## 3.1 General Requirements

### 3.1.1 Scope

The compliance software must satisfy the requirements contained in this section.

The compliance software shall be capable of modeling at least 50 thermal zones.

The compliance software shall be capable of modeling at least 15 HVAC systems.

### 3.1.2 Calculation Methods

The compliance software shall calculate the annual consumption of all end uses in buildings, including fuel and electricity for:

• HVAC (heating, cooling, fans, and ventilation).

• Lighting (both interior and exterior).

• Receptacles and miscellaneous electric.

• Service water heating.

• Process energy uses.

• All other energy end uses that typically pass through the building meter.

The compliance software shall perform a simulation on an hourly time interval (at a minimum) over a one-year period (8,760 hours) with the ability to model changes in weather parameters, schedules, and other parameters for each hour of the year. This is achieved by specifying a 24-hour schedule for each day of the week plus holidays.

3.1.2.1 Calculating Design Loads

The software shall be capable of performing design load calculations for determining required HVAC equipment capacities and air and water flow rates using accepted industry calculation methods for the standard design.

3.1.2.2 Checking Simulation Output for Unmet Loads

The software shall be capable of checking the output of the energy analysis module for the proposed design to ensure that space conditions are maintained within the tolerances specified (maximum of 150 thermal zone UMLH per year).

3.1.2.3 Adjusting Capacities

For the standard design building, the software shall be capable of modifying capacities, temperatures, or flow rates for standard design building HVAC system components causing excessive UMLH according to the procedures in Chapter 2.

3.1.2.4 Error Handling

The software shall send a warning to the user when unmet loads exceed 150 hours and provide information to the user describing the error that has occurred.

### 3.1.3 Climate Data

The compliance software shall perform simulations using the official Energy Commission weather files and design conditions documented in Joint Appendix 2.

The compliance software shall calculate solar radiation on exterior surfaces on an hourly basis from the values of direct normal irradiance and diffuse horizontal irradiance contained in the climate data, taking ground reflectance into account.

### 3.1.4 Utility Rates

The rating software shall be capable of simulating time-of-use rates and apply both demand and energy charges for each time period of the rate schedule.

### 3.1.5 Time Dependent Valued (TDV) Energy

The compliance software shall be capable of applying the Energy Commission TDV multipliers for each hour of the simulation. See Energy Commission Joint Appendix 3.

### 3.1.6 Thermal Mass

The calculation procedures used in the compliance software shall account for the effect of thermal mass on loads due to occupants, lights, solar radiation, and transmission through building envelope on the amount of heating and cooling required to maintain the specified space temperature schedules; and on variation in space temperature.

### 3.1.7 Modeling Space Temperature

The compliance software shall incorporate a dynamic simulation of space temperature that accounts for:

• Dynamics in change in heating and cooling setpoint temperatures.

• Deadband between heating and cooling thermostat settings.

• Temperature drift in transition to setback or setup thermostat schedules.

• Temperature drift in periods when heating or cooling capability are scheduled off.

• Temperature drift when heating or cooling capability of the system is limited by heating or cooling capacity, air flow rate, or scheduled supply air temperature.

• Indirectly conditioned thermal zones, where the temperature is determined by internal loads, heat transfer through building envelope, and heat transfer between thermal zones.

### 3.1.8 Heat Transfer Between Thermal Zones

The compliance software shall be capable of modeling heat transfer between a thermal zone and adjacent thermal zones.

The compliance software shall account for the effect of this heat transfer on the space temperature, space conditioning loads, and resulting energy use in the thermal zone and in adjacent thermal zones.

### 3.1.9 Control and Operating Schedules

The compliance software shall be capable of modeling control and operating schedules that can vary by:

• The hour of the day.

• The day of the week.

• Holidays, which are treated as a special day of the week.

The compliance software shall be capable of explicitly modeling all of the schedules specified in Appendix 5.4B of this manual.

