name: ashrae-baseline-guide
description: ASHRAE 90.1 Appendix G baseline system selection criteria. Use when recommending HVAC system types, creating baseline models, or answering questions about ASHRAE 90.1 compliance.
user-invocable: false
ASHRAE 90.1 Appendix G Baseline System Selection
System Selection (Table G3.1.1)
Select baseline system based on building type, heating fuel, and floor area / floor count.
Residential Buildings
(hotels/motels, dormitories, apartments)
| Heating Source |
System |
| Fossil fuel / hybrid |
System 1: PTAC (any size) |
| Electric resistance |
System 2: PTHP (any size) |
Non-Residential Buildings
| Heating Source |
< 25,000 ft2 |
25,000-150,000 ft2 |
> 150,000 ft2 |
| Fossil fuel / hybrid (<=3 floors) |
System 3: PSZ-AC |
System 3: PSZ-AC |
System 5: Pkg VAV w/ Reheat |
| Fossil fuel / hybrid (>3 floors) |
System 3: PSZ-AC |
System 5: Pkg VAV w/ Reheat |
System 7: VAV w/ Reheat |
| Electric resistance (<=3 floors) |
System 4: PSZ-HP |
System 4: PSZ-HP |
System 6: Pkg VAV w/ PFP |
| Electric resistance (>3 floors) |
System 4: PSZ-HP |
System 6: Pkg VAV w/ PFP |
System 8: VAV w/ PFP |
Heated-Only Buildings
(warehouses, garages, no mechanical cooling)
| Heating Source |
System |
| Fossil fuel / hybrid |
System 9: Gas Unit Heater |
| Electric resistance |
System 10: Electric Unit Heater |
System Summary
| # |
Name |
Equipment Level |
Heating |
Cooling |
Plant Loops |
| 1 |
PTAC |
Zone |
Electric resistance |
DX single speed |
None |
| 2 |
PTHP |
Zone |
DX heat pump + elec backup |
DX heat pump |
None |
| 3 |
PSZ-AC |
Central (single zone) |
Gas furnace or elec |
DX single speed |
None |
| 4 |
PSZ-HP |
Central (single zone) |
DX HP + elec backup |
DX heat pump |
None |
| 5 |
Pkg VAV w/ Reheat |
Central (multi zone) |
HW reheat coils |
DX two speed |
Hot water loop + boiler |
| 6 |
Pkg VAV w/ PFP |
Central (multi zone) |
Electric PFP boxes |
DX two speed |
None |
| 7 |
VAV w/ Reheat |
Central (multi zone) |
HW reheat coils |
Chilled water |
HW + CHW + condenser loops |
| 8 |
VAV w/ PFP |
Central (multi zone) |
Electric PFP boxes |
Chilled water |
CHW + condenser loops |
| 9 |
Gas Unit Heater |
Zone |
Gas unit heater |
None |
None |
| 10 |
Electric Unit Heater |
Zone |
Electric unit heater |
None |
None |
Heating Fuel Logic
The heating_fuel parameter maps to:
"NaturalGas" → fossil fuel systems (1, 3, 5, 7, 9)"Electricity" → electric systems (2, 4, 6, 8, 10)"DistrictHeating" → treated as fossil fuel path
Economizer Applicability
- Systems 3-8: Support air-side economizer (
economizer=True by default)
- Systems 1-2, 9-10: Zone equipment, no economizer possible
- Climate zone affects economizer control type (not yet parameterized)
Multi-Zone Constraints
- Systems 1-2, 9-10: One unit per zone (zone equipment)
- Systems 3-4: One air loop per zone (PSZ = packaged single-zone)
- Systems 5-8: One air loop serves multiple zones (VAV)
When user provides multiple zones:
- Systems 3-4 create separate air loops per zone
- Systems 5-8 create one shared air loop
Tool Mapping
| Action |
Tool |
Key Parameters |
| Create baseline system |
add_baseline_system |
system_type, thermal_zone_names, heating_fuel |
| List available systems |
list_baseline_systems |
(none) |
| System details |
get_baseline_system_info |
system_type |
| Modern alternatives |
add_doas_system, add_vrf_system, add_radiant_system |
thermal_zone_names |
When to Recommend Modern Templates Instead
| Scenario |
Recommendation |
| High ventilation requirements (labs, hospitals) |
DOAS with fan coils or chilled beams |
| Many small zones with diverse loads |
VRF heat pump system |
| Comfort-critical spaces, radiant heating/cooling |
Radiant floor/ceiling |
| Net-zero or high-performance target |
DOAS + Radiant or DOAS + VRF |
By