Passive Survivability and Functionality During Emergencies | U.S. Green Building Council
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LEED BD+C: New Construction | v4 - LEED v4

Passive Survivability and Functionality During Emergencies

Possible 1 point

Intent

To ensure that buildings will maintain reasonable functionality, including access to potable water, in the event of an extended power outage or loss of heating fuel.

Requirements

Meet any two of the three options in this credit – thermal resilience, back-up power, or access to potable water.

Option 1: Thermal Resilience

Intent of Option 1: To ensure that a building will maintain livable conditions in the event that all relevant power and thermal utilities are lost.

Demonstrate through thermal modeling that a building will maintain “livable temperatures” during a power outage that lasts 7 days during peak summertime and wintertime conditions of a typical year. Deviations from the defined livable temperatures are limited to the number of degree-days (degree-hours) during the analysis periods, as indicated below.

Livable temperature: Cooling: Not to exceed 9 °F SET-days (216 °F SET-hours) above 86°F SET for residential buildings. (Metric: Not to exceed 5°C SET-days (120 °C SET-hours) above 30°C SET for residential buildings.) Cooling  Not to exceed 18 °F SET-days (432°F SET-hours) above 86°F SET for non-residential buildings. (Metric: Not to exceed 10°C SET-days (240 °C SET-hours) above 30°C SET for residential buildings.)
Heating: Not to exceed 9 °F SET-days (216 °F SET-hours) below 54° SET for all buildings. (Metric: Not to exceed 5°C SET-days (120 °C SET-hours) below 12°C SET for all buildings.)
 
°F SET-days and °F SET-hours are degree-days and degree-hours in Fahrenheit degrees, using SET rather than air temperature.
°F SET hours are calculated as follows:
Cooling: Sum of the difference between the zone calculated SET and  86°F, only if the zone SET is greater than 86°F, for all hours of the extreme hot week.
Heating: Sum of the difference between 54°F and the zone calculated SET, only if the zone SET is less than 54°F, for all hours of the extreme cold week.
Use the same method for °C SET-days and °C SET-hours.
Habitable Zones: The design team may designate which zones are considered habitable zones during the a power outage. The total population in all habitable zones must be equal to or greater than the normal building occupancy.
 
Occupant Density: Habitable zones shall be modeled with the occupant density necessary to accommodate the total building population in the habitable zones. The zone occupant density shall be no greater than 1 person per 40 ft² (3.7 m2).
 
Ventilation: All habitable zones must have access to natural ventilation. Windows, doors, panels, and louvers are all acceptable.
 
The maximum available natural ventilation rate shall be calculated according to the methodology below. The maximum available natural ventilation rate shall be greater than or equal to 5 cfm per person (8.5 m3/hour per person) (based on the power outage occupant density).
 
The extreme cold week simulation shall assume a natural ventilation rate between 5 cfm/person (8.5 m3/hour per person) and the maximum available natural ventilation rate.
 
The extreme hot week simulation shall assume a natural ventilation rate between 5 cfm/person (8.5 m3/hour per person) and the maximum available natural ventilation rate.
 
The extreme cold week and extreme hot weeks may use different natural ventilation rates as long as the above criteria are met.
 
1-Sided Ventilation: For zones with operable vents on one side only:
Zone ventilation rate = 100 ft/min (0.51 m/s) x 0.4 x Vent Free Area in ft2 (m2) (Note: multiply by 3600 to convert to m3 /h)
 
Cross Ventilation: If there is an unobstructed ventilation path from a perimeter vent to another perimeter vent opposite or adjacent, the zone ventilation rate shall be increased by 2 times.*
 
Stack Ventilation: If there is an unobstructed ventilation path from a perimeter to an overhead vent, the zone ventilation rate shall be increased by 2 times.
 
Combined Ventilation: If cross ventilation and stack ventilation are both present they may NOT be combined.
 
Engineering Calculation: Alternatively, design teams may calculate ventilation rates via accepted engineering methods such as CIBSE AM10: 2005.
   
Modeling Methodology
Analysis Periods: "Extreme Hot Week" and "Extreme Cold Week" as defined in the Typical Meteorological Year climate data STAT file.
 
Model Duration: The thermal model shall simulate the hourly thermal behavior of each representative habitable zone over an entire year.
 
Natural Ventilation: The method of modeling natural ventilation shall be described by the modeler and based on the building design.  Vent operation shall be described in the Emergency Operation Plan (see Documentation).
 
HVAC Systems: Must be off during the Extreme Cold Week and Extreme Hot Week. Typical heating and cooling setpoints must be used for the rest of the year.
 
Internal Loads: No lights or equipment may be included in the thermal modeling
 
Shading Exterior vegetation and shading from exterior context shall may be included in the model. Deciduous vegetation shall be appropriately considered in summer/winter. Motorized shading may only be included if it includes a manual override or fail-safe that allows its use during a power outage.
Air Velocity: Air velocity greater than 20 fpm may not be considered in the SET calculation unless the design team provides engineering analysis demonstrating it is achieved in the occupied portion of the habitable zone without power.

* Airflow due to stack and cross ventilation depends on a number of variables that are complex to model and calculate.  Doubling the single-sided rate for cross or stack ventilation is a conservative approximation method loosely based on ASHRAE 62.1-2013, Section 6.4 mentioned above.

