Step 1

Specimen

The window, door, or curtain-wall unit under test, and its published air-leakage performance.

Specimen area: — ft² (updates as you type).

Reference pressure for the rate above: ASTM E283 is a test method — its own title is literally “...Under Specified Pressure Differences Across the Specimen,” meaning E283 itself doesn't fix a pressure. Two different documents that invoke E283 fix two different reference points, and using the wrong one here would over/under-predict required airflow by roughly 4ⁿ (≈2.5× at the default exponent below): NFRC 400 and the IECC/IRC air-leakage code sections test and report against 1.57 psf (75 Pa) — the default above and what most fenestration labels use — while some NAFS/AAMA structural testing instead reports at 6.24 psf (300 Pa). Check which one your specimen's actual label or test report cites, pick the matching option above, or enter a different figure directly via “Custom…” if your source cites something else entirely.

Step 2

Target test pressure & duration

ASTM E1105's own scope leaves the static pressure differential up to whoever specifies the test (“...factors should be considered fully prior to specifying the test pressure difference to be used”). Derive a starting figure from the window's rated Design Pressure below, or enter a project- or manufacturer-specified pressure directly — use whichever one the actual governing spec calls for.

Where 15% / 20% comes from: AAMA/WDMA/CSA 101/I.S.2/A440 (NAFS) derives a product's rated lab water-penetration test pressure as 15% of DP for R, LC, and CW performance classes, and 20% of DP for AW class (confirmed independently by FGIA, Construction Specifier, and RDH Building Science). NAFS also sets a class-specific floor and cap at the extremes (roughly 140 Pa at the low end of R class; 580–720 Pa at the top of AW class) that this simple percentage doesn't model, and these figures shift somewhat between NAFS editions — treat the DP-derived number as a starting point, not a substitute for a printed water-test pressure on the label when one exists. It's also a lab-rating formula, not automatically the field target: if the governing spec references AAMA 502/503 field-test practice, secondary trade sources report the actual field pressure as two-thirds of this lab-rated figure (with its own floor — 91 Pa / 1.9 psf for AAMA 502, 200 Pa / 4.18 psf for AAMA 503) — those two floor figures are reported consistently across trade summaries but haven't been independently confirmed against the primary AAMA text here, so verify them against the actual referenced AAMA edition before relying on them. Compute that number yourself and enter it via “Enter test pressure directly” above rather than stacking it on top of the DP derivation here.

Duration: ASTM E1105 Procedure A (uniform static pressure) holds the target pressure continuously, with water spray running at the same time, for a minimum of 15 continuous minutes — the default above. Procedure B (cyclic pressure) instead runs 5-minutes-on / 1-minute-off cycles, with the standard's actual floor being on cumulative pressurized time: total time of pressure application must not be less than 15 minutes (at least 3 cycles), more cycles per project spec. Change the field above if the governing spec calls for something different.

Step 3

Blower sizing

The blower(s) have to move air fast enough to both replace what leaks through the specimen at test pressure and make up for the temporary field chamber's own imperfect seal.

Why this is a direct CFM entry, not a percentage: no ASTM standard publishes a field-chamber leakage figure, and it isn't a minor add-on to size around — a temporary chamber sealed to a wall or window opening with tape, sheeting, and duct connections is typically the larger of the two leak paths this calculator has to cover, bigger than the specimen's own leakage below it. A percentage of specimen leakage would understate it, sometimes badly, precisely because the two aren't related to each other. The only real way to size this is a pre-test, chamber-only pressurization check: seal the chamber with the specimen opening blocked off (or otherwise isolated), pressurize it alone with nothing else running, and read off how much air it actually takes to hold the target pressure — enter that figure above. Leaving this blank does not mean zero; it means the required-airflow figure below reflects specimen leakage only and is very likely an underestimate, which the page flags below rather than silently assuming your chamber is perfectly sealed.

No default CFM, on purpose: this field is intentionally blank. Blower airflow at a given static pressure varies enormously by make, model, and impeller design — there is no “typical” number to publish here, only your actual unit's own performance curve at the pressure you're testing at.

Result

Airflow and gauge target

Each figure below shows the formula it comes from, with your current inputs plugged in, so nothing here is a black box.