Research papers

The report looks closely at the ventilation and thermal environment of Active Houses, covering the benefits and what still needs to be improved. The paper reports that Active Houses have better airtightness than what is nationally required, that the indoor air quality is of a high standard regardless of the type of ventilation system installed, that thermal comfort can be achieved with generous daylight conditions and that natural ventilation and dynamic solar shading must be applied to avoid overheating. However, work still needs to be done - the current methods in standards and legislation that are used to determine the performance of ventilative cooling need to be improved and affordable, intuitive and simple control systems for residential hybrid ventilation and dynamic solar shading are needed.

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Although energy efficiency is certainly important when building a sustainable building, this report argues that we need a more holistic approach early on in the design process. As people spend 80-90% of their time indoors, there also needs to be a strong focus on the indoor environment and consequently the health of the occupants. The VELUX Group's Active House vision adopts this holistic approach and the paper presents a number of projects, detailing the design process and how daylight levels and indoor climates can be optimised.

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This paper is a first hand account from the project managers of VELUX Group's six model Active Houses, a collection of houses in five European countries which are energy efficient, eco-friendly and have good indoor environments. The paper details how best to run an Active House, covering how to design the home, how to run the heating and cooling systems, how to manage hybrid ventilation systems, how to ensure a steady flow of sunlight but protect against overheating, and how to manage the technical control systems.

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This paper describes a proposal for a daylight standard for CEN countries. It is now widely accepted in the research community, and increasingly so amongst practitioners, that the standards/guidelines for daylight in buildings are in need of upgrading. The essence of the proposal is that the `target' for daylight provision should be founded on the availability of daylight as determined from climate. The method, founded on cumulative di use illuminance curves, could be introduced relatively swiftly since it requires only modest enhancement of existing daylight prediction tools.

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Attempts to advance standards for measuring daylight in buildings beyond the daylight factor (DF) have, so far, met with limited success. One reason is that it often appears to be impossible to advance the DF methodology by incremental means. It is now widely acknowledged that climate-based daylighting modelling (CBDM) offers the means to make a major advancement in the evaluation of daylight in buildings. Whilst metrics founded on CBDM will almost certainly form the basis for daylight standards in the medium term, there is a pressing need to progress current practice in the short term. Here, the authors propose that a long-overlooked method linking the estimation of daylight provision to prevailing climate be used as the basis for guidelines and standards.

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This study uses a domestic dwelling as the setting to investigate and explore the applicability of daylighting metrics for residential buildings. In addition to provision of daylighting and the potential for reducing electric lighting usage, we also investigate the formulation of metrics for non-visual elements such as regulation of the circadian system.

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It is generally agreed that any metric(s) to replace the daylight factor should be founded on climate-based daylight modelling (CBDM). In this paper we examine the relationship between the predicted annual occurrence of glare and one of the candidate CBDM metrics that has been proposed, called useful daylight illuminance (UDI). The setting is a residential building which we use as a ‘virtual laboratory’ in two design configurations, each evaluated under all 32 combinations of 8 European climates and 4 building orientations.

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The use of complex building simulation tools is less common in the design of residential buildings than it is for commercial buildings. Tools that allow quick evaluations of residential buildings with regards to indoor environmental quality exist, but these rarely use the dynamic simulations necessary for evaluating the performance of natural ventilation and solar shading, and rarely offer the possibility to visualize the appearance of daylight in the room. The Daylight Visualizer and Energy and Indoor Climate Visualizer are free simulation tools with a simple and intuitive user interface permitting quick evaluation of residential buildings.

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The Energy and Indoor Climate Visualizer is a tool that allows users to create detailed thermal and airflow models in order to help in the holistic design of sustainable residential buildings. It has a fast, simple and intuitive user interface and results in a single, printable report which summarises all main results on energy, air quality and thermal comfort.

