Embodied carbon of progressive timber integration in a 47-storey tropical high-rise: A Singapore public housing case study

This study assesses the embodied carbon reduction potential of progressive timber integration and the Active Timber Envelope (ATE), a prefabricated facade combining engineered timber with building-integrated photovoltaics (BIPV), in tropical super-high-rise public housing, using a 47-storey Singapore case (SkyVille@Dawson, 960 units, 149,268 m² GFA). Four scenarios were compared under EN 15978 / EN 15804+A2 with EPD data: Typical (TY, precast reinforced concrete), Hybrid Timber (HT, CLT slabs and partitions with a concrete core), All Timber (AT, adding the Unitised Timber Envelope), and Timber+PV (TP, complete ATE with facade BIPV). AT achieves 260 kgCO₂e/m² upfront (A1–A5), a 50.9% reduction from the TY baseline of 530 kgCO₂e/m². On an embodied-carbon-only basis (A–C), AT records the lowest whole-life total (591 kgCO₂e/m²) and TP records 677 kgCO₂e/m²; once an independently computed BIPV operational offset is included, TP attains the lowest net total, 554 kgCO₂e/m² (a 26% reduction from TY's 747 kgCO₂e/m²). Operational energy (Module B6) is excluded for all scenarios, and the offset is reported separately from Modules B6 and D. No scenario reaches net-zero embodied carbon over the 50-year reference period, as Singapore's incineration-dominant waste management precludes permanent biogenic carbon storage, contrasting with net-zero claims in temperate-climate literature. Among 19 reviewed timber LCA studies, none assessed buildings above 21 storeys, only two examined tropical climates, only one combined timber envelopes with BIPV, and none addressed public housing. The findings are broadly applicable to tropical high-rise construction.