I often hear engineers say: “Office buildings are easier, that’s why the code is stricter.”
But what does easier actually mean?
And stricter compared to what?
Let’s put real numbers on the table.
First: What Is the Baseline, in Simple Terms?
The baseline building is not your design.
It’s a reference building created by the energy code.
It has:
- the same area
- the same shape
- the same function
But all systems are set to minimum code requirements only.
Think of it as the answer to one question:
“How much energy would this building use if we only did the bare minimum?”
A Simple Baseline Example
Let’s say we have:
- Office building
- Climate Zone 0A
- 5,000 m² total area
After running the baseline model according to ASHRAE 90.1:
- Baseline Energy Use = 220 kWh/m²·year
This number becomes your reference.
Now the Proposed Design
You design the building properly:
- decent envelope
- efficient HVAC
- reasonable lighting
The simulation gives:
- Proposed Energy Use = 190 kWh/m²·year
At first glance, this looks good.
190 is lower than 220.
Most people stop thinking here.
But the code doesn’t.
Where the Building Performance Factor (BPF) Changes Everything
For office buildings in Climate Zone 0A, the BPF is approximately:
- BPF = 0.54
The performance path requires adjusting the proposed energy:Adjusted Proposed Energy=0.54190=352 kWh/m2⋅year
Now compare again:
- Baseline = 220
- Adjusted Proposed = 352
❌ Fail
Why Did This Fail Even Though 190 < 220?
Because office buildings are considered easier to improve.
That means:
- schedules are predictable
- loads are manageable
- systems respond well to optimization
The code expects more than a modest improvement.
In simple language, the code is saying:
“For an office building, this level of improvement is not impressive.”
Compare That with a “Harder” Building
Now imagine the same numbers for a hospital.
Hospitals typically have:
- 24/7 operation
- high ventilation rates
- strict indoor requirements
Their BPF might be around:
- BPF = 0.69
Now do the same math:190÷0.69=275 kWh/m2⋅year
Still higher than the baseline — but much closer.
And with small additional improvements, the hospital might pass.
That’s not favoritism.
That’s realism.
So What Does “Stricter Code” Really Mean?
When engineers say “the code got stricter”, they usually mean this:
- smaller margin for error
- less tolerance for oversizing
- weak schedules are no longer acceptable
For office buildings, the code assumes:
- you have many tools
- you have flexibility
- you can do better
So it raises expectations.
Why Office Buildings Are Called “Easier”
Office buildings are considered easier because:
- reducing operating hours actually saves energy
- lighting controls have a strong impact
- HVAC systems perform well at part load
- efficiency improvements are predictable
In other words, the engineering leverage is high.
And when leverage is high, the code pushes harder.
Final Thought
When an office building fails the performance path, it’s rarely because the code is unfair.
More often, it’s because the design didn’t fully use the opportunities that were already there.
Sometimes the message isn’t loud.
Sometimes it’s just a number in a table — telling you that “good enough” is no longer enough.
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