ASHRAE 90.1-2016 Section 11

Compliance measured on annual energy cost

Model two buildings, the proposed and a budget building assembled from the prescriptive requirements, then show the proposed costs no more to run. Section 11's compliance route for when the checklist won't fit.

Budget building generated to prescriptive Section 5, 6, 9 requirements

Hourly annual simulation on climate zone weather data

Envelope, glazing and HVAC trade-offs held together by cost

Section 11.7 documentation ready for the certifier

3D building model showing geometry with blue walls, teal roofs, and orange adjacent structures in a grid layout within a design software interface.

Modelling, not checklists

Designed for trade-offs, not just tables

The Energy Cost Budget Method is Section 11 of ASHRAE 90.1-2016, and it is what most people mean when they say they are doing an ASHRAE energy model. You build two versions of the same project: the proposed design as it will be built, and a budget building assembled from the prescriptive requirements. Both are simulated for a full year, both are costed against real utility rates, and if the proposed cost is at or below the budget, you comply. It is the compliance route when the checklist won't fit and you don't need the extra complexity of Appendix G ratings.

Digital floor plan highlighting Diesel Tank Room in green, adjacent to Diesel Pump Room and MSB Room, with navigation and editing tools on the interface.

Budget Building

The budget building is your building with prescriptive-compliant envelope, HVAC and lighting. Same shape, same size, same schedules, same site. Section 11.5 sets out how it is built, tightly.

Digital architectural floor plan interface showing Level B1 layout with highlighted Access Room and editing tools for opacity and color on the blueprint.

Climate Zone Weather

Both models run against the same ASHRAE climate zone weather file for the project location. TMY3 or ASHRAE-provided data is expected.

Screenshot of betterbuilding software showing a tags panel with categorized building elements like windows, walls, floors, roof, and retail, alongside a level navigation menu on the left.

Envelope Trade-offs

Better glazing can offset weaker walls, extra insulation can pay for more skylights. As long as annual cost lands, the trade-offs are yours to make.

Screenshot of a building management software interface showing a list of building levels with options to edit, duplicate, or access roof geometry for Level 03.

Glazing Optimisation

Fenestration performance in the proposed model reflects what you actually specified. If daylight harvesting or view is worth the extra load, ECB lets you prove it in energy cost.

3D building model in Betterbuilding software showing color-coded wall shading and window elements with controls and a simulations panel on the right.

Shading Geometry

Overhangs, fins and adjacent buildings are modelled as real geometry in the proposed model. The budget building gets a smaller allowance, so shading works in your favour here.

User interface of Betterbuilding software showing solar panel renewables settings including surface coverage 100%, cell efficiency 18%, azimuth 0°, tilt 5°, and row size 1.55 meters, with a rectangular solar array preview on the right.

HVAC Systems

Proposed uses your actual system with real efficiencies. Budget uses one of the system types in Section 11.5.2 selected by building type and size. Not always the fair fight it sounds.

Betterbuilding interface showing Wall tags and detailed settings for External Wall and Internal Wall, including R-value, solar absorptance, exposure, thickness, density, and heat capacity sliders.

Matched Loads

Lighting, plug loads, occupancy, ventilation and service water heating are identical between models. The comparison only holds if the loads are held constant.

Betterbuilding software interface showing Spaces tab with building zones and settings for Occupants including Design Level, Activity Level, Air Velocity, Work Efficiency, and Clothing Method.

Annual Cost Simulation

Both models are simulated for one full year at hourly resolution, then costed against project utility rates. Cost, not energy, is the ECB metric, which is not always the same conversation.

Betterbuilding software interface showing energy consumption summary for Example Building with proposed versus reference data, including bar charts and tables of electricity use by category and monthly energy breakdown.

Compliance Report

Annual energy cost of the proposed at or below the budget building, with full documentation of inputs, weather, rates and simulation software. Section 11.7 lists exactly what has to be shown.