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Moisture Buffer Value of Building Materials

Building materials and furnishing used in contact with indoor air may have a positive effect to moderate the variations of indoor humidity seen in occupied buildings. Thus, very low humidity can be alleviated in winter, as well as can high indoor humidity in summer and during high occupancy loads. This way, materials can be used as a passive means of establishing indoor climatic conditions, which are comfortable for human occupancy, or for safe storing of artefacts which are sensible to humidity variation. But so far there has been a lack of a standardized figure to characterize the moisture buffering ability of materials. It has been the objective of a recent (ongoing until mid-2005) Nordic project to come up with such a definition, and to declare it in the form of a NORDTEST method. Apart from the definition of the term Moisture Buffer Value, there will also be a declaration of a test protocol which expresses how materials should be tested. Finally as a part of the project, some Round Robin Tests will be carried out on various typical building materials. The paper gives an account on the definition of the Moisture Buffer Value, it will outline the content of the test protocol, and it will give some examples of results from the Round Robin Tests. (Less)

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.

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.

Moisture conditions in well-insulated wood-frame walls. Simulations, laboratory measurements and field measurements

Abstract Buildings for the future, that is, zero emission buildings and passive houses, will need well-insulated building envelopes, which include increased insulation thicknesses for roof, wall and floor constructions. Increased insulation thicknesses may cause an increase in humidity levels and thereby increased risk of mould growth. There is need for better knowledge about moisture levels in wood constructions of well-insulated buildings, to ensure robust and moisture-safe solutions. Various envelope constructions were simulated using HAM-tools (Heat, Air and Moisture). In addition, a laboratory experiment was performed to investigate the effect of a slower drying out of built-in moisture. Walls with varying insulation thicknesses and with a high degree of built-in moisture were instrumented with moisture sensors, and the drying speed was monitored. A field monitoring of wood moisture levels and temperatures was performed in wall and roof constructions of five passive houses in three different locations representing different climate conditions in Norway. The general conclusion is that the risk for mould growth increases somewhat in well-insulated envelopes compared to more traditional envelopes. However, in most cases this can be counteracted by making the right choices during design and construction.

Renovation status and technical condition of Norwegian dwellings

Purpose – The purpose of this paper is to gain knowledge on the renovation status for Norwegian dwellings that can be used to design attractive energy efficiency measures. Norwegian dwellings are exposed to a windy, cold and moist climate and the technical condition of existing dwellings depend on the owners priorities regarding maintenance and renovation. The paper focuses on the renovation status and technical condition of privately owned detached houses built in Norway in the 1980s constituting 10 per cent of the total Norwegian dwelling stock. These houses are high-energy spenders and are at a stage in their lifetime where major renovation such as new windows and ventilation system is expected. Design/methodology/approach – The status for redecoration, maintenance and renovation as well as the technical condition of 91 dwellings are mapped and analysed. Findings – An analysis of the empirical data identified four categories of houses when considering home upgrades and technical condition: the as built...

External wood claddings – performance criteria, driving rain and large-scale water penetration methods

Abstract In Norway, wood is widely used as an external cladding material. The performance requirements of a facade cladding can be divided into technical and aesthetic performance, where the technical performance is more distinct than the aesthetic one. Performance models for technical performance of wooden facades and deckings are under development and there is also ongoing research on the parameters that affect aesthetic performance. Wooden facades are recommended to be designed as a two-step tightening with a ventilated air gap and drainage opening on the back. The technical performance is mainly related to the ability of the construction to withstand wind-driven rain and the drying out potential of the chosen material and solutions. This work presents the results from a large-scale laboratory trial on three different wooden cladding solutions. The objective was to investigate the rain tightness of the different types of cladding, to detect water that penetrates the cladding and monitor the uptake of moisture, and the subsequent drying out. The trial showed that even at large amounts of wind-driven rain, only little water penetrated through the investigated cladding types. From a technical performance point of view, it is important to focus on an accurate mounting routine.

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.

Hot-Box measurements of highly insulated wall, roof and floor structures

The purpose of this study was to investigate how natural convection in air-permeable glass wool insulation affects the thermal transmittance in walls, roofs and floor structures. The results can be used to evaluate the need for a convection barrier in thick mineral wool layers. Natural convection is affected by several parameters. In this study, the angle of inclination, the heat flow direction and the temperature difference across the test section have been studied. Thermal transmittance and temperature distribution measured using thermocouples placed inside the insulation cavity clearly showed convection in the insulation when the test section was in pitched roof and wall positions. An efficient measure to reduce the natural convection is to divide the insulation layer into two thinner layers using a diffusion open convection barrier. A convection barrier is recommended by the authors both in wall and pitched roof structures if the insulation thickness exceeds 200 mm.

Life Cycle GHG Emissions from a Wooden Load-Bearing Alternative for a ZEB Office Concept

A major contributor to global greenhouse gas emissions is the production of concrete and steel for the construction industry IPCC (2007). To combat global warming, innovative solutions are needed in the construction industry to reduce emissions from both energy and material use in buildings. In a previous study the first phase of a GHG emissions analysis for a Norwegian ZEB office concept was presented. The aim of which was to achieve a zero emission balance where operational and material emissions are accounted for ZEB OM. The results from the first phase showed that the load bearing system accounted for a large share of the embodied emissions. In addition, the ZEB OM ambition level was not met, thus emphasizing the need for further work on alternative solutions and material choices. This paper presents the results of a comparative study between this original office concept study and a predominantly wooden alternative loadbearing structure consisting of wood trusses, glue laminated beams and columns. The wooden alternative is comparable since it has been dimensioned to fulfil the same technical requirements for bearing capacity, sound and fire resistance. In addition, the system boundary was extended to include three alternative end-of-life scenarios. It was found that the wooden alternative structure almost halved the emissions compared to the original concrete and steel ZEB office concept model. This trend is the same in the cradle to gate and all three end-of life scenario’s. The analysis clearly shows that emissions from the production process outweigh any emissions from the material’s end-of-life treatment. This means that the material choice plays a major role in embodied emissions, as well as it being crucial to reduce the required construction material quantity.