Option 2: Back-up Power

Demonstrate that adequate emergency power will be available to provide for:

  • Operation of electrical components of fuel-fired heating systems
  • Operation of a fan sufficient to provide emergency cooling if mechanical air conditioning equipment cannot operate (could be ceiling fans, plug-in window fans, or fans integral with central air distribution).
  • Operation of water pumps if needed to make potable water available to occupants
  • Lighting level a minimum of 3 footcandles (32 lux) in all building spaces to define a path of egress, to all required exits and to a distance of 10 feet (3 m) on the exterior.
  • One location for every 500 square feet (46 m2) that provides a minimum of 30 footcandles (320 lux) measured 30” (76 cm) above the floor.
  • At least one functioning electrical receptacle per 250 square feet (23 m2) of occupied space
  • Operation of cable modem and wireless router or other means of providing online access within the building.
  • Operation of one elevator in building, if applicable

These emergency power requirements can be met with:

  1. Fuel-fired back-up generator(s), with a stored fuel supply that is adequate for:
    • Residential buildings and lodging: 7 days
    • Non-residential buildings: 72 hours
    • Piped natural gas does not satisfy this requirement.
  2. A solar-electric system with battery storage
    • Battery storage must be sufficient for the following duration of critical-load power consumption (excluding elevators) assuming no sun:
      1. Residential buildings and lodging: 72 hours
      2. Other non-residential buildings: 24 hours
    • The average daily wintertime production of the solar system in kWh must equal or exceed the daily demand in kWh of all critical load circuits (assuming typical consumption and no elevator operation).
  3. A microgrid serving the building as part of a larger cluster of buildings or community. In this case, the emergency power requirements do not apply.
Option 3. Access to Potable Water
For buildings on municipal water (it is assumed here that municipal water will remain available during power outages and other emergencies):
  1. If on-site pumps are required for municipal water to reach occupied spaces in a building, either:
    1. Back-up power must be provided for these pumps, with adequate fuel for pumps to remain operational for at least seven days, or
    2. There must be a faucet on a lower floor that is served municipal water without an on-site pump at a minimum of 10 pounds per square inch (70 kPa) and that is accessible to all building occupants; for larger, multi-family buildings, there must be at least one such faucet per 75 occupants or fraction thereof.
For buildings not on municipal water systems, there must be a means of obtaining potable water in the event of a power outage in which standard well pumps do not function.

Options include:

  • Back-up, fuel-fired generator with the deep-well submersible or other pump on a critical-load circuit served by the generator, with adequate fuel for the pump to remain operational for at least seven days;
  • Stand-alone, off-grid solar system providing power to a deep-well or shallow-well pump;
  • Access to gravity-flow water from a spring or cistern (such as one that is part of a rainwater harvesting system); if this water supply is a cistern, there must be adequate storage to provide a minimum of two gallons (7.5 liters) per resident or building occupant per day for a minimum of seven days;
  • A hand pump serving a potable-water well on the property that is accessible to residents or building occupants during power outages;
  • Potable water storage in the building providing a minimum of two gallons (7.5 liters) per resident or building occupant per day for a minimum of seven days.

Documentation

General

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Pilot Credit Survey

Credit Specific

Documentation Option 1 Option
2A, 
Back-up Gen
Option
2B, 
Solar w/ Batt
Option
2C, 
Microgrid
Option 3, Municipal Water Option 3, Non-Municipal
Building plan demarcating Habitable Zones X    
Calculation of maximum available natural ventilation rate, minimum required ventilation rate and emergency occupancy for each habitable zone. X    
Summary of calculated °F SET-hours for heating and cooling for each representative habitable zone. X    
Emergency Operation Plan.  Explain how the building should be operated in the case of emergency in order to provide livable thermal conditions.  Explain the rationale behind vent operation that was modeled given likely outside temperature and humidity. X    
Wiring schematic showing emergency generator   X      
Solar system and battery details showing predicted average wintertime production and emergency power availability to critical loads in the building.     X    
 Specifications of the mircogrid serving the building or certification through the PEER Rating System.       X  
Documents showing locations and water pressure of faucets served by municipal water on lower floors.     X  
Documents showing path of access for all building occupants to faucet(s) on lower floors.     X  
Design or specification of alternative potable water system.       X
Electrical diagrams for back-up generators or solar systems being relied on for potable water.       X

Option 1: Thermal Resilience
  1. Building plans demarcating Habitable Zones
  2. Calculation of maximum available natural ventilation rate, minimum required ventilation rate and emergency occupancy for each habitable zone.
  3. Summary of calculated °F SET-hours for heating and cooling for each representative habitable zone.
  4. Emergency Operation Plan. Explain how the building should be operated in the case of emergency in order to provide livable thermal conditions. Explain the rationale behind vent operation that was modeled given likely outside temperature and humidity.
Option 2: Back-up Power
  1. Fuel-fired back-up generator(s): Wiring schematic and showing emergency generator.
  2. Solar: Solar system and battery details showing predicted average wintertime production and emergency power availability to critical loads in the building.
  3. Microgrid: Specifications of the microgrid serving the building or certification through the PEER Rating System
Option 3. Access to Potable Water
  1. Documentation of municipal water access:

    • Documents showing locations and water pressure of faucets served by municipal water on lower floors.
    • Documents showing path of access for all building occupants to faucet(s) on lower floors.
  2. Documentation of alternative method for water service.
    • Design or specification of alternative potable water system
    • Electrical diagrams for back-up generators or solar systems being relied on for potable water.

Option 1 Definitions and Methodology:

Thermal Resilience: 100% of the normal building occupancy can occupy habitable zones that maintain “livable temperatures” during a power outage for 7 days during the typical extreme hot and cold weeks of the year.

SET: Livable temperatures are defined using standard effective temperature SET as the metric. SET factors in relative humidity and mean radiant temperature and is a more relevant metric that dry-bulb temperature for defining livable conditions in buildings that lose power or fuel for space-conditioning systems. The influence of air temperature (dry-bulb temperature) and relative humidity on the SET can be seen in the CBE Thermal Comfort Tool from the Center for the Built Environment at UC Berkeley.

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