Sandwich elements are widely used in the building envelope, in walls and foundations in particular. The thickness of sandwich elements is increasing as the demand for reduced heat loss from the building envelope is required. The building industry is searching for means and alternative materials to reduce the volume of the building envelope, but at the same time obtain the same thermal performance. Sandwich element constructions might be suitable for highly effective insulation materials as VIPs (Vacuum Insulation Panels). The possibilities of optimizing the thermal performance and by the same time decreasing the thickness and reducing the volume of aggregated clay sandwich construction block systems with VIPs has been investigated. Numerical simulations with heat conduction models and also CFD-models have been performed in order to study the optimal design of the block, the influence of thermal bridges and the influence of vertical and horizontal joints on the thermal performance of a wall. The work has resulted in an optimal design for a prototype block which has been produced and general knowledge about the influence of convection in vertical joints. The simulations show that for vertical joints less than 3 mm in width there will be no significant heat transport by convection. The numerical simulations also show that an U-value of 0,08 W/m2K can be achieved for such a system, with a thickness of the block being 300 mm. The work was carried out in the framework of the Norwegian centre for Zero Emission Buildings (ZEB).
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.
A large amount of the buildings in Norway is from the 1970s. Many of these buildings have timber frame walls and are now ready to be retrofitted. Application of vacuum insulation panels (VIPs) can make it easier to improve the thermal insulation in building walls with a minimal additional thickness. Retrofitting of buildings using VIPs may therefore be done 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 standars or zero energy building requirements may be achieved. Thus, contribute to a reduction of the energy use and CO2 emissions within the building sector. This work investigates two different ways of retrofitting timber frame walls, one with VIPs on the cold side and one with VIPs on the warm side. A wall module containing four different fields is built and tested between two climate rooms with indoor and outdoor climate, respectively. The module consists of one reference field representing a timber frame wall built according to regulations in the 1970s in Norway, and three fields representing different ways of improving the thermal insulation of the reference field with VIPs. As VIP is a vapour tight barrier, the fields are tested with respect to condensation risk. A new sensor for measuring surface condensation called the wetness sensor is introduced. The results of the experiment show that this method of retrofitting may be acceptable in certain structures within limited climate zones, humidity classes, and building envelopes.
Phase change materials (PCMs) have opened a new door towards the renewable energy future due to their effective thermal energy storage capabilities. Several products have recently found their way to the market, using various types of PCMs. This paper focuses on one particular wall-board product, integrated in a well-insulated wall constructed of an interior gypsum board, PCM layer, vapor barrier, mineral wool, and a wind barrier. The wall is tested with and without the PCM layer in order to get comparative results. Experiments are conducted in a traditional guarded hot box. The hot box is composed of two full-scale test chambers, where the tested wall is located between those two chambers. There are two heaters inside the metering box: heater 1 functions as a thermostat which is used to maintain a constant air temperature (of about 20 ºC) in the metering box, while heater 2 is a normal electrical heater that provides a constant heating power when turned on. The cold chamber has a fixed temperature equal to –20 ºC. The experiments are arranged in a comparative way, i.e. comparing walls with and without a PCM layer. Temperature, heat flux, air velocity, and electrical power are recorded during testing. By applying well-distributed thermocouples, the influences of the PCM layer on the interior temperatures can be shown. Furthermore, with attached heat flux meters, the energy storage effect and convective heat flows can be determined. Finally, with the electrical power meter, the energy saving effect can also be calculated. In this paper, initial experimental results are presented, showing the indoor air and surface wall temperatures. The experiments show that inclusion of the PCM layer in the wall reduces the interior air and wall temperatures by a maximum of about 2 ºC compared to a wall without PCM. The results also show that increasing the air velocity over the interior surface during the heating period lowers the maximum air and surface temperatures by the end of the heating period.