This section outlines the procedures involved in setting up proposed and baseline building models in accordance with ASHRAE 90.1 Appendix G PRM. In the text below "Appendix G" refers to ASHRAE 90.1 Standard Appendix G.
Tip: The DesignBuilder LEED and ASHRAE 90.1 Appendix G User Guide is the main source of help for ASHRAE 90.1 analysis and MEPC report generation.
Note: you will need the DesignBuilder LEED / ASHRAE 90.1 module to access this functionality.
DesignBuilder uses the ASHRAE climate zone site level setting to identify the climate zone for generating baseline constructions and glazing according to ASHRAE 90.1 building envelope requirements. The default climate zone loaded will have been loaded from the Locations template and that value was originally derived from the value shown on the Hourly weather data dialog which in turn was derived by analysing the .epw hourly weather data. In some cases the climate zone may not be the same as defined in ASHRAE 90.1 Standard Appendix D for the model location. In this case simply select the correct ASHRAE climate zone at site level and the baseline constructions and glazing will be automatically updated to reflect the new climate zone.
For your proposed design you can improve the baseline construction (by copying and editing) or simply replacing them with definitions shown on architectural drawings or as built for existing building envelopes.
When a site is created or when the climate zone is changed, baseline constructions and glazing systems as well as construction templates are generated for the selected ASHRAE climate zone ready for assigning to the building.
Opaque construction templates
Glazing templates
When running Heating or Cooling design calculations, if the FCfactorMethod ground temperatures source data at site level has 1-Hourly weather file selected, a weather file containing ground temperatures in the header should be selected and will be downloaded (if not yet in your weather file folder on your computer) prior to the calculations. If 2-User defined is selected, the Heating and Cooling design calculations do not require the weather file.
The terminology used in the ASHRAE 90.1 constructions list gives the climate zone, a description of the construction, insulated level(s) in IP units and the U-value in IP units and in brackets the values in SI units. For example construction CZ4 Non-Res, Wall, Steel-Framed, R-13.1+R-7.4 (2.3+1.3), U-.064 (.365) indicates a non-residential steel framed wall for climate zone 4 (CZ4) with internal insulation levels of two layers of minimum 13.1 and 7.4 ft2-°F/(Btu/hr) in IP units (2.3 and 1.3 m2-K/W in SI units) and a U-value of 0.064 Btu/hr-ft2-°F in IP units (0.365 W/m2-K in SI units).
It is important for ASHRAE 90.1 based-work that the proposed and baselines buildings have identical floor areas and zone volumes. The easiest way to ensure this is to use the Simple geometry convention for both buildings. With the Simple template the block geometry drawn gives the exact surface geometry and zone volumes to be used in the simulation. This means that when you copy the proposed building to create the baseline building the zone geometry will be correct even after loading the baseline constructions.
If instead you used the External measurements template for example you would find that the baseline building surface areas, floor area and zone volumes would be different after loading the baseline constructions because these generally have a different thickness to those selected for the proposed building.
Note: When loading an activity template, it will update the lighting schedule.
For the proposed building design, where no heating or cooling systems exist or have been specified, the heating or cooling systems shall be identical to the systems modelled in the baseline building design.
Baseline DX Cooling Coil Efficiency Input
From the ASHRAE 90.1 Standard, all HVAC equipment in the baseline building design shall be modelled at the minimum efficiency levels, both part load and full load. The efficiency rating that includes the supply fan energy shall be adjusted to remove the supply fan energy so that supply fan energy can be modelled separately. To help meet this requirement, for baseline systems that use DX cooling coils, i.e., systems #1 through #6, the COP input can be calculated using a simple ASHRAE CoP calculation tool.
You can download the tool from our website. Thanks to Germán Campos from Ecoeficiente for providing this tool!
Note: The calculation requires a sizing run as the cooling capacity is a mandatory input to the program.
EnergyPlus provides a "LEED Summary" report which is displayed on the Summary tab after the simulation if the appropriate option is checked on the Output tab of the Simulation options dialog under the Summary Tables header.
To convert a standard EnergyPlus model to be treated as a proposed building go to the Regions tab at site level and set the Mandatory energy code to one of the ASHRAE 90.1 energy codes. You will be warned to check that the ASHRAE climate zone is correctly set. The default climate zone can be overridden at site level under the Location header.
"Unmet hours" of a building are the summation of the number of hours when the heating or the cooling set point temperature of a zone is not met either by the HVAC system or by the plant. The data is provided in the Summary report as:
When each zone is unmet in the specified hours as beside
Zone 1 unmet during hours: 6 8 14 16
Zone 2 unmet during hours: 6 8 12 16
Zone 3 unmet during hours: 7 8 12 13
Total number of unmet hours of the building: 7 hrs and not 12 hrs.
6 7 8 12 13 14 16
The above information on Unmet hours is sourced from a post by Ashu Gupta (and subsequent posts) on the bldg-sim mailing list