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District heating and cooling are considered effective solutions to decarbonise the energy use in the building sector. The latest generation of district heating and cooling also increases the potential of integrating heat pumps and chillers in each building substation. The benefits of such integration are the reduction of network temperature and distribution losses; the recovery of waste heat through a bidirectional network; and the decentralised production of heating and cooling. Sizing the network depends mainly on the heat flows between connected buildings. The substation performance and technical installations determine these heat flows. We present in this paper Modelica-based simulations of two design cases for substations. The first design case involves installed heat pump, chiller, and circulation pumps. Alternatively, the second design enables the heat pump to provide direct cooling through a heat exchanger. The models for these installations were developed using the Modelica language to perform continuous-time simulations. The performance in each design case was evaluated in terms of seasonal coefficient of performance and total electric energy use. An analysis on a cluster of 11 buildings suggests that the addition of the direct cooling heat exchanger can save up to 10% of the total annual electric energy use. Additional savings can be achieved by optimising the building supply temperatures and the district network temperature.

In past years, Sweden has been facing a rapid growth of photovoltaic cells, and the total PV installation capacity increased from 300 kW to 1090 MW (2006–2020). The increased number of PV users was a result of active support from the Swedish government with an aim of achieving multiple sustainable goals regarding renewable energy. This project evaluates the profitability of shared PV systems in communities of different sizes in Sweden. This study aimed to contribute to the literature by filling the research gap of presenting the financial benefits at different community scales. The electricity use profiles consisted of hourly measured electricity use that was derived from 1067 individual Swedish apartments. The profiles were then used to create multi-scaled communities with shared PV systems. The mid-market price model was implemented to simulate electricity trading among prosumers in the community using Visual Basic Applications (VBA) in MS Excel. Further, the electricity costs were used for Life Cycle Cost (LCC) assessment. To demonstrate the increase in profitability, the LCC results of households with shared PV systems were compared to households that own PV individually and households that do not own a PV system. The evaluation showed the financial benefits of shared PV systems in comparison with individually owned PV systems. This study also demonstrated the increase in profitability and the reduction in payback time for the average household if sharing a PV system as part of a larger community.

Renovating and improving the current building stock is a matter of both need and importance. In order to know if the implemented renovation measure has had an impact on the building as a system it is important to verify the impact through measurements. The aim of this project is to isolate the impact of a measure on the energy efficiency of a building as well as the indoor environmental quality. This, through detailed measurements that enable the exclusion of the impact of other factors that might affect the energy use. For this reason a mechanical ventilation system with heat recovery was installed in two apartment buildings and measurements were conducted before and after installation. Measurements were also conducted in two almost identical reference buildings, that were used as a control group for the experiment. Together with acquired data for the surrounding climate, measurements were conducted on 1) the district heat carriers to and from the buildings, 2) the temperature and relative humidity in the apartments, 3) the global horizontal radiation on site, and 4) the temperature outdoors. A survey was also conducted with the inhabitants for the assessment of the impact on the perceived indoor environmental quality. Correcting for the outdoor temperature only, a yearly reduction by 22% and 24% is achieved in the affected buildings. Changes in the global horizontal radiation clearly impact the results, however, can not be corrected for. By using the control group as a reference, further corrections can be made and the energy reduction might be determined to 15% and 34%, instead of 22% and 24% respectively.

During the last few years, there has been an increased number of overcrowded apartments, due to increased migration but also housing shortage in general, particularly in the suburbs to major cities. The question is how the indoor environment in these apartments is affected by the high number of persons and how the problems related to high residential density can be overcome. This paper aims to specify the problem by investigating and analysing the technical parameters influenced by residential density in Swedish apartments built between 1965-1974. To map the situation, 11 interviews with employees at housing companies were conducted. Based on extreme conditions described in the interviews, simulations of the indoor climate and moisture risks at some vulnerable parts of constructions were made. Simulations were focused on moisture loads and CO2 concentrations as functions of residential density and ventilation rate. Finally, measures to combat problems associated to overcrowding are suggested. The aim is that the results should be used by authorities to formulate incentives and/or recommendations for housing companies to take actions to ensure a good indoor environment for all, irrespective of residential density conditions.

When looking at energy supply on a larger scale than to a single building, such as to a neighbourhood or a city, the combined effects of peak power demands can be seen to cause problems on the production side. These can be both economic and environmental and lead to the emission of greenhouse gases when fossil fuels are used to meet these peaks. Encouraging the demand side to reduce their power demands at these time could be one way of dealing with this issue. This paper investigates the temperature drops after a power cut both through measurements in the field and comparisons of these results to simulations. A single-family dwelling in use and a multi-family dwelling about to be decommissioned were studied. The comparisons showed that the rates of the temperature drops in reality were slower than in the simulation models. A parametric study of the variables affecting the temperature drops, such as furniture, showed that they might explain these differences.

