Attic Spray Foam Insulation

Spray foam attic insulation in Oklahoma City. Convert vented attics to unvented conditioned space per IRC R806.5. Open cell and closed cell options for Climate Zone 3. REScheck performance path compliance.

Why the Attic Matters Most

In a typical Oklahoma home, the attic is the largest source of energy loss. Hot air rises, and in winter it pushes against the ceiling plane. In summer, the Oklahoma sun heats the roof to 160 degrees or more, and that heat radiates into a conventional vented attic that can reach 140-150 degrees. Your HVAC ductwork and air handler are sitting in that heat, working against it every hour of every day.

Spray foam on the attic roof deck changes the equation. You move the thermal boundary from the attic floor to the roof line, and the attic becomes part of the conditioned envelope. Ductwork and equipment now operate in a space that stays within 5-10 degrees of the living area.

How Unvented Attics Work Under Code

The International Residential Code, Section R806.5, defines the requirements for unvented attic assemblies. Oklahoma City operates under the 2018 IRC. The rest of the state follows the 2015 IRC. Both allow unvented attics with air-impermeable insulation (spray foam) applied directly to the underside of the roof sheathing.

For Climate Zone 3, the key provisions are:

  • No vapor retarder required. CZ 1-3 are exempt from the vapor retarder requirement for unvented attic assemblies. This simplifies the installation and reduces cost.
  • Air-impermeable insulation applied in direct contact with the roof sheathing. Both open cell and closed cell spray foam meet this requirement. No air gap between the foam and the sheathing.
  • R-value compliance via performance path. The 2009 IECC (adopted statewide) calls for R-30 at the ceiling. That prescriptive value assumes a vented attic with insulation on the floor. When you move to an unvented assembly, you file a REScheck energy analysis using the performance path. The home is evaluated as a complete system — walls, windows, doors, foundation, and roof. A well-sealed spray foam attic combined with other envelope components routinely passes REScheck in Oklahoma.

Open Cell vs. Closed Cell in the Attic

Open Cell — 5.5 Inches at the Roof Deck

Open cell sprayed to the full depth of 2x6 rafters gives you R-20.35. It fills every gap, seam, and penetration in the roof deck. It is vapor permeable, which means if a roof leak occurs, water passes through and shows on the ceiling — you see it and fix it. This is the most common attic application we install across the OKC metro. Cost-effective, code-compliant, and proven.

Closed Cell — 3 Inches at the Roof Deck

Closed cell at 3 inches delivers R-19.5 and adds a Class II vapor retarder. This is the right choice when rafter depth is limited (2x4 rafters in older homes), when the roof assembly has unusual moisture exposure, or when the homeowner wants the additional structural rigidity that closed cell provides. It costs more per square foot than open cell, and in most Oklahoma attics, the additional vapor resistance is not required by code.

What the Installation Looks Like

We mask off soffits, gable vents, and ridge vents — sealing the attic from outside air. The foam is applied to the underside of the roof sheathing and along the gable end walls. Penetrations for plumbing vents, electrical wiring, and recessed lights get sealed as part of the application. The result is a continuous, unbroken air and thermal barrier at the roof line.

Most residential attics take one day. We coordinate with your HVAC contractor if duct modifications are needed, and we handle any existing insulation removal on the attic floor if you choose to go that route.

The Result

A cooler attic in summer. A warmer attic in winter. Lower energy bills. Quieter living space. Equipment that runs less and lasts longer. That is not theory — that is what homeowners in Oklahoma City tell us after the first utility cycle.

Frequently Asked Questions

Do I need a vapor retarder in my attic if I use spray foam?
No. Per IRC Section R806.5, unvented attic assemblies in Climate Zones 1 through 3 do not require a vapor retarder when air-impermeable insulation is applied directly to the underside of the roof deck. Oklahoma City falls in Climate Zone 3. Both open cell and closed cell spray foam qualify as air-impermeable insulation under this code section. This is one of the reasons spray foam is straightforward to install in Oklahoma attics — no additional vapor retarder membrane or coating is needed.
Will spray foam void my roof warranty?
Most asphalt shingle manufacturer warranties address ventilation requirements for vented attics. When you convert to an unvented attic assembly, you are changing the system. Some manufacturers have specific guidance for unvented assemblies. We recommend checking with your shingle manufacturer. That said, unvented attic assemblies per IRC R806.5 are an established, code-approved building practice used in millions of homes. The foam does not contact or damage the roofing material — it is applied to the underside of the roof deck sheathing.
What about my existing blown insulation on the attic floor?
When we spray the roof deck and convert to an unvented attic, the existing blown insulation on the attic floor is no longer the primary thermal boundary — the roof deck is. We typically recommend removing the old floor insulation so the conditioned air from your HVAC system can reach the attic space and keep it within a reasonable temperature range. Leaving it in place creates a double thermal boundary that can cause the attic to overheat or undercool.
Open cell or closed cell for my attic — which is better?
Both are code-compliant in Oklahoma's Climate Zone 3. Open cell at 5.5 inches (R-20.35) is the more common choice for attic roof decks because it costs less, provides excellent air sealing, and allows moisture visibility if a roof leak occurs. Closed cell at 3 inches (R-19.5) is appropriate when you need the higher R-value per inch due to shallow rafter depth, or when the attic has exposure to unusual moisture conditions. We evaluate each attic and recommend based on what we find.

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