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DERZAWı
Architecture Studio
DASLab / 07

Envelope & U-value

Thermal transmittance of wall and roof build-ups, layer by layer.

Experimental tool — evolving and open to suggestions: info@derzawi.com

U-value — Wall (horizontal heat flow)

0.218 W/m²K

R total 4.59 m²K/W · 375 mm thick · Rsi 0.13 / Rse 0.04 (ISO 6946)

insideoutside15Gypsum plaster, R = 0.04 m²K/W200Reinforced concrete, R = 0.09 m²K/W150EPS, R = 4.29 m²K/W10Cement / sand render, R = 0.01 m²K/W19.4°19.3°18.9°0.2°0.2°

Indicative targets

UK Part L 2021 — limiting (dwellings)0.26 → meetsApproved Document L vol. 1 (2021) Table 4.1
UK Part L 2021 — notional (dwellings)0.18 → exceedsApproved Document L vol. 1 (2021) notional dwelling
Passivhaus guidance (cool-temperate)0.15 → exceedsPHI guidance, U ≤ 0.15 W/m²K for opaque elements

Steady-state, one-dimensional. Thermal bridges (studs, ties, frames), moisture and condensation (Glaser / WUFI) are not included. λ values are typical design values; use the manufacturer's declared values.

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