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Publications

Visible-Light Driven Photochromism of Hexagonal Sodium Tungsten Bronze Nanorods
Authors: Publication Year: 2013

Single-crystalline sodium tungsten bronze (Na-WO3) nanorods with typical diameters of 10−200 nm and lengths of several micrometers were prepared via hydrothermal synthesis. The as-prepared Na-WO3 nanorods crystallized in a hexagonal structure (space group P6/mmm) with unit cell parameters a=7.3166(8) Å and c= 3.8990(8) Å and elongated along the ⟨001⟩direction. Chemical analyses indicated a stoichiometry of Na0.18WO3.09·0.5H2O, revealing the existence of tunnel Na+ ions and water molecules in the structure, as confirmed also by the vibrational spectroscopic study. The as-prepared Na-WO3 nanorods exhibited a direct-allowed electronic transition with band-gap energy of about 2.5 eV, which allows a visible-light-driven photochromism related to…
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Passive House at the crossroads: The past and the present of a voluntary standard that managed to bridge the energy efficiency gap
Authors: Publication Year: 2013

Improving energy efficiency in dwellings is generally seen as the low-hanging fruit of climate change mitigation. In particular decreased heat loss through better insulation is suggested as one of the most cost-effective means to achieve the ambitious national and international goals of climate gas reduction. However, the literature shows that a profitable technological solution is not sufficient to reach the energy goals. Aspects such as a lack of information, unobserved costs, and heterogeneity among users can compromise the success of technical innovation. Still, there are successful concepts that drive the technological development in the construction sector. The Passive House is…
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Engaging complexity: Social Science Approaches to Green Building Design
Authors: Publication Year: 2013

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Solar Radiation Glazing Factors for Windows Panes, Glass structures and Electrochromic Windows in Buildings - Measurement and Calculation
Authors: Publication Year: 2013

Window panes, glass structures and electrochromic windows in buildings may be characterized by a number of solar radiation glazing factors, i.e. ultraviolet solar transmittance, visible solar transmittance, solar transmittance, solar material protection factor, solar skin protection factor, external visible solar reflectance, internal visible solar reflectance, solar reflectance, solar absorbance, emissivity, solar factor and colour rendering factor. Comparison of these solar quantities for different glass fabrications enables one to evaluate and thus select the most appropriate glass material or system for the specific buildings and applications. Measurements and calculations were carried out on various glass materials, including three electrochromic window devices,…
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Framing Transitions
Authors: Publication Year: 2013

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Between Research and Practice: Experts on Implementing Sustainable Construction
Authors: Publication Year: 2013

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Paraotwayite-Type α-Ni(OH)2 Nanowires: Structural, Optical and Electrochemical Properties
Authors: Publication Year: 2013

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Robustness classification of materials, assemblies and buildings
Authors: Publication Year: 2013

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.
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Interior Insulation Retrofit of a Brick Wall Using Vacuum Insulation Panels: Design of a Laboratory Study to Determine the Hygrothermal Effect on Existing Structure and Wooden Beam Ends
Authors: Publication Year: 2013

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Heat pump options for low energy office buildings in cold climate
Authors: Publication Year: 2013

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Navigating standards – constituting engineering practices – how do engineers in consulting environments deal with standards?
Authors: Publication Year: 2013

Standards and regulations can play a central role in policies to achieve environmentally sound and energy-efficient buildings. This paper sets out to explore how consulting engineers relate to standards designed to impose sustainability in the construction of new buildings and in waste management. The paper addresses four cases of engineering practices. The first case describes practical skills and tools involved in what the engineers considered as ‘normal’ practices when performing energy calculations in the development of new buildings. The second and third cases deal with energy in new buildings as well, but address practices that supported or enabled the engineers…
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Frame Stability of Tunnel-Structured Cryptomelane Nanofibers: The Role of Tunnel Cations
Authors: Publication Year: 2013

