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PAQE: Building Envelope and Environmental Control Systems

PAQE · Work through your exam, one topic at a time.

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Building Envelope and Environmental Control Systems

The envelope and environmental control domain tests control-layer continuity, condensation logic, glazing performance, and how HVAC, ventilation, and controls follow from the loads the envelope creates.

Core rules

  • Four control layers, each continuous: water (drainage plane), air, vapor, and thermal. Continuity matters more than the nominal R-value of any single product - a 2% gap in the air barrier can halve performance.
  • Condensation logic. Determine the dew point of interior air and keep the condensing surface warmer than it, or place the vapor retarder on the warm side in cold climates and use variable-permeance or no retarder in mixed/hot-humid climates where inward drying matters.
  • Thermal bridging. Balconies, shelf angles, slab edges, and steel studs bypass insulation. Continuous exterior insulation or thermal breaks are the standard remedy and are required by most energy codes.
  • Glazing metrics: U-factor (heat flow), SHGC (solar gain), and visible transmittance (daylight). Low SHGC reduces cooling load but can dim the interior; window-to-wall ratio drives the trade-off. ASHRAE 90.1 and IECC set envelope and system minimums; ASHRAE 62.1 sets ventilation (office ≈ 5 cfm per person plus 0.06 cfm per SF of breathing zone).
  • System selection follows load shape. VAV for variable internal loads, chilled beams or radiant for sensible-dominated loads, dedicated outdoor air systems where ventilation and humidity control must be decoupled from temperature control.

Worked example

Interior at 70°F and 35% relative humidity has a dew point near 42°F. If the back of exterior sheathing sits at 38°F in winter, moisture condenses there. Solutions: move insulation outboard so the sheathing stays warm, add a continuous air barrier, or install a smart vapor retarder that closes in winter and opens in summer.

Traps

  • Specifying high R-value while allowing metal studs to short-circuit it.
  • Putting a vapor barrier on both sides of a wall, trapping moisture.
  • Choosing low-SHGC glass everywhere, then paying for permanent electric lighting.
  • Setting ventilation rates without accounting for the zone-level distribution and controls.