REScheck and Performance Path Compliance for Spray Foam Insulation

REScheck is free software developed and maintained by the U.S. Department of Energy (DOE) for evaluating residential energy code compliance. It is not proprietary. It is not a paid service. It is a public tool available to anyone — contractors, builders, code officials, homeowners — for verifying that a building’s thermal envelope meets the applicable energy code.

The software takes the building’s envelope data — insulation R-values, assembly areas, window specifications, door specifications, foundation type — and evaluates whether the proposed design meets or exceeds the energy code for the specific climate zone and jurisdiction. The output is a compliance report: a document that states whether the building passes or fails, and by what margin.

REScheck supports multiple energy codes including the 2009 IECC, which Oklahoma uses for residential energy compliance. It is accepted by building inspectors across Oklahoma and nationally as the standard compliance tool for the performance path.

The software runs on Windows and is also available as a web application. The DOE maintains it, updates it for new code editions, and provides it at no cost. There is zero barrier to any contractor using REScheck on every job. The question is whether they choose to.

The prescriptive path is the simpler of the two compliance methods. The energy code publishes a table of minimum R-values for each building component, organized by climate zone. If every component meets or exceeds its prescriptive minimum, the building passes.

For Oklahoma’s Climate Zone 3 under the 2009 IECC:

The prescriptive path is binary for each component: meet the number or fail. There is no credit for exceeding the requirement on one component if another component falls short. R-50 ceilings do not compensate for R-10 walls under the prescriptive method.

For traditional insulation — fiberglass batts, blown cellulose, mineral wool — the prescriptive path works well. These materials are installed at standardized depths in standardized framing cavities, and the R-values are well-established. An installer puts R-30 batts in the attic, R-13 batts in the walls, and each component passes on its own.

The prescriptive path also has a limitation: it evaluates only the labeled R-value of the insulation. It does not account for installation quality, air sealing, thermal bridging through framing members, or the real-world performance difference between insulation types. R-30 fiberglass batts compressed into a 6-inch cavity, with gaps around every electrical box and plumbing penetration, get the same prescriptive credit as R-30 installed perfectly. The prescriptive path cannot see the difference.

The performance path evaluates the building envelope as an integrated system. Instead of checking each component against a fixed number, it compares the proposed building’s total envelope energy performance against a reference building — a theoretical building with the same geometry built exactly to prescriptive requirements.

If the proposed building’s envelope performs equal to or better than the reference building, it passes. Individual components can fall below prescriptive values if the total system compensates.

This is not a loophole. It is a more accurate evaluation of actual building energy performance. The performance path accounts for factors the prescriptive path ignores:

Air sealing contribution. The performance model includes infiltration as a component of envelope energy performance. A building with R-19 on the roof deck but 2 ACH50 infiltration may outperform a building with R-30 on the attic floor but 7 ACH50 infiltration — because the air leakage energy loss in the second building exceeds the conductive loss difference.

Continuous insulation vs. cavity insulation. Spray foam fills the entire cavity without gaps, compression, or voids. The effective R-value of the installed assembly is closer to the rated R-value than cavity insulation that is interrupted by framing, wiring, plumbing, and electrical boxes. The performance path can model this difference.

Duct location. When insulation moves from the attic floor to the roof deck, ductwork moves from unconditioned to conditioned space. The performance path accounts for the elimination of duct losses, which can represent 15 to 25% of total HVAC output in a vented attic configuration.

Trade-offs between components. Higher-performing walls can compensate for a ceiling that falls below prescriptive. Better windows can offset a lower floor R-value. The performance path allows the designer and builder to optimize the envelope as a system rather than treating each component in isolation.

Spray foam installations frequently use the performance path because of the practical economics of foam depth.

Consider an attic roof deck application in Climate Zone 3. Prescriptive requires R-30 at the ceiling. To hit R-30 with spray foam:

• Closed cell (R-6.5/in): 4.6 inches needed. That is a substantial quantity of closed cell material, which is the more expensive foam type per board foot.
• Open cell (R-3.7/in): 8.1 inches needed. That exceeds the depth of most standard rafter framing (2x6 = 5.5 inches, 2x8 = 7.25 inches) and represents a large volume of material.

Bo’s standard depths — 3 inches closed cell (R-19.5) or 5.5 inches open cell (R-20) — fall below R-30 prescriptive. But when modeled in REScheck as part of the complete envelope, these depths consistently pass the performance path.

The math works because spray foam brings performance advantages that the prescriptive table cannot capture:

1. Air sealing. The spray foam air barrier reduces infiltration to levels that traditional insulation cannot achieve. Spray-foamed homes routinely test at 2 to 3 ACH50. The 2018 IRC requires new construction to achieve 5 ACH50 or less — spray foam beats this standard by a significant margin. The energy saved by eliminating air leakage offsets the R-value delta on the roof deck.

2. No installation defects. Spray foam does not sag, settle, compress, or leave gaps. The installed R-value equals the rated R-value across the entire application area. Traditional insulation’s installed R-value is almost always lower than rated due to compression, voids, and incomplete coverage.

3. Duct loss elimination. In an unvented attic, ductwork operates in conditioned space. The energy recovery from eliminating duct losses is substantial — often the single largest factor in the REScheck compliance calculation.

