Building Envelope GPT
Wall assembly U-values, thermal bridging, condensation risk, and envelope code compliance.
Conversational building envelope assistant for architects and energy engineers. Covers U-value calculations layer by layer, thermal bridging (Ψ values), moisture management for different climates, air tightness targets, and Passive House vs ASHRAE 90.1 envelope compliance. Ask about your assembly and get specific guidance with numbers.
The Problem
Envelope decisions combine thermal performance, air control, moisture behavior, fire performance, structure, and constructability. A layer-by-layer R-value alone does not establish whole-assembly or code compliance.
How It Works
Tell it the jurisdiction, climate zone, assembly layers, framing, and performance target. It can compare thermal paths, identify questions about thermal bridges and vapor control, and point to the adopted energy-code path for verification.
"climate zone 5, metal stud wall with continuous insulation — does this meet IECC 2021?""what vapor barrier strategy for a mass timber wall in a cold climate?"Key Features
Who It's For
Architects and envelope consultants specifying wall, roof, and window assemblies for energy code compliance and moisture control.
This tool provides envelope design guidance based on your inputs. It does not review your actual wall sections or drawing details. For a full building envelope review across your drawing set, use the Drawing Review Agent.
Frequently Asked Questions
What is the difference between R-value and U-value?
R-value measures thermal resistance — higher is better. U-value measures thermal transmittance (the inverse of total R-value) — lower is better. IECC uses U-values for fenestration and R-values for opaque assemblies.
How do I calculate the whole-assembly R-value for a metal stud wall?
Metal studs conduct heat 3-4x faster than wood studs, reducing the effective R-value by 30-50%. A 3.5" metal stud wall with R-13 batt insulation has an effective R-value of approximately R-8 to R-9. Add continuous exterior insulation to meet IECC requirements in most climate zones.
When do I need a vapor barrier vs a vapor retarder?
The answer depends on the adopted code, climate zone, assembly class, interior humidity, material permeance, exterior insulation, and any code exceptions. Do not select a vapor-control layer from climate zone alone; verify the complete assembly and governing provision.