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In order to reduce CO2-emissions it is necessary to reduce the energy use in the existing building stock significantly. Gadehavegard – a social housing built-up area consisting of 19 similar blocks of flats with nearly 1000 dwellings situated in Denmark – needed renovation and therefore a block was selected for testing an ambitious renovation that would result in a significant reduction in energy use and CO2 emissions. The ambition was to reach the German Passivhaus standard for the building, i.e. a very strict requirement, especially for a renovation project. The renovation included insulating the facades from the outside, replacing all windows, insulating the roof, installing decentralized mechanical ventilation systems with efficient heat recovery and a photovoltaic system on the roof. In addition, the balconies were included in the apartments by installing foldable glass facades. This paper gives a detailed description of the renovation project along with measurements of the energy use and indoor climate before and after renovation. Comparing the achieved results to the Passivhaus requirements show that the original goal is not achieved, however, the building fulfils the less strict requirements of the Passivhaus renovation certification EnerPHit and is still a very good example on how significant reductions in energy use can be achieved for these types of buildings. Results before and after renovation are compared using the energy signature and shows that heating energy consumption has been reduced by more than 50% even though indoor temperature on average has increased from 21.7 °C to 23.3 °C.

Under current rules in the Danish Meter Order at least 40% of the total heating costs in multi-story blocks of flats should be distributed by metering the consumption in individual apartments. This fixed share is the result of a previous study that showed that 40% of the total heating costs were used for space heating, 35% for production and heat loss associated with hot water consumption and finally 25% of heat losses in the heating system. It is interesting to investigate whether this distribution remains representative in both existing buildings, where older buildings still dominate, as in newer and future standard of blocks of flats. Intuitively, we would like to settle 100% of the costs attributable to space heating, by individual meters. Thereby, tenants will pay for their own consumption which encourages energy savings. This is an excellent method for electricity, gas and water but for heating it is a much more complex issue. For instance, if a pensioner wants or needs a higher indoor temperature the expenses will become disproportionate due to heat transmission through internal walls, floors and ceilings. This is particularly pronounced in well-insulated buildings where the heat loss to the outdoor climate constitutes only a small proportion of the total heating consumption. It is therefore interesting to investigate the consequences for the distribution of heating costs by differentiated indoor temperatures in both older and new multi-story apartment buildings. This paper describes an analysis of the possibilities regarding individual metering and fair distribution of heating costs in multi-story apartment buildings. The overall conclusion of the analysis is that there are several significant problems related to this issue, and it becomes even more complicated when space heating only accounts for 30% in new buildings (2010 requirement) and 5-10% in future buildings (2020 requirement).

The aim of this paper is to present two Danish typologies for residential buildings developed in the EU-financed project TABULA. The building typologies focus on energy performance and can be used in the analyses of, e.g., political strategies for planning the future upgrading of the energy performance of the residential building stock. Overall, the typologies consist of two types of building models—real example models and average designed models. The main purpose of developing the building typologies was to establish a tool able to calculate different energy-saving scenarios for the entire residential building stock. To make such calculations of scenarios, similar average designed building models were established based on extracted average values from the Danish Energy Performance Certification Scheme database. The two building typologies had the same overall composition, i.e., three main building types: single-family houses, terraced houses and blocks of flats. Each main building type is presented for nine periods representing age, typical building tradition and insulation levels. Finally, an energy balance model of the residential building stock was devised to validate the average designed building models. Compared with the official statistics on energy consumption in Denmark 2010, the results showed a difference below 4%.

Energy labels have generally received positive response from consumers and have moved the market for white goods and cars in the direction of more energy-efficient products. On the real estate market, it was expected that an energy label, rating the energy performance of a property based on a national energy performance certificate (EPC) might receive similar response. However, in Denmark no response to the energy performance rating was observed for 15 years. This was a surprise considering that Denmark was the first country to implement an A to G rating of the energy performance of buildings. A statistical examination of data on property sales prices and energy performance ratings was carried out. All relevant property transaction data from 2007 till 2012 were examined and they showed that energy performance ratings had an impact on property sales prices. However, before June 2010, the impact was modest, whereas after June 2010 the impact of energy performance ratings on property sales prices increased significantly as a result of an EU requirement to display the energy performance rating in connection with property sales. On this background, it was concluded that a public display of the energy performance rating is fundamental for market response.

