Planning laws are working counter to their own aims of increasing energy efficiency and access to the northerly sun, according to the president of the ACT Institute of Architects Tony Trobe.

Solar passive design in Canberra - which minimises the need to consume energy - usually exposes as much of the house as possible to the north so it can be warmed during the winter as the sun moves low across the sky, a design that also protects a home from the high summer sun with the help of eaves.

But Mr Trobe said too few rectangular blocks were being drawn up with the long sides facing north and south.

He said he was advised by people within the ACT government that the reason blocks were being oriented the wrong way for solar passive design was that subdivision designers were trying to fit in with the planning law that restricts shadowing of neighbouring properties.

''At a casual glance it appears that some of the professionals who design the subdivision layouts for the new suburbs are struggling to come to terms with the new regulations,'' Mr Trobe said.

''While architects can design around these complexities, it costs more money both in the short term with construction and in the long-term energy demands of the building, extra money many homebuyers do not have,'' he said.

''A brief look at the recently released subdivision layout for Lawson is a good case in point where there are very few residential blocks with a long east-west axis optimised for solar orientation.''

As many Canberrans know, blocks that have their long sides facing the east and west also can be hot in summer as the afternoon sun beats into the western-facing rooms.

The vice-president of the Housing Industry Association for the ACT and southern NSW, Glen Dowse, said a compromise needed to be found in the planning laws.

''On east-west blocks we are seeing larger southern yards as houses are pushed to the north and usable northern yard is sacrificed to stay within the envelope,'' Mr Dowse said.

''I would have thought that acceptance of an increased amount of overshadowing by a neighbour to the north in the middle of winter for the gain of additional usable yard in summer would make sense.

''However, the argument changes when we consider overshadowing of windows that are being used for passive heating.

''Good planning isn't about absolutes. We need to decide as a community what level of compromise is acceptable.''

An Environment and Sustainable Development spokeswoman said estate design was complex and had many factors to be balanced, including responding to topography, retention of natural features, bushfire risk, housing affordability and diversity, as well as sunlight.

''A home owner should have the security of knowing that if they design a solar passive home on their block that this won't then be overshadowed by a new house next door,'' she said.

''Lawson was designed to comply with the provisions of the draft variation 306 for solar access.

''The Land Development Agency needs to provide a range of block sizes to offer housing choice within an estate, providing a range of price points.''