Air Permeability and Thermal Performance of Concrete Block Wall Sections PDF

Air permeability of 1.25 × 1.25 m block wall sections was measured in the 0–200 Pa range by means of a pressure box. Extrapolating results to a standard 100 m² dwelling indicated that nonrendered autoclaved-aerated-concrete block walls are extremely airtight, leading to an estimated leakage rate of 0.01–0.02 ach under 150 Pa; nonrendered regular-aggregate-concrete block walls, as well as lightweight-aggregate-concrete blocks, are highly permeable, with estimated rates of ~2–6 ach and ~5–10 ach under 50 and 150 Pa, respectively. An external 3 mm cementitious brown coat reduced these values to 0.07–0.16 ach and 0.18– 0.21 ach. An internal 10 mm lime-cement rendering reduced them to 0.07–0.13 ach and 0.16–0.19 ach. Thermal resistances of the hollow-core specimens were estimated by comparing temperature differences across specimens, measured by means of an insulated box, to estimated room-side surface resistances. A small pressure difference induced across specimens (0.1–1.0 Pa) decreased the estimated heat-flow rates but did not affect estimated R-values.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: SI