Why Create Different Alternatives in Trace700: Understanding the Role of Alternative Scenarios in HVAC Design Software

Trace700 is a load calculation and energy analysis tool widely used by mechanical engineers and HVAC designers to model building systems. One of its core workflow features is the ability to create multiple alternatives within a single project file. If you've opened Trace700 and wondered why that option exists — or whether you should be using it — the answer has a lot to do with how professional HVAC design actually works.

What "Alternatives" Mean in Trace700

In Trace700, an alternative is essentially a complete version of your building model with its own set of system configurations, equipment selections, and design assumptions. Think of it like saving parallel versions of the same project, but integrated directly into the software rather than scattered across separate files.

Each alternative can have:

• Different HVAC system types (e.g., VAV vs. fan coil vs. DOAS)
• Different equipment sizing or efficiency ratings
• Different zoning configurations
• Different ventilation strategies
• Different control sequences or setpoints

All of these alternatives share the same base building geometry and envelope inputs, which is what makes the comparison meaningful. You're changing the mechanical system, not rebuilding the building from scratch.

Why Engineers Create Multiple Alternatives 🔍

1. System Comparison and Design Optimization

The most common reason is straightforward: comparing systems side by side. An engineer might model a conventional rooftop unit system as Alternative 1, a variable refrigerant flow (VRF) system as Alternative 2, and a chilled water system as Alternative 3. Running all three through the same load and energy simulation allows direct comparison of predicted energy use, peak loads, and sizing outcomes.

Without alternatives, you'd have to create separate project files, manually reconcile inputs across them, and risk inconsistency. The alternatives feature eliminates that friction.

2. Meeting LEED or Code Compliance Requirements

Many energy codes and green building standards — including ASHRAE 90.1, Title 24, and LEED energy modeling pathways — require a baseline building model compared against a proposed design model. In Trace700, this is typically handled by designating one alternative as the code-baseline system and another as the proposed design.

The software can then generate comparative reports showing the energy cost savings or efficiency improvement between the two. This structured comparison is often a deliverable requirement, not just a design preference.

3. Value Engineering and Client Presentations

During the design phase, clients and project owners frequently ask: What's the cost-benefit tradeoff between a higher-efficiency system and a standard one? Alternatives let engineers produce a structured answer. Rather than giving a verbal estimate, the engineer can present modeled data showing predicted annual energy consumption differences across options — which becomes useful input for budget and lifecycle cost discussions.

4. Design Development Iterations

Building design doesn't happen all at once. As architectural drawings evolve, occupancy assumptions change, or mechanical room space gets revised, engineers often need to preserve earlier model states while moving forward. Creating a new alternative captures a snapshot of the model at a given point in the design process without overwriting earlier work.

This is particularly useful in projects with long timelines or multiple design review milestones.

Key Variables That Shape How Alternatives Are Used

Not every project uses the alternatives feature the same way. Several factors influence how many alternatives make sense and how they're structured:

What Happens If You Only Use One Alternative

Using a single alternative isn't wrong — it just limits what you can do within that project file. You'll still get valid load calculations and energy estimates. But you lose the ability to run side-by-side system comparisons within the same model, and you may have to manage compliance documentation differently if a baseline comparison is required.

For simple projects with a predetermined system type and no compliance modeling requirement, a single alternative is often sufficient. For anything involving system selection, energy code compliance, or lifecycle cost analysis, multiple alternatives are where the feature earns its place. 🏗️

The Spectrum of Use Cases

At one end are engineers doing a quick feasibility load calculation on a small commercial space — one alternative, one system type, done. At the other end are large institutional or mixed-use projects where five or six alternatives might be modeled to compare system combinations, meet multiple compliance pathways, and produce deliverables for an owner's project requirements document.

In between, there are projects where two alternatives cover everything needed: the code baseline and the proposed design. The feature scales with the complexity of the work.

The Part That Depends on Your Situation

How many alternatives you should create — and what each one should contain — depends entirely on what your project requires. A school project pursuing LEED certification has different modeling obligations than a tenant build-out on a standard lease. A firm with an established Trace700 template library uses alternatives differently than an engineer setting up a project from scratch.

The software gives you the structure. What goes into each alternative, and how many you need, comes down to the specifics of the project in front of you. 🎯