Pressure equalisation as design strategy for watertightness

Due to rising energy prices and a higher ecological awareness there is a growing attention for energy efficiency and sustainability in building construction. New concepts and techniques for well insulated and airtight buildings require adapted construction methods for weathertightness. This research project aims at developing design guidelines for new building envelope systems concerning weathertightness. Most building envelope systems rely on pressure moderation to achieve a good weathertightness. By separating the airtightness plane from the water shedding surface a drained cavity can be pressure moderated to limit the amount of water that enters the construction. A better understanding of those phenomena makes way for more rapid evolution in energy efficient and sustainable building envelope design

Analysis of different frost indexes and their potential to assess frost based on HAM simulations

To reach the climate goals of 2020 our buildings have to become a lot more energy-efficient. This challenge rests mainly on the shoulders of the renovation sector because new buildings are only a small part of our building stock. Old buildings mainly cannot get insulated on the outside because the facade is historically valuable or because of urban planning restrictions. In those cases interior insulation or - if possible - cavity insulation are the only options. However, these renovation strategies may induce severe risks for the existing structure. One of the main risks is frost damage: the interior insulation lowers the temperature of the exterior facade and decreases the drying potential to the inside which leads to an increased risk of frost damage. Most of the studies that assess the risk of frost damage struggle with the dependency of the highly variable material properties of the façade

Probabilistic assessment of the impact of material properties on the risk of frost damage in masonry constructions

Historically valuable buildings often contain a huge energy saving potential due to their current lacking thermal performance of the building envelope. Next to this, unfortunately insulation measures, which normally occur at the inside, induce a decrease in the temperature and drying potential of the structure which results in a risk for frost damage. To validate this risk Heat, Air and Moisture simulations are a valuable tool. Heritage facades often consist of masonries, which are known to have a complex hygrothermal behaviour. Therefore nowadays a homogenization of the masonry, for example to a homogenous brick wall, is often assumed to save computational time. Nevertheless these homogenizations, which include neglecting mortars, can have a drastic impact on the hygrothermal behaviour of masonries. Hence this study compares the impact of basic material parameters for the brick, pointing mortar and bed mortar of a masonry separately under a constant indoor and outdoor climate based on probabilistic simulations. The evaluation is done for three frost related criteria. Generally, the main impact parameters for the one and a half brick construction are found to be quite similar for interior insulated and not insulated cases but diverse between the chosen criteria

On the feasibility of watertight face-sealed window-wall interfaces

Watertightness is still a major source of concern in the performance of the building envelope. Even very small deficiencies can cause a significant amount of water leakage which may result in structural degradation or malfunctioning of the insulation. The risk of water infiltration is highest at joints between different building components and in particular at the window-wall interface due to the complexity of these joints. This paper focuses on the performance of different solutions to ensure the watertightness of the window-wall interface, e.g. self-adhesive foils, liquid applied coatings, prefabricated frames, self-expanding sealing strips. The performance of these solutions is evaluated for different wall assemblies, i.e. ETICS, masonry, structural insulated panels and wood-frame construction. Laboratory experiments were conducted on a full-scale test setup with a window of 1,01 m high and 0,56 m wide. Test results showed that it is not evident to obtain watertight face-sealed window-wall interfaces without an additional airtight layer or drainage possibilities. Water ingress was often recorded at lower pressure differences

Eerste dak in België met vacuümisolatie

Vandaag is het de normaalste zaak van de wereld om elke woning te isoleren, maar eigenlijk is dit nog maar een zeer recente evolutie. Naar aanleiding van het Palestijns-Israëlisch conflict hebben de Arabische landen in 1973 de olietoevoer naar het Westen op een laag pitje gezet, waardoor de olieprijs spectaculair de lucht in schoot. In de nasleep van deze eerste oliecrisis is het besef gegroeid dat we zuinig moeten omspringen met fossiele brandstoffen, zij het om politieke, economische of ecologische redenen. In België heeft zich dat vertaald in het eerste isolatiedecreet in 1991, de EPB-wetgeving in 2006, en de huidige – verstrengde – EPB-wetgeving in 2011. Maar dit is nog niet het eindpunt: Europa heeft beslist dat in 2021 alle nieuwbouwwoningen bijna nul-energie gebouwen moeten zijn. De komende 10 jaar moet de bouwwereld dus nog een stap zetten die minstens zo groot is als de evolutie in de laatste 50 jaar. Energiezuinig bouwen bestaat niet uit één oplossing, maar is een combinatie van doordacht ontwerp, efficiënte technieken, en veel isolatie. Helaas zijn dikke pakketten isolatie niet altijd zo eenvoudig in te passen in een plat dak, of wordt een strakke detaillering van sommige aansluitingen onmogelijk. Maar mogelijks komt er hulp uit onverwachte hoek: misschien kan vacuümisolatie de oplossing bieden voor een aantal problemen. Dit innovatief isolatiemateriaal isoleert tot 5 maal beter dan traditionele isolatiematerialen, maar er zitten enkele adders onder het gras

Drainage and retention of water in small drainage cavities : experimental assessment

Water that enters the drainage cavity of a rain screen wall assembly through deficiencies in the cladding will either be drained or retained by absorption or adhesion on the drainage surfaces. The objective of this study is to gain insight into the different factors that affect the quantity of water drained or retained in a drainage cavity. Drainage tests have been conducted for water flowing between two vertical polycarbonate plates with different gap widths to determine the effect on the drainage rate. Tests showed that even small cavities with a width of 1 mm can already drain more water than the amount that would enter the cavity during a rain event. Experiments were performed to determine the contact angle of water on a range of different sheathing materials such as asphalt saturated building paper, spun-bonded polyethylene wrap and cross-woven polyolefin wrap by the use of an optical goniometer. Drainage tests have been conducted for different combinations of these materials to quantify the effect of surface energy on the drainage rate. A larger contact angle results in a smaller quantity of water retained during the drainage test. These tests result in a retained portion of water and a drainage rate for different combinations of materials. The retained portion of water may be considered as a moisture load applied to the outer-most layer of the wall assembly’s back-up wall in hygrothermal simulations

Results of Belgian quality control framework for cavity wall insulation

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