Energy Efficiency and Sustainability
Core Principles
Understand the building thermal envelope: insulation R-values, window U-factors and SHGC, air sealing, and thermal bridging. Know the difference between prescriptive and performance compliance paths, and the role of commissioning. Recognize concepts like daylighting, economizers, heat recovery, and renewable readiness. Understand that energy code compliance is verified through plans review and inspection, including envelope and mechanical checks.
Traps to Watch
Questions often confuse R-value (thermal resistance) with U-factor (conductance); they are reciprocals. Watch for SHGC questions: low SHGC reduces solar gain in cooling climates but may be undesirable for passive heating. Another trap is assuming efficient equipment alone meets the code; envelope and air sealing matter. Beware of claims that a performance path removes inspection requirements.
Worked Example
A designer wants large west-facing windows in a cooling-dominated climate. Rule of thumb: west glazing drives peak cooling load. The answer is to reduce glazing area, specify lower SHGC glass, or add exterior shading, rather than simply upsizing the air conditioner. Efficient equipment cannot offset a poor envelope without increasing energy use.
Key Points
- R-value and U-factor are reciprocals.
- Low SHGC helps cooling but can hurt passive heating.
- Air sealing and thermal bridging affect real performance.
- Prescriptive and performance paths both require verification.
- Envelope choices drive peak loads more than equipment size.