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The energy performance of two hybrid residential ventilation systems is investigated and compared to an all-mechanical system, with hybrid systems under manual and automatic control. Three different climates were investigated (Helsinki, Berlin and Paris). Results show that the energy demand of the hybrid systems is less than the all-mechanical system, with the automatic control showing larger efficiency potential. Natural ventilation is more energy efficient than mechanical ventilation for much of the year. As the legislation on energy demands is tightened, so automatic hybrid ventilation control becomes increasingly attractive.

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It is well known that sleep affects your health and that it impacts your performance at work and school. This paper focuses on how the physical environment, the thermal conditions and indoor quality affect your sleep. It also reports that room temperature above thermoneutrality influences sleep quality in the sense that slow-wave sleep, REM-sleep and total sleep time are reduced. The report concludes that there is a distinct lack of studies on air quality and sleep and calls for more research.

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Medical research indicates that humans need higher levels of light in order to ensure long-term beneficial health effects. This study looks at typical daylight levels in European houses and evaluates the electricity consumption required to reach ideal light levels with artificial lighting. The study shows that windows are efficient low-energy light sources.

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The discovery of intrinsically photoreceptive retinal ganglion cells (ipRGCs) in 2001 was a great leap forward in photobiology, and ignited strong interest in the possibility of using light exposure to improve health and well-being. CIE in 2004 promulgated five “principles of healthy lighting”, and proposed that these principles should lead to a renewed emphasis on architectural daylighting. This review focuses on application in residential buildings. This paper briefly reports on the review and summarizes the research questions that we think are most urgently in need of answers.

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This paper explores the Model Home 2020 project, six sustainable demo buildings across Europe, and how sustainable living can be achieved in an indoor environment that prioritises natural living conditions. It touches upon the aim to recreate the nurturing properties of an outdoor experience without compromising basic needs for heat and shelter. Findings from the post occupancy evaluations and monitoring of the model homes confirm that access to more daylight and fresh air has a positive impact on the inhabitants’ wellbeing and even a direct beneficial effect on asthma and allergies.

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This report details the post-occupancy evaluation of five families in Germany, Austria, France and the UK living for a year in the Model Home 2020, an experiment launched by the VELUX Group to contribute actively to the development of sustainable buildings of the future. The survey was carried out seasonally during the year and the questionnaire covered energy consumption and production, indoor climate and air quality, daylight and electric lighting, house automation and sustainability. In general, the families reported that their expectations were fulfilled. They reported high satisfaction with the indoor environment, improved wellbeing and fewer sick days, improved sleep quality, that the house automation was easy to use and that being able to follow energy consumption and production is extremely helpful.

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This report presents the post-occupancy evaluation of five families in Germany, Austria, France and the UK living for a year in houses which are part of the Model Home 2020 project, an experiment launched by the VELUX Group to contribute actively to the development of sustainable buildings of the future. In general, the families reported that their expectations were fulfilled. The occupants in each of the houses reported high satisfaction with the indoor environment, improved wellbeing and fewer sick days, improved sleep quality and that the house automation was easy to use. The report also notes how physical measurements were made in all rooms, revealing that the houses had high daylight levels but did not overheat.

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This paper introduces RenovActive - the first affordable, scalable and easy to reproduce renovation project in Brussels. Renovated within the budget for social housing, the house lives up to the Active House principles, combining energy efficiency and an excellent indoor climate. It details how the house will be equipped with demand-controlled natural ventilation and mechanical ventilation for winter. When completed, the house will be occupied by a family and physical measurements, as well as social scientific enquiries will be carried out.

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This paper is an analysis of the indoor environment at Solhuset, a kindergarten built in 2011 according to the Active House principles. It reports how the kindergarten has achieved high daylight factors in all rooms and how it has reduced its dependency on electrical lighting during the summer. It also reports that Solhuset has a comfortable thermal environment and details how ventilative cooling through window openings helps to maintain this.

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Here, the thermal environment of Sunlighthouse, a residential building in Austria, is investigated with a particular focus on summer and the role of solar shading and natural ventilation. The house has generous daylight conditions and is designed to be CO2 neutral, with a good indoor environment. The thermal environment was evaluated according to the Active House specification and it is found that the house has a comfortable environment in summer, with window openings playing an important role and external solar shading used frequently.

