Building Envelope & Energy Audit Flashcards

During functional performance testing of a building envelope, a commissioning professional uses a 'hose test' on a window assembly. What is this test designed to detect?

Answer: Water infiltration through seals and flashing details

A hose test (following ASTM E1105 or AAMA 501.2) simulates wind-driven rain to detect water infiltration through window seals, flashing transitions, and other envelope penetrations.

A commissioning professional is reviewing an existing building's envelope for an energy retrofit. The building has 2-inch polyisocyanurate insulation on the exterior of a concrete masonry unit (CMU) wall. What is the primary energy advantage of exterior versus interior insulation placement?

Answer: Exterior insulation eliminates thermal bridging through the structure and keeps the CMU as thermal mass on the conditioned side

Exterior continuous insulation eliminates thermal bridging through structural elements and positions the thermal mass of the CMU wall on the interior conditioned side, improving thermal storage and reducing peak loads.

When performing a Measurement & Verification (M&V) plan for an envelope retrofit, which IPMVP Option is most appropriate when isolating envelope savings requires a control period comparison?

Answer: Option C — Whole Facility Measurement

Option C uses whole-facility utility meter data with regression analysis to determine savings, making it appropriate for envelope retrofits where individual component isolation is impractical.

A commissioning professional reviewing an energy model notices the building envelope inputs use 'assembly R-value' rather than 'clear-field R-value.' Why does this distinction matter for modeling accuracy?

Answer: Assembly R-value accounts for thermal bridging and is always lower than clear-field R-value, yielding more accurate energy predictions

Assembly R-value accounts for thermal bridging through framing and fasteners, resulting in a lower effective R-value than the nominal clear-field (insulation-only) R-value, and must be used for accurate energy modeling.

During an energy audit of a 1970s office building, a commissioning professional discovers single-pane aluminum-frame windows with a U-factor of approximately 1.1 Btu/h·ft²·°F. Replacement with triple-pane low-e windows (U-0.20) is proposed. What additional building system impact must be analyzed before recommending this ECM?

Answer: HVAC system resizing because reduced heat loss may cause overheating from existing oversized heating equipment

Dramatically reducing window U-factor decreases heating load, potentially causing existing oversized heating equipment to short-cycle or create comfort problems, requiring HVAC system rebalancing or resizing as part of the retrofit.

A commissioning professional is documenting an energy audit finding where heat recovery from exhaust air is being lost due to envelope air leakage bypassing the ERV. What term describes this phenomenon?

Answer: Envelope bypass

Envelope bypass occurs when uncontrolled air infiltration enters the building separately from the mechanical ventilation system, bypassing heat recovery ventilators and increasing heating/cooling loads.

In an energy audit, which metric is used to determine whether an energy conservation measure (ECM) is financially justified using a time-value-of-money approach?

Answer: Net Present Value (NPV) or Internal Rate of Return (IRR)

NPV and IRR account for the time value of money and risk, providing more rigorous financial justification for ECMs than simple payback, which ignores cash flows beyond the payback period.