The study presented in this paper originated from observations made regarding the thermal conditions during winter in highly insulated dwellings with mechanical ventilation with heat recovery (MVHR). Previous observations indicate an oversupply of heat to bedrooms and a successive extensive window ventilation, which leads to an increased space-heating demand.
Detailed simulations were conducted to explain the causes for the observed thermal conditions and to elaborate improved solutions for heating and ventilation during winter. Various MVHR solutions and control strategies, as well as building design solutions, were investigated regarding their impact on the thermal conditions in bedrooms and on the space-heating demand.
The results clearly illustrates that the supply-air temperature and the temperatures in the living room and bathroom have substantial effects on the thermal conditions in the bedrooms. A one-zone MVHR solution, with approximately the same the supply-air temperature to all rooms, has clear limitations regarding the provision of thermal comfort in bedrooms.
The clear potential of a two-zone MVHR solution, where the supply-air temperature to the bedrooms is controlled independently from other rooms, was observed. With a two-zone MVHR solution, the thermal conditions in bedrooms can be improved and the space-heating demand can be reduced.
The substantial reduction of required heating load in passive house buildings has led to an integration of heating in the ventilation system by post-heating the supply-air, called air-heating. The incorporation of heating in the ventilation system constitutes a departure from a well-established customary practice of strictly separating heating and ventilation in the indoor climate design. It is therefore imperative to thoroughly investigate and evaluate air-heating with regard to effects on the indoor air quality (IAQ) and thermal comfort. Simulations and laboratory measurements suggest that air-heating has no adverse effects on IAQ and thermal comfort. The purpose of this paper is to investigate the acceptability and suitability of air-heating from the occupants' point of view. A comprehensive literature study is performed in order to assess the perception of IAQ, thermal comfort and general experiences with the operation of air-heating in comparison to other heating strategies. The evaluation is based on studies on multifamily passive house buildings in temperate and continental climates. No proof for the general unsuitability of air-heating in residential passive house buildings with regard to perceived IAQ and thermal comfort was found, but clear limitations were determined in buildings where the heating is based on air-heating only. Based on the findings it is suggested that air-heating always should be supplemented with an extra heat source in bathrooms and it should be possible to adjust the supply-air temperature in the bedroom independently from other rooms.
Experience with low-energy and passive house buildings forms the basis for the further development of zero-emission buildings. A post-occupancy evaluation of the Løvåshagen cooperative is therefore conducted by means of user surveys and measurement of indoor climate parameters, energy use and window opening time.
The goal of the post-occupancy evaluation is to obtain information about how occupants use and experience low-energy and passive house dwellings, especially with regard to heating and ventilation. In addition, the impact of user behavior on the indoor climate and energy use will be assessed.
In this paper, the results of the user survey regarding user habits and occupant satisfaction are presented.
The results show that low-energy and passive house apartments are used in ways that have a substantial impact on the indoor climate and energy use. The assessed extent of window ventilation and use of floor heating throughout the year around definitely increase energy use substantially and therefore partially explain the difference between the calculated and measured energy use. This difference will be quantified by measurements and parametric simulation in the continuation of the study.
Most respondents are satisfied or very satisfied with living in a low-energy or passive house dwelling. Nevertheless, a clear need for improvement with respect to heating and ventilation systems is detected.
It can be concluded that increased attention to the interaction between the occupant, the building design and the technical installation is needed in the development of zero-emission buildings.
The passive house (PH) standard is seen as the future minimal requirement for buildings in Norway, where a specific definition has been developed (NS 3700). Nevertheless, the relation between this standard and air heating (AH) is not clear while both concepts are often associated. The present contribution investigates challenges for AH in terms of thermal dynamics (e.g. temperature distribution and control) as well as the feasibility of the AH concept. This is done using detailed dynamic simulations on a typical detached house typology. Results show some limitations of the AH concept in Nordic countries, as well as provide guidelines for the design procedure.