The grounds of the Vitos health centre in Marburg, near Frankfurt, are dotted with mature trees and historic buildings from the late 19th century, which have served as a psychiatric clinic for 140 years. At the northern edge of the open grounds, the city of Marburg has established one of the first children’s day-care centres in Germany to achieve the plus energy standard Effizienzhaus Plus (Efficiency House Plus).

Project: new building +e Kita (plus-energy-/solar- building) in Marburg
Architects: opus Architekten BDA / Prof. Anke Mensing, Andreas Sedler / Ploenniesstraße 14-16 / 64289 Darmstadt
Employees (involved in the project): Kristin Egermann, Uwe Kühn, Jessica Mazur, Tina Ritter Builder-owner: Magistrat der Universitätsstadt Marburg, vertreten durch Fachdienst Hochbau / Günter Böth, Oliver Kutsch / Town council of the City of Marburg
Project management: SEG Marburg / Uta Brämer Location: Cappeler Straße 68 / 35039 Marburg Completion: december 2014
Photo credits by: Eibe Sönnecken / Wenckstraße 32 / 64289 Darmstadt

Nursery +e in Marburg by Opus Architekten - Sheet2
©Eibe Sönnecken / Wenckstraße 32 / 64289 Darmstadt

The building is expected to achieve an annual energy surplus both in terms of final energy and primary energy. The site of the new build slopes gently from east to west. opus architects res- ponded with a double- storey building that allows its young inhabitants access from both levels out into the open: on the upper floor, to the hillside adjacent to the east facade, and on the lower floor, to the west. On this side the architects had a number of trees felled to produce a semi-circular clearing surrounded by hedges. As well as allowing carers better visibility over the play area, the clearan- ce of some trees was also necessary to avoid compromising the electrical yield from the roof and facade-mounted photovoltaic modules.

A pavilion in the park

At first glance the new building looks more like an exhibition pavilion or a restaurant in an urban park than a childcare centre. This is due to its transparency; the distinctive saw-tooth roof (which is continued in the west facade), and the unusually dark facade cladding. The southfacing parts of the roof and the southwest-facing facade surfaces are completely clad in black mono-crystalline photovoltaic modules made from laminated glass.

Two entrances − one on the ground floor from the south and a second entrance from the hillside − lead into the childcare centre, which is organised into five groups, each with ten babies and toddlers up to age three. Three of the group rooms are located on the upper floor and the other two are located on the ground floor. The ground floor also accommodates a manager’s office, general-purpose room, kitchen, storage, technical room and staff room.

Nursery +e in Marburg by Opus Architekten - Sheet4
©Eibe Sönnecken / Wenckstraße 32 / 64289 Darmstadt

Balancing privacy and transparency

The manner in which the architects succeeded in combining child appropriate details with trans- parency and permeability is particularly striking on the upper floor. Here the folding roof form with its pinewood cladding is a dominant presence as the inner walls only extend up to 2.4 meters, and above this height, unframed glazing separates the rooms. However,

the architects created visual connections between different areas by means of small windows positioned at children’s eye level in the interior partition walls. Each group has their own group room, toilets, quiet room and a play area; furthermore there is a multipurpose room shared between two groups each. Areas that require little daylight, like toilets and sleeping areas, are located in the core of the building, whilst group rooms and multipurpose rooms are arranged along the facades. Apart from the colourful artwork of the children, interior colour accents are restricted to furnishings and internal wall finishes. The latter consists mainly of three- ply spruce wood panels, which have either been left in natural wood finish or finished in various shades of green. As a unifying element the floor is finished in neutral grey linoleum.

The first essential component of the plus-energy concept was a well-insulated building envelope. The U-values are almost in the range of typical passive house construction. The same also goes for air tightness, for which the blower-door test resulted in a value of 0.69/h. Deep overhangs on either side of the building are key to reducing unwanted summer heat gains. Additional awnings can also provide temporary shading along the three ‘sunny’ facades to the east, south and west.

Nursery +e in Marburg by Opus Architekten - Sheet6
©Eibe Sönnecken / Wenckstraße 32 / 64289 Darmstadt

When external temperatures are mild, the rooms are ventilated by manually operated, room-height ventilation apertures in the facade which can be seen externally by their metal

louvered cladding. Further ventilation is via skylights above the central staircase. In contrast, in the cold winter months a central ventilation system with heat recovery is utilised.

Fresh air is circulated into the group rooms and extracted from the toilets and sleeping rooms.

Nursery +e in Marburg by Opus Architekten - Sheet8
©Eibe Sönnecken / Wenckstraße 32 / 64289 Darmstadt

As most activities take place at floor level, an underfloor heating system was installed in the new building. A 25 kW air/water heat pump brings the heated water to a flow temperature of 35 °C. A second compact air/water heat pump warms the potable water to 55 °C. Due to this separation between heating and hot water, the systems operate far more efficiently than a single heat pump for both functions. According to calculations by an energy consultant, the building (in- cluding kitchen and office equipment) has an electrical requirement of 37,000 kWh per year. With a capacity of 52 kWp the photovoltaic installation provides about 41,000 kWh. In theory the annual surplus of 4,000 kW would be sufficient to drive an electric car for approximately 24,000 kilome- tres.


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