Evaluation of the energy and comfort performance of a plus-energy house under Scandinavian winter conditions

A plus-energy house was studied in terms of indoor environmental conditions and energy balance, during Scandinavian winter conditions. The studied building, EMBRACE, is a single-family detached dwelling of 59 m² with two floors. The house also integrates a semi-outdoor space, covered by a glazed envelope, whose thermal environment has been investigated. The house is located in Nordborg, Denmark and was undergoing a year-round measurement campaign, of which are hereby presented the results from 16/11/2015 to 04/03/2016. During this period, the house was operated in heating mode, with five different cases investigated, combining different set-points (20 to 22°C) and ventilation heat recovery settings.
The thermal comfort indoors proved to be satisfactory, depending on the chosen set-point. Up to 92 and 98% of the time was reported within the range 21-25°C (Category I of EN 15251) respectively on the ground and first floors when the set-point was 22°C. The electrical energy balance resulted to be negative, with a photovoltaic (PV) production of 432 kWh and a consumption from the mechanical systems of 1521 kWh during the studied winter period of almost four months. Put into perspective with the summer evaluation, these results show an encouraging trend towards achieving an annual positive energy balance as designed for this plus-energy house. The thermal environmental conditions in the semi-outdoor space resulted more comfortable than the outdoors, with reduced wind velocity, protection from rain, and temperature increase of up to 2-3°C during sunny days, which increases the possibilities of occupancy in this area.