ASHRAE 90.1 Energy Compliance Basics

The Quick Answer

ASHRAE 90.1 has four prescriptive envelopes: Envelope (Section 5), HVAC (Section 6), Service Water Heating (Section 7), and Lighting (Section 9), plus a Performance Path (Section 11) that allows tradeoffs via energy modeling. Compliance documentation is typically a "compliance form" (COMcheck or the state-specific equivalent) showing each element meeting requirements.

Climate Zones

Climate zone (1A through 8) determines all envelope and most HVAC requirements. Zones are defined by ASHRAE Climate Zone Map (Section B1):

• 1A (very hot/humid): Miami, Hawaii, Puerto Rico
• 2A/2B (hot): Houston, Phoenix, New Orleans
• 3A/3B/3C (warm): Atlanta, Los Angeles, San Francisco
• 4A/4B/4C (mixed): Washington DC, Seattle, Portland
• 5A/5B (cool): Chicago, Denver, Boston
• 6A/6B (cold): Minneapolis, Helena
• 7/8 (very cold/subarctic): Duluth, Fairbanks

The climate zone should appear on the cover sheet and on the compliance form.

Envelope (Section 5)

Envelope requirements cover thermal performance:

• Wall, roof, and floor U-factor or R-value
• Window U-factor, SHGC, and visible light transmittance
• Door U-factors
• Vestibule requirements at major entrances
• Continuous air barrier (required since 2010 edition)
• Window-to-wall ratio caps (typically 40% prescriptive) and Daylight Responsive Control areas

Review the wall type schedule against the prescriptive R-value for the climate zone.

HVAC (Section 6)

HVAC requirements cover equipment efficiency and controls:

• Equipment minimum efficiency tables (by type, size, and category)
• Economizer required above 33,000 BTUH (packaged) or 54,000 BTUH (chilled water)
• Demand control ventilation for spaces >500 sf or >40 cfm outdoor air
• Fan power limits per HVAC system
• Duct sealing and insulation class requirements
• Energy recovery on systems above certain OA fraction thresholds

These all appear in the mechanical schedule and sequence of operations; see our mechanical drawings guide.

Lighting (Section 9)

Lighting Power Density (LPD) limits lamp watts per square foot by space type. Table 9.5.1 (space-by-space) or 9.6.1 (building area):

• Office: 0.79 W/sf (2019 space-by-space)
• Classroom: 0.84 W/sf
• Conference room: 0.97 W/sf
• Warehouse: 0.39 W/sf
• Retail: 0.95 W/sf (with additional trade lighting allowance)

Lighting controls are required: occupancy sensors, daylight harvesting, time-based controls. Check the lighting plan against the LPD table on the compliance form. Our lighting plans guide covers what to look for.

Commissioning (Section 4.2.5)

Buildings over 10,000 sf (2013 and later) require commissioning of HVAC, lighting control, domestic hot water, and renewable systems per ASHRAE Guideline 0 or equivalent. A commissioning plan must be submitted with the permit package, and a commissioning report must be submitted before occupancy.

Compliance Paths

Three main paths:

• Prescriptive: Each element meets the applicable table
• Envelope Trade-Off: Overall envelope performance equals or exceeds prescriptive via COMcheck or envelope calculation
• Performance Path (Section 11): Energy model shows the proposed building uses no more energy than the prescriptive-equivalent baseline

Performance path allows aggressive daylighting or high-performance glazing to offset other tradeoffs. LEED-tracking projects typically use Performance Path.