EBLE – Evaluation of Buildings with a Low Energy Demand, 2015

This project aims to get knowledge about residential buildings with a low energy demand through an evaluation of projects. Through the evaluation of passive houses the project aimed to get insight to solutions, the need for innovation and potential. 64 passive houses and 10 residential buildings on TEK10 level were studied. The data included interviews with 38 residents, interviews with participants in the building process, raw data on energy- and indoor climate, in addition to humidity levels in construction.

Summary of findings:
Residents have high expectations for indoor climate and comfort in new buildings, both in passive houses and TEK10 homes. These expectations are fulfilled in the evaluated projects. Aspects such as price and location were the main arguments for buying the houses. The fact that the houses are passive houses were described as a bonus. The results from the interviews indicates that most residents are satisfied and very satisfied with the indoor temperature. The measures also show that the buildings in the various projects have a high indoor temperature with some exceptions. The measures also show that there are greater differences in temperature between residential buildings within the project than between different projects. No systematic differences in indoor temperature between TEK10 houses and passive houses were found.

All the residents who were interviewed, except one, wanted indoor temperatures between 22-24°C in the living room. There is also an overall wish for lower temperatures in the bedroom, 15-19 °C. Adjusting the temperature between different rooms in the house can be perceived as a challenge. Overheating is experienced as a minor problem if it occurs in short periods of summer. Most residents were also pleased by the air supply and air quality. Some experience the air as dry during winter periods. In several houses low relative humidity was measured during the winter, which confirms the residents' experience. Dry air and low relative humidity during winter is a general problem in residential buildings. The residents needed good and easily accessible information about the management, regulation and maintenance of the technical installations, especially where there were innovative and unknown solutions.

Lower energy demand was found in passive houses compared to houses at TEK10 level. In average passive houses use 40% less energy than TEK10 homes. Measured energy consumption is on average 23% higher than calculated for passive houses and 21% higher for TEK10 houses. Further energy consumption is clearly dependent on the behavior and habits of the residents. The requirement for heating is underestimated in the energy calculations and is an important explanation factor in deviation between measured energy consumption and the estimated needs. Residents' attitudes towards energy use were ambivalent. Most of them thaught it was beneficial to save power, but a general tendency was that you do not want to sacrifice comfort to save more.

The participants involved in the building process report that increased time is spent and also higher costs for building passive houses. Cost levels are associated with greater uncertainty, more expensive windows, thicker walls with more materials. The choice of heating system were considered as a challenge. There was a lack of well documented solutions. Quality assurance requirements have also increased with increased energy requirements. The measured levels of humitidy in the passive house projects confirm that housing constructions can be built according to principles documented in Trehusboka (Edvardsen & Ramstad 2015), among others, and instructions in the Building Research Series.