Lesson 0.1Lesson 0.1 · Foundations of Building Performance Simulation
What Building Performance Simulation Is
Predicting how a building will behave — energy, comfort, light, air — before it exists
You cannot feel a building's energy bill on a drawing. Simulation lets you test it before a single brick is laid.
A drawing tells you what a building looks like. It says almost nothing about what it will be like to occupy - whether the west rooms overheat in May, whether the offices need lights on at noon, what the running costs will be. Building performance simulation answers those questions by building a physics-based virtual model and running it against a real climate.
That is the entire premise of this course. Simulation turns 'I think this will be comfortable' into 'this design uses 30% less cooling energy than that one, and holds comfort for 92% of occupied hours.' It moves design from opinion to evidence - and, crucially, it does so while the design is still cheap to change.
Simulate to decide, not to decorate. Compare options. Read critically. Do it early.
Simulate to decide, not to decorate
The single most important idea in this course is why we simulate. A performance simulation is not a certificate you generate at the end to prove a building is 'green'; it is a decision-support tool you use during design. Its job is to answer a question you actually have: Which orientation keeps this house coolest? How deep should this shade be? Is double glazing worth it here? Will this atrium be bright enough without electric light?
So every simulation begins with a question and a set of options to compare. You model the design, run it against the local climate, and read the result relative to an alternative - option A versus option B, this glazing versus that one. The absolute number matters less than the difference between choices. A designer who treats simulation this way makes better buildings; a designer who runs it once at the end, to tick a box, has wasted its real power. Simulation is most valuable exactly when a decision is still open.
A simulation answers a design question. No question, no simulation - just numbers nobody uses.
What 'performance' actually means
'Performance' is not one thing - it is a family of behaviours, and this course works through each. Energy: how much electricity and fuel the building needs to keep occupants comfortable (heating, cooling, lighting, fans). Thermal comfort: whether the people inside actually feel comfortable - too hot, too cold, or in the acceptable band - which is not the same as low energy. Daylight: how much useful natural light reaches the space, and whether it brings glare. Air: ventilation, fresh air and airflow, indoor air quality. And increasingly carbon: the operational and embodied emissions behind all of it.
These are linked but distinct, and they trade off against each other - more glass brings daylight but also heat gain and glare; more insulation cuts winter heating but can trap summer heat. The reason a building needs simulation rather than a rule of thumb is precisely that these effects interact in ways you cannot reliably guess. The course gives you a module for each domain - climate, comfort, physics, energy, daylight, solar, airflow - so you can reason about the whole.
The earlier you simulate, the more it is worth
There is a well-known curve in design: your ability to influence a building's performance is highest at the very start - when you are still choosing site, orientation, form and massing - and it falls steadily as the design locks in. Meanwhile the cost of making a change rises. Put those together and the conclusion is unavoidable: the value of a simulation is greatest early, when a five-minute massing study can steer a decision that determines half the building's energy use.
This is why the field emphasises fast, early, approximate models over slow, late, precise ones. A rough shoebox energy model in week one, testing orientation and window-to-wall ratio, changes the building. A meticulous, fully-detailed model in month nine, when the facade is fixed, mostly confirms what you can no longer change. Good practice front-loads simulation - and the tools you will meet (Ladybug, quick energy models) are built for exactly that early, iterative use.
Influence high + change cheap = simulate EARLY. A shoebox in week 1 beats a perfect model in month 9.
A career skill - and a growing one
Building performance is one of the fastest-growing specialisations in the built environment, pushed by energy codes, climate targets and green-building ratings. There are dedicated roles - environmental designer, energy modeller, sustainability or ESD consultant, daylighting specialist - and every serious practice now needs someone who can run and interpret a simulation. In India specifically, ECBC, the Eco Niwas Samhita and GRIHA have turned this from a nice-to-have into a compliance-and-differentiation skill.
But like any modelling, it rewards judgement over button-pushing. The value is not in knowing which menu runs an energy model; it is in framing the right question, choosing sensible assumptions, and reading a result without being fooled by it. That judgement - the theme of this whole course - is what makes a simulationist trustworthy, and it is exactly what studios and consultancies are short of.