The role of tunnel K+ ions on the growth and stability of tunnel-structured cryptomelane-type MnO2 nanofibers (denoted as cryptomelane nanofibers hereafter) has been discussed by means of X-ray diffraction and electron microscopy. Cryptomelane nanofibers with typical diameters of 20–80 nm and lengths of 1–6 μm have been synthesized by means of a simple hydrothermal reaction of KMnO4 and MnSO4 aqueous solutions at 140 °C. The growth of cryptomelane nanofibers under hydrothermal conditions follows a dissolution–recrystallization process and involves a morphological transformation from a layered precursor to the tunnel-structured cryptomelane, in which the K+ ions play important roles in templating and…
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Energy Performance Assessment of Advanced Integrated Facades by Means of Synthetic Metrics
Authors: Publication Year: 2013

Façades play an important role in architecture, with deep implications in both the quality of the indoor environment and the appearance of the building. R&D in the field of energy conservation is moving toward advanced integrated façades (AIFs): these are innovative and dynamic façades deeply connected with the building equipment. Their dynamic features allow the energy performance of the façade to be optimized, adapting its behavior to different boundary conditions. The substantial lack of synthetic performance parameters to assess and to characterize the energy performance of AIFs is one of the main limitations to the widespread of these technologies. This…
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A net zero emission concept analysis of a single-family house
Authors: Publication Year: 2014

The paper aims to investigate whether it is possible to achieve a net Zero Emission Building (nZEB) by balancing emissions from the energy used for operation and embodied emissions from materials with those from on-site renewables in the cold climate of Norway. The residential nZEB concept is a so-called all-electric solution where essentially a well-insulated envelope is heated using a heat pump and where photovoltaic panels (PV) production is used to achieve the CO2eq balance. In addition, the main drivers for the emissions are revealed through the CO2eq calculation for a typical Norwegian, single-family house. This concept building provides a…
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Resilience the urban landscape as a social-ecological system
Authors: Publication Year: 2014

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Advanced control of heat pumps for improved flexibility of Net-ZEB towards the grid
Authors: Publication Year: 2014

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Experimental assessment of the energy performance of an advanced responsive multifunctional façade module
Authors: Publication Year: 2014

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Aerogel-Incorporated Concrete: An Experimental Study
Authors: Publication Year: 2014

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Analysis of the air heating in Norwegian passive houses using detailed dynamic simulations
Authors: Publication Year: 2014

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Experimental analysis of the energy performance of a PCM glazing system
Authors: Publication Year: 2014

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Insulating glazing units with silica aerogel granules: The impact of particle size
Authors: Publication Year: 2014

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Experimental analysis of an advanced dynamic glazing prototype integrating PCM and thermotropic layers
Authors: Publication Year: 2014

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Robustness classification of materials, assemblies and buildings
Authors: Publication Year: 2014

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Interior insulation retrofit of a historical brick wall using vacuum insulation panels: Hygrothermal numerical simulations and laboratory investigations
Authors: Publication Year: 2014

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Vacuum Insulation Panel Products: A State-of-the-Art Review and Future Research Pathways
Authors: Publication Year: 2014

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Integration of life cycle assessment in the design of hollow silica nanospheres for thermal insulation applications
Authors: Publication Year: 2014

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A net zero emission concept analysis of a single-family house
Authors: Publication Year: 2014

Published in Journal papers

Zero energy buildings and the rebound effect: A solution to the paradox of energy efficiency?
Authors: Publication Year: 2014

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Lightweight and thermally insulating aerogel glass materials
Authors: Publication Year: 2014

Abstract Glass represents an important and widely used building material, and crucial aspects to be addressed include thermal conductivity, visible light transmittance, and weight for windows with improved energy efficiency. In this work, by sintering monolithic silica aerogel precursors at elevated temperatures, aerogel glass materials were successfully prepared, which were characterized by low thermal conductivity [k ≈ 0.17–0.18 W/(mK)], high visible transparency (Tvis ≈ 91–96 % at 500 nm), low density (ρ ≈ 1.60–1.79 g/cm3), and enhanced mechanical strength (typical elastic modulus Er ≈ 2.0–6.4 GPa). These improved properties were derived from a series of successive gelation and aging steps during the desiccation of silica aerogels. The involved sol → gel → glass transformation was investigated by means…
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Energy performance assessment of an advanced integrated façade through experimental data analysis
Authors: Publication Year: 2014