Apartments built in Sweden during the record years 1961–1975 with the aim to remedy thehousing shortage and abolish poor standards, were designed for a normal-sized family of 2–4 persons.The mechanical ventilation system, if existing, was primarily designed to ensure an air exchange inthe apartment according to Swedish building regulations. During the last few years, the number ofovercrowded apartments has increased due to housing shortage in general but also due to migration.Another aspect is that the ventilation in many apartments built during the record years is alreadyinsucient at normal occupant load. The question is how doubling or tripling the number ofoccupants and thus, the moisture load will aect the risk of bad air quality and moisture damage.To find out, simulations were made to estimate whether it is possible to obtain sucient air qualityand low risk of moisture damage by only increasing the ventilation rates in existing systems orintroducing new ventilation systems with and without heat recovery and what the consequencewould be in terms of the additional energy demand. Measurements from earlier studies of CO2 andmoisture supply in Swedish apartment buildings were used as input data. (This article belongs to the Special Issue Energy and Technical Building Systems - Scientific and Technological Advances)

District heating and cooling systems have evolved through several development stages in order to improve their energy efficiency. The latest development reached the fifth generation where customers can be producers and/or consumers of thermal energy flows towards the network. The variety and complexity of system configurations and interactions between connected customers poses a challenge in adopting a suitable modeling paradigm capable of simulating each design case. Modelica language and the Functional Mock-up Interface standard are computational tools opted by the International Energy Agency for simulating building and community energy systems. This work aims to analyze the current status in literature where these tools are utilized in building and energy simulation with focus on district heating and cooling systems. Bibliographic maps and networks are presented to analyze the literature based on different bibliometrics. Among others, the analysis shows that coupled simulation between district and building energy models is a novel research area and can benefit in reducing the oversizing of space heating and cooling systems. In addition, the analysis demonstrates that the fifth generation district heating and cooling systems require advanced control strategies. These strategies need accurate and upfront specifications to decide a proper control strategy for each design case.

Literature and experience show that the differences between calculated and measured building energy performance still exist. The literature shows that user-related parameters are significant with regard to energy performance in low-energy buildings and this means that the choice of parameters is one of the main factors leading to this difference. However, the parameters themselves are associated with uncertainty when predicting and calculating their effects. One of the identified research gaps is the lack of data on behavioral energy use and profiles. The aim of this study is to provide relevant feedback, which will help the building industry and research communities to predict more accurately the user-related impacts on energy performance and, subsequently, enable reduction of the differences between calculated and measured energy performance. This article analyses measured user-related parameters and building energy usage in seven recently built low-energy schools in Sweden. Regression analysis is applied when analysing the parameters and their influence on energy usage. With the help of the measurements carried out, all the studied schools were determined to be low-energy schools. The results show differences between calculated and measured building energy performances in the studied schools and these vary from –44 to +28%. At least 33% of measured energy usage depends on the user-related parameters. Ventilation rates and running times as well as space heating set points were found to be the user-related parameters that have the most significant effects on total energy usage. Finally, some important recommendations for good building operation practice and measurement methodology are presented.

Heritage buildings are usually culturally protected as well as naturally ventilated. With natural ventilation it is difficult to control the airflow, which depends on the temperature outdoors as well as the wind. This causes issues with the thermal comfort and the indoor air quality. In this study, status determinations were conducted for 12 heritage buildings with offices, across Sweden. Field measurements on temperature, relative humidity, CO2, and air change rates in the indoor climate, together with a questionnaire with the occupants, confirmed these issues in these buildings. In addition, for two of the buildings, field measurements were used together with building energy performance simulations in order to determine the impact of two different non-invasive ventilation measures on the indoor environmental quality and the energy use. A mechanical ventilation system with heat recovery, hidden inside a chimneypot, was shown to reduce CO2 concentrations and potentially reduce the energy use by up to 39 kWh∙m−2 (or 47%). Dampers for the reduction of the ACRs after-hours, installed in the pathways for the natural airflow through chimneypots, were shown to potentially reduce the energy use by up to 16 kWh∙m−2 (or 12%).

In order to calculate building energy usage, apart from the technical characteristics, user related factors needs to be determined. Unless the user related factors are determined by specific project, the idea is to apply a standardized list of input data for a normal operation during a normal year, so the calculated energy value does not depend on variation of these factors. Such list was issued by Boverket (The Swedish National Board of Housing, Building and Planning) in a document named BEN1 in 2016, and updated in BEN2 in 2017. A disadvantage of this list is that, the part about schools is based on references that are rather older and sparse and needs to be updated. This paper investigates the user related input data in 10 newly built low energy schools in Sweden and compares those to BEN2. It also compares the schools’ calculated energy performance to the BBR25 requirement, the latest national building codes and recommendations. The schools are investigated in this research as there is a demand for about 1000 elementary schools to be built in Sweden in the coming 10 years. The paper shows significant user related effect to energy usage and importance for the standardized user related input data for energy calculations. Future research aims to verify these calculations and user related input data with measured data for the chosen schools.

