal insulation and waterproofing with a suitable protective coat. See roof waterproofing.

1) Health first

The US Environmental Protection Agency stresses that the key ingredient in spray foam is isocyanates, and that exposure can cause asthma, sensitisation, lung damage, other respiratory problems, and skin and eye irritation1. Therefore:

  • Building occupants must vacate during installation2.
  • Ventilation during and after installation is essential to protect workers and residents1.
  • Review the product's safety data sheets and hazard labels1, and only workers wearing personal protective equipment should be present during spraying2.

2) When can you go back in?

The EPA explains that some manufacturers recommend waiting 24 hours after applying two-component high-pressure systems, that one-component foam may take about 8 to 24 hours to cure, and that the manufacturer or supplier sets ventilation and re-entry times for each product and situation2.

Ask the contractor in writing for: the product name, the safety data sheet (SDS), the ventilation plan, and the manufacturer's recommended re-entry time. Don't allow spraying with children, older people or asthma sufferers in the building.

3) Application quality

Practical notes.

  • The surface must be clean and dry.
  • Thickness must be even and achieve the required insulation value; ask for it to be measured.
  • On exposed roofs the foam needs a UV-protective coat that is inspected and renewed periodically. See membranes and coatings.

4) Pros and cons

Pros

  • A continuous, seamless layer that closes gaps around openings.
  • Lightweight, and can be applied to irregular surfaces.
  • Can combine thermal insulation and waterproofing on roofs.

Cons and cautions

  • Health risks during application require vacating the building.
  • Quality depends heavily on the installer's skill and the weather.
  • Needs sun protection and periodic maintenance of the protective coat.

Sources

The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.

  1. 1Spray Polyurethane Foam (SPF) Insulation and How to Use it More Safely — U.S. EPA — Safer Choice
  2. 2Vacate and Safe Re-Entry Time — Spray Polyurethane Foam Application — U.S. EPA — Safer Choice
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This guide is for general information and planning, based on standards and technical guides. Standards are revised periodically; in Saudi Arabia the binding reference is the Saudi Building Code and the instructions of the competent authorities. For design and execution, use a licensed engineer or technician. Found an error? Tell us.