Cold houses are no accident, they are there by design

18 October 2018

Some of the newest design ideas and trending building techniques are coming from those advocating smarter, healthier and more energy efficient homes. French architect and now Christchurch City Council’s Eco Design Advisor Julie Villard, has just completed her own new home in Lyttleton proudly achieving a 9 Homestar built rating.

After living on site for two years in a self-contained Bedford house-bus, ''next to the dream'', Julie jokes she is now living ''in'' the dream, her house “from the future”. A gentle dig at the New Zealand Building Code being “20 years behind Europe and the UK when it comes to thermal performance”.

The building is a compact yet (105m2 + Mezzanine), spatially aware, modern two story dwelling. From the street the building presents itself as small scale, single story, gable roofed form, where in reality, a two-story building emerges as the site falls away. Both gable ends are glazed to maximize the natural light and the stunning surrounding views. The kitchen joinery module is also designed to provide privacy from the busy street, allowing extra storage on both sides of the cabinetry.

The structure is a Hybrid system CLT panel - steel portal frame, all prefabricated off site. All remaining framing is LVL (Laminated Veneer Lumber) for superior strength and straightness. The foundation system is also Hybrid: combining the benefits of timber shallow piles with the efficiency of a fully insulated waffle slab to accommodate a complex and uneven ground.

The building is insulated from the outside (over the CLT), minimising the thermal bridges and allows the house to remain warm with a good heating system in every room. ''The more you insulate the less you need to heat''. Julie followed the higher standard UK building code for insulation and installed a hydronic central heating system connected to a 3.8 Kwh heat pump.

For improved indoor air quality, Julie applied the advice she gives her clients to choose materials, paints and finishes with no or low "Volatility Organic Compounds" (VOC) to minimise airborne toxins. “Then ventilate,” says Julie, “either passively or actively to avoid moisture build-up and eliminate CO2 emission and other toxins. Opening your windows (even in winter) for three minutes a day is enough, and if you can't be bothered, well, invest in a system that will do it for you.”

Team:

  • Architect / designer: Julie Villard, working at the time for Bob Burnett Architecture.
  • Builders: Pomeroy Builders / Steve Pomeroy.
  • Engineers: DO - Davis Ogilvie / Greg Clark

Sustainability and innovative features:

  • Prefabricated house constructed from Cross Laminated Timber from Hasslacher Norica Timber/ Welstruct NZ. The CLT remains visible on the inside walls of the home.
  • Seam roof and wall cladding Hiland Tray from Stratco, for a design without gutters.
  • Water is collected at the bottom of the walls with a surface drain redirected to water tanks.
  • Wood fibre semi rigid external insulation - NZ’s firsthome
  • Pro Climabreathable membranes in wall to control vapour diffusion
  • Thermally broken aluminium window frames, from Hagley Windows, with high performance glazing are recessed into the warm part of the wall to reduce condensation
  • Topping slab on top of CLT to provide thermal mass
  • Underfloor heating throughout both levels, with H2 Flow underfloor heating
  • Passive ventilation system with 2 roof windows from Velux,
  • Active ventilation system with decentralised HRVS from The Heating Company.
  • Schneider smart home system Nero with Energy efficient LED lighting.
  • Seamless kitchen from Elite Joinery, Christchurch.
  • No permeable surface for landscaping, and native plantings.

The Christchurch City Council offers free eco-design advice sessions with Julie. To book a consultation phone 03 941 8999 or use the following link: https://www.ccc.govt.nz/eco-design-advice/

Find out about getting a Homestar rating for your project.