Spray foam insulation comes in two fundamentally different formulations — open-cell and closed-cell — with meaningfully different performance characteristics, costs, and appropriate applications. Atlanta’s hot, humid climate makes the right choice especially important. Here’s a straight comparison for Georgia homeowners.
Open-Cell Spray Foam
What It Is
Open-cell spray foam has a lower-density structure with interconnected cells that remain open after curing. It’s softer, more flexible, and expands to fill cavities aggressively. R-value: approximately R-3.5 to R-3.7 per inch — lower than closed-cell, requiring more thickness to reach target R-values.
What It Does Well
Excellent air sealing — even open-cell foam effectively seals air infiltration pathways. Good sound dampening — its softer structure absorbs sound better than closed-cell. Lower cost — typically $0.44–$0.65/board foot vs. $1.00–$1.50 for closed-cell. Good for interior applications where moisture resistance isn’t critical.
Limitations in Atlanta’s Climate
Open-cell foam is vapor permeable — moisture can pass through it. In Atlanta’s humid climate, this means open-cell foam in exterior applications — crawl spaces, roof decking — can allow moisture infiltration and vapor drive that damages structural materials over time. This is the source of the concern about open-cell foam in humid climates, and why it needs to be specified carefully for Georgia applications.
Best Applications in Atlanta
Interior walls for sound control, attic floor applications where cost is the primary concern, and interior conditioned spaces. Not recommended for crawl space walls, basement walls, or roofline encapsulation in Georgia’s humid climate.
Closed-Cell Spray Foam
What It Is
Closed-cell spray foam has a rigid, dense structure with completely enclosed cells. Higher R-value: R-6 to R-7 per inch. Rigid after curing — adds structural strength to walls and roof decking. Acts as a vapor barrier — moisture cannot pass through it at standard installation thicknesses.
What It Does Well
The best all-around performance in Georgia’s climate. High R-value per inch means less thickness is required. Vapor barrier properties prevent moisture infiltration in humid applications. Structural rigidity adds racking strength to walls and roof decking. Resistant to mold growth. The correct choice for crawl spaces, rim joists, and roofline encapsulation in Atlanta’s humid environment.
Cost
$1.00–$1.50 per board foot installed — 2–3× the cost of open-cell. For applications where moisture resistance matters, the premium is justified by the significantly better performance and longevity in Georgia’s climate.
Best Applications in Atlanta
Crawl space walls and rim joists, attic roofline encapsulation, basement walls, and any exterior application where moisture resistance is important. The right choice for most structural applications in Georgia’s humid climate.
Which Is Right for Your Atlanta Home?
The answer depends on where you’re applying it:
Attic floor (over drywall ceiling): Either product works. Open-cell is more cost-effective; closed-cell provides better moisture resistance if the attic has humidity concerns.
Attic roofline encapsulation: Closed-cell. Open-cell on roof decking in humid climates has documented moisture issues. Closed-cell is the correct specification.
Crawl space walls and rim joists: Closed-cell. No exceptions for Georgia’s humid climate.
Interior walls for sound: Open-cell. Cost-effective, excellent sound performance, moisture resistance not needed.
For a free spray foam assessment in Atlanta or anywhere in the metro, call (404) 620-6333. We specify the right product for each application in your home.
Can mice get through foam insulation?
Mice can chew through both open-cell and closed-cell spray foam — neither is rodent-proof. Spray foam is not a pest exclusion product; it’s an insulation and air sealing product. For homes with rodent intrusion concerns, pest exclusion (sealing entry points with hardware cloth or metal mesh) should be completed before insulation work begins. We note any evidence of rodent activity during our free inspection.
Why is it hard to sell a house with spray foam insulation in Atlanta?
This concern specifically relates to open-cell spray foam applied directly to roof decking in humid climates — some home inspectors and lenders flag it because moisture can accumulate against the roof deck. Properly installed closed-cell spray foam on roof decking doesn’t have this issue. In Atlanta’s market, a home with properly installed closed-cell spray foam insulation typically sells at a premium, not a discount — energy-efficient homes command higher prices in Georgia’s expensive-to-cool climate.