What does this building say about BSkyB? James Murdoch gives Jonathan Glancey an exclusive view of his first big architectural commission: a colossal TV factory

'It's not meant to be pretty," says James Murdoch, chairman of BSkyB, of its new broadcasting centre. This might seem an odd thing to say about the first building BSkyB has commissioned, yet this steel and glass colossus – rising from the heart of BSkyB's jumble of buildings at Osterley, on the Heathrow flight path – is no conventional beauty. In fact, Harlequin 1, a colourful and even comic name for a decidedly serious building, has the look of some futuristic power station: a strange way, perhaps, to express BSkyB's corporate values.

As Murdoch, lean, personable and surprisingly ruminative, emerges from the long shadow of his father Rupert, you might expect to find him and his bright young staff (average age: 27) plotting an expanding empire from some racy new structure designed by Rem Koolhaas or Zaha Hadid. But I get the impression that BSkyB has grown so quickly that, until now, there has been no time for the luxury of architecture.

Founded in 1990, the company's turnover has grown from £93m in 1991 to £5.4bn last year. It now employs 16,500 full-time staff up and down the country, and broadcasts 26 Sky channels. As it's grown, its Osterley base has sprawled out into a ragbag of old industrial sheds and rental offices. The company itself doesn't even seem to take these buildings seriously: in the lobby of the head office, larger-than-life Simpsons mannequins sprawl on a sofa.

"It's very dangerous when companies start building," Murdoch says. It's a curious notion, yet one that makes sense for a business that still has the feel of a muscular young streetfighter looking to take on all comers – rather than that of a long-established and self-consciously cultured set-up like the BBC, whose Broadcasting House looks like an art deco ocean liner carved in stone. "We don't want to build monuments," says Murdoch, "but we've tried to ask what would be the building Sky would build?"

And the £130m Harlequin 1 is the answer: a vast glazed steel box, interrupted by towering columns that prove to be chimneys removing hot and stale air from studios and editing suites. Clearly, Harlequin 1 is not meant to be a contemporary version of the BBC's elegant Broadcasting House. No: with its factory-like bulk, its sleek cladding and forest of chimneys, it's a refined brute of a building. As for its green credentials, it boasts the world's first naturally ventilated recording studios and, despite its scale, daylight and fresh air reach virtually every workspace.

"We've lived in a Portakabin world as we've grown," says Jeremy Darroch, BSkyB's chief executive, sitting alongside James Murdoch. "No, we haven't been after a 'great' building, but one that allows us to change and grow and move on. Harlequin 1 is a factory where we can make and record programmes, edit them and broadcast them under a single roof. It's got eight flexible studios, so we can experiment as we move forward. We've come a long way from the BSkyB people once seemed to associate solely with TV in pubs."

"We're young, slightly raw, dynamic," adds Murdoch. "But we also put out a greater coverage of the arts on Sky than the entire BBC."

As I walk into the lobby with architect Declan O'Carroll of Arup Associates, the building begins to make sense, especially in terms of how Murdoch and Darroch pitch BSkyB. Although essentially hard-edged, Harlequin 1 manages to be both dynamic and even tasteful. A striking black steel stair climbs up to a glazed roof, far above. One wall is sheathed in polished plaster: a crafted and, dare I say it, luxurious touch. Another wall, glazed, offers glimpses of the distant West End, and of jets making their final approach to Heathrow. It's like having a ringside seat at an aerial parade.

The lobby stair leads to cafes and "break-out" spaces for informal meetings, all sharing these panoramas. This part of the building, the place where it relaxes and puts its feet up, is housed in a cantilevered steel and glass tower that seems to be breaking away from the main structure. It promises to be a lively, attractive spot when Harlequin 1 goes live next year, ahead of schedule and £5m under budget.

"The building really is a big machine," says O'Carroll, as we take an exhaustive tour. The eight studios are cave-like spaces fronted by huge sliding steel doors. The Sky Sports studio sits at its heart: set behind clear glass screens, it will be on view to the public as they tour Harlequin 1. "We definitely want people to come and see us," says Murdoch. "We're not trying to hide out in the boondocks. We're already involved with local schools and the community. We want Harlequin 1 to be somewhere people feel they are a part of."

It is not hard to see how this mighty machine would be fun to work in. Part ocean freighter, part James Bond set, part Darth Vader battleship, it will suit a young, creative and energetic staff, the kind of people who find slick, corporate headquarters alien. Corridors loop around each floor like giant racetracks making everything easy to find, while floors are raised up on steel props to accommodate 50km of cabling. There is little in the way of plush carpets, exotic veneers and plump armchairs, yet the building is anything but unfriendly. "Wherever possible," says O'Carroll, "people work around the perimeter. Here, they have real control over their environment: opening windows, daylight, views . . ."

This might sound obvious, but all too many people work in buildings where they have little control over how hot or cold, bright or dark, humid or dry it is. "Energy costs should be a third less than a conventional building of this kind," says O'Carroll, on the benefits of those chimneys. "The aim has been to create a carbon-neutral design. No one pretends this is easy, and of course the cooling and ventilation system has a back-up, in case it gets stifling."

If planning permission comes through, Harlequin 1 will be topped with a wind turbine on its west side. Meanwhile, rainwater will flush toilets, and a wood-chip burner will fuel the cooling and heating systems. It all adds up to one very big green machine – or at least as green a machine as something of this size can be. But creating an environmentally friendly building was not Murdoch's only concern: "The question of how you reconcile an increasingly digital world with a real world is so important. In the end, we're producing a stream of ones and zeros beamed out to satellites and back to TVs, laptops and mobiles, but I've wanted to get something of the feeling newspapers once had."

Murdoch enthuses about the days when newspaper buildings were great story-weaving machines: the chipping of typewriters, the calls for copy, the whisky bottles. "And the way," he beams, "complete buildings used to rumble and sway as the presses rolled. I want our staff to share that kind of excitement, but brought up to date."

Murdoch is also busy with the redevelopment of News International's Fortress Wapping (a nickname he bridles at), which is to be transformed by adventurous new architecture, currently under wraps. As the rest of the BSkyB campus at Osterley is transformed, and as BSkyB matures, I hope Murdoch and his team will learn to relax with architecture. Had they done so earlier, they might have encouraged their architects to give Harlequin 1 a little more urban drama. Yes, this new broadcasting centre is an impressive beast, but if only those chimneys had been more forcefully expressed, if only those facades hadn't been so relentlessly smooth.

As I leave, Murdoch asks if the Guardian's conference room at its newish King's Place HQ really does have beanbags for staff to flop on. Sadly, no. But it does have a giant yellow sofa: Homer Simpson would approve. Harlequin 1 might be hard-edged and modern, yet, in its own dynamic, digital way it has a lot in common with the mighty media works of yore. As Murdoch says, it's "not fancy, not slick – it's there to show what it does, and not to show off".