Spray Foam is the apex predator of insulation, but it commands a premium price tag. Homeowners are often shocked by the delta between fiberglass ($2K) and foam ($7K+). Here is exactly how that price is calculated and why the math heavily favors foam if your AC is entirely located in the attic.
The Square Foot Multiplier
| Material Variant | Current DFW Rate (Per Sq Ft of Roof Deck) | Primary Application |
|---|---|---|
| Open-Cell Foam (6" Depth) | $1.50 - $3.50 | Standard residential roof decks. Breathes water. |
| Closed-Cell Foam (3" Depth) | $3.00 - $7.00 | Metal buildings, sub-floors, and severe moisture barriers. |
The Setup Fee Variable
Spray foam requires driving a massive box truck containing two pressurized chemical vats (A-side ISO and B-side Resin) heated to 130°F. The sheer mobilization cost of deploying this rig to a house means the "cost per square foot" drops dramatically the larger the house is. Very small jobs carry a heavy premium baseline.
The ROI Equation
If an open-cell retrofit costs $7,500, but immediately drops extreme summer electric bills by $150/month and winter bills by $80/month, the sheer mechanical stress relief on the HVAC system alone prevents a premature $12,000 unit replacement. Foam pays for itself twice: once in utility cash, and once in deferred capital expenditure.