Friday, September 13, 2019

Understanding Spray Foam Insulation

When building an energy-efficient, net-zero home in Missouri, it is vital to eliminate or significantly reduce energy loss with a high-performance thermal envelope. Spray foam insulation, an alternative to traditional building insulation such as fiberglass, saves on energy costs and dramatically lowers utility bills.
Studies by the US Department of Energy show that 40% of a home’s energy is lost as the result of air infiltration through walls, windows, and doorways. Buildings treated with spray foam insulation typically insulate as much as 50% better than traditional insulation products.

Spray Foam insulation blocks all three forms of heat transfer:
  • Conductive heat transfer – The flow of thermal energy through a substance from a higher to a lower temperature area.
  • Radiant heat transfer – The process by which heat energy in the form of light is emitted more strongly by warm surfaces and absorbed by other materials, especially those of low IR reflectivity.
  • Convective heat transfer – Heat which is created elsewhere that is transported utilizing a fluid, such as water or in our case air.

How it Works

Spray foam insulation has a two-part spray process, starting with two 55 gallon drums – one with urethane material, and water-based blowing agent in the other.
Two chemicals mix at the spray nozzle and instantly expands to 100X applied thickness, adhering to the sprayed surface, and filling all gaps and voids to make an excellent air barrier.
Open Cell Foam –
  • Air barrier, but water vapor permeable
  • Primarily used on interior applications against the wood to prevent condensation from being trapped against the framing.

Closed Cell Foam –
  • Air and water vapor barrier
  • Primarily used on exterior applications where a vapor barrier is needed, i.e., crawlspaces
  • Approximately 2X cost of open-cell foam

Spray Foam Insulation Pros & Cons

The Good
  • Excellent air sealing
  • Easy retrofit in the attic
  • Places insulation at the roof deck
    • puts mechanicals inside conditioned space
  • Keeps loft within 8-10° of living space
  • Reduces mechanical sizing requirements
  • Approximately 25% energy reduction

The Bad

  • Contains polyurethane
  • Off-gasses VOCs for a couple of days
  • When applied to full-fill walls, can result in lots of landfill trash
  • More costly than batt insulation

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