TheSIS - Thermal renovation with internal insulation systems - investigation and development of moisture-proof solutions

Starting point / motivation

For the renovation of buildings with listed facades, the use of internal insulation is often the only way to significantly reduce transmission heat losses. However, in order to avoid moisture related damages and health hazards caused by mould growth, the insulation system must be carefully planned and implemented.

Moisture-adaptive vapor retarders represent a promising solution in this context, as they enable vapor diffusion from the indoor air to be inhibited during winter without preventing the wall from drying out during summer. Existing products consist of foils (e.g., polyamide membranes) whose vapour diffusivity increases with the water content.

Scientific works show, however, that despite the advantages of such moisture-adaptive vapor retarders, improvements are required to achieve better adaptation of their properties to the environmental conditions and construction-specific requirements.

Contents and goals

The aim of the project TheSIS is the development, characterization and hygrothermal optimization of moisture-safe and innovative solutions for the renovation of building envelopes with internal insulation. The focus is on a moisture-adaptive vapor retarder in form of a paint coating, with expected major building physics-related advantages compared to the current state of the art (moisture-adaptive vapor retarders based on foils).

While commercially available foils present predefined properties and crucial limits regarding the Sd-value variability, a coated vapor barrier can be very flexibly adapted to specific building physics and environment-related requirements. The adaptation occurs by using suitable binders and varying the layer thickness. The coating can be applied to products for internal finishing (such as calcium silicate, OSB, clay or gypsum boards) directly in the factory on a large industrial scale.

In the TheSIS project, the particular application of the newly developed moisture-adaptive vapor retarder in connection with a sustainable material consisting of biochar and clay (CarbonClay) is investigated. The material is manufactured in shape of boards coated with the moisture-adaptive vapor retarder. The boards can be very well combined with recycled insulation materials such as cellulose blow-in insulation. After system removal, the polymer coating is separated from the board and both components are recycled.

Methods

The knowledge of the materials' hygrothermal properties is essential for an accurate analysis of an internal insulation system. A suitable hygrothermal characterization of the vapour retarder by means of acknowledged experimental methods is therefore planned in the project. Concerning the coating, classic test methods are used, as the "Universal Surface Tester" and mechanical / thermal analysis (TGA and DMA).

After the materials' characterization and optimization, the research activity moves on towards the optimization of the entire insulation system and its interaction with the room climate under realistic boundary conditions. The limits of the system in relation to the risk of moisture damages and mould growth are determined using hygrothermal simulation.

In addition, the interaction between the insulation system and the room climate (humidity and temperature) is examined with the aim of ensuring high indoor comfort and hygiene. In order to validate numerical results and test the system limits, the system variants are subjected to a stress test in climatic chambers under controlled indoor and outdoor conditions.

Expected results

The expected results of TheSIS include the development, hygrothermal characterization and optimization of an innovative moisture-adaptive vapor retarder to be used in combination with sustainable and durable internal insulation systems. Through the cooperation with materials' suppliers (Adler, Natürlich Bauen), the solutions developed in the project will have a direct impact on the market and hence on the users.

Application guidelines are delivered, aiming at facilitating and extending building refurbishment with internal insulation. The energetic, economic and comfort-related advantages of the developed retrofit solutions are thus made available.

Project management

Universität Innsbruck, Institut für Konstruktion und Materialwissenschaften

Project or cooperation partners

• ADLER-Werk Lackfabrik Johann Berghofer GmbH & Co KG
• Natürlich Bauen OG
• Universität Innsbruck, Institut für Chemieingenieurwissenschaften

Michele Bianchi Janetti
Technikerstraße 13
A-6020 Innsbruck
Tel.: +43-512-507-63604
E-mail: michele.janetti@uibk.ac.at
Web: www.uibk.ac.at/bauphysik