SBi-anvisning 266, Småhuse - indeklima og energi, omhandler generelle krav og anbefalinger til indeklima, energiforbrug og tilknyttede installationer i nybyggede småhuse i henhold til Bygningsreglement 2015 (BR15). Anvisningen indgår i en serie af SBi-anvisninger om småhuse. Småhuse omfatter fritliggende og sammenbyggede enfamiliehuse med lodret lejlighedsskel i indtil to etager samt eventuelt kælder. Det omfatter også kæde- og rækkehuse samt sommerhuse. Målgruppen for SBi-anvisning 266 er projekterende arkitekter, ingeniører samt udførende og tilsynsførende. Anvisningen kan desuden anvendes af den kommende bygningsejer og som lærebog ved byggetekniske uddannelser.

The aim of this article is to present and discuss the experience gained from a low-energy house in Sisimiut, Greenland, over the 5 years of operation since its inauguration in April 2005. The house was designed to test and present new low-energy technologies in the Arctic climate and to improve sustainability in Greenlandic buildings. The article presents some measurements, analyses, and comparisons of theoretical simulations and some steps that were taken to improve the house with impacts on energy consumption. The results include energy consumption, temperatures, and solar heating production. Also presented are the results of several investigations carried out in the house, such as blower-door tests and inspection of the ventilation system. The initial target for the heating demand of the house was that it should be restricted to 80 kWh/(m2·a), but in reality it has varied over the past 5 years from 139 to 150 kWh/(m2·a). Currently the house is on the way to presenting a good energy solution, ...

This paper aims to present an economic overview of the opportunities for energy renovation of single-family houses in Denmark financed over the long term. The paper focuses on the economic difference between energy savings and the repayment of investment. Taking out the average remaining 20% equity in long-term property mortgage loans and utilising it for extensive energy renovation improves both the economy and the extent of included measures. Approximately 30% of energy consumption in Denmark is used for space heating. The existing 1 million single-family houses account for approximately half of this, thus making energy renovation a key factor for the reduction of CO2 emissions. The conclusions were that in average the possible budget for renovation varied between €20,000 and 40,000 per single-family house. The equity of the house was particularly dependant on geographical location and construction period. Different energy renovation measures were analysed in terms of economy showing that a wide range of specific measures had a positive economic balance for the homeowner from year 1. The economic balance between saved energy and repayment of the investment is however very dependent on the assumed future energy price. An example showed that a typical house from 1925, still in its original form, could yield annual savings for the homeowner of approximately €2600, assuming a future energy price of 0.2 €/kW h. At the current energy price level of 0.1 €/kW h energy renovation in general is almost economically neutral for the homeowner.

Using mechanical ventilation with highly efficient heat-recovery in northern European or arctic climates is a very efficient way of reducing the energy use for heating in buildings. However, it also presents a series of problems concerning condensation and frost formation in the heat-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes into account the effects of condensation and frost formation. The model is developed as an Excel spreadsheet, and specific results are compared with laboratory measurements. As an example, the model is used to determine the most energy-efficient control strategy for a specific heat-exchanger under northern European and arctic climate conditions.

In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure drop. Preheating the inlet air (outdoor air) to a temperature above 0 °C before it enters the exchanger is one solution often used to solve the problem, however, this method reduces the energy saving potential significantly. To minimize the energy cost, a more efficient way to solve the freezing problem is therefore desirable. In this paper, the construction and test measurements of a new counter flow heat exchanger designed for cold climates are presented. The developed heat exchanger is capable of continuously defrosting itself without using supplementary heating. Other advantages of the developed heat exchanger are low pressure loss, cheap materials and a simple construction. The disadvantage is that the exchanger is big compared with other heat exchangers. In this paper, the new heat exchanger's efficiency is calculated theoretically and measured experimentally. The experiment shows that the heat exchanger is capable of continuously defrosting itself at outside air temperatures well below the freezing point while still maintaining a very high efficiency. Further analysis and development of a detailed simulation model of a counter flow air-to-air heat exchanger will be described in future articles.