Abstract This paper deals with the experimental assessment of the energy performance of two Advanced Integrated Façade modules (AIF) characterized by two very similar configurations. The two AIF modules were installed on the south-exposed façade of an outdoor test cell facility (a real-scale mockup of an office building) and continuous measurements were carried out for more than one year. Data collected during the experimental campaign were analyzed to evaluate the energy performance and thermo-physical behaviour of the AIF modules. The performances of the two systems were assessed by comparison and by means of conventional and advanced synthetic metrics. The results…
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Solar shading control strategies in cold climates – heating, cooling demand and daylight availability in office spaces
Authors: Publication Year: 2014

Abstract Modern office buildings often have large glazed areas. Incident solar radiation can lead to large cooling demands during hot periods although the solar radiation can help reduce heating demands during cool periods.Previous studies have shown that large parts of the net energy demand of an office building is related to window heat loss and cooling demands induced by solar irradiance. In this article, the authors found that, even in what traditionally has been considered to be a heating-dominated climate, cooling demands dominate the net energy demand of an office building. Solar shading systems are vital to reduce the cooling…
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Thermal superinsulation for building applications – From concepts to experimental investigations
Authors: Publication Year: 2014

Abstract The application of traditional thermal insulation materials requires thicker building envelopes in order to satisfy the requirements of the emerging zero energy and zero emission buildings. This work summarizes the steps from the state-of-theart thermal insulation materials and solutions, like vacuum insulation panels (VIP), gas-filled panels (GFP) and aerogels which all have various drawbacks, to our concepts and experimental investigations for making superinsulation materials (SIM) like e.g. nano insulation materials (NIM).
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Net-zero buildings: incorporating embodied impacts.
Authors: Publication Year: 2014

Abstract The design and assessment of net-zero buildings commonly focus exclusively on the operational phase, ignoring the embodied environmental impacts over the building life cycle. An analysis is presented on the consequences of integrating embodied impacts into the assessment of the environmental advantageousness of net-zero concepts. Fundamental issues needing consideration in the design process – based on the evaluation of primary energy use and related greenhouse gas emissions – are examined by comparing three net-zero building design and assessment cases: (1) no embodied impacts included, net balance limited to the operation stage only; (2) embodied impacts included but evaluated separately…
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Life cycle analysis of two nZEB concepts
Authors: Publication Year: 2014

Abstract The net-zero emissions building (nZEB) performance is investigated for building operation (EO) and embodied emissions in materials (EE) for Norway's cold climate. nZEB concepts for new residential and office buildings are conceived in order to understand the balance and implications between operational and embodied emissions over the building's life. The main drivers for the CO2 equivalent (CO2e) emissions are revealed for both building concepts through a detailed emissions calculation. The influence of the CO2e factor for electricity is emphasized and it is shown to have significant impact on the temporal evolution of the overall CO2e emissions balance. The results…
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Spectral and angular solar properties of a PCM-filled double glazing unit
Authors: Publication Year: 2015

Abstract: Background Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations.   Methods The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because…
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Review of heat/energy recovery exchangers for use in ZEBs in cold climate countries
Authors: Publication Year: 2014

Abstract Realisation of Zero Energy Buildings (ZEB) for residential use cannot succeed without: minimising leakages, increasing thermal insulation and using reliable and energy efficient system solutions. However, very airtight houses may have a negative impact on thermal comfort and indoor air quality. Focussing on ventilation systems then becomes a requirement. In cold climates, temperature differences between indoor and outdoor air often exceed 40 °C during winter. State-of-the-art heat recovery systems may not be able to handle these differences while providing proper air quality and preventing excessively dry indoor air. The present study of energy recovery systems focuses on apartment buildings located…
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The impact of an ideal dynamic building envelope on the energy performance of low energy office buildings
Authors: Publication Year: 2014

