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HL-LAB-2026-ENV02Published: 2026-09-13

Student Laboratory Manual: Building Envelope Thermal Transmission, Fenestration SHGC Modeling, and Infiltration Sizing per ACCA Manual J

An interactive engineering laboratory curriculum contrasting 1975 versus 2025 IECC envelopes and demonstrating the physical failure of empirical 1-ton-per-500-sq-ft shortcuts.

By HVACLogic Research Group • Miad S.
📄Download Official PDF Whitepaper🎓Read on Academia.eduDA 93↗🏛️Internet Archive MonographDA 96↗🤗Hugging Face Dataset (DOI 10.57967/hf/10401)DA 91↗📊Figshare Dataset (DOI 10.6084/m9.figshare.33702643)DA 91↗

Abstract

Accurate determination of residential peak cooling and heating thermal loads is fundamental to mechanical equipment selection, indoor humidity control, and decarbonization. This laboratory manual guides engineering and technology students through the quantitative formulation of multi-layer Fourier conduction, fenestration solar heat gains (SHGC), and pressure-driven blower door air leakage (ACH50) normalized via Sherman-Grimsrud LBL correlation factors. A comparative case study of a 2,500 sq ft home illustrates why legacy contractor heuristics oversize equipment by 80% to 120%, resulting in short-cycling and latent moisture extraction failure.

Key Technical Findings & Code Impacts

  • Legacy rules of thumb (1 ton / 500 sq ft) specify 5.0 tons for a 2,500 sq ft modern home whose true Manual J peak cooling load is only 2.20 tons (a 127% oversizing error).
  • Continuous exterior polyisocyanurate insulation (R-5) combined with dense-pack cavity batt reduces whole-wall assembly U-factor from 0.143 to 0.038 BTU/(hr·ft²·°F), a 73% conductive load reduction.
  • Upgrading fenestration to Low-E Argon units (U-0.28, SHGC 0.22) cuts direct solar radiative heat gain by 73% on west-facing glazing exposures.
  • Blower door tightness improvements from 9.5 ACH50 to 2.0 ACH50 with balanced mechanical ventilation decrease sensible infiltration loads by 79% while protecting indoor relative humidity.

Governing Industry Standards & Codes

🏛️ACCA Manual J (8th Edition)
🏛️ASHRAE Handbook — Fundamentals (2021)
🏛️IECC 2021 / 2024 Residential Energy Provisions
🏛️ASTM E779 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization

Mathematical Formulations & Governing Equations

Multi-Layer Assembly Thermal Resistance & Reciprocal U-Factor

governing_model_eq_1.math
PEER-REFERENCED
01U_{\text{assembly}} = \frac{1}{R_{\text{si}} + \sum_{i=1}^n \frac{x_i}{k_i} + R_{\text{cavity}} + R_{\text{se}}}

💡 Evaluates overall heat transmittance across composite wall or ceiling assemblies by inverting total series-parallel thermal resistance.

Fenestration Conductive and Solar Radiation Heat Gain

governing_model_eq_2.math
PEER-REFERENCED
01Q_{\text{fenestration}} = U \cdot A \cdot (T_{\text{outdoor}} - T_{\text{indoor}}) + A \cdot \text{SHGC} \cdot E_{\text{solar}} \cdot \text{IAC}

💡 Decouples conductive temperature differential heat transfer from direct and diffuse solar irradiance transmitted through glazing.

Pressure-Driven Natural Infiltration Heat Load

governing_model_eq_3.math
PEER-REFERENCED
01Q_{\text{inf, sensible}} = 1.08 \cdot \left(\frac{\text{ACH}_{50} \cdot V_{\text{building}}}{60 \cdot N}\right) \cdot (T_{\text{outdoor}} - T_{\text{indoor}})

💡 Converts empirical blower door depressurization metrics (ACH50 at 50 Pa) into continuous natural design infiltration CFM via climate-specific LBL correlation factors.

Companion Calculation Engines & Simulation Models

Heating & Cooling BTU Load Calculator

Calculate whole-house heating and cooling loads, room-by-room CFM, and Manual J sensible/latent distributions.

Launch Live Simulator →

Wall & Roof Assembly R-Value Calculator

Determine multi-layer composite assembly U-factors, thermal bridging, and insulation R-values.

Launch Live Simulator →

Academic Citations & BibTeX

To cite this technical report in university coursework, dissertations, or engineering research:

APA Format:

HVACLogic Research Group, & S., M. (2026). Student Laboratory Manual: Building Envelope Thermal Transmission, Fenestration SHGC Modeling, and Infiltration Sizing per ACCA Manual J (Courseware Report No. HL-LAB-2026-ENV02). HVACLogic Open Educational Resources. https://doi.org/10.57967/hf/10401

BibTeX Entry:

@techreport{hvaclogic_2026_student_lab_02,
  author = {{HVACLogic Research Group} and S., Miad},
  title = {Student Laboratory Manual: Building Envelope Thermal Transmission, Fenestration SHGC Modeling, and Infiltration Sizing per ACCA Manual J},
  institution = {HVACLogic Open Educational Resources & Monograph Series},
  year = {2026},
  number = {HL-LAB-2026-ENV02},
  doi = {10.57967/hf/10401},
  url = {https://hvaclogic.org/research/student-lab-building-envelope-thermal-transmission}
}