KEY POINTS:
New homes will be better protected from icy weather under tougher insulation rules being extended on Monday.
Changes to the building code requiring more insulation and, in most cases, double-glazed windows, will apply to all houses south of Auckland.
Builders in Auckland and Northland are already preparing for
the changes, which will cover the whole country from October 30.
So how much will the changes cost?
The Government says the new rules add between $3000 and $5000 to the cost of building a house, which it says will be recovered in lower heating bills within seven years for a home in Auckland, six years in Wellington, four years in Christchurch and three years in Dunedin.
The Herald asked energy efficiency consultants Righthouse to do their own calculations for an average Auckland home.
Righthouse found the extra cost for a 120 sq m home with timber frames would be $2084. If the home was constantly heated to the World Health Organisation recommendation of 18C, the added insulation would save $262.20 a year in energy costs - paying for itself in just under eight years.
Chris Mason, of the New Zealand Institute of Architects, said many architects would already be using the new requirements. The new rules are already in force in the South Island and North Island's central plateau.
Bob Lloyd, director of the energy studies programme at Otago University, said the average new home using an electric bar heater or gas heater would use about a quarter less heating under the new rules.
Total electricity bills would be 11 per cent lower, but homes with a heat pump installed would not save as much because they used less electricity to start with, he said.
The building code does not require double glazing, but Master Builders chief executive Pieter Burghout said double-glazed glass would be the easiest way to meet new energy efficiency requirements.
While it was taking some work for the building industry to increase supply and installation capacity for double glazing in the North Island, Mr Burghout had not heard any negative comments from builders about the changes. Mr Mason said architects had long pushed for double glazing to be used in more homes.
However, both Mr Burghout and Mr Lloyd questioned whether double glazing was necessary in Northland.
$2000 COST FOR OLDER DWELLINGS
The new insulation requirements will make new homes warmer but most homes will still be out in the cold.
Housing research company Beacon said more than a million of New Zealand's 1.5 million homes were built before 1979, when home insulation became compulsory.
A study presented last month by the Centre for Research Evaluation and Social Assessment (CRESA) showed more than a fifth of Kiwi living rooms were colder than 16C on a winter evening - a level that interfered with the respiratory system and put strain on the heart.
The World Health Organisation recommends a minimum temperature for living areas of 18C, or 21C if there are babies, children or elderly people in the house.
Kay Saville-Smith, from CRESA, said people often gave up heating older homes because it was too difficult.
People were likely to spend more on heating if the heat stayed in.
However, bringing an existing home up to new insulation standards can be expensive.
Research by the Otago University energy studies programme found it cost between $20,000 and $30,000 to fit out an existing house to the standard new homes have to reach.
However, Beacon general manager Nick Collins said spending a few thousand dollars on insulation could make a large difference to quality of life in a home.
He said adding insulation to the walls and ceiling could cost just $2000.