Henrietta Lynch, a sustainability consultant at BDP, writes: Building legislation in the UK is finally coming into step with what the scientists have been telling us since the 1970s: that global climate change is unavoidable and fossil fuel supplies are in demise. Part L, the EU Energy Performance of Buildings Directive and Planning Policy Statement 22 could look daunting to some architects, many of whom see legislation working against design freedom. But I believe these requirements empower architects. Where their hands might have been tied by clients who question the economics of sustainable design, there is now the perfect opportunity to steer clients in an appropriate direction.

Part L takes effect from April 6, and the EU Energy Performance of Buildings Directive will be phased in until it bites with full force in January 2009. From then, all buildings, new and old, will be given a rating in terms of their energy performance. Planning Policy Statement 22, known as "the Merton law" after the first London borough to adopt it, requires 10% carbon dioxide savings to be produced from on-site renewable technology, such as photovoltaic cells, solar collectors, wind turbines, biomass or gas fuel, on all developments over 1,000sq m in England and Wales. Although not mandatory, it is proving effective at incorporating renewables in buildings.

I believe all this legislation deals architects a stronger hand. The client that uses a value engineering exercise to omit energy-saving features will have to consider the costs of a failed building control application.

The client that says "we've always done it this way", will be forced to approach design with a more open mind. What many clients, and some architects, may not appreciate is that it will be impossible to meet Part L by dusting off an off-the-shelf design and retro-fitting a few sustainable features.

Only buildings designed to conserve energy from the outset, through solar orientation and the building fabric, will make the grade. It will be impossible to take an energy-inefficient design and hope that the services engineers will somehow be able to fix it. The EU directive could have a phenomenal impact. In the past, architects trying to design energy-efficient buildings have come up against the problem that their client wouldn't be the one paying the fuel bills - that was the tenant's problem.

The balance of power will shift in favour of the consultant who can future-proof the client's investment - the architect . For architects in the commercial sector, or working on PFI projects, Part L and the directive will mean it's no longer business as usual. They can deliver new developments that are more durable, have less environmental impact and are more efficient. The legislation could also provide the basis for a more integrated design process. The days when architect and client could work up a scheme well beyond concept stage before consulting a services specialist are numbered. It also offers the potential to regain traditional design skills.

Certain types of vernacular architecture evolved specifically because of their relationship to the local climate. A return to these materials and forms opens up new areas of design opportunity, while increased use of passive solar design techniques should mean increased opportunities to use environmental forces to directly model designs - skills that have sometimes been forgotten in the last 30 years or so. While some of this legislation and policy has had - and will have - teething problems, these new developments are there for a very good reason, not as tools with which to beat up designers.