Assessment, Testing and Data Collection
What gets assessed
Assessment in multifamily work combines visual survey, diagnostic testing, and data collection. Candidates should know the purpose and limits of each test. Blower door testing measures envelope and compartment leakage; in multifamily, whole-building and guarded unit testing answer different questions. Duct leakage testing applies to both central and in-unit distribution. Infrared thermography finds thermal defects, moisture, and air leakage, but only under adequate temperature difference and with correct interpretation. Pressure diagnostics (zone pressure testing, zonal pressure pans) map leakage pathways between units and common areas.
Sampling and data quality
Multifamily buildings have many similar units, so sampling is common. Understand that a sample must be representative: mixing unit types, orientations, floors, and renovation histories matters. Know how to document pre-retrofit conditions, collect utility data with appropriate weather normalization, and record assumptions so results are reproducible. Poorly documented data is a frequent cause of failed savings claims.
Traps to watch for
Questions may confuse what a test measures with what it diagnoses. A blower door number alone does not locate leakage; it quantifies it. Another trap is treating a single unit's test result as representative of the building. Watch for questions about test conditions - wind, stack effect, and temperature difference all bias results, and tests should be conducted under controlled or at least documented conditions.
Worked example
If you test 8 of 80 units, you have sampled 10 percent. Before generalizing, confirm the sample spans floor levels, orientations, and unit types. If all 8 are top-floor corner units, your estimate of average leakage is likely biased high.