2 Energy Demand
What is the energy demand of a building? This is one of the most common questions in building science.
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2.1 Simple Ballpark Estimates
To start, we look at the simplest way to get a ballpark number. This might involve looking at historical energy use intensity (EUI) for similar buildings in the same climate zone.
“A good estimate is better than a precise error.” - Anonymous Building Scientist
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| Building Type | Typical EUI (kWh/m2/yr) | Peak Load (W/m2) |
|---|---|---|
| Residential | 100 - 150 | 40 - 60 |
| Office | 150 - 250 | 60 - 100 |
| Retail | 200 - 300 | 80 - 120 |
2.2 When to Attempt a Simulation
If a simple estimate is insufficient, a simulation may be necessary. We detail the different levels of complexity involved in simulating energy demand, starting from basic RC models.
2.2.1 RC Models (e.g., R51C)
RC (Resistance-Capacitance) models provide a simplified dynamic representation of a building’s thermal behavior.
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2.2.2 Full Energy Balance
A full energy balance model considers all heat flows, internal loads, and HVAC system interactions.
The general heat balance equation can be expressed as:
\[ Q_{load} = Q_{solar} + Q_{internal} + Q_{conduction} + Q_{ventilation} \pm Q_{storage} \tag{2.1}\]
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