This paper focuses on the indoor climate in new Danish low-energy houses and discusses the issue of overheating in relation to evaluation methods and user satisfaction. The user satisfaction has been evaluated among 370 owners of new low-energy class 2015 detached single-family houses based on a questionnaire survey. The survey evaluated overall satisfaction, and more specifically satisfaction with the indoor climate parameters temperature, draught, air quality, noise and daylight, and also technical installations of the house. The survey showed satisfaction with living in new low-energy houses and more than 90% perceived the indoor environment as satisfactory both in summer and winter. The majority perceived the various indoor climate parameters to be better in their new low-energy house compared to conditions in their former house. Compared with earlier studies on previous generations of low-energy houses, problems with overheating seem to have decreased, as only 12% found temperature conditions to be unsatisfactory in summer.

A study has been conducted analysing the energy savings for space heating and domestic hot water in the Danish building stock due to renovation of building components at the end of their service life. The purpose of the study was to estimate the energy savings until 2050 as building components are energy upgraded according to the requirements stipulated in the Danish Building Regulations 2010. Furthermore, scenario analyses was made for the potential impact on the energy consumption of introducing different levels of tightening of the energy requirements for existing buildings in the Danish Building Regulations.Compliance with the requirements in the Danish Building Regulations will potentially result in energy savings for space heating and domestic hot water around 30 % until 2050. Further tightening of the component insulation level requirements will only result in marginally higher savings, due to the level of the current requirements. Higher energy savings can, though, be achieved e.g. by setting requirements for balanced mechanical ventilation with heat recovery and use of solar heating for domestic hot water. A study has been conducted analysing the energy savings for space heating and domestic hot water in the Danish building stock due to renovation of building components at the end of their service life. The purpose of the study was to estimate the energy savings until 2050 as building components are energy upgraded according to the requirements stipulated in the Danish Building Regulations 2010. Furthermore, scenario analyses was made for the potential impact on the energy consumption of introducing different levels of tightening of the energy requirements for existing buildings in the Danish Building Regulations.Compliance with the requirements in the Danish Building Regulations will potentially result in energy savings for space heating and domestic hot water around 30 % until 2050. Further tightening of the component insulation level requirements will only result in marginally higher savings, due to the level of the current requirements. Higher energy savings can, though, be achievede.g. by setting requirements for balanced mechanical ventilation with heat recovery and use of solar heating for domestic hot water.

En undersøgelse udført af Statens Byggeforskningsinstitut (SBi) viser, at jo bedreenergimærke et enfamiliehus har, jo højere en kvadratmeterpris opnår huset ved salg. Samtidig viser undersøgelsen, at energimærket har haft stigende indflydelse på salgspriserne, især siden 2010 hvor det blev et lovkrav, at salgsannoncer skal indeholde husets energimærke.

In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements on a prototype heat exchanger for cold climates.

This paper presents three different low energy windows for residential buildings which have been developed at the Technical University of Denmark during the last 8 years. The three windows are designed to maximize the net energy gain. The net energy gain of windows is the solar gain minus the heat loss integrated over the heating season. The solar gain can be calculated for one orientation or averaged over different orientations representing a standard house. Calculation of the net energy gain assumes that all of the solar gain from the windows can be utilized for space heating during the heating season in residential buildings. Problems with overheating in the summer period must be solved with overhang or moveable solar shading devices. To increase the net energy gain slim frame profiles have been developed to increase the glazing area and thereby the solar gain. The challenge when developing slim frame profiles is to make enough space for hinges and fasteners and still maintaining the functionality and strength of the window. Proposals for new hinges and alternative mounting method for windows are also presented in this paper. The first window constructed was made of wood profiles and a low energy double glazing unit. The other two windows were made of fiber-reinforced plastic (plastic reinforced by fine fibers made of glass). This composite material is a weatherproof material with very low thermal conductivity and high mechanical strength. These properties make the material very suitable for frame profiles due to lower heat loss and longer durability of the window. The glazing in these fiber reinforced polyester windows is both unsealed and sealed triple glazing units. The paper also presents the results of a U-value measurement of one of the fiber-reinforced plastic windows which confirms the thermal calculations. The measurement showed a U-value of 1.03 W/m²K for a window in standard size (1480 mm • 1230). The net energy gain for a standard single-light window in Denmark is approximately minus 40-50 kWh/m² per year. The windows presented in this paper have a positive net energy gain of 0 - 20 kWh/m² per year.