Simulation engine (EnergyPlus)
The physics 'solver' that computes energy and comfort
The free US-DOE engine behind most whole-building energy tools; you rarely touch it directly - interfaces drive it. Module 4.
Ladybug Tools
Environmental analysis plug-ins (Ladybug, Honeybee)
Free, Grasshopper-based; great for early, visual climate/solar/daylight/energy studies. Used across the course.
The performance gap
Difference between simulated and real measured performance
Real buildings use more energy than models predict, mostly due to occupancy and operation - why results are comparative, not absolute.
EPW (weather file)
A typical-year hourly climate file for a location
Every simulation runs against one; the result is only as representative as the weather data. Module 1.
Workshop — frame a real performance question
You don't need any software to start. The first and most important skill is framing a design question that a simulation could answer - because a simulation without a real question is just numbers nobody uses.
None - just a building you know and a notebook. (Later modules use free tools: Ladybug Tools in Rhino/Grasshopper, EnergyPlus/OpenStudio, and Radiance; a student machine is enough to follow along.)
Goal: learn to turn a design worry into a testable performance question Inputs: any building you know well (your home, studio or a project), a notebook Time: ~25 minutes
- 1Pick a building or project you know. Walk through it mentally and list three things about how it performs that you are unsure of - e.g. 'the west bedroom feels hot in the afternoon', 'this office needs lights on even at noon', 'the running costs feel high'.
- 2For each, write it as a comparative question a simulation could answer, e.g. 'Would a 0.6m overhead shade cut the afternoon overheating hours in the west bedroom?' or 'Does raising the window from 1.2m to 1.8m tall bring useful daylight past midday?'
- 3For each question, note which domain it belongs to - energy, thermal comfort, daylight, or airflow - and which design variable you would change (the option A vs B).
- 4Now list the assumptions the answer would depend on: the local climate, how the room is used and when, what it is built of. Notice how much the answer rides on these.
- 5Keep the sheet. As you finish each module, come back and refine one question into something you could actually model - it becomes your running project.
You’ll walk away with
Three design worries rewritten as comparative, domain-tagged performance questions, each with its key variable and assumptions listed. This is how every real simulation begins.
Three altitudes on the same idea
Read the band that fits you — or all three.
For you, simulation turns sustainability from a slogan into a design tool. Orientation, massing, window-to-wall ratio, shading, envelope - these are your decisions, and simulation lets you make them on evidence while they are still cheap to change. Bring it in at concept stage and it shapes the building; bring it in at the end and it only grades one.
Interiors are where performance is actually felt - the glare on a screen, the cold draught, the stuffy meeting room, the daylight that makes a space feel alive. Daylight and thermal-comfort simulation speak directly to your work: they let you argue for the right glazing, the right shading and the right layout in terms of how the space will feel, not just look.
Green-building skills are among the most hireable you can build right now. Energy modelling, daylight analysis and comfort simulation are exactly what sustainability consultancies, ESD teams and code-compliance work demand - and the field is growing faster than the supply of people who can do it. A studio project backed by a real performance study stands out immediately.
“A simulation tells you exactly how much energy the building will use.”
Do it yourself
No software - reason it through.
- 1In one sentence, what is building performance simulation for?
- 2Name four distinct 'performances' a building can be simulated for.
- 3Why is a simulation result best read comparatively (A vs B) rather than as an absolute number?
- 4What is the 'performance gap', and what mostly causes it?
- 5Why is a rough model early in design often worth more than a precise model late?
The one line to carry out
Peer-reviewed journals & authoritative standards
- 01Hensen, J. L. M. & Lamberts, R. (eds) — Building Performance Simulation for Design and Operation (2nd ed.) — Routledge, 2019.
- 02IBPSA — International Building Performance Simulation Association — ibpsa.org, 2026.
- 03EnergyPlus — Whole-building energy simulation engine — US Department of Energy, 2026.
If simulation is about answering design questions, the natural next step is to see the range of questions it can answer and the payoff of each. So next we look at why we simulate - the concrete decisions, savings and risks that make it worth the effort.
The author
Amogh N P
Architect, interior designer, and creative polymath. Studio Matrx began in his notebooks — his vision of design made honest, useful, and open to everyone. Its Academy is written and taught in his memory, and free, forever.
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