| 1. |
- Bankvall, Claes, 1942, et al.
(author)
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Air transport in and through the building envelope
- 2004
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469.
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Conference paper (peer-reviewed)abstract
- A national R&D program dealing with air transport in and through the building envelope is presented, including some overviews of results. The program develops predictive models for evaluating air movements in and through the building envelope. These models are coupled to the outside climate and pressure situation and to the inside climate through the interaction with models defining the building services system. A major aim of the program is to analyze problems of relevance to the building process. This includes site inventory, modeling of typical situations, and laboratory testing for input data and to validate the models. The objective is to develop tools to help design and evaluate building elements and to give the necessary foundation for estimating the convective transport of heat and moisture in the envelope, which is decisive for the indoor climate, the consumption of energy, and the durability of the construction. The research program is ongoing and this presentation is to invite communication with others.
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| 2. |
- Johansson, Pär, 1986, et al.
(author)
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Field Testing of Interior Super Insulation Materials on a Brick Wall in an Industrial Building
- 2019
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469. ; , s. 635-643
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Conference paper (peer-reviewed)abstract
- Conventional thermal insulation materials, such as fiber glass and EPS, demand a thick layer of insulation to reach the energy targets. Super insulation materials (SIM) are thermal insulation components with a 3-10 times higher thermal resistance than conventional insulation materials, such as vacuum insulation panels (VIP) and aerogel blankets (AB). They are efficient in increasing the thermal performance of walls when retrofitting, without significantly tampering with the wall thickness. Usually other measures such as changing windows or heating system are preferred before adding insulation to the walls, but to improve the thermal comfort and energy performance further, interior insulation is a possible alternative. In this study, an industrial building from 1896 with a 470 mm (1.5 ft) homogenous brick masonry wall is investigated regarding the hygrothermal performance and thermal inertia of the wall with interior insulation. Earlier research has shown that interior insulation decreases the drying-out capacity of the exterior wall and increases the risk for freeze-thaw damages in brick walls. In this study measurements from field investigations and simulations of a homogenous brick wall with 20 mm (0.8 in) interior VIP and 20 mm (0.8 in) aerogel blankets are compared to a non-insulated reference wall. The measurements showed that the wall was wet throughout the measurement period while the measured U-value was reduced with 82-83% for the AB and 81-84% for the VIP layers.
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| 3. |
- Karim, Ali Naman, 1992, et al.
(author)
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Duration of Early Stage Drying of Aerogel-based Renders: Field Tests and Simulations in Four Swedish Cities
- 2022
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469. - 9781955516280 ; 2022
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Conference paper (peer-reviewed)abstract
- Aerogel-based renders are considered as suitable solutions for energy retrofitting of building envelopes due to their energy and space-saving potentials. Their thermal conductivity measured in laboratory and dry state is within 0.03-0.05 W/(m·K) (0.21-0.35 Btu·in/h·ft2·℉), around one tenth of conventional renders. However, previous research showed higher thermal conductivities measured in field than the declared values measured in laboratory. Aerogel-based renders are wet during the early stage of application until the initial built-in moisture is dried out. This higher initial moisture content is often given as an explanation for the higher values measured in field. To investigate the influence of the elevated initial moisture content further, the early stage drying performance of aerogel-based renders in Swedish climate conditions was studied experimentally and numerically. A section of a historical brick building in Gothenburg, Sweden, was renovated by applying a 30-40 mm (0.10-0.13 ft) thick layer of a commercial aerogel-based render. The construction was equipped with temperature and moisture sensors. Also, the exterior air temperature and relative humidity were measured. Numerical hygrothermal (heat and moisture) simulations were used to calculate the required drying time of the initial built-in moisture in aerogel-based renders. Several locations, representing different climates, and different application times of the aerogel-based render were considered in the simulations. The results of the field testing showed that a drying period longer than three months was required before the initial built-in moisture was completely dried out. According to the hygrothermal simulations conducted, a drying period of around 128-355 days could be expected for the built-in moisture in aerogel-based renders to dry out in four Swedish cities. The drying time depends on the time of application and the corresponding outdoor climate conditions during the early stage drying.
