How to fill out a REScheck yourself: a step-by-step walkthrough.

Short answer: REScheck-Web is a free, browser-based tool published by the U.S. Department of Energy's Building Energy Codes Program.² You register, start a project, tell it your code and location, describe your ceiling/wall/floor/window assemblies, and it runs a UA calculation - the sum of each assembly's U-factor times its area - against the same calculation for a code-minimum house.² If your building's total UA is equal to or lower than the code building's, it passes. For a house with a handful of wall types and a straightforward window schedule, that is a real do-it-yourself job. The two things that make people redo a report are guessing an input instead of gathering it first, and not knowing what to do when the summary comes back short.

What you need before you open the software

Gather these from the plan set before you touch the keyboard. REScheck will accept anything you type; it has no way to know a number is wrong.

• The plan set - floor plans, elevations, and wall sections. This is where every area and assembly type comes from.
• A window and door schedule with the manufacturer's NFRC-certified U-factor and SHGC for each window type, not a marketing spec or a glass-only number. Where those numbers actually live is its own guide if the schedule doesn't already have them.
• Insulation R-values called out for the ceiling or roof, above-grade walls, floor, and any basement or crawl space walls, and whether each is cavity insulation, continuous insulation, or both.
• Gross area of each assembly - gross wall area (not net of openings), ceiling area, floor area, and each window and door's area by type. REScheck's own guidance defines wall assemblies by "gross wall area, cavity/continuous R-value... and orientation," so area has to be gross, not window-deducted.⁴
• Orientation of the building's front face relative to north. The software asks for this as an angle in degrees on the building characteristics screen.¹

If any one of these is missing from the drawings - a window schedule with no NFRC values, a wall section with no R-value called out - get it before you start. An input you invent to keep moving is the input a plan reviewer catches.

Choosing the right code edition and climate zone

Two separate questions, and getting either wrong changes every number downstream.

Which code edition? Ask your building department which edition of the IECC it enforces, or whether it has adopted a state-specific amendment. REScheck-Web supports the 2009 through 2024 IECC editions plus a handful of state codes, and its "What's my code?" link on the Project screen will suggest one based on your project location.² Treat that suggestion as a starting point, not a substitute for calling the department - a few states run their own energy code entirely and REScheck isn't the right tool for those.

Which climate zone? The IECC assigns a climate zone to every U.S. county in a table in its general requirements chapter (Table R301.1 in the 2021 edition), and a location not listed there is assigned a zone by the method in the following section.⁵ REScheck-Web looks this up automatically once you select your city or county on the Project screen, but it is worth checking against the table yourself - a house entered under the wrong county can pass a report it should fail, or fail one it would otherwise pass.

The five steps

This follows the sequence in DOE's own REScheck-Web getting-started guide, condensed to what you will actually see on screen.¹

1. Pick your code and climate zone. Register, log in, and click New Project. On the Project tab, enter a project title, select the energy code for your location, enter the location itself (city or zip code), choose the project type - new construction, addition, or alteration - and pick a compliance method. If you're not sure which method, the UA trade-off is the default most residential projects use. Then enter the building characteristics: construction type, conditioned floor area in square feet, the building's orientation in degrees, and a short set of yes/no feature questions.
2. Enter the envelope assemblies. Move to the Envelope tab and add each building component that separates conditioned space from unconditioned space or outside air: ceilings and skylights, walls (with their windows and doors), and foundations. You don't have to add one row per room - if every exterior wall shares the same framing and R-value, add their combined gross area as a single row. Foundation components have their own logic: use the basement-wall entry for a conditioned basement, the floor entry for a floor over unconditioned space, and the crawl-wall entry for an unvented crawl space with an uninsulated floor above it. For anything that doesn't fit a preset wall type, an "Other" entry lets you enter a calculated overall U-factor directly.
3. Enter windows and doors. Each window and door type gets its own row under the wall it belongs to, with area, U-factor, and SHGC. Use the values from the NFRC label or the manufacturer's certified sheet - not a center-of-glass number, and not a value copied from a similar-looking window elsewhere in the schedule. Where a product genuinely has no certified rating, the code provides a default table keyed to frame type and pane count, and the defaults are set low on purpose so an unlabeled product doesn't get an easy pass.⁶
4. Read the compliance summary. The Compliance tab shows your building's assembly-by-assembly performance against the code requirement, plus a set of mandatory requirements - air leakage, mechanical equipment and controls, service water heating, and duct construction and testing - that you answer separately from the UA calculation. Each mandatory item asks you to confirm it will be met, mark it exempt, or mark it not applicable, and to note how compliance will be documented; that note carries through to the report's Comments/Assumptions column.³
5. Export the PDF. Once compliance shows and the mandatory requirements are answered, go to Reports and choose what to generate: a Compliance Certificate, an Inspection Checklist, and a Panel Certificate are the standard options.³ Save periodically as you work - the project lives on your dashboard and can be reopened and edited until you're ready to submit.

What "Fails" means, and the honest fixes

A failing summary is REScheck telling you which number to look at again, not a judgment on the house. DOE's own troubleshooting guidance for a failing compliance check is worth following in order: confirm every component was entered, confirm your area takeoffs, confirm insulation values including whether you entered cavity versus continuous correctly, confirm the fenestration U-factor and SHGC on each window against the label, compare your proposed U-factors to what the climate zone table requires, and then look at the assembly-by-assembly UA breakdown to see which component is actually driving the shortfall.³ Most failures trace back to one of those, not to the house being genuinely non-compliant.

