Prospective from a Pupil of Passive Homes. Diving deeper into different components that make up a passive house.

In this blog post, I explain how constructing in the Passive house way keeps the warmth in, and the cold out.

“If you build it they will come” whispers through the wind and into Kevin Costner’s ear in the 1989 movie Field of Dreams. This is not a review of that pure on-screen Americana, nor is it a analytical breakdown of how baseball, and its 162-game regular season will never find its place in Aotearoa’s back-to-back cricket, rugby and alcohol/music fuelled new years festival seasons.

But baseball is a great analogy for Passive housing, Number 1: it’s a foreign concept that Kiwis are reluctant to commit to, Number 2: it’s all about the numbers with many components performing differently for the good of the team. And Number 3: the bats are round, not rectangular. Ok, ok the last one is a little bit on the nose, but shows how a few different rules and components can lead to a completely different result.

Imagine you are building a brand new home, or extending out the back of your existing one. In order to obtain a Code of Compliance Certificate (CCC), it will need to be built to the minimum requirements under the building code. Why should such a massive piece of a persons wealth, only be built to the minimum requirements? Requirements that are continuously being superseded by new ones. This is where the extra investment mentioned in the previous post is utilised. 

Again the pillars of Passive housing are:

  • Building location and orientation 
  • Building layout
  • Window design
  • Thermal performance
  • Ventilation
  • Insulation

They can all play their own part, and ideally in the construction process they can all be considered equally. But in some instances they cant be.

Kainga Ora, (the government agency for Homes and Communities) have been renovating and retro-fitting existing housing stock with Passive House building components throughout Wellington and the Hutt Valley. This has meant that old state homes have become incredibly energy efficient homes using products that are readily available to use in all construction.

Kainga Ora Retrofit Programe

At this point, I should be clear. Passive house concepts are not just for new builds. By using better quality building products that exceed existing minimum standards, every house can be warmer, drier, healthier and more energy efficient. These products are all pillars of Passive housing, the are Insulation, Ventilation and Window design. Even though they aren’t the most sexy parts of construction. If they are of high quality, then you’ll be feeling a lot more comfortable to take your clothes off.


Insulation requirements in New Zealand (rated as an R value, which measures thermal resistance) depend on what region of the country you are in. At the time of writing there are currently 3 different regions. Zone 1 encapsulates Auckland, The Coromandel and Northland regions. Zone 2 is the rest of the North Island except the Central Plateau and Zone 3 is the South Island and the Central Plateau. Zone 1 & 2 are very similar, both their requirements for ceiling, wall and underfloor is R2.9, R1.9 and R1.3 respectively. While for Zone 3 the requirements are R3.3, R2.0 and R1.3. Not really that different when you think about how the climate is different in each region of New Zealand.

Mineral insulation

If we want to have a warmer house, we need to increase the R-Value of insulation. The highest R-Value insulation that is readily available, is Pink Batts R7.0 for Ceilings, R4.0 for Walls and Bradfords R2.6 for underfloor. These are all very high quality products but still are no where near international standards. Ireland, which shares a similar climate to ours has a minimum R5.6 in their walls, and a minimum R.6.25 for Ceilings.

Statistically, Irelands wall insulation standards have increased by 200% in a little under 3 decades, whilst New Zealand’s has only increased by 27% over 42 years.

Consideration also has to be made for what the insulation is made from, you will notice in some spaces like roofs, that were insulated long ago, what was once plump and full is no more, this is because some products shrink over time and slowly become less and less efficient. The same happens in the walls. Because of the restrictive nature of being in the wall, we need to make sure that the product wont shrink but its also installed correctly so no cold air can pass through. Insulation that are made from mineral wool, such as Rockwool is a great alternative as it wont shrink or crumble overtime. Passive housing also features two unique elements surrounding Insulation that separate it from conventional building. Service cavities and internal underlay wrap.

Service Cavities

More applicable to new construction, service cavities allow for everything like wiring and plumbing to be run, without having to hack at the insulation to make everything fit, and by having more intact insulation, it means more heat is retained.

Internal building wrap

Intello is a common product. The underlay which extends around all the walls and over the ceilings is designed and installed to stop any draughts that may find their way into the house. It also acts as a vapour barrier that stops cold air from bridging through a homes cladding and framing onto the interior linings, likewise it acts a barrier so that the warm internal air cannot escape outwards. 

A service cavity installed over internal building wrap

Passive house shouldn’t be restricted to new builds, we can renovate and make our existing homes happier and healthier, but it will take time to learn, we need to listen to others and do our research. All the components are there, it’s just about playing the game a little bit differently. Kind of like…