Invisible Load Calculations: Latent Heat Errors in Modern Buildings

For decades, HVAC design has been built on a comforting assumption: that we understand how buildings “load” heat and moisture. Sensible heat is calculated with relative precision, infiltration is estimated with familiar multipliers, and latent heat is often treated as a secondary, simplified component.

That framework worked reasonably well when buildings were leakier, materials were less complex, and occupancy patterns were more predictable.

But modern buildings have changed the rules without changing the equations.

Today’s environments are tighter, more insulated, more glazed, and more controlled than ever before. Airtight envelopes reduce natural moisture relief. High-performance glass shifts surface temperatures in subtle ways that are not always captured in standard models. Internal loads—from people, equipment, and processes—have become dominant. And yet, in many design practices, latent heat is still treated as a fixed percentage or an oversimplified estimate.

This gap between real moisture behavior and calculated latent load is no longer a minor inaccuracy—it is a systemic design risk.

This book explores that gap.

It focuses on the “invisible” part of HVAC design: the moisture that does not show up clearly in load spreadsheets but manifests later as condensation, discomfort, mold, overcooling, or excessive energy consumption. It challenges conventional assumptions and brings attention to the dynamic nature of latent loads in modern building envelopes.

The goal is not to discard traditional HVAC methods, but to expose their limitations in today’s context—and to encourage a more realistic, physics-based understanding of moisture behavior in buildings.