ENERGY EXEMPLARS

Pennie Varvarides finds out how Southsea Library became one of the most energy efficient in the UK

At a time when most libraries in the UK are grappling with budget cuts, Portsmouth’s Southsea Library has moved to a new site – albeit one that was previously a branch of Woolworths, another victim of the recession.

The building is in the retail centre of the town – unlike the old site south of the city. The council hopes the library will attract 80,000 visitors a year while broadening the appeal of the town centre, supporting local retailers and the economy.

Lighting is crucial to the success of the project. The library is open eight hours a day, seven days a week, but special events such as evening workshops and storytimes are also held there. This means lighting is used for about 16 hours a day.

A library must be a relaxing space, but it must also encourage those studying to concentrate. Part of the brief for the lighting scheme was to produce high quality ambience and design. It was important to get the right lux levels in the various areas.

Technological leaps

RHB Partnership, the consulting engineer for the project, says: ‘We opted for LED lighting because LED technology has had a big jump in recent years. We did look at compact fluorescents, which have a better lumen output, but they had a warm-up period, had shorter lives and were too large.’

The move to LED lighting was justified in the light of soaring energy prices. RHB calculated that savings of £21,221 would be possible over five years – a reduction of 80 per cent – using LEDs rather than conventional sources. Obviously, carbon dioxide emissions would also be cut by 80 per cent.

Harvard Goddard, an associate partner at RHB, says: ‘It was about finding the most efficient way to run the building and bring the space alive. We worked with the interior designer to make sure our designs complemented theirs.’

Equivalent to MR11

In seating areas for talks, workshops and individual study, PhotonStar’s Laser Micro fittings – equivalent in size and light output to MR11 – with a narrow beam angle ensure high lux levels. The fitting has a low-glare darklight baffle and can be tilted by 15 degrees.

In this application, its light source is the Pluto 300 light engine. It delivers 57 lumens per circuit watt.

LED downlights were installed to replace 35 and 50W halogens two areas. PhotonStar’s CeilingStar TTs with both Mercury 810 and 630 light engines were fitted. The Mercury 810 light engine delivers 63.5 lumens per circuit watt at 4000K and the 630 delivers 75.3 lumens per circuit watt.

Adjustable LED spotlights replaced halogen sources for reading comfort. PhotonStar’s Track Spot Aero with the Mercury 810 light engine operates from a trailing edge dimmable driver and delivers 66.6 lumens per circuit watt at 4000K.

LEDs were installed to replace 35 and 50W halogens

Two-year payback

Compared to halogen equivalents, payback is calculated at 24 months for the LED fittings.

Goddard says: ‘We’ve got to reduce the carbon footprint. The way LED technology is evolving, it was the preferred lighting at the time.’ A two-tier control system from iLight splits the building into front and back zones.

The library has been designed with modernity in mind and using the lighting to direct – and draw in – visitors. PhotonStar says the aim was to ‘create a space inviting a younger generation to use a local social meeting space with a subtle educational twist’

RELATED
Another level

The answer to the energy challenge at building company Hanson’s new corporate HQ in Bedfordshire was to cut lux levels by nearly half. Richard Brass reports

RELATED
LEDs take a back seat

Conventional, not solid state, light sources dominate the lighting toolkit for future Pret A Manger stores. But that doesn’t mean it is inefficient, as Mark Burgess discovers