The IECC also gives you a legitimate way to close a small gap: the Total UA alternative. If your building's total envelope UA is less than or equal to what the same building would produce using the code's required U-factors, it complies, even if one individual assembly - say, a wall that's a little under the table value - doesn't meet its number on its own.⁷ In practice that means a stronger ceiling or a better window package on one elevation can legitimately offset a weaker wall elsewhere, as long as the SHGC requirement and the maximum fenestration U-factor are still met.⁷

What that does not mean is typing in a U-factor your windows don't have to force a pass. That number ends up on a plan set a reviewer compares to your window schedule, and on a house where an inspector can read the NFRC label. What actually happens when a REScheck's inputs don't match what got built is its own guide - the short version is that the honest fix is almost always available, and it is cheaper than the alternative.

When a project is too complex to DIY safely

REScheck itself doesn't get harder to click through as a project gets more complicated - the risk of an unnoticed wrong input does. A few signals it's worth having someone who does this daily take a pass:

• Multiple wall or ceiling types. A house with three or four different wall assemblies, mixed framing, and a couple of roof types has more places for a cavity/continuous mix-up or a mismatched area to hide, and each one changes the UA total.
• Sunrooms or conditioned basements. Spaces that are conditioned but built differently from the rest of the house - a sunroom with its own glazing package, a finished basement with foundation walls partly above and partly below grade - have their own entry logic and their own requirements, and are the most common place a self-prepared report gets the assembly type wrong.
• A UA result that fails by a small margin you can't explain. If the summary is close and you can't point to which input is driving it, that's the moment to stop guessing rather than start adjusting numbers until it turns green.
• A state amendment on top of the base IECC. A handful of states layer their own thresholds or exceptions onto the national code, and some don't use REScheck at all - check the state finder before assuming the national tables apply.
• A jurisdiction that wants a named preparer. Some building departments ask who prepared the report, independent of whether the software itself is free to use. If yours does, that's worth confirming before you submit, not after a correction notice.

What we need from you

If you'd rather hand it off after gathering the plan set, we work from the same inputs described above: the plan set, the window and door schedule with NFRC values, and the insulation callouts. Every input on the report is annotated with where it came from, so your building department can verify it without a phone call.

Frequently asked questions

What information do I need before I start?

The plan set, a window and door schedule with NFRC U-factor and SHGC per type, insulation R-values for each assembly, gross areas, and the building's orientation. Gather all of it before opening the software.

How do I know which code edition and climate zone apply?

Ask your building department which IECC edition or amendment it enforces, then check your county against the IECC's climate zone table. REScheck-Web suggests both automatically from your project location, but the department has the final word.

Where do the window numbers come from?

The NFRC label or the manufacturer's certified spec sheet - never a center-of-glass number from a glass supplier, and never a guess. Unlabeled products fall back to the code's default table, which is deliberately conservative.

What does "Fails" mean on the summary?

It flags which input or assembly is driving the shortfall, not a verdict on the house. Work through areas, insulation values, and fenestration values in order, and consider whether the Total UA alternative closes the gap honestly.

Is REScheck-Web free?

Yes, it's published by the DOE Building Energy Codes Program and free to register for and use in a browser.

When should I stop and get help?

Multiple wall or ceiling assemblies, sunrooms or conditioned basements, a close UA result you can't explain, a state amendment on the base code, or a department that wants a named preparer are all signals worth a second set of eyes.

Sources

1. U.S. DOE Building Energy Codes Program, "REScheck-Web Getting Started" guide - project dashboard, project sharing, and the step-by-step sequence for creating a new project (Project tab, Envelope tab, Compliance tab, Reports). energycodes.gov. Read 2026-09-02.
2. U.S. DOE Building Energy Codes Program, "REScheck" program page - REScheck-Web description, supported code editions, and the UA (U-factor x Area) calculation methodology. energycodes.gov/rescheck. Read 2026-09-02.
3. U.S. DOE Building Energy Codes Program, "REScheck Basics" (2022 National Energy Codes Conference bootcamp slides) - Compliance tab mandatory requirements, "Compliance Failing" troubleshooting steps, and the Compliance Certificate / Inspection Checklist / Panel Certificate report options. energycodes.gov. Read 2026-09-02.
4. U.S. DOE Building Energy Codes Program, FAQ "How is Cavity and Continuous Wall Insulation Calculated in REScheck?" - wall assemblies defined by gross wall area, cavity/continuous R-value, and orientation. energycodes.gov. Read 2026-09-02.
5. International Energy Conservation Code, 2021 edition, R301.1: climate zones are assigned from Figure R301.1 or Table R301.1; a location not listed is assigned a zone under Section R301.3. codes.iccsafe.org. Read 2026-09-02.
6. International Energy Conservation Code, 2021 edition, R303.1.3: fenestration U-factors determined by NFRC 100 and labeled and certified by the manufacturer; products lacking a labeled rating default to Table R303.1.3(1) or (2), values keyed to frame type and pane count. codes.iccsafe.org. Read 2026-09-02.
7. International Energy Conservation Code, 2021 edition, R402.1.2 (insulation and fenestration criteria table by climate zone) and R402.1.5 (Total UA alternative: proposed total building thermal envelope UA compared to the UA of the same building at code-required U-factors; SHGC requirements and maximum fenestration U-factor must still be met). codes.iccsafe.org. Read 2026-09-02.

Section numbers and the compliance methodology above are quoted from the 2021 IECC and DOE's own REScheck-Web documentation; the 2024 edition renumbers some sections, and several states amend the base code or don't use REScheck at all. Check the state finder for the edition your jurisdiction has adopted. Final authority rests with your building official.