With the opening of the Hepworth Gallery in Wakefield and Turner Contemporary in Margate, David Chipperfield is having a moment in the UK, so it's fitting that he should be the designer of this year's Size + Matter project, unveiled annually on the South Bank during London Design Festival. Consisting of 28 glass panels which incorporate a new reflective metal mesh, the piece - titled Two Lines - has a sculptural, ghostly quality which changes with the light. We caught up with him to find out more.

Do you see your installation as a piece of sculpture or engineering?
David Chipperfield: It's ambiguous. It's not architecture or sculpture. Glass is the material of our time and the installation is about trying to show a new material (called Sefar) in a positive way and make an object out of it. Mainly, though it's a flag for the London Design Festival, which is a great initiative.

In what way?
Over the 25 years that I have worked in London, it has completely changed. In the early days, there were a few cavalier figures - Tom Dixon, Ron Arad, Neville Brody, and Peter Saville - but they were isolated, doing one-off things and persisting in London which was not a culture that really helped them. One had to go to Milan or Paris. I admire those founding fathers; they have helped create a design culture here, and now all of a sudden they all have incredible status. London has adopted design and you can buy modern furniture, create modern interiors, which has to be a good thing and the festival is part of the process.

How was it working on this (busy) site?
There were many limitations. At first we wanted to make a room or a space, but the piece of land has to be accessible for people to walk through it. More than three quarter of a million people will pass by during its month-long life time. Then there was the usual struggle of how to build it and how to get it paid for. Sculptors have it easy - Anish Kapoor just designs something and has carte blanche! Like I said, it's bunting. There's festival going on and we are decorating it.

Two Lines will be outside the Royal Festival Hall until 16 October 2011