ACT government change to rules covering overshadowing of neighbours' houses are strongly backed by builders, but have attracted some vehement opposition from solar passive house designers and residents in older suburbs.
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The move might also buy a fight with the Greens, with party convenor Sophie Trevitt calling on the government not to water down solar rules.
The planning directorate is considering more than 100 submissions on new solar building rules, to replace the rules introduced in 2013 amid opposition from builders and developers. The 2013 rules, according to submissions, complicate the design of houses on small blocks, especially blocks of less than 250 square metres in new suburbs.
Developers say they are forced into expensive earthworks to dig houses lower, and homes are being built close to northern boundaries with their outdoor space to the south.
At the moment, new houses must ensure that neighbours to the south still get at least three hours of inside sunlight between 9am and 3pm on the winter solstice.
The rule is being replaced by a requirement for at least four square metres of glass on the northern side of a house, but only where it is "reasonable".
The government is also increasing the height of the "solar fence", which determines how much shadow can be cast into the north side of a neighbour's property.
It says while the move might "increase the amount of shadow a house can cast on its southern neighbour", solar access would be improved.
But Narrabundah architect Stan Bevanda said the change to the solar fence would allow shadows to extend up to five metres into a neighbour's property at the winter solstice.
People with two-storey houses to their north were already living in shadow, and the change would only make that worse, he said. "All this is doing is provide for larger houses whereas the current solar envelope allows for sufficiently large house as they are."
Three hours of sun was the bare minimum for good passive design, and jettisoning it was a major backward step. The new four square metres of glass was meaningless without the requirement for direct sunlight on the glass, he said.
The Griffith Narrabundah Community Association said problems with existing rules, if they existed, were on small blocks in new suburbs such as Wright, Coombs and Lawson. It called on the government to publish reliable data on the scale and location of problems before making sweeping changes for the whole of Canberra.
"Every block owner in Canberra with a neighbour on their northern boundary is threatened with the potential loss, at any time in the future, of at least some of their existing solar access," the council said.
The Greens said the government should consider whether freestanding houses were suitable for small blocks.
But many submissions from builders urged the government to push ahead.
The Institute of Architects said the increase in the height of the solar fence would allowed more flexibility in house design and siting. The 2013 rules had led to more blocks with a north-south longitudinal axis, rather than east-west. Half of the houses on those blocks had their street frontage – typically just 12 metres – to the north, with solar access to that side limited by garage and entry porches.
The Housing Industry Association said the changes would maintain "reasonable access" to sunlight for neighbours and "flexibility in siting and design" for new buildings. The Master Builders Association said current rules were "simply unrealistic" for sloping sections. They encouraged new developments towards the north of a site, and homes being dug into the ground.
