Interior insulation retrofit of a historical brick wall using vacuum insulation panels: Hygrothermal numerical simulations and laboratory investigations

Old listed buildings need to be retrofitted to reduce the energy use for heating. The possible thickness of the insulation layer is limited by the existing construction. Vacuum insulation panels (VIPs) require less thickness than conventional insulation materials to reach the same thermal resistance. Therefore, it could be more appropriate to use VIPs than conventional insulation materials when retrofitting the building envelope of listed buildings. The aim of this study is to investigate the hygrothermal performance of a brick wall with wooden beam ends after it was insulated on the interior with VIPs. One- and two-dimensional hygrothermal numerical simulations were used to design a laboratory study in a large-scale building envelope climate simulator. The wall was exposed to driving rain on the exterior surface and a temperature gradient. The relative humidity in the wall increased substantially when exposed to driving rain. The moisture content in the wooden beams also increased. There was no significant difference between the relative humidity in the wooden beam ends for the cases with and without VIPs. However, it was found that the reduced temperature in the brick after the VIPs were added led to a higher relative humidity in the wooden beams. It was also clear that when VIPs were added to the interior, the drying capacity to that side of the wall was substantially reduced. Finally, calculations of the U-value showed a large potential to reduce the energy use using VIPs on the interior of brick walls

Possibilities for characterization of a PCM window system using large scale measurements

The introduction of dynamic envelope components and systems can have a significant reduction effect on heating and cooling demands. In addition, it can contribute to reduce the energy demand for artificial lighting by better utilization of daylight. One of these promising technologies is Phase Change Materials (PCM). Here, the latent heat storage potential of the transition between solid and liquid state of a material is exploited to increase the thermal mass of the component. A PCM layer incorporated in a transparent component can increase the possibilities to harvest energy from solar radiation by reducing the heating/cooling demand and still allowing the utilization of daylight. Measurements have been performed on a state-of-the-art, commercially available window that integrates PCM using a large scale climate simulator. The glazing unit consists of a four-pane glazing with an integrated layer that dynamically controls the solar transmittance (prismatic glass) in the outer glazing cavity. The innermost cavity is filled with a PCM, contained in transparent plastic containers. When dynamic components are incorporated in the building envelope, it makes the characterization of static performance (e.g. the thermal transmittance, U-value; the solar heat gain coefficient) insufficient in giving the full picture regarding the performance of the component in question. This article presents a series of preliminary measurements, and the related methodologies, carried out on a window with incorporated PCM. The tests have been carried out using several test cycles comprised of temperature and solar radiation cycling, where the aim has been to delve deeper into the possibilities for the characterization of dynamic building envelope components by full scale testing in a climate simulator, showing potentials and limitations of this approach and measurement facility. It was found that even for temperatures similar to a warm day in Nordic climate, the potential latent heat storage capacity of the PCM was fully activated. Long periods of sun combined with high exterior temperatures are needed.Acknowledgements. This work has been supported by the Research Council of Norway and several partners through the NTNU and SINTEF Research Centre on Zero Emission Buildings (ZEB).publishedVersio

Window with integrated solar collector : Climate resistance evaluation report

The NorDan solar collector is a window/solar collector combination which can be mounted as a traditional window in the façade of a new building. The component is originally designed for new buildings, but the research and experiments carried out in Retrokit2 focus on developing solutions for retrofitting. Air- and rain tightness tests have been carried out at SINTEF Byggforsk`s Laboratory facilities in Høgskoleringen 7B in Trondheim. The U-value of a wall element with a solar collector for retrofitting has been calculated. A laboratory experiment of the moisture performance was carried out to investigate constructional details of the building integration and how the building integration can be solved without the risk of moisture condensation and mould growth behind the solar collector. Laboratory experiments and U-value calculations verify that the NorDan solar collector function as designed. The NorDan solar collector is air- and rain tight and can replace the exterior cladding of new and existing buildings as a fully building integrated element for solar thermal energy production.publishedVersio

Thermal conductivity of high-performance insulation - a laboratory study. Realistic design values for use in energy-efficient buildings.

