Loads on Buildings & Occupants
P02 defined the stressors outside the building. This session covers the “loads” we create (and must manage): structural, thermal, moisture, and operational. The point is not math—it's avoiding surprises.
Potential agenda
- Intro (2 min): Loads = what the building must resist, store, or move.
- Desired outcome (6–8 min): A realistic “load profile” for the project and its occupants.
- Common failures (6–8 min): What breaks when loads are assumed instead of understood.
- Core concepts (6–8 min): Avoiding load-driven surprises
- Peak vs average (design for peaks)
- Moisture is a load you generate indoors
- Internal gains matter (people, appliances, sun)
- Operation is part of design (controls and habits)
- Takeaways (2–3 min): A quick way to sanity-check loads without a spreadsheet.
- Discussion (30–45 min): Compare real-world loads and where teams get surprised.
Desired outcome: a practical load profile
By the end, you should be able to say: “Here are the loads that matter most for this project, and here’s where we need margin.” We’ll keep it conceptual—later sessions go deeper into specific systems.
Load categories
- Snow + wind: roof and lateral loads; drift/edge effects; exposure matters
- Soil movement: settlement, expansive soils, drainage effects
- Use loads: decks, stairs, guardrails—where failures become injuries
- Cold snaps: peak heating demand and comfort risk at the margins
- Solar + internal gains: overheating and glare (even in cold climates)
- Plug loads: real-world energy use that defeats “modeled” expectations
- Occupant moisture: showers, cooking, plants, humidifiers, laundry
- Events: parties, guests, wet gear—short peaks that matter
- Operation: how people actually use systems and openings
Potential discussion prompts
- Biggest mismatch: Where do modeled vs lived loads diverge the most?
- Overheating: Have you seen overheating in “efficient” homes in cold climates?
Common failures (load mismatch)
A lot of “mystery” comfort, durability, and cost problems come from the same root cause: the building was designed for one set of loads, and reality delivered another.
Common failure patterns When the load is bigger, longer, or more frequent than expected
- Comfort complaints: cold rooms, drafty zones, big temperature swings
- Moisture trouble: indoor humidity peaks that overwhelm drying capacity
- Overheating: solar + internal gains + insufficient shading/venting strategy
- Energy surprises: plug loads and “always-on” devices blowing up bills
Examples (for discussion)
Example 1 — “The bonus room is always cold”
Peak load in an exposed zone is higher than expected → comfort complaints and endless tweaking.
Example 2 — “It’s efficient, but it overheats”
High solar gain + internal gains → summer discomfort despite good insulation.
Example 3 — “Humidity spikes and musty smell”
Short, intense moisture events + limited ventilation strategy → recurring mustiness.
Potential discussion prompts
- Peak events: What “peak load” surprises have you seen (heat, moisture, occupancy)?
- Operational reality: What assumptions do teams make that occupants never follow?
Core concepts
Design for peaks, not averages
Most complaints come from the worst week, not the average month.
Moisture is a load you create
Cooking and showers are “events.” A good design expects them—and handles them gracefully.
Gains drive comfort as much as losses
Sun and internal heat can be your friend in winter and your enemy in shoulder seasons and summer.
Operation is part of design
If a house only works when used perfectly, it doesn’t work. Keep the “happy path” obvious.
Takeaways
- A habit of asking: What are the peak loads? (not just averages)
- A simple indoor load inventory: people + sun + appliances + moisture events
- A way to spot risk early: zones with big exposure, big glass, or odd geometry
- A reminder that “performance” includes how people live in the house
Further reading & references
These are broad frameworks. We’ll go deeper on HVAC/IAQ and moisture-specific strategies later in the series.
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BSD-003: A House Is a System
A strong foundation for why loads and behavior matter as much as assemblies.
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JLC: Building Science collection
Field-based articles that often expose “load mismatch” problems in real homes.