Compare one and two storeys for the same programme and usable floor area. Storey count alone does not determine energy performance.
Envelope areas
A two-storey option may reduce roof and ground-floor area but changes wall and junction areas. Calculate each option’s actual geometry.
Stairs and usable space
Stairs, circulation and accessibility affect required gross area. Do not compare equal external dimensions when the usable programme differs.
Services and airtightness
Routes may be shorter or more complex depending on layout. Check envelope penetrations, vertical shafts and room airflow, not just pipe length.
Summer and lifetime use
Upper rooms need their own solar, roof and cooling checks. Ground-floor bedroom accessibility may matter more than a small calculated energy saving.
Common mistakes
Do not choose storey count solely from A/V or foundation cost. Compare complete cost, structure, comfort and future needs using identical inputs.
| Item | Parameter | Check / result |
|---|---|---|
| One storey | Roof and ground | Areas |
| Two storeys | Walls and stairs | Geometry |
| Both | Same programme | Complete balance |
What this means for your project
Prepare comparable concepts with the same room needs. Assess energy alongside accessibility and delivery cost.
Sources and scope of review
Related reading
- Building Compactness and Heat Loss
- House Design Brief: What It Should Include
- Air Conditioning in a Passive House