Abstract This paper shows the results of a research activity aimed at assessing the advantages of an ideal adaptive building skin over conventional building envelope systems. The basic idea underlying the research consists in imagining an ideal building envelope system characterised by the capability of continuously changing (within a certain range) some of its thermo-physical and optical properties. The reason for the continuous tuning of thermo-physical and optical properties lies in the assumption that an optimised (fixed) configuration, where the properties do not change over time, is not able to minimise the total energy demand of the building at each…
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Optimization of solar energy potential for buildings in urban areas – a Norwegian case study
Authors: Publication Year: 2014

Abstract The paper presents a case study of an office building with a façade integrated PV system in Norway. Due to the urban surrounding the PV system is subject to significant overshadowing. The aim is to optimize the solar energy potential of the building in order to propose improved alternatives to the current system applying a multi-level simulation approach. The first level is performed to calculate the maximum solar potential on the building envelope in an unobstructed scenario. The second level examines the shading effect on the building in its urban context. The analyses allow localizing the areas of the…
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Case study on residential building renovation and its impact on the energy use and thermal comfort
Authors: Publication Year: 2014

Abstract In Norway, a large portion of the building stock originates from the period from 1955 to 1990. Many of these buildings fail to comply with the current building regulations regarding the energy consumption. In this study, the possibility for upgrading a hypothetical apartment building with an oil-based heating system has been investigated employing simulations from the IDA Indoor Climate and Energy software. For the construction of the original building, customs and regulations from the period 1981-90 were employed, and the building envelope was upgraded to the requirements of the Norwegian research centre on Zero Emission Buildings. Two alternative heating…
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The influence of different electricity-to-emissions conversion factors on the choice of insulation materials
Authors: Publication Year: 2014

Abstract The current practice of building energy upgrade typically uses thick layers of insulation in order to comply with the energy codes. Similarly, the Norwegian national energy codes for residential buildings are moving towards very low U-values for the building envelope. New and more advanced materials, such as vacuum insulation panels (VIPs) and aerogel, have been presented as alternative solutions to commonly used insulation materials. Both aerogel and VIPs offer very high thermal resistance, which is a favourable characteristic in energy upgrading as the same insulation level can be achieved with thinner insulation layers. This paper presents the results of energy…
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Analysis of load match and grid interaction indicators in net zero energy buildings with simulated and monitored data
Authors: Publication Year: 2014

Abstract The main objective of this paper is to contribute to the discussion on the role of Net Zero Energy Buildings (Net ZEBs) on future energy systems by the interplay between on-site generation and the building loads, often called load matching, and the resulting import/export interaction with the surrounding electricity grid, commonly named grid interaction. This investigation analyzes five case studies with high resolution data, three of which are based on real monitored buildings. The research aims at selecting and suggesting a limited set of quantitative indicators that: (a) can provide practical information for building as well as grid designers…
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Analysis of grid interaction indicators in net zero-energy buildings with sub-hourly collected data
Authors: Publication Year: 2015

Abstract This paper aimed to contribute to the discussion about the role of net zero-energy buildings (ZEBs) or nearly ZEBs in future energy systems, from the perspective of the resulting import/export interaction with the surrounding energy grid (commonly named grid interaction (GI)). This investigation analyses three buildings with measured data at sub-hourly time resolution. The goal of this paper was to quantify the effect of using high-resolution data (one or a few minutes) versus hourly resolution in the GI analysis of buildings with an on-site generation system. A limited set of quantitative GI indicators have been selected: the generation multiple,…
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Low-emissivity materials for building applications: a state-of-the-art review and future research perspective
Authors: Publication Year: 2015

