How much cost does upgraded insulation required under the revised H1 add to a new build? Much less than anecdotal figures bandied about in the media, according to some solid research released last month.
“EBOSS and New Zealand Certified Builders (NZCB), with design input from Architects Designgroup Stapleton Elliott (DGSE), teamed up with quantity surveying firm YourQS to put real numbers to the cost of the increased insulation standards… This was a direct response to the Minister of Construction announcing a review was underway into the cost implications of the new H1 Thermal Insulation standards.
“The cost of improved insulation for Kiwi homes is far less than the $40,000-50,000 cited by some—and can even be as low as $2,179 for a 3-bedroom house built in Auckland or Tauranga (Climate Zone 1), if factored in during the design phase of a project.
“We looked at two good examples, and in both the cost increase is marginal, so we know you can spend a little more money and get much greater thermal performance—contributing to drier, healthier, warmer homes with reduced energy consumption,” wrote EBOSS managing director Matthew Duder.
The analysis used two real-life standardised plans designed by architects DGSE that will form part of a new NZCB Studio range of designs. These designs in fact significantly exceed the H1 regulations, but the research focused on identifying the least costs required to merely meet H1 minimum requirements. The cost of using the schedule method was compared to the calculation method*, with illuminating results.
“Using the schedule method, H1-compliant insulation added $10,609 to pre-2023 build costs for the 3-bedroom 140m² house plan, but brings all the health benefits and savings on heating that comes with having a properly insulated home.
“The research found that these additional costs could be reduced to just $2,179 over the pre-2023 build cost by using the more sophisticated calculation method.”
They also ran a member survey and the resulting average was a 213 sqm building and a cost increase of $18,125 or 2.4% of the total build cost. This was considered consistent with the modelled results from YourQS.
There’s at least one building scientist who will feel vindicated that their modelling work done years ago has been pretty well confirmed. MBIE commissioned research as part of consulting on the H1 improvements. That report “Thermal, financial and carbon review of NZBC energy efficiency clause H1/AS1 thermal envelope requirements for residential and small buildings,” (Jaques, et al BRANZ 2020) modelled the benefit-cost ratio of the marginal cost increase and energy savings of the insulation increases.
The EBOSS/NZCB work is timely as I’ve heard we may have new H1/AS1 changes come out for consultation again quite soon. I’ve tried to influence some positive change or at least stem regression. It is shameful that anyone in the construction industry in New Zealand–and anyone setting policy or approving it—would want to stave off much-needed change.
* The ‘schedule method’ means architects and designers follow a standardised table outlining the minimum insulation values required for each key building element (floor slab, roof, walls and glazing) in a particular climate zone. This is currently the most common method used to demonstrate compliance with the building code.
The ‘calculation method’ sees architects and designers work out the total heat loss of the proposed building from all the areas and construction R-values (thermal performance) for that building, which is then compared to the heat loss of a reference building to determine compliance.