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This paper explores how to evaluate sunlight provision in buildings across Europe and presents basic rules for the design of insulated buildings. It covers how buildings are designed according to minimum illuminance requirements to achieve acceptable visual conditions, however, circadian rhythm studies have reported the importance of higher illuminance levels to stimulate human activities and the proper functions of the body's organs. The study also looks into workplaces when protection against excessive sunlight causing glare and overheating has to be controlled by sun devices.

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In this study, the energy performance and thermal comfort of three passive cooling methods are investigated for a typical building in four cities in warm climates, as compared to mechanical cooling. They are: venting via windows, solar shading and night cooling via windows, with variations of manual and automatic operation and control. Results show that the energy demand can be substantially reduced by using passive cooling methods without compromising the thermal environment.

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As people spend around 90% of their time indoors, good ventilation of buildings is essential to maintain good health. Additionally, ventilation has a significant impact on the quality of the building e.g. in very tight buildings, there is a greater risk of mould and damp if the air is not changed regularly. This paper assesses the impact of different types of ventilation systems in homes and schools on the occupant's health. A literature review has also been conducted to assess the influence of ventilation on health.

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Although occupants spend most of their time at home sleeping in their bedroom, up until now, optimising the indoor environment for sleep has been given very little attention. Consequently, this has led to substandard indoor environments in many bedrooms. This report argues that there is a need for more occupant responses on indoor environmental conditions during sleep, especially in naturally ventilated situations.

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Here we present the potential socio-economic benefits of upgrading the indoor air quality in Danish schools to the level of Swedish schools. The OECD “PISA” score is used to quantify the effects, together with the Danish Rational Economic Agent Model (DREAM). The paper details how improved air quality could result in higher PISA scores, increasing productivity and could lead to a reduction in the duration of education. It also notes how improved air quality could reduce the rate of absenteeism amongst teachers. The report then concludes that improved air quality in Danish schools could result in an increase in the Gross Domestic Product (GDP) of €173 million per annum, and in the public finances of €37 million per annum.

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How much sunlight can enter a room? This paper provides you with a methodology to answer this question and introduces an innovative new measure - the Sunlight Beam Index (SBI). The new measure, which presents a cross-sectional area of the sunlight beam that passes through a window and enters the main volume of internal space, is described and examples are given for a typical residential house. It concludes that the measure is suited for rating, planning and/or guideline purposes as the SBI can be calculated on a yearly or monthly basis.

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“One experiment is better than a thousand expert assumptions” formed the point of departure for a cross-European demonstration programme of six Active Houses. Here, we look into post-occupancy evaluations. The paper presents the main common denominators among the houses and identifies learnings by analysing quotes from the families, and via methodology, developed as a result of social monitoring. The scientific reports and conclusions form a platform for discussion, definition and suggestion of common denominators. It concludes with recommended learnings which can be transferred to the wider housing stock, new as well as existing.

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Three houses within the VELUX Model Home 2020 project are investigated with a particular focus on the strategies used to achieve thermal comfort, along with the role of solar shading and natural ventilation. It is found that ventilative cooling through window openings plays a particularly important role in maintaining thermal comfort and that both window opening and external solar shading is used frequently.

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Using the Energy and Indoor Climate Visualizer, the performance of ten ventilation and cooling strategies are tested in four different climatic zones across Europe. Thermal comfort and indoor air quality (IAQ) are evaluated according to the EN15251 standard for the summer period. Results show that thermal comfort can be achieved by passive means in all four locations. Natural ventilation was capable of achieving a very good IAQ and a reduction in energy consumption in all locations, when compared with mechanical ventilation or mechanical cooling.

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Our common experience is that windows are desirable and in recent years science has begun to explain why. Here, we present a comprehensive review of available literature as well as ideas for the development of a research agenda to move activity forward towards practical applications. The review identified three broad processes through which residential windows and skylights can affect people in their homes, either positively or negatively.

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