As requirements regarding energy efficiency are getting tougher, buildings in the arctic, as well as the rest of the world, need to be more energy efficient without compromising a good indoor climate. This article presents measured moisture supply and occupancy level in a Swedish arctic multi-family apartment block. Measurements were done over 1 year every 30 minutes in a building consisting of 51 apartments located in Kiruna, at latitude 67.9°. Averages and typical variations on different timescales, year and day, are presented for the different parameters, as well as correlations between the parameters; for example, moisture supply as a function of occupancy level. The results can be used when input data for simulations of energy use, moisture conditions and indoor climate are chosen, as well as a reference to compare measurements to during verifications. In energy efficient buildings, occupant behavior generally has an extensive impact on building performance, which means that the characteristics of be...

Low energy buildings are usually characterized by a very well insulated building envelope and an efficient ventilation system that makes use of the heat in the exhaust air. Internal heat gains from residents and their use of appliances can cover the heating demand to a certain extent. The magnitude of internal heat gains that cover demand are often modelled in a simplified way and thus can be associated with a large uncertainty. Hourly measurements of household electricity use in over 1000 apartments over a year, serves as a foundation for this study. These measurements show a large variation between households with regard to the annual electricity-use. Furthermore, each measurement series representing the unique behaviour in an apartment, shows a variation in household electricity use over time. Through Monte Carlo simulations that use the measurements as stochastic input, this study shows that heating energy demand can vary by up to 50% due to the different habits of residents in a building. This study also shows that the detail at which internal heat gains are modelled is not negligible regarding relative impact on energy and power demands for low-energy buildings. Reducing the resolution of the measurements from hourly to monthly means neglects important variations in the data, which in turn underestimates the heating power-demand.

Within a period of ten years a large number of schools need to be built in Sweden and these new schools need to be nearly zero energy buildings. School classrooms are required to provide healthy learning environments to help children perceive and process information. This means that classrooms must provide adequate levels of indoor air quality and thermal comfort. This article investigates CO2 concentration levels and indoor air temperatures in several recently built, low-energy schools in Sweden, and compares them with design criteria stipulated in specific international standards and Swedish regulations to provide feedback to the building construction industry. Field measurements of CO2 concentrations, indoor air temperatures and ventilation rates in seven low-energy schools, with a total of 145 classrooms, taken during several months spanning both summer and winter periods, are analysed in this article. All the schools in the study have mechanical supply and exhaust ventilation systems with demand control devices in the classrooms. The study shows that all the classrooms, in general, comply with the design criteria regarding indoor air temperatures and CO2 concentrations in EN15251, ASHRAE 62.1 and the Swedish national regulations and recommendations. Median values of indoor air temperatures were between 19 and 23.5 °C in all classrooms during school hours. The 90-percentile levels of CO2 concentrations were below 1000 ppm in 60 of 61 classrooms in which these measurements could take place. It is concluded that during this long-term measurements in the studied seven low-energy schools, modern HVAC systems with demand control and heat recovery, in general, provided satisfactory indoor climates in terms of CO2 levels and indoor air temperatures. (Less)

The occupancy level of dwellings is an important parameter to know to determine the energy efficiency, energy use and indoor air quality, especially in low-energy buildings where the user-related energy uses, such as household electricity and domestic hot water heating, are significant parts of the energy balance in a building. For residential buildings, there is a lack of occupancy level data, which also needs to be resolved over time, in a way so that both short term and long term variations can be described. As a part of an ongoing study, occupancy levels were measured as building average levels in 18 apartment buildings containing 342 apartments in total with readings every 30 min for more than a year. Averages and standard deviations of occupancy level, and variation in occupancy during the year, week and day respectively are presented. The results show a highly varying occupancy level over time, which indicates the potential of demand controlled ventilation in dwellings. (C) 2011 Elsevier B.V. All rights reserved.

The use of household electricity and domestic hot water has been measured for 72 apartments in an apartment building located in the south of Sweden. The measurements were carried out with samples every 6 s, a tenfold increase in resolution compared to available published data, during a measurement period of five days, in the winter season, including a weekend. The influence of the time resolution on the distribution of data was analysed by integrating the 6 s data to represent longer logging intervals. Extreme values, especially the high values, are shown to be reduced if the time interval is increased. The maximum household electric power was 50% higher at a 6 s resolution compared to 60 s and the corresponding difference for domestic hot water flow was 40%. Daily variations has to be considered for photovoltaic installations and solar thermal collectors, energy simulations of buildings need at least hourly data and all kind of power design in a building or its services benefits from much more resolved data. (C) 2011 Elsevier Ltd. All rights reserved. (Less)

Windows of a building is generally known to increase the use of energy if the lighting system is not carefully co-designed with window and solar shading system. Usually, it is not, and the window acts as a piece of wall with lack of insulation most of the year and as a heat gain raiser part of the year, usually increasing both annual heating and cooling energy use. If it is assumed that a certain window area is the case, due to architectural reasons or other, it is not an alternative to change the window area. Solar shading can be used to decrease the cooling power demand and energy use but that also reduces the possible benefit for heating with the solar gain. The apparent solution is to shade when there is a cooling need and gain when there is a heating need. This paper presents measured data and energy use calculations on such a system set up in an office in southern Sweden. The result shows that the energy use can be reduced remarkably compared to a case with fixed solar shading.