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.
Vacuum insulation panels (VIP) is a high performance thermal insulation material solution with thermal conductivity values reaching as low as 4.0 mW/(mK). With time the thermal performance of the VIPs will degrade as moisture and gas permeate through the barrier envelope of the panels. To better evaluate these ageing effects, accelerated ageing experiments are needed. VIPs consist of a porous core of pyrogenic silica (SiO2) and a gas and vapour tight envelope. The external factors that are found to contribute most to ageing of VIPs are temperature, moisture and pressure. Several experiments have been initiated to evaluate the acceleration effects by the application of severe temperature, moisture and pressure conditions, including: 1. Thermal ageing at 80°C for 180 days according to CUAP 12.01/30 2. Exposure to cyclic climate in a vertical climate simulator according to NT Build 495. One VIP sample is fully exposed in the simulator and one is placed in a wooden frame structure. 3. Exposure to high vapour pressure by storage at 70°C and 90-100 % RH for 90 days. The increases in thermal conductivity during ageing were relatively small compared to the initial thermal conductivity of the VIPs, which is in agreement with the theoretical predictions. The temperature and moisture experiment seemed to achieve a rather large acceleration effect. In addition, the thermally aged VIP and the exposed VIP in the climate simulator show physical alterations. E.g. swelling, curving and delamination of the outer fire protection layer are observed.
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.
Electrochromic (EC) materials that change their optical transmittance under an external electrical field may form the basis of “smart windows”, which are of great interest in forthcoming building technologies. Nanostructured EC materials or assemblies have revealed remarkable improvement on colouration efficiency and switching time due to their small featured sizes and large surface areas. Here, the recent progress of nanoelectrochromics is reviewed; the scientific and technical issues related to material preparation and device assembly for large-area and large-scale window applications are discussed.
Nanotechnology and possibilities for the thermal building insulation materials of tomorrow are explored within this work. That is, we are looking beyond both the traditional and the state-of-the-art thermal building insulation materials and solutions, e.g. beyond vacuum insulation panels (VIP). Thus advanced insulation material (AIM) concepts like vacuum insulation materials (VIM), gas insulation materials (GIM), nano insulation materials (NIM) and dynamic insulation materials (DIM) are introduced and defined. The VIMs and GIMs have closed pore structures, whereas the NIMs may have either open or closed pore structures. The objective of the DIMs are to dynamically control the thermal insulation material properties, e.g. solid state core conductivity, emissivity and pore gas content. In addition, fundamental theoretical studies aimed at developing an understanding of the basics of thermal conductance in solid state matter at an elementary and atomic level will also be carried out. The ultimate goal of these studies will be to develop tailor-make novel high performance thermal insulating materials and dynamic insulating materials, the latter one making it possible to control and regulate the thermal conductivity in the materials themselves, i.e. from highly insulating to highly conducting.
While window frames typically represent 20%"30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low conductance glazings. Developing low-conductance window frames requires accurate simulation tools for product research and development. The Passivhaus Institute in Germany states that windows (glazing and frames, combined) should have U-factors not exceeding 0.80 W/(m² K). This has created a niche market for highly insulating frames, with frame U-factors typically around 0.7-1.0 W/ (m² K). The U-factors reported are often based on numerical simulations according to international simulation standards. It is prudent to check the accuracy of these calculation standards, especially for high-performance products, before more manufacturers begin to use them to improve other product offerings. In this paper, the thermal transmittance of five highly insulating window frames (three wooden frames, one aluminum frame, and one polyvinyl chloride frame), found from numerical simulations and experiments, are compared. Hot box calorimeter results are compared with numerical simulations according to ISO 10077-2 and ISO 15099 (ISO 2003a, 2003b). In addition, computational fluid dynamics simulations were carried out in order to use the most accurate tool available to investigate the convection and radiation effects inside the frame cavities. Our results show that available tools commonly used to evaluate window performance, based on ISO standards, give good overall agreement, but specific areas need improvement.