ASHRAE Standard 183
HVAKR implements ANSI/ASHRAE/ACCA Standard 183 - Peak Cooling and Heating Load Calculations in Buildings Except Low-Rise Residential Buildings.
To see every requirement in sections 5 through 10 and how HVAKR meets it, see ASHRAE 183 Compliance.
Standard Overview
Section titled “Standard Overview”Purpose
Section titled “Purpose”Standard 183 establishes:
- Minimum requirements for load calculations
- Acceptable calculation methods
- Required documentation
Applies to:
- Commercial buildings
- Institutional buildings
- Industrial buildings
- High-rise residential
Calculation Methods
Section titled “Calculation Methods”Cooling Loads
Section titled “Cooling Loads”Standard 183 does not name one method. It requires that the method account for convective heat gain, radiant heat gain, and the thermal mass effect on cooling load. In practice this means a method from ASHRAE Handbook - Fundamentals:
- Radiant Time Series (RTS)
- Heat Balance (HB)
HVAKR uses the Radiant Time Series (RTS) method.
Heating Loads
Section titled “Heating Loads”Steady-state calculation:
- Based on design conditions
- No solar or internal credits
- Conservative for equipment sizing
Radiant Time Series Method
Section titled “Radiant Time Series Method”Overview
Section titled “Overview”RTS accounts for:
- Thermal storage in building mass
- Time delay of heat gains
- A 24-hour load profile for every month of the year, not one design day. HVAKR takes the peak month and hour from those 288 points. See Cooling Loads
Process
Section titled “Process”- Calculate hourly heat gains. Wall and roof conduction first passes through the conduction time series (CTS) of the Wall Mass Data or Roof Mass Data selected on the wall or roof type
- Split into convective and radiant portions
- Convert radiant to cooling load using radiant time factors
- Sum for total load
Radiant Time Factors
Section titled “Radiant Time Factors”HVAKR takes the radiant time factors from the Building CTS Data selection on the Building Data card. The choices are the 24 ASHRAE building types:
- LW, MW, or HW — lightweight, medium-weight, or heavyweight construction
- w Carpet or no Carpet
- 10%, 50%, or 90% glass
- Six Interior types, by construction weight and carpet, with no glass
Each type carries a solar and a non-solar series. Beam solar gain through windows and skylights uses the solar series. All other radiant gains use the non-solar series. A window with Internal Shading uses the non-solar series for its beam solar gain too.
Cooling loads cannot compute until a Building CTS Data type is selected.
Required Inputs
Section titled “Required Inputs”Weather Data
Section titled “Weather Data”Per Standard 183:
- Design temperatures from the ASHRAE or CIBSE weather data set. See Weather
- Solar data for the location
- Humidity conditions
Building Data
Section titled “Building Data”Required information:
- Envelope U-values
- Building CTS Data, and the Wall Mass Data and Roof Mass Data of each wall and roof type
- Window SHGC
- Internal loads
- Schedules
Occupancy
Section titled “Occupancy”Occupancy characteristics:
- Occupancy
- Activity levels
- Schedules
Design Conditions
Section titled “Design Conditions”Outdoor Conditions
Section titled “Outdoor Conditions”ASHRAE design data:
- 0.4%, 2%, 5%, or 10% cooling design
- 99.6% or 99% heating design
- Coincident humidity
Indoor Conditions
Section titled “Indoor Conditions”HVAKR reads the indoor setpoints from each space type — Summer (Cooling), Winter (Heating), and Relative Humidity under Indoor Design Conditions on the Space Types page. It ships no default for them. Typical values are 75°F and 50% RH for cooling and 70°F for heating.
Load Components
Section titled “Load Components”Required Components
Section titled “Required Components”Standard 183 requires accounting for:
- Transmission through envelope
- Solar radiation
- Internal gains (people, equipment, lighting)
- Ventilation
- Infiltration
Component Breakdown
Section titled “Component Breakdown”HVAKR provides detailed breakdown for verification.
Documentation
Section titled “Documentation”Required Documentation
Section titled “Required Documentation”Standard 183 requires:
- Input data listing
- Calculation method identification
- Results summary
- Assumptions
HVAKR Reports
Section titled “HVAKR Reports”HVAKR generates compliant documentation:
- Loads Summary report
- Component breakdown
- Design conditions
HVAKR Implementation
Section titled “HVAKR Implementation”Automatic Compliance
Section titled “Automatic Compliance”HVAKR automatically:
- Uses approved RTS method
- Applies ASHRAE or CIBSE weather data
- Calculates all required components
- Documents assumptions
Verification
Section titled “Verification”Check your calculations:
- Review load components
- Verify design conditions
- Compare to benchmarks