The thermal envelope separates temperature-controlled rooms from outdoors and unconditioned spaces. Trace it continuously through plans and sections.
Conditioned zones
First identify the spaces whose temperature will be maintained. Storage, garages and entrance lobbies do not automatically belong inside the envelope because they share a roof.
Foundation and floor
Trace floor insulation to the wall and inspect the slab edge. Coordinate insulation and foundation geometry with loads, groundwater and suitable materials.
Walls and windows
The envelope passes through the frame, not an abstract opening. Show insulation and air-barrier connections at jambs, heads and sills.
Roof and loft
For a cold loft the envelope follows the ceiling; for a conditioned attic it follows the roof slopes and gables. Detail hatches, eaves and service penetrations separately.
Basements, garages and lobbies
Including a basement changes envelope area and the services strategy. If a garage is outside, adjoining walls, doors and floors become boundary elements.
Gaps and drawing checks
Cross-check plans, sections and details: the line must not disappear at balconies, stairs or services. Trace the air barrier separately; it may not coincide with insulation.
| Item | Parameter | Check / result |
|---|---|---|
| Loft | Unconditioned | Insulated ceiling |
| Attic | Conditioned | Insulated slopes |
| Garage | Outside | Insulate separating surfaces |
What this means for your project
Mark thermal and airtight boundaries in two colours. Request a detail wherever either crosses a structure or service.
Sources and scope of review
Related reading
- Thermal Bridges: Where They Occur and Why They Matter
- Airtightness: What It Is and Why It Matters
- Insulated Raft Foundation: When It Makes Sense
- Installing Windows in the Insulation Layer