Abstract Low-emissivity (low-e) materials can be used in order to reduce energy usage in both opaque and transparent areas of a building. The main focus for low-e materials is to reduce the heat transfer through thermal radiation. Furthermore, low-e materials will also influence on the daylight and total solar radiation energy throughput in windows, the latter one often characterized as the solar heat gain coefficient (SHGC). This work reviews low-e materials and products found on the market, and their possible implementations and benefits when used in buildings. The SHGC is often left out by many countries in energy labellings of…
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Phase Change Materials for Building Applications: A State-of-the-Art review and Future Research Opportunities
Authors: Publication Year: 2015

Abstract Phase change materials (PCM) have received considerable attention over the last decade for use in latent heat thermal storage (LHTS) systems. PCMs give the ability to store passive solar and other heat gains as latent heat within a specific temperature range, leading to a reduction of energy usage, an increase in thermal comfort by smoothing out temperature fluctuations throughout the day and a reduction and/or shift in peak loads. The interest around PCMs has been growing significantly over the last decade. Hence, several commercial products have arrived on the market with various areas of use in building applications. This…
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The legal dwelling: how Norwegian research engineers domesticate construction law. Engineering Studies
Authors: Publication Year: 2015

Abstract The considerable amount of energy spent on the construction, maintenance, and demolition of buildings draws attention to sustainable development in the construction sector. Regarded as both tools and frameworks, laws are expected to sustain and speed technological innovation. With the STS (Science and Technology Studies) theory of domestication and in-depth interviews with building researchers studying zero emission buildings in Norway, I discuss the role of research engineers in the domestication of law, that is, the translation of European Directives for building codes and technical requirements, and the mediation of these legal frameworks for industry and practitioners. I classify two…
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Experimental Investigations of Aerogel-Incorporated Ultra-High Performance Concrete
Authors: Publication Year: 2015

Abstract Improvements to concrete will have a large impact in the construction and building sector. As the attention is drawn towards energy-efficient and zero emission buildings, the thermal properties of concrete will be important. Attempts are being made to decrease the thermal conductivity of concrete composites while retaining as much as possible of the mechanical strength. In this study experimental investigations of aerogel-incorporated mortar (AIM) with up to 80 vol% aerogel are prepared utilizing a reduced ultra-high performance concrete (UHPC) recipe. It was found that at 50 vol% aerogel content, the AIM sample possessed a compressive strength of 20 MPa and a thermal…
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Zero emission building and conversion factors between electricity consumption and emissions of greenhouse gases in a long term perspective
Authors: Publication Year: 2014

Abstract The CO2 emissions from a building’s power system will change over the life time of the building, and this need to be taken into account to verify whether a building is Zero Emission (ZEB) or not. This paper describes how conversion factors between electricity demand and emissions can be calculated for the European power system in a long term perspective through the application of a large scale electricity market model (EMPS). Examples of two types of factors are given: a conversion factor for average emissions per kWh for the whole European power system as well as a marginal factor for…
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Thermal performance of in-between shading systems in multilayer glazing units – Hot-box measurements and numerical simulations
Authors: Publication Year: 2015

Abstract 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…
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Spectral and angular solar properties of a PCM-filled double glazing unit
Authors: Publication Year: 2015

Abstract Background Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations. Methods The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because of…
Published in Journal papers

Influence of the occupant’s behavior on the heating needs and the energy system performance : A case of well-insulated detached houses in the cold climates
Authors: Publication Year: 2015

Abstract Modeling simplification related to occupant’s behavior is a major cause of gap between actual and model’s predicted energy use of buildings. This paper aims to identify those parameters of realistic occupants-related heat gains that actually cause this gap. The investigation therefore, systematically distinguishes the occupant behavior using three behavior parameters, namely: the occupancy behavior, the appliance use behavior and the family size. The effect of these parameters is investigated on a building for two different insulation standards using heat pump as energy supply system. The results identifies the occupancy patterns and the household size as two major parameters that explains a large portion…
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