BPI Building Analyst common mistakes
BPI Building Analyst · Understand the traps and how to avoid them.
Treating a blower-door CFM50 reading as a direct air-leakage rate and reporting it as ACH without converting through the conditioned volume and correcting for building height and climate.
Candidates memorize the number 50 and forget that CFM50 is a pressure-standardized measurement, not natural infiltration; they also skip the conditioned-volume lookup or use gross floor area instead.
What to do instead
Practice the full chain: measure conditioned volume, compute ACH50 = (CFM50 x 60) / volume, then apply the appropriate natural-infiltration conversion factor (such as the LBL or ASHRAE method) and state assumptions explicitly.
Writing a work scope that lists air-sealing and insulation measures without quantifying baseline conditions, target metrics, or a verification method for each measure.
Candidates draft scopes as generic to-do lists because they have not practiced translating diagnostic results into measurable performance targets.
What to do instead
For every proposed measure, state the existing condition with the measured value, the target value, and the post-installation test that will confirm it (for example, pre- and post-blower-door CFM50 with a stated reduction goal).
Diagnosing a pressure-boundary or thermal-boundary defect from a single infrared image without confirming with a blower door, pressure pan, or smoke pencil.
Thermal imaging is visually compelling and candidates over-trust it, forgetting that solar gain, emissivity differences, and duct leakage create false signatures.
What to do instead
Always triangulate: use IR to locate candidate defects, then confirm air movement with a smoke pencil or pressure pan under induced pressure before writing it into the report.
Skipping combustion appliance zone (CAZ) worst-case depressurization testing and instead checking draft only under normal operating conditions.
Candidates test appliances individually and in a quiet house, missing that combinations of exhaust fans, dryers, and doors can reverse draft and spill flue gases.
What to do instead
Set up worst-case conditions (all exhaust devices on, interior doors positioned per protocol), then measure CAZ pressure relative to outdoors and verify each appliance's draft and spillage before and after air sealing.
Assuming air sealing will improve combustion safety and omitting a post-sealing CAZ test from the scope.
Candidates associate tighter houses only with energy savings and forget that reduced make-up air can worsen depressurization and spillage.
What to do instead
Treat combustion safety as a required pre- and post-measure test, and include a provision for make-up air or vented combustion air in the scope whenever tightening is proposed.
Sizing HVAC equipment from rules of thumb (such as square footage or tons per 500 square feet) instead of a room-by-room load calculation.
Rules of thumb are widely repeated in the field and candidates default to them under time pressure, especially after envelope improvements change the load.
What to do instead
Perform or verify a Manual J-style load calculation using post-retrofit envelope values, and check that the proposed equipment matches the calculated sensible and latent loads.
Ignoring duct leakage and duct location when modeling or scoping, treating the distribution system as outside the building envelope.
Candidates focus on walls and attics and overlook that ducts in unconditioned space lose both energy and pressure balance.
What to do instead
Include duct leakage testing (total and to outside) and duct location in the assessment, and model duct losses explicitly rather than assuming a fixed efficiency.
Reporting modeled savings from a single run of an energy model without documenting inputs, baselines, or sensitivity to key assumptions.
Candidates treat model output as a prediction rather than an estimate and omit the input assumptions that drive the result.
What to do instead
Record every input value and its source, run a baseline and a proposed case, and state the range of savings under plausible variation in the most sensitive inputs.
Installing insulation without first establishing air sealing and without verifying coverage, density, and contact with the air barrier.
Candidates sequence measures incorrectly and treat insulation as a standalone fix, producing gaps, compression, and convection loops that erase the rated R-value.
What to do instead
Sequence air sealing before insulation, specify the target R-value and installation standard, and verify with visual inspection and, where applicable, thermal imaging after installation.
Presenting test results and recommendations to the client without translating technical metrics into health, safety, comfort, and cost terms, and without documenting client decisions.
Candidates are trained on instruments and numbers but not on client communication, so reports read as raw data dumps and clients cannot act on them.
What to do instead
Structure the report around findings, implications, and prioritized recommendations with clear cost and benefit language, and record client approvals and declined measures in writing.