Influence of hydrophobation and deliberate thermal bridge on hygrothermal conditions of internally insulated historic solid masonry walls with built-in wood

Abstract

A large share of the Danish building stock contains historic multi-storey buildings. A considerable energy saving potential exists, achievable through thermal insulation of the façades. Previous research has elucidated problems regarding poor hygrothermal conditions when interior thermal insulation is applied to the façade, but examples exist with positive results. Eight 1x2 m solid masonry test walls with wooden members were installed in an insulated container. The hygrothermal implication of applying 100 mm AAC as interior thermal insulation system was investigated with variations including use of hydrophobation and substitution of insulating material with a deliberate thermal bridge. Highlights • Conditions behind thermal insulation reached critical values for mould growth. • Conditions can be altered by hydrophobation and deliberate thermal bridges. • Hydrophobation reduced relative humidity in summer, with rapid increase in winter. • Relative humidity in built-in wood can be reduced by incorporating thermal bridge. • Example of fit between wind driven rain model and measurements.

Long term in situ measurements of hygrothermal conditions at critical points in four cases of internally insulated historic solid masonry walls

“…al. [34]. In regard to the in situ measurements, it should be noted, that during the long term measurement period, re-calibration of the sensors was not possible, and the results might drift to a little extent [35], however the results give clear indications of the actual hygrothermal conditions.…”

Experimental investigations of wooden beam ends in masonry with interior insulation: Measured data in real-scale experimental walls exposed to semi-continental climatic conditions

“…The interior thermal insulation unfortunately worsens the hygrothermal performance of the masonry wall. The temperature of masonry drops, increasing the risk of water vapor condensation at the original masonry surface behind the thermal insulation (Odgaard et al, 2018). The temperature of the masonry with interior insulation is systematically low during the cold season.…”

“…The moisture content of wood is therefore higher than it would be if the wooden beam end was placed on the warm side of the building enclosure, as follows from the sorption curve. The degree to which conditions in the joist pocket are exacerbated depends on the interior and exterior boundary conditions and the amount of moisture entering the construction from both sides (Odgaard et al, 2018).…”

Guidelines for internal Insulation of historic Buildings

“…The potential benefits are at present studied in a number of projects, e.g. in Denmark and Belgium, being part of or connected to RIBuild [2], [3], [4].…”