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Photo @ Adam Moerk
The black of the exterior is artfully juxtaposed with the white window frames, the blue tones of the PV panels, and the green of the roof.


Solhuset Climate-Friendly Nursery

Christensen & Co. Architects
Hoarsholm, Denmark

Northern Exposure: A net-positive energy child-care center sets a new standard for high-performance and healthy indoor air quality.

By Jane Kolleeny
March 2012

During a mid-afternoon play period at Solhuset Nursery ("sunhouse" in English), rosy-cheeked children run energetically through the light-drenched rooms of the 13,000-square-foot facility 15 miles north of Copenhagen. This being Scandinavia in January, the days are short; in fact, the sun will set in less than two hours. Nevertheless, abundant sunlight enters deep into the building until the day terminates, showing how apt the name is, on the one hand, while warming the inhabitants, on the other.


Location Hoersholm, Denmark (Zealand Is. watershed)

Gross area 14,000 ft2 (1,300 m2)

Completed May 2011

Cost $4.2 million

Annual purchased energy use (predicted) -2.5 kBtu/ft2 (-29 MJ/m2)

Annual carbon footprint (predicted) 0 lbs CO2/ft2 (0 kg CO2/m2)

Program 44 rooms—kitchen/dining, offices, playrooms




Skylights Velux GGU U04

Windows Velfac (facade windows) 200i

Exterior cladding Superwood facades, Superwood aart profil

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Solhuset Climate-Friendly Nursery
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Designed by Christensen & Co. Architects for kindergarten age and younger, this solar-powered building accommodates 100 children and 30 staff. The building is sited on a triangular lot in the wealthy bedroom community of Hoersholm; the population here earns some of the highest incomes in the country.

The site's triangular shape was dictated by the intersection of three existing roads, which suggested to the architect that the building could also follow suit with three sides. Its two longest facades are positioned southeast and southwest, with the third facing north. Working in concert with multiple skylights, the glazed southern elevations capture enough daylight to equal three to four times that of a standard building. Outdoor perimeter areas are for play, landscaped to represent various landforms of Denmark—such as woodlands and beach.

The building's roofline seesaws up and down on each side, establishing an interesting pattern while allowing the alternating facades to capture direct sun in the south and directional light from the north. "The connecting roof plates shape the building, creating a lively, playful envelope, with enormous variations in light during different times of the day." explains architect Michael Christensen. "From the low winter sun, to high summer sun, the interiors receive constant daylight." Combined with the intelligent siting are the high-performance glass and insulation on the envelope, which ensures that the building will use less energy than standard requirements set by the 2015 Danish building regulations. The solar energy strategies bump up energy efficiencies even further. "We used an advanced heating system which includes solar panels, heat pumps, and vertical pipes in the ground around the building," explains mechanical engineer Niels Treldal of Ramboll A/S.

The roof's design was ideal for mounting the photovoltaic and solar thermal panels, which are positioned to capture the most light possible. With 2,691 square feet of PV panels, "the building produces 0.75 kWh per square foot more than it consumes each year," according to Treldal, exporting energy during the eight months of the year with the most sunlight, and importing it during the four months of shorter days. A green roof of sedum is interspersed among the panels, cooling the building, the panels, and controlling storm-water runoff. High-performance wood, compressed to ensure hardness, clads the exterior.

Solhuset is designed according to the Denmark-based Active House system, where green buildings are classified according to ten criteria at four levels of achievement (Solhuset is designed to meet the highest level). This system was developed in 2010 by the Active House Alliance, an association of building product manufacturers, architects, and universities united under VKR Holding (see activehouse.info). "Companies contribute systems and products, as well as expertise," says Per Arnold Andersen of Velux, on behalf of VKR Holding. The entity also monitors the completed buildings and installed products to gauge performance for their consortium of companies. With respect to Solhuset, VKR Holding partnered with the municipality, which owns the facility, and Lions Children House, which runs it.

Colorfully painted indoor spaces link together in a meandering pattern, which the architect refers to as streets. "The inspiration behind the nursery's layout is that of a small village, placing the most common areas, such as dance and music, on the main square, with all group rooms gathered around the perimeter," explains Christensen.

The design team used the building's sustainable strategies as an educational platform for the kids. For example, an electricity crank powers lighting in an outdoor shed where bikes and toys are stored—kids rotate the mechanism to get the light to turn on inside. A greenhouse allows the children to grow plants, learning about stewardship of the environment. Collected rainwater irrigates the gardens.

Throughout the design process, sophisticated software was used to evaluate the design of the building. These tests resulted in improvements to the planned energy systems and daylighting levels. Since the building opened in May 2011, VKR Holding has monitored its performance. "In 40 years, the nursery will have produced enough energy to pay back its carbon footprint, i.e., building cost, transport, and production of materials and [cost of] the building site itself," says the architect.

When asked if the design team would have done anything differently, Christensen chuckled and said that the only problematic surprise was the snails who inhabit the green roof during warm weather, crawling inside the nursery at night when the skylights are open for venting. Excepting that, the project has been a huge success and amenity for the neighborhood.


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