In 2005 a low-energy building was inaugurated in Sisimiut, Greenland, just 50 km north of the Arctic Circle. The 200 m2 building was supposed to be a building with an energy consumption for heating of only half of the maximum permissible according to requirements of new Greenlandic Building Regulations. Thus, the target heating consumption was set to 80 kWh/(m2∙year). The low energy feature was accomplished by using well insulated structures without cold bridges, a ventilation system with heat recovery, advanced windows and a solar heating system. In addition, it was an ambition that the indoor climate should be comfortable and healthy, and the highly insulated structures should remain free from moisture problems. Since its invention the building has functioned, in one half, as residence of a Greenlandic family, and as an exhibition in the other half. The building has been instrumented with sensors and a data logging system that measure the energy performance of the various parts of the system, and sensors for detection of moisture conditions in the building envelope and in the indoor environment. The energy performance data can be followed on the Internet on a day to day basis. The paper will present the house and the experiences from the first two years of its operation. An account will be given of the measured energy performance data. Some of the equipment did not function completely as anticipated, but some corrective measures are described, and the most significant challenges are discussed.

In 2005 the Danish Building regulations introduced two low energy classes for buildings in addition to revised minimum requirements. The low energy class 1 and low energy class 2 correspond to total energy use, i.e. energy use for heating, ventilation, cooling and domestic hot water, as 50% and 75% of the minimum requirement respectively. The main purpose of introducing the low energy classes were to further support and encourage the development of low energy buildings. In 2010 it is expected that demands in the Building Regulations are tightened by 25-30% and in 2015 it is expected that the minimum demand will correspond to the low energy class 1 demands of today. In order to secure this development in the demands, it is essential to demonstrate that the goal is well within reach of the Danish building industry. This paper describes the development of a low energy class 1 type house. The house is based on a standard type house, and through an optimisation process of the building constructions and heating and ventilation systems, the total energy consumption for the type house has been reduced in order to meet the low energy class 1 demands. The paper describes the development of the house along with detailed calculations of the energy consumption and indoor climate.

In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Often the low exterior air temperature results in condensation and freezing in the heat exchanger and defrosting strategies have to be employed. In order to investigate different design options and defrosting strategies there is a need for a dynamic model that takes into account condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements on a prototype heat exchanger for cold climates.

In 2005 the Danish Building regulations introduced two low energy classes for buildings in addition to tightened minimum requirements. The low energy class 1 and low energy class 2 correspond to total energy use, i.e. energy use for heating, ventilation, cooling and domestic hot water, as 50% and 75% of the minimum requirement respectively. The main purpose of introducing the low energy classes were to further support and encourage the development of low energy buildings in Denmark.In 2010 it is expected that demands in the Building Regulations are tightened by 25-30% and in 2015 it is expected that the minimum demand will correspond to the low energy class 1 demands of today. In order to secure this development in the building regulations, it is essential to support the development of low energy solutions and demonstrate that the goal is well within reach of the Danish building industry.This paper describes the development of a low energy class 1 typehouse. The house is based on a standard typehouse, and through an optimization process of the building constructions and heating and ventilation systems, the total energy use for the typehouse has been reduced in order to meet the low energy class 1 demands. The paper describes the original typehouse solution, optimization process and detailed simulations of the energy use and indoor climate of the optimized solution.

This paper presents a two-dimensional simulation model of the heat losses and temperatures in a slab on grade floor with floor heating which is able to dynamically model the floor heating system. The aim of this work is to be able to model, in detail, the influence from the floor construction and foundation on the performance of the floor heating system. The ground-coupled floor heating model is validated against measurements from a single-family house. The simulation model is coupled to a whole-building energy simulation model with inclusion of heat losses and heat supply to the room above the floor. This model can be used to design energy efficient houses with floor heating focusing on the heat loss through the floor construction and foundation. It is found that it is important to model the dynamics of the floor heating system to find the correct heat loss to the ground, and further, that the foundation has a large impact on the energy consumption of buildings heated by floor heating. Consequently, this detail should be in focus when designing houses with floor heating.