Spray Insulation

Alias(s): Open-cell polyurethane foam, open-cell, soft foam, half-pound foam
R-value per Inch: 3.5 - 4
Weaknesses: Does not prevent radiant heat transfer (The primary source of heatflow in and out of your structure). More expensive than batts or cellulose. It will absorb moisture. Not DIY friendly. Installation produces excess foam that must be trimmed and disposed of. Ongoing debate in industry about fire resistance in exposed applications. It is subject to minimum and maximum temperature restrictions during installation.

Alias(s): Closed-cell polyurethane foam, closed-cell, hard foam, two-pound foam
R-value per Inch: 5 - 6.8
Weaknesses: expensive, not do-it-yourself friendly, ongoing debate in industry about fire resistance in exposed applications, installer experience/training critical as improperly installed foam is prone to failure, subject to minimum and maximum temperature restrictions during installation.

Alias(s): Kit foam, can foam, DIY foam
R-value per Inch: 5 - 6
Weaknesses: Expensive especially if used for large areas. Not user friendly- requires know how to both select the right product and install it properly. It is subject to minimum and maximum temperature restrictions during installation.

Alias(s): Wet spray cellulose, spray cellulose, dense pack cellulose ("dense pack" is an incorrect term often used to describe wet spray cellulose, see "dense pack" under injected insulation)
R-value per Inch: 3.5
Weaknesses: Not do-it-yourself friendly. Installed wet and concerns about moisture release and mold have surfaced in the industry. Adhesion to wall surfaces can break down over time so the tight installation may not be long term.