Closed Cell
Definition & Basics
Closed cell foam is a high‑density (2 lb/ft³) polyurethane insulation with an R‑value of ~7.0 per inch. Its tiny, gas‑filled cells make it an exceptional air, moisture, and vapor barrier—all in one product.
Key Benefits at a Glance
- R‑value: ~R‑7.0 per inch
- Acts as a continuous air seal
- Water and vapor resistant
- Adds structural rigidity
- Long‑term durability (25 + years)
Key Performance Attributes
- Air & Vapor Barrier
- Its closed cells trap gas and block air infiltration, reducing drafts and energy loss.
- Acts as a Class II vapor retarder at 1 inch thickness—ideal for Florida’s high‑humidity climate.
- Water Resistance
- Doesn’t absorb liquid water; prevents mold, mildew, and wood rot in attics, walls, and crawlspaces.
- Bridges small cracks and gaps, ensuring continuous moisture control.
- Structural Reinforcement
- Adds up to 300% more shear strength to stud walls and roof decks, reducing racking and deflection.
- Bonds directly to substrate—minimizes panel movement or vibration in metal buildings.
- Long‑Term Durability
- Stable over decades: won’t sag, settle, or lose R‑value.
- Resistant to chemicals, oils, and UV (when covered with protective coating).
What is the cost of Closed Cell Spray Foam?
Note: The pricing ranges below are approximate—final costs depend on your project’s square footage, location, required prep work (e.g., cleaning, masking, substrate repairs), and the difficulty of spray (access, geometry, and height). Complex, hard‑to‑access projects may exceed these ranges, while larger, straightforward jobs may fall below.
- 1.5 Inches (R‑Value ≈ 10.5): $1.90 – $2.60 per sq ft
- 2 Inches (R‑Value ≈ 14): $2.40 – $3.15 per sq ft
- 3 Inches (R‑Value ≈ 21): $2.95 – $4.00 per sq ft
True Square Footage Calculation:
Pricing is based on the actual insulated surface area, not just flat measurements. Roof pitches, gable ends, partition walls, and any angled or vertical surfaces must be measured and included to determine the true square footage of your project
Minimum Project Size: Most installations carry a minimum charge (typically $2500) to cover setup and mobilization.
Application Types
Metal Buildings & Barndominiums
Air‑Tight Insulation
- Fills every corrugation and fully encapsulates fastener penetrations—eliminating the tiny gaps and seams where air would otherwise seep in or out.
- Creates a continuous, monolithic seal that minimizes drafts and pressure imbalances for consistent indoor comfort.
Condensation & “Roof Drip” Prevention
- Closed cell spray foam acts as both a thermal and vapor barrier to stop warm, moisture‑laden interior air from reaching cooler metal surfaces and condensing.
- Eliminates hidden “roof drip” that causes corrosion, stained finishes, and potential mold growth.
Water‑Tight Seal
- Chemically locks around screws, purlins, and panel overlaps to form an impermeable barrier against rain and wind‑driven moisture.
- Prevents leaks along screw lines and seam joints—no more patchwork after every storm.
Panel Bonding & Structural Support
- Bonds directly to steel panels, transforming each sheet into part of a unified, composite assembly.
- Increases panel rigidity, reduces flutter, and helps resist wind uplift, ensuring long‑lasting protection and structural integrity.
Hybrid Comfort Upgrade
- 1.5 inches of closed‑cell for sealing and moisture control
- 3.5 inches of open‑cell to boost R‑value and add sound‑absorbing properties for a quieter interior environment.
New‑Construction Walls
- Thermal Envelope
- Sprayed into 2×4 or 2×6 stud cavities for continuous, cavity‑fill insulation (2–3 inches typical).
- Pest & Insect Barrier
- Seals gaps at plates, headers, and utility penetrations—blocks termite, ant, and rodent entry.
- Unlike batt insulation, no voids remain for pests to tunnel through.
- Air‑Sealing Details
- Foam adheres to OSB or sheathing; eliminates reliance on tape/sealants that can fail over time.
- Assembly Compatibility
- Works under house wraps, structural sheathing, fiber cement, brick veneer, or siding systems.
New‑Construction Roof Decks
- Thermal & Air Seal
- Sprayed directly to underside of roof sheathing (OSB or plywood).
- Achieves a fully conditioned attic space, reducing HVAC loads and “hot attic” issues.
- Condensation Control
- Stops humid Florida air from contacting hot roof sheathing; eliminates roof deck sweating.
- Structural Stiffening
- Increases diaphragm strength, helping roofs resist uplift in storms.
- Installation Considerations
- Typical thickness: 3–4 inches (R‑value ~20–26).
- Requires proper ventilation planning if staying vented (e.g., baffles) or conversion to unvented attic.
- Must allow for foam curing time (typically 24 – 48 hours) before decking weights or foot traffic.
Subfloors & Crawlspaces
- Encapsulated Crawlspaces
- Foam applied to rim joists and underside of floor sheathing seals out ground moisture and radon.
- Creates a dry, conditioned subfloor cavity—improves indoor air quality and energy efficiency.
- Floor Thermal Performance
- Keeps floors warmer to the touch; reduces HVAC cycling due to floor‑to‑air heat transfer.
- Moisture Control
- Blocks humid exterior air from entering; prevents joist rot and mold in wood‑framed systems.
- Pest Resistance & Insulation Integrity
- Unlike fiberglass batts—where pests nest in the dry, off‑ground insulation—closed‑cell foam bonds directly to the substrate, leaving no hollow cavities or loose material for rodents or insects to inhabit or chew through.
Concrete & Foundation Applications
- Slab Edge & Footing Insulation
- Foam applied vertically along slab edges to minimize thermal bridging at grade level.
- Interior Foundation Walls
- Direct‑to‑concrete spray creates a moisture barrier; effective for stem walls and basement walls.
- Joint & Crack Sealing
- Fills construction joints or gaps between foundation and framing, blocking air and water infiltration.
Next Steps
- Project Assessment
We evaluate your building type, climate considerations, and code requirements to recommend the right thickness and system. - Professional Installation
Our team uses calibrated proportioners to ensure consistent density and performance. - Warranty
We back every closed‑cell install with a Lifetime Warranty, giving you long‑term peace of mind.
Get Started Today
Are you ready to improve your home or commercial space with the best insulation available? Contact Truly Sealed today for a free, no-obligation estimate tailored to your project needs.