4. Thermal bridging reduction. Foam applied to the underside of the roof deck covers both the rafter bays and (partially) the rafters themselves. The continuous nature of the application reduces the thermal bridging penalty that a prescriptive calculation assumes.

These factors compound. The REScheck model captures them in aggregate and produces a compliance result that reflects the actual energy performance of the spray foam assembly — not just the R-value of the foam per inch multiplied by depth.

A REScheck report is a straightforward document. It includes:

Project information. Address, builder or contractor name, code edition (2009 IECC for Oklahoma residential), climate zone (Zone 3 for Oklahoma City).

Envelope component specifications. Every component of the building envelope is listed with its area (in square feet) and its insulation R-value:

• Ceiling/roof deck: area and R-value
• Above-grade walls: area and R-value
• Windows: area, U-factor, SHGC
• Doors: area and U-factor
• Floor over unconditioned space: area and R-value
• Foundation walls: area and R-value

Compliance result. The report states whether the proposed building passes or fails the performance path. It also shows the compliance margin — how far above or below the reference building the proposed design performs.

Signature/certification. The report identifies who prepared it and when.

The report is typically one to two pages. It is specific to the project — it uses the actual dimensions, areas, and specifications of the building being insulated. It is not a generic document.

The REScheck report serves multiple purposes beyond the initial building inspection:

Code inspection. When the building inspector evaluates the insulation, the REScheck report provides the compliance documentation. The inspector can verify the installed depths against the report’s specifications and confirm that the performance path calculation supports the installation. Without a REScheck, the inspector evaluates against prescriptive — and R-19.5 on the roof deck does not pass R-30 prescriptive.

Appraisal. Home appraisals increasingly consider energy features. A documented, code-compliant spray foam installation supported by a REScheck report demonstrates a measurable improvement to the building envelope. The appraiser has a basis for valuing the energy upgrade. Without documentation, the appraiser sees spray foam in the attic but has no way to evaluate its compliance or performance claims.

Insurance. In the event of a claim involving the building envelope — storm damage, water intrusion, fire — the insulation installation becomes relevant. A documented, code-compliant installation supported by REScheck is a stronger position than an undocumented installation with no compliance verification.

Resale. When you sell the home, the buyer’s home inspector will evaluate the insulation. A REScheck report in the home’s file answers the compliance question immediately. Without it, the inspector may flag the sub-prescriptive R-value on the roof deck as a concern — creating a negotiation issue that proper documentation would have prevented.

Future renovations. If the home is expanded, remodeled, or the HVAC system is replaced, the existing REScheck provides a baseline. The contractor working on the renovation knows what the existing envelope delivers and can plan accordingly.

At Bo’s Spray Foam, REScheck is integrated into every project workflow:

Before the job: We measure the building envelope — roof deck area, wall areas, floor areas, window specifications. We run the REScheck with the proposed insulation depths to confirm compliance before we quote the job. The homeowner sees, before work begins, that the proposed depths will pass code.

During the job: We install to the specified depths. Depth is verified during application with measurement pins and post-application with core samples or probe measurements where appropriate.

After the job: The completed REScheck report is provided to the homeowner as part of the job documentation package, along with the foam product specifications, the intumescent coating documentation (if applicable), and the application details.

At inspection: If the jurisdiction requires inspection of the insulation, the REScheck report is available for the inspector. The report matches the installed work. There are no surprises, no questions about why the R-value is below prescriptive, and no compliance ambiguity.

This process adds time. Running a REScheck takes 30 to 60 minutes of data entry and analysis per project. Measuring the envelope requires a site visit or accurate plans. Some contractors view this as unnecessary overhead and skip it.

We view it as the minimum standard of professional practice. A spray foam installation without a REScheck is an undocumented claim. A spray foam installation with a REScheck is a verified, code-compliant building improvement. The difference matters — at inspection, at appraisal, at resale, and to the homeowner who deserves to know that the work meets code.

If you are evaluating spray foam contractors in Oklahoma, ask these questions about REScheck and code compliance:

“Will you provide a REScheck report for this project?” The answer should be yes, without hesitation. If the contractor does not know what REScheck is, that tells you something about their code compliance practices.

“What depths are you proposing, and do they meet prescriptive or performance path?” The contractor should be able to tell you exactly what they plan to spray, at what depth, and how it complies with code. “3 inches of closed cell on the roof deck, R-19.5, complying via performance path per REScheck” is a specific, verifiable answer. “We spray about 3 inches” is not.

“What foam product are you using?” The contractor should name the manufacturer and product line. Different products have slightly different R-values, fire ratings, and ESR approvals. The product specification should be documented in the job file.

“Can I see a REScheck from a previous project?” A contractor who files REScheck reports regularly should be able to show you an example (with the previous client’s identifying information removed). The format and content will be consistent because it is generated by DOE software.

“What documentation will I receive when the job is complete?” The answer should include, at minimum: REScheck report, foam product spec sheet, application depths, and ignition barrier documentation (product and ESR number) for attic and crawlspace applications.

These are not trick questions. They are basic competency questions that any professional spray foam contractor should answer immediately and specifically. The answers distinguish contractors who do documented, code-compliant work from contractors who spray foam and walk away.