Start with the basics. Everything after this is optional refinement — the calculator always has a sensible default, so you can stop at any point and still get a usable number.
Scope
Landed typology
Sets how much of the perimeter is exposed external wall.
All enclosed floors including basement, if any.
Use 2.5 for a two-storey with attic.
Auto = build-up area ÷ storeys. Override if the ground floor is much larger or smaller.
Drives external wall area.
Step · Form
How is the house shaped?
Shape decides how much wall, roof and substructure you buy for the same floor area. These are the cheapest carbon decisions to change — they cost nothing at concept stage.
Plan compactness
Measured against a square plan, which is the minimum possible perimeter for a given footprint.
Basement
Applies to substructure only. Include basement floor area in the build-up area on the previous step.
Existing structure retained
Percentages are the share of new material still required. Retained substructure is credited separately, since kept foundations avoid almost all of their carbon.
Roof geometry
Façade articulation
Glazing as a share of façade
Step · Structure
What holds it up?
Substructure and frame are usually the two largest slices for a landed house in Singapore. Rates are kgCO₂e per m² of the relevant area (A1–A3, cradle to gate).
Foundation / substructure — per m² footprint
Includes the ground-floor slab, so the ground floor is not counted again under suspended slabs.
Frame — beams & columns — per m² GFA
Floors are counted separately below, so this covers vertical structure and beams only.
Suspended floors — per m² of upper floors
Applied to build-up area minus the ground floor footprint.
Step · Envelope
What is it wrapped in?
Roof, wall and glazing choices. In a tropical house the glazing and shading trade-off matters twice — once here in embodied carbon, and again in operational cooling.
Roof build-up — per m² roof
Opaque façade — per m² wall
Glazing system — per m² glass
External shading & screens
Area taken as a share of total façade, at 83 kgCO₂e/m² (aluminium / powder-coated metal assumed).
Balconies & external terraces
Extra slab, balustrade and waterproofing beyond the enclosed floor area, at 78 kgCO₂e/m².
Step · Interiors & services
What goes inside?
Partitions, air-conditioning, lift and the interior fit-out. Fit-out is often underestimated — carpentry-heavy landed interiors can rival the frame.
Internal partitions — per m² GFA
Air-conditioning system — per m² served
Share of floor area air-conditioned
Home lift
Estimated as a 4,700 kgCO₂e car and machinery allowance plus 950 kgCO₂e per storey served.
Interior fit-out standard — per m² GFA
How much of the house is fitted out?
Step · Site, energy & allowances
Everything outside the building line.
Pool, driveway, boundary walls and solar. For landed houses these are routinely left out of concept estimates and routinely turn out to matter.
Allowance of 550 kgCO₂e per m² of pool — shell, excavation, tiling and plant.
External works
Driveway, boundary walls, gate, landscape hardscape and drainage, as a percentage of the building total.
Solar PV
Embodied carbon only. Operational savings are not modelled here — a roof array typically pays back its embodied carbon in roughly 2–4 years in Singapore.
PV coverage
Construction stage & concept contingency
Everything above is cradle-to-gate (A1–A3) only. This uplift covers transport to site, construction and site energy (A4–A5), material wastage, and the uncertainty of estimating at concept stage.
Step · The fit-out
What kind of renovation?
Fit-out carbon is dominated by carpentry, stone and replaced finishes rather than structure.
Fit-out standard — per m²
Extent of works
Air-conditioning replaced?
Construction stage & contingency
Covers delivery, installation, wastage and demolition disposal of what is stripped out.
Result
Your concept-stage carbon footprint.
An order-of-magnitude estimate for early design conversations. Change anything on the previous steps and this updates instantly.
Total embodied carbon
0 tCO₂e
Intensity
0 kg/m²
Indicative band
—
Where the carbon sits
Quantities used
0m² build-up area
0m² footprint
0m² suspended floors
0m overall height
0m² façade
0m² opaque wall
0m² glazing
0m² roof
Benchmark
Low <250 · Moderate 250–450 · High 450–650 · Very high >650 kgCO₂e/m². Indicative only: benchmarks for tropical landed housing are not standardised, and these bands are calibrated against European whole-life carbon guidance adapted for local practice. Compare projects against each other with confidence; treat the absolute band with caution.
Tree offset, for scale
0trees to plant
0 kgabsorbed per tree over the period
+10%survival buffer applied
Read this as scale, not as a solution. Trees absorb carbon slowly and only while they live; embodied carbon is emitted once, up front, before anyone moves in. Reducing carbon at source — retaining structure, using less concrete, simplifying form — is always worth more than offsetting it later.
Method & limitations
Rates are cradle-to-gate (A1–A3) generic European EPD averages, uplifted by the construction-stage allowance you selected. They are not Singapore-specific EPDs.
Façade area is derived from a square perimeter, 4 × √footprint, then adjusted for typology, plan compactness and articulation. It is a proxy, not a measured elevation.
Excluded: operational energy (B6), maintenance and replacement (B2–B5), end of life (C), sanitary and plumbing, electrical containment, kitchen appliances, furniture, and site preparation or demolition of the existing house.
Timber and CLT figures exclude biogenic carbon storage and end-of-life release; treat them as fossil-carbon only.
Suitable for comparing options at concept stage. It does not replace a full LCA for Green Mark or any certification submission.
Treehaus Carbon Calculator, stepped edition. Free to use. If the calculator or its outputs appear in any publication, presentation, report or public-facing material, please credit Treehaus Architects Pte Ltd.