Q: Do you need a vapor retarder or a vapor barrier with SPF insulation?
It depends of the use of the building, the climate and the materials of construction. In normal
occupancies and moderate climates, SPF insulation typically does require a vapor retarder.
climate and building use may require vapor retarders/barriers. Check with your design professional for
specific recommendations and refer to SPFA technical document, AY 118, Moisture Vapor Transmission for
Q: How does SPF reduce energy use in buildings?
- SPF provides a continuous air barrier.
- SPF prevents moisture infiltration through air leakage.
- SPF minimizes dew point problems and condensation.
- SPF avoids thermal bridging.
- SPF resists heat movement in all directions.
- SPF provides reliable performance under varying conditions.
Q: What is the difference between a vented and unvented attic?
A: Unvented (conditioned) attics use air-impermeable insulation as a barrier to prevent moisture
condensation on the underside of roof decks. Vented attics minimize condensation by allowing the escape
of moisture to the exterior by air flow.
Q: If you spray the underside of a roof deck with SPF insulation, should you vent the attic?
No, the application of SPF insulation to the underside of the roof deck minimizes the potential
for condensation. The SPF insulation develops a thermal and moisture gradient that avoids the development
of dew point conditions in the attic.
Because of this, moisture won't condense or accumulate and, therefore,
does not need to be vented to the exterior.
Q: Is SPF a good soundproofing material?
A: Both low and medium (2lb/cubic/ft) density SPF effectively reduce noise from outside sources by
sealing cracks and gaps that allow sound to travel through the walls, floors and ceilings into the building.
They are less effective against noise caused by vibration.
Q: What is the difference between low density, open cell SPF and medium density closed cell SPF?
- 1/2 lb Spray Polyurethane Foam (SPF)
Low density, open cell SPF refers to a generic spray polyurethane SPF that weighs between 0.4 to
0.6 lbs per cubic ft when fully cured. It is spray applied to a substrate as a liquid and expands
about 100-150 times its original volume to form a semi-rigid/flexible, non-structural SPF
insulation. The SPF has an R-value around 3.5 per inch and typically uses water as the blowing
- Medium Density, Closed Cell Spray Polyurethane Foam (SPF)
Medium density, closed cell SPF used in interior applications typically refers to generic spray
polyurethane foam that weighs between 1.5 to 2 lbs per cubic ft when fully cured. It is also spray
applied as a liquid to a substrate and expands about 35 to 50 times its original volume to form a
rigid, structural SPF insulation with a compressive strength between 15 to 25 PSI. The SPF has an
R-value of around 6.0 per inch (aged R-value) and uses high R-value blowing agents.
Both products are excellent air barriers in buildings, provide great insulation, can assist in the
control of condensation within buildings and have great environmental benefits.
Q: Why do you need coatings or coverings over SPF?
A: SPF is water resistant without other coverings, however, the surface of SPF can deteriorate
under the sun's ultraviolet (UV) rays. Typically, elastomeric coatings or aggregate coverings are used to
protect the SPF against UV radiation.(note include other coating benefits.)
Q: How long has SPF been around?
A: Spray polyurethane foam was first used commercially in the US in the 1960s for cold storage and
industrial insulation projects. SPF roofing systems evolved from exterior applications to tanks and pipes
in the late 60s to early 70s.