Raglan Passive House Waikato
Architecture & Passive House Design MOAA Architects (Brooke Cholmondeley-Smith) – www.tawaarch.co.nz
The owners were among the first to choose to build to the Passive House standard in New Zealand and everyone involved in the project broke new ground. The owners discovered the concept through their own research and specified it to their architect, Brooke Cholmondeley-Smith. He promptly undertook training and qualified as one of New Zealand’s first Passive House Designers in 2011.
There were no certified Passive Houses in New Zealand when design began. At the time, there was no certified climate data for New Zealand and this caused considerable delay. Likewise, there was no-one in New Zealand qualified to certify the project then, so this was done by a certifier in the UK.
Lots of work was required to determine the right materials and building assemblies for the house to ensure they would meet the performance criteria. Key components like windows were checked with the certifier before ordering to make sure they would comply. Windows were imported from Germany because no-one could supply them in New Zealand. (How things have changed since 2011!)
The three bedroom, two-storey home is built using Ecoblock ICF walls. Construction was extremely quick using this material: walls were erected in two days and filled with concrete on the third. The truss roof is insulated with fibreglass batts above an Intello air control layer.
The home’s heating demand is massively below the Passive House maximum, a laudable achievement all the more impressive given the timing of the project.
Passive House Metrics
- Heating Demand4 kWh/m2/year
- Heating Load5 W/m2
- Frequency of Overheatingless than 10%
- TFA125 m2
- Form Factor-
- Air leakage @ 50Pa0.4 ACH/hour
- PE demand89 kWh/m2/year
This Certified Passive House built close to Raglan was one of the very first in New Zealand. When the design was started there were no Certified Passive Houses in the country and this was one of the groundbreaking homes that introduced Passive House. Brooke Cholmondeley-Smith was responsible for designing the house and meeting the Passive House standards while also meeting the couple’s desires for how they want to live in the house. “We always take energy efficiency into account in our designs, but Passive House takes it a step further. There are certain performance criteria to be met and they affect the design. Very exciting, it makes it one, large integrated project that both meets Passive House standards and what [the clients] want from the house”, Brooke CS, director of TAWA Architecture says.
Without adventurous clients and architects like this, willing to stretch the boundaries of what is built in New Zealand to do what they know if right for their families and the planet, we will always do what we have always done. Glenn Murdoch former Passive House Institute of New Zealand Chairman- has pointed out the huge potential for Passive House in New Zealand. “Currently, residences use approximately 35% of all of the electricity produced in New Zealand. Most of that is used in very inefficient ways, to attempt to heat homes and to heat water. This amount of electricity usage can be significantly reduced over time by addressing the way in which we build our homes. If we extend this to commercial buildings as well, the amount of energy that can be saved across the country rises considerably.” In addition to reducing the heating energy of this home by ~90% over a NZ Building Code home of the same configuration the indoor air quality and winter thermal comfort will be the best possible in any home anywhere in the world.
As one of the first Certified Passive Houses the design team had to search to find the right materials and building assemblies to meet Passive House performance criteria such as the Mechanical Ventilation with Heat Recovery (MVHR) system. A Zehnder Comfoair MVHR was installed to provide fresh air at all times throughout the entire home assuring good indoor air quality and a warm healthy home. The design team selected Ecoblock wall construction which has a continuous EPS insulation inside and outside of a reinforced concrete structure. The roof is a truss roof with fiberglass batt insulation above an Intello air control layer installed to fully cover the edges of the walls preventing thermal bridges.
Construction Details Average Values
- U-value External Walls0.29 W/(m2K)(R3.4)
- Insulated Concrete Form (ICF) and Plaster
- U-value Floor0.26 W/(m2K)(R3.8)
- 100mm concrete over 100mm XPS
- U-value Roof0.20 W/(m2K)(R5.0)
- Rockwool and timber over Intello
- U-value Glass1.10 W/(m2K)(R0.9)
- Double glazed low-e and argon
- U-Windows1.21 W/(m2K)(R0.8)
- Timber + Purenit
- Air Control Layer
- Ecoblock ICF, Concrete Slab, Intello
- Ventilation Efficiency82.6%
- Zehnder ComfoAir 350 Luxe
Photos courtesy of ecowindows. Drawings courtesy of MOAA Architects (Brooke Cholmondeley-Smith). Graph courtesy of the building owners.