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Thursday31 July 2014

North Carolina Museum of Art by Thomas Phifer & Partners

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Arup’s innovative solution allows the North Carolina museum’s permanent collection to be viewed by natural daylight.

Location
Raleigh, North Carolina

Architect
Thomas Phifer & Partners

Daylighting design
Arup

Completed
April 2010

If you thought museum visits were best saved for overcast, rainy days, you’ve never been to the North Carolina Museum of Art. Go in the summer, and for the main part of the day you’ll get to see something special – the permanent collection, spread over 6,000sq m, lit only by natural daylight.

The museum reopened this year after an $86 million, three-year expansion project designed by New York-based practice Thomas Phifer & Partners.

The project involved creating a new west wing building or large pavilion, to house the permanent collection, and refurbishing the 1980s east wing. The single-storey west wing contains 362 skylights, which appear as rhythmic undulations across the roof. In the summer months, they allow in enough sunshine to show the entire collection under natural light from approximately 10am until 3pm.

“Natural daylight puts people in touch with nature allowing a sense of subtle changes during the day and from season to season,” says practice principal Thomas Phifer.

It is also far more sustainable, considerably reducing power consumption. As well as the huge array of skylights on its roof, the west wing is lit by large expanses of glass along its perimeter. But this is no giant greenhouse. The challenge was not simply to get as much daylight into the building as possible, but to keep out direct sunlight, and to minimise variation in light levels as clouds pass overhead.

Another consequence of having 22,000sq m of glazing is the limits it puts on display space. “Much of the glass faces interior sculpture courts,” says Phifer. “[Moveable] art walls have been placed adjacent to the glass where needed, providing a view of the sky above.”

This ingenious daylighting solution was developed by the architects in collaboration with Arup, and took several years to resolve. It builds upon natural lighting approaches in recent North American museum projects, but develops a solution that addresses the museum’s particular aspirations.

Daylighting Solution

The west wing of the museum is only one storey high, to allow the best, most consistent natural light. Its roof is covered in a grid of vaulted coffers, each with a circular opening at the top.

Each skylight is made in a tight-packed, four-layer form. Outermost are the fixed linear louvres, beneath which are two layers of glass. The inner glass layer defracts the light so that it falls on the walls, rather than the floor. Finally a fabric layer, stretched over a series of hoops, can be popped up inside the skylights like a tent to protect the most sensitive exhibits, such as textiles.

This passive system blocks out direct light, and, as it is north-facing, eliminates the most extreme variations of light levels, which can change tenfold as the sun dips in and out of the clouds. There are also two sets of electric lights, controlled by sensors, which come on one at a time to boost light levels as they fall outside.

Fabric hoops being installed.

Fabric hoops being installed.

As well as maximising the amount of natural light entering the building, this four-layer solution minimises glare. It also brings light into the centre of the floorplate. And, at the bottom of each skylight is the track to accommodate the electric lighting, to keep the two light sources as close together as possible.

Despite the delicacy of this solution, Andy Sedgwick, the director of Arup who led the daylighting design studies, says it was the glazed facade he was least confident about.
“I was more concerned about it than the skylights,” he says. “You can get very uncontrolled light. But the architect insisted on doing it.”

He is happy to admit he was wrong though. “The eventual solution was to use three layers of fabric,” he explains. “It brings the light level down without losing that luminous feel.
It works remarkably well.”

Another consideration was UV radiation, which will cause photo damage to exhibits if the glass is not laminated with the appropriate filter. Again, there was a balance to be struck – select too strong a filter and you lose the light from the purple end of the visible spectrum, giving everything a jaundiced, yellow glow.

“After a lot of research we used a filter that gets rid of everything under 400 nanometres. We used it everywhere, even in the lobby spaces,” says Sedgwick.

Staff and visitors at the museum are delighted with the new exhibition space, viewing it as the antithesis of the traditional black box with spotlights. In North Carolina, at least, people no longer wait for a rainy day before heading to the museum.

The Engineer’s view: Evolving attitudes to natural light in Museums

Andy Sedgwick, director of Arup, writes: Many art galleries built in the US during the 20th century reflected the preferred curatorial approach of the time: to exhibit art in “black box” conditions, using focused electric lighting on each work to create a directed and theatrical visitor experience.

The narrative of an exhibit under these conditions is dictated by the curator - the visitor is led from piece to piece, and dialogues between works are established by design and not by chance.

One aspect of the country’s museum boom in the late 20th century was the growing influence of European architecture, and the growing popularity of European architects for new arts buildings.

A key feature of the European approach has been to bring daylight into display galleries to create a connection to the outdoor environment, and to provide an ambient background light that reveals the architecture of the gallery spaces. In most museums of this type the majority of light on the art is, however, still provided by track-mounted electric light that is on whenever the museum is open.

The drive towards more sustainable operations and reduced operating costs in a time of rising energy prices is now providing a new impetus to greater use of daylight to illuminate art spaces. A typical paintings exhibition lit with tungsten halogen spotlights may require a power density of up to 60W per sq m. As well as the direct electrical energy used by the light fixtures, the heat from the lights is often the largest load on the gallery air-conditioning system.

Tom Phifer’s expansion of the North Carolina Museum of Art is one of very few North American museums that uses daylight as the primary illuminant of the art as well as the space: the new building will operate without electric light through most of the summer months.

This low-energy approach, and the open enfilade layout of the galleries, creates a new type of visitor experience: one in which ancient and modern are seen together close up and from a distance under a balanced, even but dynamic light.

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