Nick Raynsford's decision to make buildings greener by overhauling the Building Regulations was always going to have dramatic consequences for the industry. When first mooted in 2000, it threatened everything from masonry construction to the dear old lightbulb – and might have forced the Queen to fit PVCu windows in Buckingham Palace. Well, none of that looks likely. But the new Part L of the regulations, which comes into force on Monday, will still be one of the most profound legislative changes to hit the industry for a generation.

There are, for one thing, a myriad winners and losers. The great victors are services engineers, who may suddenly emerge as king of the consultants. Housebuilders, who appeared likely to suffer most when the first drafts of the new Part L appeared, now have little to fear. Unlike contractors, they won't have to pressure-test new homes for airtightness, and – after vigorous lobbying by material producers – they won't have to abandon brick-and-block construction in favour of timber-frame. Contractors are unquestionably the big losers, particularly those (mostly small) firms that will have to bear the cost of making complex calculations to prove a building's compliance, as well as funding the pressure tests. This will add about £35,000 to the cost of, for example, a single call centre – and if the tests fail, the structure may have to be ripped apart. From now on, no contractors will freely offer clients a guaranteed maximum price. Clients themselves will have to pay more and and wait longer for their buildings.

The impact of the new rules doesn't stop there. Certain staples of modern architecture and popular methods of procurement will change too. Most staggering of all is the suggestion that design and build may become uneconomic if more detailed design and specification has to be done at an earlier stage – negating its main financial benefits. That would alarm the proponents of this cheap-and-cheerful form of construction. But if the effect is to compel clients to assemble its supply chain earlier – as Sir John Egan would like – then all well and good. Architects and services engineers will certainly have to work more in tandem – which may lead to a few unlikely mergers. For architects, the rules may put an end to those sculptural glazed office towers so beloved of the Foster/Rogers generation. With no scope for extensive air-conditioning, the offices of the future will have smaller windows, with lots of solar shading – Rogers has already designed a prototype in Hemel Hempstead. According to its developer, Akeler, the pressure tests will also alter design, as they favour concrete frames over steel. Finally – in the most welcome effect of all – airtightness will require far better workmanship.

There's no doubt that implementing Part L will cause pain and financial hardship. Ron Decaux of services consultant Roger Preston and Partners predicts chaos. On balance, though, the changes are A Good Thing. Buildings account for half of carbon dioxide emissions, and the UK is well behind Scandinavia in making them sustainable. Part L is the industry's biggest contribution to a greener future; to fulfil their side of the bargain, Raynsford et al must acknowledge that new buildings are only 1% of the total stock and find ways of bringing existing ones up to the same standard. Otherwise, this epoch-making change will be an utter waste of, yes, energy.