Air permeability and thermal performance of concrete block wall specimens

Abstract

Air permeability of 1.25 × 1.25 m2block wall specimens was measured in the 0—600 Pa range using a pressure box described later in the text. Extrapolating results to a standard 100 m2dwelling in a multi-story residential building indicated that (a) autoclaved aerated concrete block walls are extremely airtight (0.22 ± 0.04 m3/m2/h at 150 Pa), leading to estimated rates of 0.01—0.02 air changes per hour (ACH) under a pressure difference of 150 Pa across the front or side wall; and (b) regular and lightweight aggregate concrete block walls, are highly permeable (121.3 ± 0.9 and 74.2 ± 0.9 at 150 Pa, respectively), with estimated rates of ∼ 2.3—9.5 ACH under pressure differences of 50—150 Pa across the front or side wall. An exterior 3 mm brown coat reduced these values to 0.07—0.2 ACH. A 10 mm interior lime—cement rendering had a similar effect. Both layers reduced them to 0.01—0.07 ACH. An insulated hot box was used to study the effect of a small positive pressure difference (0.1—1.2 Pa) across the hollow-core block wall specimens on their thermal performance. The small pressure differences did not affect estimated R-values.