Steinar Grynning

Aging effects on thermal properties and service life of vacuum insulation panels

Vacuum insulation panels (VIPs) represent a high-performance thermal insulation material solution offering an alternative to thick wall sections and large amounts of traditional insulation in modern buildings. Thermal performance over time is one of the most important properties of VIPs to be addressed, and thus the aging effects on the thermal properties have been explored in this article. Laboratory studies of aging effects are conducted over a relatively limited time frame. To be able to effectively evaluate aging effects on thermal conductivity, accelerated aging experiments are necessary. As of today, no complete standardized methods for accelerated aging of VIPs exist. By studying the theoretical relationships between VIP properties and external environmental exposures, various possible factors for accelerated aging are proposed. The factors that are found theoretically to contribute most to aging of VIPs are elevated temperature, moisture, and pressure. By varying these factors, it is assumed that a substantial accelerated aging of VIPs can be achieved. Four different accelerated aging experiments have been performed to study whether the theoretical relationship may be replicated in practice. To evaluate the thermal performance of VIPs, thermal conductivity measurements have been applied. The different experiments gave a varying degree of aging effects. Generally, the changes in thermal performance were small. Results indicated that the acceleration effect was within what could be expected from theoretical relationships, but any definite conclusion is difficult to draw due to the small changes. Some physical changes were observed on the VIPs, i.e., swelling and curving. This might be an effect of the severe conditions experienced by the VIPs during testing, and too much emphasis on these should be avoided.

Improving thermal insulation of timber frame walls by retrofitting with vacuum insulation panels – experimental and theoretical investigations:

Many of the Norwegian buildings from the 1960s–1980s with timber frame walls are ready for retrofitting. Retrofitting of these buildings with vacuum insulation panels (VIPs) may be performed without significant changes to the buildings, e.g., extension of the roof protruding and fitting of windows. Effectively, U-values low enough to fulfill passive house or zero energy requirements may be achieved; thus, contributing to a reduction of the energy use and CO2 emissions within the building sector. Retrofitting with VIPs on the exterior side is normally considered as a better solution; however, it may cause condensation in the wall. To investigate this and the interior option, four different wall fields were tested. One of them was a reference wall field built according to Norwegian building regulations from the 1970s, and three other fields represent different ways of increasing the thermal insulation level. In addition to the experiments, numerical simulations were performed where temperature, relative humidity, and surface wetness were measured. In total, the results from the experiments, simulations, and condensation controls conclude that timber frame buildings insulated with 100 mm mineral wool, might be retrofitted at the outside by adding 30 mm VIPs. However, this method for retrofitting provides limits to outdoor temperature, indoor moisture excess, and indoor temperature.

Hot box investigations and theoretical assessments of miscellaneous vacuum insulation panel configurations in building envelopes

Vacuum insulation panels (VIPs) are regarded as one of the most promising existing high performance thermal insulation solutions on the market today as their thermal performance typically range 5—10 times better than traditional insulation materials. However, the VIPs have several disadvantages such as risk of puncturing by penetration of nails and that they cannot be cut or fitted at the construction site. Furthermore, thermal bridging due to the panel envelope and load-bearing elements may have a large effect on the overall thermal performance. Finally, degradation of thermal performance due to moisture and air diffusion through the panel envelope is also a crucial issue for VIPs. In this work, laboratory investigations have been carried out by hot box measurements. These experimental results have been compared with numerical simulations of several wall structure arrangements of vacuum insulation panels. Various VIP edge and overlap effects have been studied. Measured U-values from hot box VIP large-scale experiments correspond well with numerical calculated U-values when actual values of the various parameters are used as input values in the numerical simulations.

Robustness Classification of Materials, Assemblies and Buildings

Reliable methods are needed for classifying the robustness of buildings and building materials for many reasons, including ensuring that constructions can withstand the climate conditions resulting from global warming, which might be more severe than was assumed in an existing building’s design. Evaluating the robustness of buildings is also important for reducing process-induced building defects. We describe and demonstrate a flexible framework for classifying the robustness of building materials, building assemblies, and whole buildings that incorporates climate and service life considerations.

Moisture Robustness During Retrofitting of Timber Frame Walls with Vacuum Insulation Panels: Experimental and Theoretical Studies

A large amount of the buildings in Norway is from the 1960s–1980s. Many of these buildings have timber frame walls and are now ready for retrofitting. Application of vacuum insulation panels (VIPs) may make it easier to improve the thermal insulation in timber frame walls with a minimal additional thickness. Retrofitting of timber frame walls using VIPs may therefore be performed without large changes to the building, e.g. extension of the roof protruding and fitting of windows. Additionally, U-values low enough to fulfil passive house standards or zero energy building requirements may be achieved, thus contributing to a reduction of the energy use and CO2 emissions within the building sector. This work investigates different ways of retrofitting timber frame walls with VIPs on the exterior or the interior side. Timber frame walls retrofitted with VIPs on the exterior side is interesting because it allows for a continuous layer of VIPs over the building envelope, and it is also considered as a more robust solution than VIPs at the interior side (less risk of puncture). However, application of VIPs on the exterior side may cause condensation in the wall. To investigate this, a wall module containing four different wall fields was built between two climate rooms with indoor and outdoor climate, respectively. One field represents a reference wall built according to Norwegian building regulations from the 1970s. The three other fields represent different ways of improving the thermal insulation of the reference field, with VIPs at the interior or the exterior side. To minimize the size of the thermal bridge caused by traditional methods of fastening VIPs, a tailor-made VIP fastening bracket was applied in the build-up of the fields. Temperature, relative humidity (RH), and surface wetness was measured during the experiment. The surface wetness was measured on the wind barrier with a tailor-made surface wetness sensor consisting of double-sided tape, metal electrodes and paper sheets. In addition to the experimental investigations, numerical simulations and condensation control calculations were performed for the same wall fields with hygrothermal robustness performance as the main objective. In overall, the results from the experiments, simulations, and condensation controls conclude that timber frame buildings insulated with 100 mm mineral wool, might be retrofitted at the outside by adding 30 mm VIPs. However, this method for retrofitting provide limits to outdoor temperature, indoor moisture excess and indoor temperature.

Thermal performance of in-between shading systems in multilayer glazing units: Hot-box measurements and numerical simulations

Shading systems are widely used, also in Nordic climates, in conjunction with glazed facade in office buildings. The primary functions of the solar shading devices are to control solar gains leading to cooling needs during operational hours and reduction of discomfort caused by glare. A secondary property of shading devices incorporated in glazing units is that they can be utilized as an additional layer in the glazing unit when the shading device is deployed. This can improve the thermal transmittance value (U-value) of the windows. It can be deployed during night-time or in periods when a blocked view does not have any consequences for the users of the building. This article presents hot-box measurements of thermal transmittance values (U-values) performed for three insulated glazing units with integrated in-between pane shading systems. The shading devices are venetian-type blinds with horizontal aluminum slats. The windows with double- and triple-pane glazing units have motorized blinds. The window with a 4-pane glazing has a manually operated blind placed in an external coupled cavity. The measurements are compared to numerical simulations using the WINDOW and THERM simulation tools. The results showed that only minor reductions of U-values of the glazing units were obtained as function of shading system operation. It was, however, found that the introduction of shading devices in the window cavities will increase the total U-value of the window due to thermal bridging effects caused by shading device motor and the aluminium slats of the blinds. coupled cavity.