Under the Hood: The Physics Engine of CoreLoad
An explicit breakdown of the geometry, barometric thermodynamics, and solar multipliers driving the CoreLoad engine.
CoreLoad is not a UI toy. It is a strict, mathematical implementation of the ACCA Manual J simplified block-load methodology. Every architectural input you provide actively alters the thermodynamic equations in the background. Here is exactly how the engine handles the physics of your building.
### Altitude and Air Density As elevation increases, air pressure drops. Thinner air carries less thermal energy, which radically alters infiltration loads and equipment capacity. When you adjust the elevation slider, CoreLoad runs the Standard Barometric Formula: `Density Multiplier = (1 - 0.000006875 * elevation)^5.2559`
At sea level, this is 1.0. At Denver's 5,280-foot elevation, the multiplier is approximately 0.83x. This multiplier is strictly applied to all sensible infiltration calculations (`Infiltration = Volume * ACH * 0.018 * ΔT * Density Multiplier`).
### Architectural Geometry When you change the Footprint Shape from Rectangle to L-Shape or U-Shape, the engine applies geometric multipliers (1.15x and 1.25x respectively) to the base perimeter to account for the additional external wall surface area created by inside/outside corners. If you check "Vaulted Ceilings," the engine switches to trigonometry: `Math.sqrt(halfWidth² + vaultedHeight²)`. This calculates the exact hypotenuse of the roof slope, increasing the roof surface area and adding massive cubic footage to the air volume calculation, heavily impacting the final infiltration load.
### Solar Heat Gain Coefficients Solar heat gain is highly dependent on orientation. The engine applies a baseline 1.0x solar multiplier to North-facing windows but a brutal 1.8x multiplier to West-facing windows. If you input 500 sqft of glass on the West wall instead of the North wall, the required cooling tonnage will skyrocket, exactly as it would in reality.
### Duct Thermodynamics If you place ducts in a "Vented Attic" instead of a "Conditioned" space, the engine applies severe thermodynamic penalties. It assumes the attic will hit 135°F+ in the summer and calculates the heat transfer directly through the duct insulation into the 55°F supply air (`Heat Gain = Surface Area * U-Value * ΔT * 1.5`). This adds massive sensible and latent cooling penalties to your final required tonnage.
We expose these exact mathematical penalties dynamically in the "Physics Modifiers & Telemetry" section of every generated report.