In June 2017, a new 4-star hotel opened on the shores of Bostalsee, a lake and eponymous recreational area in Saarland. The hotel houses 100 rooms and suites, a 2.000 m² (21,560 sf) spa, a restaurant, a bar, and conference facilities. To run a luxury hotel, a beautiful view to the lake is not enough. The customer experience must also be exceptional. Transsolar’s role was critical in creating high quality comfort and cost-effective operation. One target of the project is to demonstrate that such comfort can be achieved without increasing the energy demand. Through an iterative design process and the use of thermal, daylight and CFD simulations, Transsolar worked with the architect and client to develop the energy and comfort concept.
A challenge of the project was to maintain an unobstructed view of the lake while limiting the solar heat gains in summer. The hotel room balconies and the exterior suspended wooden lamella were optimized for sun protection, daylight and views. Motorized awnings are installed on the ground floor to provide shade for the patio, lobby, restaurant and event rooms while allowing for unobstructed views and free passage.
In the hotel rooms, thermally-activated concrete ceilings provide the basic heating and cooling. During winter, the room temperature can be controlled via convectors. Guests can also decide how fresh air enters the room: they may either open the balcony door and windows or they can switch on the bathroom fan which draws outdoor air through façade trickle vents.
A gas-powered combined heat-and-power plant provides heat and electricity for the base load; the waste heat from the chiller is used to preheat the domestic hot water and the pool water in the spa area.