BPI Envelope flashcards
BPI Envelope · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- R-value
- A measure of thermal resistance per unit area; higher R-value indicates better insulation performance. It quantifies a material's ability to resist heat flow by conduction.
- U-factor
- The reciprocal of R-value (U = 1/R); it measures the rate of heat transfer through a material or assembly. Lower U-factor means better thermal performance.
- Stack effect
- The upward movement of air in a building caused by temperature and pressure differences; it drives infiltration at lower levels and exfiltration at upper levels.
- Dew point
- The temperature at which air becomes saturated (100% relative humidity) and water vapor begins to condense. Surfaces below dew point risk condensation.
- Thermal bridge
- A path of high thermal conductivity that bypasses insulation, reducing effective R-value and creating cold spots where condensation may occur.
- Air barrier
- A continuous layer that controls air leakage through the building enclosure. It must be sealed at joints and penetrations to be effective.
- Blower door
- A diagnostic tool consisting of a fan and manometer used to measure building air leakage by pressurizing or depressurizing the building to a reference pressure, typically 50 Pa.
- ACH50
- Air changes per hour at 50 Pascals; calculated as (CFM50 × 60) divided by building volume in cubic feet. It standardizes air leakage measurements across building sizes.
- Rim joist
- The structural member at the perimeter of a floor system; a common air leakage path that should be sealed and insulated to improve energy efficiency and moisture control.
- Vapor retarder
- A material that resists the diffusion of water vapor; classified by permeance (Class I, II, III). Placement depends on climate to avoid trapping moisture.
- Permeance
- A measure of a material's ability to transmit water vapor, typically expressed in perms. Lower permeance indicates greater resistance to vapor diffusion.
- Capillary action
- The movement of liquid water through porous materials due to surface tension and adhesion; it can draw moisture upward into building assemblies.
- Rain screen
- A building envelope design that includes a drainage plane and an air gap behind the cladding to allow water to drain and walls to dry.
- ASHRAE 62.2
- A standard that specifies minimum whole-building ventilation rates and exhaust requirements for residential buildings, based on floor area and number of bedrooms.
- HRV
- Heat Recovery Ventilator; a balanced ventilation system that transfers sensible heat from exhaust air to incoming fresh air, reducing heating energy loss.
- ERV
- Energy Recovery Ventilator; a balanced ventilation system that transfers both sensible heat and latent moisture between exhaust and incoming air streams.
- MERV
- Minimum Efficiency Reporting Value; a rating for air filters indicating particle capture efficiency. Higher MERV captures smaller particles but may increase pressure drop.
- Radon
- A radioactive soil gas that can accumulate indoors and increase lung cancer risk; mitigation includes sub-slab depressurization and sealing foundation entry points.
- SHGC
- Solar Heat Gain Coefficient; the fraction of solar radiation admitted through a window as heat. Lower SHGC reduces cooling loads in warm climates.
- NFRC label
- A certification label on windows and doors that reports U-factor, Solar Heat Gain Coefficient, Visible Transmittance, and Air Leakage ratings.
- Window air leakage
- The rate of air infiltration through a window assembly, measured in cubic feet per minute per square foot (cfm/ft²) at a specified pressure difference; lower is better.
- Low-E coating
- A thin metallic oxide coating on glass that reduces radiant heat transfer by reflecting infrared energy, improving window thermal performance.
- Flashing
- Material installed to direct water away from building assemblies at joints and penetrations; integrated in shingle fashion with the water-resistive barrier.
- Duct blaster
- A diagnostic tool that pressurizes a duct system to measure air leakage, typically reported in cubic feet per minute at 25 Pascals (CFM25).
- Pressure pan
- A diagnostic tool placed over a register to measure pressure differences and infer duct leakage to unconditioned spaces; readings above 3 Pa suggest significant leakage.
- Manometer
- An instrument that measures pressure differences, often in Pascals (Pa), used in building diagnostics to assess air leakage and pressure imbalances.
- Infrared thermography
- A diagnostic technique using an infrared camera to visualize temperature differences caused by air leakage, missing insulation, or thermal bridging.
- Zonal pressure diagnostics
- A method using a blower door and manometer to measure pressure differences between zones (e.g., attic, garage) to locate air leakage paths.
- Balometer
- A flow hood instrument used to measure air volumetric flow at registers and exhaust grilles, typically in cubic feet per minute (CFM).
- Effective R-value
- The actual thermal resistance of an assembly after accounting for thermal bridging, gaps, compression, and convective loops; often lower than nominal R-value.
- Closed-cell foam
- A high-density insulation material that provides thermal resistance, air sealing, and can act as a vapor retarder when installed at sufficient thickness.
- Attic hatch sealing
- Weatherstripping and insulating the attic access opening to prevent air leakage and heat loss between conditioned space and the attic.