Development of air tightness prediction method of masonry walls

Abstract

Recently, the construction of external walls of various blocks, which are externally insulated with mineral wool thermal insulation layer, with ventilated air gap and external finishing (ventilated wall structures) is becoming popular for public and office buildings. These blocks are used without internal rendering because they have a good interior surface, stable dimensions, and various filling of masonry joints provide an attractive architectural appearance. This reduces the cost and duration of construction work, however, problems with airtightness of such walls often occur. The air can penetrate through blocks or their joints, and the thermal insulation and wind protection layer does not usually provide the required air tightness of the wall. Currently, there are no standard methods to predict the air tightness of such wall, in practice, samples of particular walls are produced and their air permeability is measured at the laboratories. This is a costly job, which is only suitable for a combination of particular building materials. For the broader use of results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from blocks, made of ceramic, expanded clay and aerated concrete with various joints, were used for the research; mineral wool boards of various air permeability were used for thermal insulation and wind protection layer. After measuring the air resistance of masonry units, thermal insulation and wind protection boards, the air flow resistances of the walls of different construction were calculated. The comparison of calculated and measured air permeability of wall samples showed that in cases where the nature of air movement (laminar to turbulent) through a single material remains similar with the nature of air movement through the product incorporated in the structure, the calculation and measurement data differ no more than 12-15%. In structures with building products with very different air permeability properties, especially at high thicknesses of air permeable thermal insulation products, air movement parameters change occurs and calculated and measured results have larger differences.

Investigation the Effect of Design Parameters on Air Tightness with Examples of Balikesir Houses

“…[21]. Besides, study of Paukštys et al indicated a hollow clay unit wall caused 7-11% less airtightness compared to a sand-lime block Wall unit [22]. It is known that the construction year of the building also has an effect on the airtightness performance.…”

Experimental Assessment of Different Sealing Methods for Windows to Improve Building Airtightness in UAE Residential Buildings

“…The final air leakage results were expressed as a rate of leakage per hour per square meter of the villa envelope at a reference pressure differential of 50 Pa (m 3 •h −1 •m −2 @50 Pa). This was calculated by dividing the total leakage flow rate (Q 50 ) by the envelope area (A E ) [39]. Thus:…”

“…Obviously, the leakage is apparent in the gaps of the frame, making significant infiltration. This was calculated by dividing the total leakage flow rate (Q50) by the envelope area (AE) [39]. Thus: AP50 = Q50/AE (3) where: Q50 = CL × 50 n , AP50 = air permeability, Q50 = air leakage rate at a pressure differences of 50 Pa, AE = envelope area m 2 , CL = air leakage coefficient, 50 n = differential pressure.…”

“…Obviously, the leakage is apparent in the gaps of the frame, making significant infiltration. This was calculated by dividing the total leakage flow rate (Q50) by the envelope area (AE) [39]. Thus:…”