### 3.1.10 Loads Calculation

The load calculations described in this section relate to the simulation engine, and not to the procedure used by the design engineer to size and select equipment.

3.1.10.1 Internal Loads

The compliance software shall be capable of calculating the hourly cooling loads due to occupants, lights, receptacles, and process loads.

The calculation of internal loads shall account for the dynamic effects of thermal mass.

The compliance software shall be capable of simulating schedules for internal loads in the form given in Appendix 5.4B.

The simulation of cooling load due to lights shall account for:

• The effect of the proportion of radiant and convective heat, which depends on the type of light and on the dynamic response characteristic.

• A portion of heat from lights going directly to return air; the amount depends on the type and location of fixture.

3.1.10.2 Building Envelope Loads

The compliance software shall calculate heat transfer through walls, roofs, and floors for each thermal zone, accounting for the dynamic response due to thermal characteristics of the particular construction as defined in the Building Descriptors in Chapter 5.

The calculation of heat transfer through walls and roofs shall account for the effect of solar radiation absorbed on the exterior surface, which depends on orientation and absorptance of the surface.

The compliance software shall calculate heat transfer through windows and skylights, accounting for both temperature difference and transmission of solar radiation through the glazing.

Calculation of cooling load due to transmission of solar radiation through windows and skylights shall account for:

• The variation of thermal properties of the fenestration system with ambient temperature.

• Orientation (azimuth and tilt of surface).

• The effect of shading from overhangs or side fins.

3.1.10.3 Infiltration

The compliance software shall be capable of simulating infiltration that varies by the time of day and day of the week. Schedules are provided in Appendix 5.4B.

### 3.1.11 Systems Simulation

3.1.11.1 General

The compliance software shall be capable of modeling:

• The standard design building systems defined in Chapter 5.

• The lighting, water heating, HVAC, and miscellaneous equipment detailed in Chapter 5.

• All compulsory and required features, as detailed in Chapter 5.

The capability to model multiple zone systems shall allow at least 15 thermal zones to be served by one multiple-zone system.

The compliance software shall be capable of modeling plenum air return.

3.1.11.2 HVAC Zone Level Systems

The compliance software shall be capable of simulating the effect on space temperature and energy use of:

• Limited capacity of terminal heating devices.

• Limited capacity of terminal cooling devices.

• Limited rate of air flow to thermal zone s.

3.1.11.3 HVAC Secondary Systems and Equipment

The compliance software shall be capable of simulating the effect on energy use and space temperature in thermal zones served by the HVAC system of:

• Limited heating capacity.

• Limited cooling capacity.

The simulation of HVAC systems shall account for:

• Temperature rise of supply air due to heat from supply fan, depending on the location of the fan.

• Temperature rise of return air due to heat from return fan.

• Temperature rise of return air due to heat from lights to return air stream.

• Fan power as a function of supply air flow in variable air volume systems.

3.1.11.4 HVAC Primary Systems and Equipment

The compliance software shall be capable of simulating the effect on energy use of limited heating or cooling capacity of the central plant system.

If the compliance software is not capable of simulating the effect of limited heating or cooling capacity of the central plant system on space temperature in affected thermal zones, then it shall issue a warning message when loads on the central plant system are not met.

3.1.11.5 Equipment Performance Curves

The compliance software shall be capable of modeling the part-load efficiency and variation in capacity of equipment as follows:

• Furnaces as a function of part load

• Boilers as a function of part load, supply hot water temperature, and return hot water temperature

• Water-cooled compressors including heat pumps and chillers as a function of part load, evaporator fluid, or air temperature and condensing fluid temperature

• Air-cooled compressors including heat pumps, direct expansion cooling and chillers as a function of part load, ambient dry-bulb temperature, and wet-bulb temperature returning to the cooling coil

• Evaporative cooling systems as a function of ambient wet-bulb temperature

• Cooling towers as a function of range and ambient wet-bulb temperature

3.1.11.6 Economizer Control

The compliance software shall be capable of modeling integrated air- and water-side economizers.