Aerogel insulation blankets could be the solution to some of the challenges encountered when designing (energy efficient) buildings. However, uncertainties regarding performance in different applications and environments may limit their use in cases where they could otherwise be employed to advantage. The purpose of this study was to examine how to best adapt European standards for the measurement of thermal insulation properties to aerogel insulation and highlight important aspects to be aware of when evaluating material parameters. We have systematically varied measurement parameters for thermal conductivity and compressive strength to map the impacts on reported material properties. Furthermore, we have compared the measurement conditions to actual conditions in selected building applications. In conclusion we propose that the European (EN) standard for measuring compression behavior for insulation materials should be revised and clarified with regards to materials that do not exhibit a clear elastic domain. We also suggest that the thermal conductivity of aerogel insulation blankets should be measured with a slight compressive load on the material, but that the calculation of the thermal conductivity should nevertheless be based on the measured sample thickness

Retrofitting a brick wall using vacuum insulation panels: measured hygrothermal effect on the existing structure

Old listed buildings need to be retrofitted to reduce the energy use for heating. Vacuum insulation panels (VIPs) require less thickness than conventional insulation materials to reach the same thermal resistance. The aim of this paper is to investigate the hygrothermal performance of a brick wall with wooden beam ends after it was insulated on the interior with VIPs. The paper presents the first part of a laboratory study where a brick wall was built in the laboratory and exposed to simulated driving rain. Different measurement techniques of the relative humidity in the construction have been used. The relative humidity in the wall increased substantially when exposed to driving rain. The moisture content in the wooden beams also increased. However, it has not been possible to fully determine the influence by the added insulation layer. It is clear that the drying capacity to the interior side is substantially reduced. These investigations are ongoing and will be reported in future publications

Interior Insulation Retrofit of a Brick Wall Using Vacuum Insulation Panels: Design of a Laboratory Study to Determine the Hygrothermal Effect on Existing Structure and Wooden Beam Ends

The increasing demand on energy-efficient buildings requires energy retrofitting measures in the existing building stock. Conventional thermal insulation materials, such as mineral wool and expanded polystyrene (EPS), demand a thick layer of insulation to reach the energy targets. Vacuum insulation panels (VIPs) are a novel thermal insulation component with 5-10 times lower thermal conductivity than the conventional insulation materials, depending on the VIP ageing state. The thermal transmittance of the building envelope can thereby be substantially reduced using a limited additional insulation thickness. Previous research has shown that interior energy retrofitting of exterior walls may increase the moisture content of the walls and increases the risk of freeze-thaw damages at the surface. This study analyzes the hygrothermal consequences on a 250 mm (9.8 in.) thick brick wall retrofitted with 20 mm (0.8 in.) interior VIP (glued directly on the plastered brick wall). Hygrothermal simulations in WUFI 2D are used to study the hygrothermal effects by different material properties and boundary conditions. Apart from the material properties, the amount of driving rain available at the surface is the most important influential parameter in the simulations. The conclusions from this study are used to plan a measurement study in a climate simulator where driving rain and solar radiation will be simulated

Interior Insulation Retrofit of a Brick Wall Using Vacuum Insulation Panels: Design of a Laboratory Study to Determine the Hygrothermal Effect on Existing Structure and Wooden Beam Ends

The increasing demand on energy-efficient buildings requires energy retrofitting measures in the existing building stock. Conventional thermal insulation materials, such as mineral wool and expanded polystyrene (EPS), demand a thick layer of insulation to reach the energy targets. Vacuum insulation panels (VIPs) are a novel thermal insulation component with 5-10 times lower thermal conductivity than the conventional insulation materials, depending on the VIP ageing state. The thermal transmittance of the building envelope can thereby be substantially reduced using a limited additional insulation thickness. Previous research has shown that interior energy retrofitting of exterior walls may increase the moisture content of the walls and increases the risk of freeze-thaw damages at the surface. This study analyzes the hygrothermal consequences on a 250 mm (9.8 in.) thick brick wall retrofitted with 20 mm (0.8 in.) interior VIP (glued directly on the plastered brick wall). Hygrothermal simulations in WUFI 2D are used to study the hygrothermal effects by different material properties and boundary conditions. Apart from the material properties, the amount of driving rain available at the surface is the most important influential parameter in the simulations. The conclusions from this study are used to plan a measurement study in a climate simulator where driving rain and solar radiation will be simulated

Retrofitting a brick wall using vacuum insulation panels: measured hygrothermal effect on the existing structure

Old listed buildings need to be retrofitted to reduce the energy use for heating. Vacuum insulation panels (VIPs) require less thickness than conventional insulation materials to reach the same thermal resistance. The aim of this paper is to investigate the hygrothermal performance of a brick wall with wooden beam ends after it was insulated on the interior with VIPs. The paper presents the first part of a laboratory study where a brick wall was built in the laboratory and exposed to simulated driving rain. Different measurement techniques of the relative humidity in the construction have been used. The relative humidity in the wall increased substantially when exposed to driving rain. The moisture content in the wooden beams also increased. However, it has not been possible to fully determine the influence by the added insulation layer. It is clear that the drying capacity to the interior side is substantially reduced. These investigations are ongoing and will be reported in future publications