ASHRAE
ASHRAE 90.1
ASHRAE 90.1 is a US standard that provides minimum requirements for energy efficient designs for buildings except for low-rise residential buildings. The original standard, ASHRAE 90, was published in 1975, in the aftermath of the energy crisis in 1973. It was since been updated in 1999, 2001, 2004, 2007, 2010, 2013, 2016, 2019 and 2022 (current edition).
Each section of ASHRAE 90.1 describes the scope of the provisions (e.g., definitions and relevant building elements), lists the mandatory provisions, and lists the requirements for complying with the standard.
- ASHRAE 90.1 Section 5.4 describes mandatory provisions for insulation installation (5.4.1); window, skylight, and door ratings (5.4.2); and air leakage (5.4.3). Section 5.5 contains the prescriptive provisions for fenestration and opaque assemblies.
Prescriptive building envelope requirements are determined based on the building’s climate zone classification (ASHRAE Standard 90.1, Tables 5.5-1 to 5.5-8). For projects following the prescriptive compliance method, all building envelope components must meet the minimum insulation and maximum U-factor and solar heat gain coefficients (SHGC) requirements listed for the project’s climate zone. Window area must be less than 40% of the gross wall area, and the skylight area must be less than 5% of the gross roof area.
The project may exceed the envelope prescriptive requirements if the project uses an energy simulation model to document points earned for EA Credit 1, Optimize Energy Performance.
The requirements of Section 6 apply to all building HVAC systems. Mandatory provisions for HVAC performance are documented in ASHRAE 90.1, Section 6.4, and include minimum system efficiency requirements (6.4.1), load calculation requirements (6.4.2), controls requirements (6.4.3), HVAC system construction and insulation requirements (6.4.4), and completion requirements (6.4.5).
ASHRAE 90.1, Section 6.4.3.4, lists minimum control schemes for thermostats (off-hours, including setback and optimum start/stop), stair and elevator vents, outdoor air supply and exhaust vents, heat pump auxiliary heat, humidification and dehumidification, freeze protection, snow- and ice-melting systems, and ventilation for high-occupancy areas.
ASHRAE 90.1, Section 6.5, provides a prescriptive compliance option. Prescriptive provisions are included for air and water economizers (6.5.1); simultaneous heating and cooling limitations (6.5.2); air system design and control, including fan power limitation and variable speed drive control (6.5.3); hydronic system design and control, including variable flow pumping (6.5.4); heat rejection equipment (6.5.5); energy recovery from exhaust air and service water heating systems (6.5.6); kitchen and fume exhaust hoods (6.5.7); radiant heating systems (6.5.8); and hot gas bypass limitations (6.5.9).
These requirements include mandatory provisions (7.4) and a choice of prescriptive (7.5) or performance-based compliance (Appendix G). Mandatory provisions include requirements for load calculations (7.4.1), efficiency (7.4.2), piping insulation (7.4.3), controls (7.4.4), pool heaters and pool covers (7.4.5), and heat traps for storage tanks (7.4.6).
These requirements address mandatory provisions related to voltage drop.
These requirements apply to all lighting installed on the building site, including interior and exterior lighting. Mandatory provisions include minimum requirements for controls (9.4.1), tandem wiring (9.4.2), luminaire source efficacy for exit signs (9.4.3), exterior lighting power definitions (9.4.5), and luminaire source efficacy for exterior lighting fixture (9.4.4). Per 9.4.1.2, occupancy controls are required in classrooms, conference rooms, and employee lunch and break rooms. Interior lighting compliance must be documented using either the building area method (9.5) or the space-by-space method (9.6). See the Implementation and Calculations sections for additional guidance on lighting power calculations.
This section includes mandatory provisions for electric motors (10.4).
Appendix G provides specific guidance on the rules and procedures to use to simulate building energy use when the objective is to substantially exceed the requirements of 90.1. Appendix G is especially useful to demonstrate compliance with LEED EA prerequisiste 2 “Minimum Energy Performance” and LEED EA credit 1 “Optimize Energy Performance”.
ASHRAE 62.1
ASHRAE 62.1 standard specifies minimum ventilation rates or other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects. The standard specifies that ventilation systems be designed to prevent uptake of contaminants, minimize growth and dissemination of microorganisms, and if necessary, filter particulates.
The standard applies to all spaces intended for human occupancy.
First published in 1973, Standard 62.1 has undergone some key changes over the years, reflecting the ever-expanding body of knowledge, experience, and research related to ventilation and air quality.
The standard outlines a ventilation rate procedure and an IAQ procedure for compliance. The ventilation rate procedure prescribes outdoor air quality levels acceptable for ventilation; treatment measures for contaminated outdoor air; and ventilation rates for residential, commercial, institutional, vehicular, and industrial spaces.
LEED prerequisite IEQp2 “Minimum Indoor Air Quality Performance”
Requires to establish minimum indoor air quality (IAQ), thus contributing to the comfort and well-being of the occupants. The prerequisite requires to meet the minimum requirements of Sections 4 through 7 of ASHRAE standard 62.1 “Ventilation for Acceptable Indoor Air Quality”. Mechanical ventilation systems must be designed using the ventilation rate procedure or the applicable local code, whichever is more stringent.
LEED credit IEQc1 “Increased Ventilation”
Encourages to provide additional outdoor air ventilation by increasing breathing zone outdoor air ventilation rates to all occupied spaces by at least 30% above the minimum rates required by ASHRAE Standard 62.1.
ASHRAE 55
ASHRAE 55 identifies the factors of thermal comfort and the process for developing comfort criteria for a building space and its occupants. The standard specifies the combinations of indoor space environment and personal factors that will produce thermal environmental conditions acceptable to 80% or more of the occupants within a space.
The environmental factors addressed are temperature, thermal radiation, humidity and air speed; the personal factors are those of activity and clothing.
LEED encourages to provide a comfortable thermal environment that promotes occupant productivity and well-being.
LEED credit IEQ7.1 “Thermal Comfort – Design”
Requires to design heating, ventilation and air conditioning (HVAC) systems and the building envelope to meet the requirements of ASHRAE Standard 55 “Thermal Environmental Conditions for Human Occupancy”. For Core & Shell projects, the building’s mechanical systems must allow for the tenant build-out to meet the requirements of this credit. Moreover, LEED encourages to assess the building occupants’ thermal comfort over time.
LEED credit IEQ7.2 “Thermal Comfort – Verification”
Requires to conduct a thermal comfort survey of building occupants within 6 to 18 months after occupancy. This survey should collect anonymous responses about thermal comfort in the building, including an assessment of overall satisfaction with thermal performance and identification of thermal comfort problems. In addition, the credit requires to develop a plan for corrective action if the survey results indicate that more than 20% of occupants are dissatisfied with thermal comfort in the building.
ASHRAE Guideline 0
The purpose of this guideline is to describe the Commissioning Process capable of verifying that a facility and its systems meet the Owner’s Project Requirements.
For more information and standards, visit ASHRAE website
