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Choose an HVAC System

Walk your building through the choices that fix an HVAC concept: how it gets fresh air, how it heats and cools, and what plant sits behind that. The tool draws the resulting system as a schematic and explains each part, then helps you reason about its carbon and a low-carbon pathway. It does not pick a winner or a size for you: that judgement, and the loads from your DesignBuilder model, stay yours. Use it to structure the argument you will make in Assignment 2 and defend in Week 11.

1. Your building

Describe the building you are carrying through Assignments 1 and 2. This sets the context the later choices are judged against. Nothing here is a load calculation: your loads come from DesignBuilder.

Set the context every later choice is judged against.

Program, climate zone and scale do not size anything, but they steer which HVAC families make sense: a hot-humid tower and a cool-temperate office pull toward very different systems. Fill these in so the fit prompts in the later steps reflect your actual building. The peak loads themselves stay with your DesignBuilder model.

A minimum of 3 for Assignment 1.

Sets the scale (small tenancy vs whole tower), not the load.

2. Fresh air

How the building brings in outdoor air is the first structural decision. It separates buildings that mix fresh air and conditioning in one air stream from those that supply fresh air on its own and condition the space some other way.

How outdoor air reaches the space: the first structural fork.

Ventilation can ride along in the same air stream that heats and cools (an all-air system), or arrive on its own through a dedicated outdoor-air unit while a separate system conditions the space. This one choice splits the whole taxonomy: "mixed with conditioning" leads to VAV or CAV, while DOAS leads to a water or refrigerant terminal system in the next steps.

Can the building rely on opening windows?

How is outdoor air delivered?

3. Heating and cooling

What does the building actually need active plant for? In most Australian commercial climates the answer is both, but a mild-marine or a warm-humid site can shift the balance. Your DesignBuilder peak loads are the evidence for this.

What the building actually needs active plant to do.

Most Australian commercial climates need both heating and cooling, but a warm-humid or mild-marine site can tip the balance toward one side. This decides how hard each half of the plant works and where the carbon sits. Your DesignBuilder peak loads are the evidence. This step is the framing, not the number.

4. System architecture

Pick the system family for your building. Every option below is used in the Australian commercial sector. The fit badge reflects your climate, program, and fresh-air choice, but it is a prompt, not a verdict: a well-argued case can override it. Read the trade-offs, then choose the one you will justify.

Pick the system family you will justify.

The options differ mainly in what medium carries the conditioning, and so in what occupies the building: all-air, air-plus-water, or refrigerant. The fit badge weighs your climate, program and fresh-air choice to surface likely candidates, but it ranks rather than decides. Read the pros and cons and choose the case you can defend.

5. Plant and heat source

The plant behind your terminals is where most of the carbon decision sits. What makes the cooling, what makes the heat, and which refrigerant runs through it all shape the operational emissions you will discuss in Assignment 2.

Choose the plant that makes the heating, cooling and carbon.

Behind the terminals sits the plant, and this is where most of the operational-carbon decision lives: what makes the cooling (a chiller or direct expansion), what makes the heat (heat pump, gas or resistance), and which refrigerant runs through it. Electrifying the heat source and avoiding a high-GWP refrigerant are the two biggest levers you have.

6. Your system

Read your system as a diagram, then build the low-carbon argument.

The schematic draws your choices as a labelled concept diagram, and the notes below explain each part from fresh air through to the plant. The carbon section then ranks the levers that would lower its emissions. It is a reasoning scaffold: it does not size plant or declare a winner. That judgement, and the loads, stay yours.

Carbon and a low-carbon pathway

Carry this into Assignment 2

Write, in your own words, why this system suits your building and how you would lower its carbon. This is the core of the A2 system-selection and decarbonisation argument, and what the panel will probe in the Week 11 defence. The tool cannot make this case for you.

What this tool does and does not do

It maps your choices onto a named system, draws it, and explains the parts and the carbon story. It is a reasoning scaffold for the concept design in Assignment 2.

It does not size plant, estimate loads or energy, or tell you which system is correct. Sizing is pro-rated from your DesignBuilder loads (Assignment 1); the choice and its justification are your professional judgement (Assignment 2 and the Week 11 defence). Do not paste any figure from this tool into an assignment as a result.