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| 4. |
- Karlsson, H., et al.
(author)
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Performance factor for floor heating systems using new analytical formula
- 2016
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469. ; 2016-December, s. 356-363
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Conference paper (peer-reviewed)abstract
- A recently developed analytical formula for the self-regulation ability of low temperature water-based floor heating systems is experimentally validated. By controlling the feed-forward supply temperature, keeping it rather constant during the year, any thermal perturbance is counteracted by a corresponding shift in the opposite direction of the supplied heat flux. This will give a more stable indoor temperature and an enhanced use of heat gains. Buildings with small heat losses, such as well insulated single-family houses, in combination with a high equivalent thermal conductance from the supply of the pipe circuit towards the interior, yield a high self-regulation utilization factor. Hence, self-regulation is an integrated phenomenon that depends on both the design of the floor heating element and the building. The theory behind self-regulation floor heating is outlined and an experimental setup using climate chambers is presented. Both light and heavy floor heating systems with embedded hydronic pipes are studied. Steady-state and dynamical tests are used in the validation.
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| 5. |
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| 6. |
- Larsson, Bengt, 1943-, et al.
(author)
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The Effect and Cost Impact of Poor Airtightness : Information for Developers and Clients
- 2007
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - Orlando : ASHRAE. - 2166-8469. - 9781933742281
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Conference paper (peer-reviewed)abstract
- Air movements in and through the building envelope affect the flows of not only heat, but also moisture, gases and particles, in a building. They often play a decisive part in determining moisture conditions, and thus indoor environmental conditions in the building, and ultimately, the durability of the building structure. Air flows affect thermal comfort and ventilation, and thus air quality. In addition, they also cause heat loss, both directly via ventilation, and through their effect on the performance of what are intended to be high-insulation structures.A previous joint project between SP Technical Research Institute of Sweden and Chalmers University of Technology investigated the importance of airtightness in the construction process. The project found that many types of damage and problems were caused by poor airtightness, that airtightness was seldom given the proper consideration that it deserved and that there was a major need for information on the effect of poor airtightness. One of the conclusions was that it is important to get developers/clients to treat airtightness more seriously.The objective of the follow-on project that is described here is therefore to make developers/clients (more) aware of the potential damage that can be caused by poor airtightness, together with the “cost” of this damage/problem in a life-cycle perspective. Hopefully, developers/clients will then specify and monitor airtightness requirements more clearly. The aim is therefore to develop tools and methods for informing developers/clients of the importance of good airtightness, and of the resulting extra costs that incur from paying insufficient attention to airtightness.The project has identified and assessed various consequences of poor airtightness, such as increased energy use, reduced thermal comfort, reduced air quality and moisture damages.The cost calculations show that the developer/client would benefit in most cases from an increased standard and follow up on airtightness. We have projected the work with three different levels of ambition: 0.2, 0.4 and 0.6 l/m2s (at 50 Pa pressure difference), and believe that the optimal airtightness lies somewhere in the region of these values, depending on the buildings use and equipment.
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| 7. |
- Nielsen, Anker, 1945, et al.
(author)
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Sustainability of the Swedish built environment towards climate change. Hygro-thermal effects and design criteria for buildings with respect to future climate scenarios
- 2007
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469. ; 10th
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Conference paper (peer-reviewed)abstract
- The most of predictable climatic impacts on buildings can be successfully managed by an adequate construction. However, possible deviations in predicted loads and especially the long-term ones may change the building designed, e.g. expected response. For example, changes in snow and wind loads and short-time precipitation are of a great interest for constructions with large flat roofs. Climate projections from climate models point to a warmer climate with an intensified hydrological cycle in the future. Warmer summers lead to increased demand for cooling energy, while a warmer and more humid climate will possibly increase risks for moisture and mould-growth problems. This paper gives some outlines from a new research project on sustainability of Swedish built environment towards climate changes. The project will be conducted at Chalmers University of technology, Sweden, in cooperation with the climate research unit Rossby Centre at the Swedish Meteorological and Hydrological Institute.
