Earlier this year the New Zealand Government introduced new building code changes for the H1 category, which covers new homes and major renovations. The H1 portion of the building code “Provides for the efficient use of energy and sets physical conditions for energy performance”, while these changes were intended to improve the energy efficiency of new homes, many experts believe that they fell short of the mark. The new update addressed three main changes but neglected to look at some areas that were screaming out for change. They have also created more climate zones with different rules changing it from three zones to seven zones. Between the zones there are little changes but for the purpose of this article I’m going to be referencing the Canterbury zone changes.
I’m a big fan of improving the health for occupants in houses and improving the energy efficiency of new homes because it doesn’t make sense to live in a cold damp house or spend a big chunk of your paycheck on a heating bill. The root cause of high energy consumption in homes is often related to poor design, outdated construction practices & a lack of awareness with consumer options. Many construction companies are building homes to meet the building code, but that is the absolute worst performing house you can legally build. People think that since a house is double glazed and new it will be warm but some people still have $700 per month power bills in winter in their brand new homes. Homes that are not properly sealed and insulated, for example, will require more energy to maintain a comfortable temperature. Similarly, homes that are not oriented in a way that maximises natural light and passive solar gain will be more reliant on artificial lighting and expensive heating.
I believe that the ROI (return on investment) was not taken into account at all with the changes and some builders have said these changes ended up costing the average homeowner between $20k-40k per house. I can get a lot of energy efficiencies into a new house for $20k-$40k, I’m a massive fan of making your money stretch as far as possible and if we are talking about energy efficiencies most of it is measurable so we can easily calculate the ROI and calculate the time frame in which an investment will start recouping its energy savings.
The first major change is the minimum ceiling insulation has doubled, in most areas of NZ. I have no issues with this change as it doesn’t cost a lot more to add extra insulation while someone is already installing it but why didn’t they increase the wall insulation? In Canterbury the old code minimum was an R2.0 wall insulation and the new code is also R2.0 wall insulation. Better wall batts exist and it wouldn’t cost very much to change from an R2.0 to an R2.8 insulation. It doesn’t even require a change to the type of construction. There was big push back from suppliers at the time around the access to materials because there was a timber shortage and other shortages on materials but if you can double the amount of batts in a ceiling there is no reason you can’t also increase the walls by 40%.
The second major change was the R value of the foundation of the house, now all foundations need to be insulated. While this is a good step forward it is an expensive exercise and this cost could have been spent elsewhere for a better ROI like making the walls thicker. While I myself live in a house that has an insulated slab, including edge slab insulation, it was an added expense that I had to calculate. For me the expense was only worth it because I wanted to use my slab for thermal mass, I have the whole house underfloor hydronic heating and I had upgraded to 140mm framing. For most houses if you had the option between paying for a thermally broken slab that exposes about 200mm to the elements or upgrading to a 140mm thick external wall where over 2,000mm is exposed to the elements it isn’t hard to tell where your heat loss is going to be coming from.
The third change was to do with R value for windows and doors so as well as improved glass technology a new home now needs to have all windows and doors joinery to be thermally broken. This is a great step forward, I myself upgraded my windows and doors to be thermally broken but the cost was quite high. When I upgraded my windows and doors to be thermally broken the added cost was 20% extra direct from the supplier (about $10k now adjusted for inflation). This is a lot of added cost for what probably calculates to be 4–6m2 of exposed surface area to the inside of the house but there is one massive flaw with this, they didn’t mandate a thermally broken front door. It costs about $300 extra to upgrade from a normal aluminium front door to a PIR (polyisocyanurate) insulated front door that has a surface area of about 2m2. Would it not have made sense to mandate an insulated front door to start with, it would be the best $300 investment. What is an absolute shocker though is that many houses that are being built to the new code are still coming with a normal aluminium front door (not thermally broken & an uninsulated), that is just a giant heatsink to the outside world defeating the purpose of upgrading to thermally broken joinery.
Overall, the H1 building code changes this year have been a disappointment for the construction industry & the homeowner. While there are some positive changes, the lack of attention to the root cause of energy consumption and failure to consider ROI makes me wonder who is leading the change and do they know what they are doing. In next week’s article I’ll touch on what should have been implemented instead. If the New Zealand Government were to be graded on their efforts to improve the energy efficiency of new homes, it would certainly receive a “very disappointing, must try harder”.
