Havelock North expoHaus Havelock North
Architecture & Passive House Design eHaus – ehaus.co.nz
Mechanical Design ecoBuild Developments Ltd
Builder eHaus Hawkes Bay - Welch Builders and Construction Ltd.
Certifier Sustainable Engineering Ltd – sustainableengineering.co.nz
New Zealand’s newest certified Passive House is the first in Hawkes Bay and it’s doing a great job of promoting high-performance building to homeowners in the region.
This handsome three bedroom, two bathroom home plus office was designed by Vlada Acimovic and completed a year ago by eHaus licensee Welch Builders & Construction Ltd. It initially served capably as a show home. It’s now home to owners Ian and Sharon Welch.
This house demonstrates the flexibility afforded by Passive House design. The site is not tiny (741m2) but access and proximity to neighbours dictated an east-west orientation. That’s not ideal solar access but the house stays warm in winter and overheating has not been an issue either. A very small split-cycle air conditioner is used to top-up heating or cooling but the deep eaves on the west side of the house also do a great job of keeping out unwanted heat on summer afternoons and evenings.
It’s also notable for not being a simple rectangle like many Passive House buildings. More corners mean more thermal bridges to mitigate but this house has no less than 18 corners, due to setbacks for outdoor living on two sides, a front entrance and an offset double garage (outside of the thermal envelope). The design looks more complex than it is, according to Ian; the form flows from the combination of two different roof types.
Living in the house gives the Welchs a visceral experience of living in a Passive House, making them more effective advocates. “We know what we’re talking about based on experience,” says Sharon. They felt the concrete floor warm up over the course of the first winter as the heat from occupancy accumulated in the slab. It’s very comfortable to walk on and show-stopping to look at (many visitors assume the floor is tiled because of the high-gloss finish and the one square metre sections).
The business is being run from their home office, which is perfect for demonstrating to potential clients the unique features of a Passive House. Potential clients can see for themselves the thickness of the walls, the impressively engineered airtight external doors and the high-performance windows.
The Welchs made a deliberate decision to not install a rangehood or heated towel rails. They wanted to prove the point that these are not necessarily required because of the effectiveness of the mechanical ventilation system at removing damp, stale air. (Ian notes that a rangehood is still a good idea in homes where a lot of spicy or fatty food is cooked). “Inside, it’s like summer all year round. I shower at night and when I get up in the morning, the towel in the bathroom is dry.”
The Welch Builders team have just begun work on their eighth eHaus. Ian is a certified Passive House tradesperson and more staff will go through the training and certification next year. He is delighted to have taken on a new apprentice recently, whose was motivated to train as a carpenter because of his interest in Passive House.
Passive House Metrics
- Heating Demand20.3 kWh/m2/year
- Heating Load9.8 W/m2
- Frequency of Overheating1.2%
- TFA161.3 m2
- Form Factor 3.7
- Air leakage @ 50Pa0.5 ACH/hour
- PER demand50.7 kWh/m2/year
Construction Details Average Values
- U-value External Walls 0.24 W/(m2K)(R3.8)
- 140mm Timber Framed wall with R4 batts and 45mm service cavity with R1 batts
- U-value Floor0.18 W/(m2K)(R4.3)
- 100mm Concrete slab with 200m EPS underneath
- U-value Roof 0.12 W/(m2K)(R6.7)
- Both flat and cathedral ceilings with 220mm R5 batts, 115 R3.2 batts and a 90mm service cavity with R1.8 batts
- U-value Glass1.14 W/(m2K)(R0.8)
- Thermadura - Double glazed (ClimaGuard Premium2) (4:/18/4 Ar 90%)
- U-Windows1.38 W/(m2K)(R0.7)
- Thermadura Natureline 90
- Ventilation Efficiency 75.60%
- Zehnder - ComfoAir Q350 HRV