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| 8. |
- Olsson, Lars-Erik, 1949
(author)
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Laboratory Study of Rates of Inward Leakage in Seven Different Gaps in a Facade Exposed to Driving Rain or Water Splash
- 2016
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings. - 2166-8469. ; 2016-December, s. 415-422
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Conference paper (peer-reviewed)abstract
- Water or rainwater can leak into outer walls and facades to a greater or lesser extent, but there is a general lack of specific information how much water usually penetrates. If we simply rely on theoretical analyses with only limited knowledge of the amounts involved in such inward leakage, we run serious risks of damp-related damage, indoor health problems, and failure to meet requirements in terms of energy efficiencies. The purpose of this laboratory study was to examine the significance of water splash, different wind pressures, and different rain loads, as well as combinations of all three, on inward leakage through various gaps in a facade. The study was restricted to seven small or invisible gaps created in a facade element. The results show that the proportion of inward leakage for several gaps was around 2% (0.03 L/min per gap) with an applied rain load equivalent to heavy driving rain on multistory buildings. These figures include conditions where no wind load was present. In cases where there is a risk exist of inward leaking water collecting locally or becoming concentrated inside the wall, the results may be applied as a point load in two-dimensional, or mainly three-dimensional, moisture calculations. The results also indicate significant volumes of inward leakage from water splash alone, meaning that inward leakage in facades may occur every time it rains, regardless of whether the rain is driving rain.
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| 9. |
- Ranefjärd, Oskar, et al.
(author)
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Investigating the Potential of Latent Heat in Hygroscopic Insulating Materials
- 2022
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In: Thermal Performance of the Exterior Envelopes of Whole Buildings XV International Conference. - 2166-8469. - 9781955516280 ; , s. 85-94
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Conference paper (peer-reviewed)abstract
- Energy from buildings accounts for almost 40% of global energy-related carbon emissions. A way to reduce both energy consumption in buildings as well as their environmental impact is to use bio-based insulation materials such as cellulose, wood or hemp fiber insulation. Experiences from modern buildings built with a timber-frame structure and insulated with bio-based materials show that these buildings have lower energy needs in the operational phase than what was initially expected from energy simulation models. However, these experiences have thus far been anecdotal, and they have not yet been validated through measurements. It is common that energy models only focus on thermal properties of materials and thermal flows through the building envelope, without considering moisture loads or hygrothermal behavior of building materials. A relevant difference between bio-based insulation materials and their polystyrene or mineral wool-based counterparts is that the former is more hygroscopic, with a generally high moisture capacity. It is hypothesized that latent heat and moisture transfer from the higher hygroscopicity of bio-based insulation materials could account for the discrepancy between modelled energy needs and measured energy needs in the operational phase. A numerical study was conducted to evaluate the energy performance of materials with varying hygroscopic properties. A numerical model of an exterior wall assembly with hygroscopic insulation materials was created in COMSOL, enabling parameters to be varied, without the manual input commonly required by some other commercial programs. Studied parameters included moisture buffering capacity and insulation thickness. Furthermore, the influence of the indoor and outdoor climate on the hygrothermal performance of the wall assembly was studied. The output evaluated focused primarily on the heat flux through the wall from the interior side. Results of the study showed that there is a potential for energy saving using hygroscopic insulation materials, as their higher moisture capacity could contribute to reduced energy needs for space heating. Results from this study also indicate that latent heat should be evaluated when insulation materials with hygroscopic properties are used in the building envelope, otherwise the energy use from heating could be underestimated.
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| 10. |
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