Closed-Cell Vs. Open-Cell Spray Foam: What’s Best For Texas Attics And Metal Buildings?

Choosing spray foam for your San Antonio home or shop is a smart move, especially as cooler nights hit and humidity sticks around. The next question is which type fits your space best. Closed-cell and open-cell spray foam both seal air leaks and improve comfort, but they behave differently with heat, moisture, sound, and structure. In this guide, you will get clear answers to the most common questions we hear from Texas homeowners and metal building owners. You will also learn how thick is thick enough, when a vapor retarder matters, what local codes expect, and how to avoid lender or insurance confusion.

Quick overview: how the two foams differ

• Density and rigidity
  • Closed-cell is dense and rigid. It adds noticeable structural strength to roof decks, wall panels, and metal skins.
  • Open-cell is lighter and more flexible. It is excellent at sound absorption but does not add as much strength.
• R-value per inch
  • Closed-cell averages around R-6 to R-7 per inch. A common figure used in planning is about R-6.5 per inch.
  • Open-cell averages around R-3.6 to R-4 per inch.
• Moisture behavior
  • Closed-cell is highly resistant to water absorption and can act as a vapor retarder at sufficient thickness.
  • Open-cell is vapor permeable. It lets assemblies dry to one side when designed correctly.
• Air sealing
  • Both create an effective air seal when installed by a trained crew.
• Sound and noise
  • Open-cell reduces airborne noise better due to its softer, open structure.
  • Closed-cell helps with noise too, but open-cell usually wins for acoustics.

What works best in San Antonio attics

For most attic encapsulations in our climate zone, both foams can work, but they fit different goals.

• If you want maximum R-value in limited space, or you need extra roof deck rigidity and moisture resistance, closed-cell is a strong choice.
• If your priorities include sound control, cost efficiency per R, and the ability for assemblies to dry inward, open-cell is often ideal.

In attic applications, code requires achieving the target R-value for your assembly and meeting fire safety and ignition barrier rules. In Bexar County and surrounding areas, many projects target R-20 to R-30 at the roofline for encapsulated attics, with final thickness set by design and framing depth. We size the system to your roof pitch, HVAC loads, and air leakage levels so you get the right performance without overpaying.

What works best in metal buildings and shops

Metal buildings see big temperature swings and can sweat on the inside if moisture condenses on metal panels. Closed-cell spray foam adheres directly to metal and helps control condensation. It also adds stiffness to panels and resists wind-driven rain. For many shops and barndominiums, closed-cell is the go-to on exterior metal skins. That said, open-cell can still be used on interior partitions for sound control and cost savings, while closed-cell handles the envelope.

R-value per inch and typical thickness

• What is the value per inch of closed cell insulation? Plan on about R-6 to R-7 per inch. Many manufacturers list R-6.0 to R-7.0 at one inch.
• Is 3 inches of closed cell spray foam enough? It depends on the assembly and code target. In a metal building wall, 2 to 3 inches can dramatically cut condensation risk and heat gain. For rooflines where you want higher total R, you may need more. We often recommend 3 inches in metal walls, 2 inches on metal roofs as a starting point, then adjust based on load calculations and budget.
• For open-cell, 5.5 inches typically lands near R-20, and 7 to 10 inches are common in roofline encapsulations when space allows.

Moisture, vapor control, and ventilation

• Does closed-cell foam need a vapor barrier? Often no, because closed-cell becomes a class II vapor retarder at roughly 1.5 to 2 inches. In humid Texas conditions, that can be beneficial on exterior walls or metal skins. Placement and thickness are important, so design matters.
• Open-cell is vapor permeable. In rooflines, it calls for a smart approach to moisture control. That means a continuous air seal, balanced ventilation strategy, and possibly a dedicated dehumidification plan in very tight homes. Your HVAC plays a key role in managing indoor humidity once the attic is encapsulated.

In encapsulated attics, make sure existing passive vents are addressed correctly. You do not want wind washing across foam or a mix of vented and unvented approaches. We set up a consistent, code-compliant strategy that keeps the air barrier continuous and the assembly dry.

If your project includes removing old materials before upgrades, we can design a custom insulation removal plan in universal city that protects indoor air quality and sets the stage for a clean, successful install.

Cost ranges and what affects them

• How much does closed cell insulation cost? In Texas, installed closed-cell spray foam often lands higher per square foot than open-cell due to material density and yield. Price varies with thickness, access, prep, fire coatings, and whether we are spraying wood or metal. Open-cell is typically more budget friendly for higher R totals in big attic spaces.

We provide detailed proposals after an on-site evaluation, including options that meet energy goals at different price points. If you need a ballpark or financing options, ask our team during your visit.

Common myths about lenders and insurance

• Myth: “Spray foam voids roof warranties.” Reality, manufacturers and roofers focus on ventilation and moisture management. A properly designed and documented attic encapsulation is compatible with many roofing systems. We coordinate details so you have clear records.
• Myth: “Insurers do not like spray foam.” Reality, insurers care about risk. Spray foam can reduce ice damming, moisture damage, and energy waste. With correct ignition or thermal barriers and code compliance, coverage is typically unaffected.
• Myth: “Appraisers and lenders cannot value spray foam.” Reality, many do, especially in Texas markets. Clear documentation, modeled energy savings, and contractor credentials help.

We help you prepare the right paperwork and photos so transactions go smoothly.

Downsides and how to avoid them

What are the downsides of closed cell spray foam? Higher upfront cost, more rigid feel that is less forgiving if later wire runs are needed, and the need for careful design to avoid trapping moisture if combined with other vapor layers. These are solved with a proper plan, correct thickness, and trained installers. Can mold grow on closed-cell foam? Spray polyurethane foam is not a food source for mold. If bulk water or high humidity is present, mold can grow on dust or adjacent materials. The real solution is moisture control, not just material choice.

Air sealing and comfort you will feel

Both foams seal cracks and gaps around penetrations and irregular framing. That means fewer drafts, steadier temperatures, and reduced workload on your HVAC system. Many Texas homeowners notice quieter interiors and more consistent rooms within days.

If you are replacing old, dusty insulation, we can create a clean slate and then complete universal city insulation installation after removal for a seamless upgrade.

Lifespan and maintenance

• What is the lifespan of closed cell spray foam? Properly installed, both closed and open-cell foams are long-lasting and typically match the life of the building shell. They do not settle or sag. The key is solid substrate prep, correct mix and temperature, and verified coverage.

Is open cell spray foam better than closed cell?

It depends on your goals:

• Choose closed-cell for metal buildings, condensation control, maximum R per inch, and added rigidity.
• Choose open-cell for attic encapsulation with strong sound control, cost effectiveness per R, and assemblies that benefit from drying potential.

Many projects blend both, using closed-cell where moisture or thin space is the challenge, and open-cell where acoustic comfort or high R at lower cost is the priority.

Your next step

Every home and building is unique. A quick site visit lets us check your roof deck, metal panels, current ventilation, and HVAC so you get the right foam at the right thickness. Reach out to schedule a free on-site evaluation. If you are nearby and exploring spray foam for a new project, our team also provides universal city spray foam services with the same careful, family-oriented approach.

We will give you straight answers, clear pricing, and a design that meets code, protects your investment, and keeps you comfortable in every Texas season.