Green Home of the Year: Energy-Efficient Compact House

Above-and-beyond energy saving features in this cost-effective New Zealand home won over Green Home of the Year judges.

Sometimes, small things can lead to a bigger one. That’s the case for the Emay Crescent Home in Pahi, Northland, New Zealand, which is the Grand Winner of Green Builder’s 2021 Green Home of the Year competition.

The four-person family home, designed by architect Duncan Firth, founder of Solarei Limited, and constructed by Grant Eager, director of Brogan Builders Limited, is a mere 785 square feet. It appears even smaller, thanks to its location on a very steep, west-facing 22,388-square-foot site. 

According to homeowner Margriet Geesink, building a tiny sustainably focused home was an effort to keep things affordable, avoid a big mortgage, and attain a more flexible lifestyle.

“Sustainable” and “solar” are two key words. Emay Crescent Home was designed as a vernacular-inspired model that incorporates traditional New Zealand materials, site-specific environmental design principles, passive solar gain with ample winter sunlight, and a sensitive westerly orientation, which optimizes harbor views while reducing solar gain. The home design also maximizes air flow and promotes outdoor living.

The floor plan is orientated on an east-to-west axis to achieve economy of construction, practical vehicle access, outdoor living, and optimization of westerly views. A 200-square-foot loft space over bedrooms creates more livable space.

A north-facing veranda roof brings low-angled winter sunlight into the front aspect of the home during winter and also provides shade to the outdoor living area during summer. The roof veranda opening is specifically designed to achieve winter sunlight and summer shading. Living spaces also receive direct passive solar gain with westerly outlooks over the neighboring Kaipara Harbour.

During summer the home is designed for optimized passive cooling using stack effect (hot air rising principle) and cross ventilation. Windows are specifically positioned to maximize passive air flow and cooling, reducing heat buildup from westerly afternoon solar gain.

The house is designed for an anticipated electrical energy load of 1,500-2,000 kWh annually or an annual energy index of approximately 24.5kWh per square meter. Internal temperatures passively peak at 24 degrees Celsius during later afternoon mid-winter, with the extreme low being 17 degrees Celsius during the early morning. 

Green technologies and features which have been used for this home include off-site prefabrication, structurally insulated panels in the walls, metal-insulated panels in the roof, and above code insulation for floor, walls, and ceiling. There is also New Zealand-made metal cladding, Canadian cedar fascia boards at roof edges, and a timber subfloor clad in a 10mm recycled native hardwood called “kauri”.

Indoors, you’ll find argon gas insulated glass, energy-efficient appliances, water-efficient taps in the bathroom and kitchen, and breathable bio-paints for interior finishes. Living spaces receive direct passive solar gain with westerly outlooks over the Kaipara Harbour.

In terms of irrigation and moisture management, there is an onsite tiger worm composting system that treats black and grey water (Geesink notes that it was “time to get some new pets” — worms for the waste tanks), a hot water heat pump that sucks heat out of the air, and capacity for 10,000 gallons of rainwater harvesting and fire water storage.

A limestone chip driveway aids with irrigation efforts. “Our land is very muddy and sticky,” Geesink notes. “Limestone chip is the material of the land, and it comes from a quarry not far away. The water can easily drain, and the lighter color matches the landscape and beach area around us.”

The bottom line: The combination of standardized construction methods, site-specific environmental design, passive solar gain, passive cooling, energy-efficient technologies, and building technology create a small, desirable, sustainable family home.

1. The Emay Crescent Home’s doors and windows feature highly efficient Rylock glass, designed to reduce excess sunlight and withhold heat when desired.
2. Decks are all-wood, locally sourced New Zealand Pinus radiata timber.
3. Interior floors are made of New Zealand natural hardwood and recycled kauri flooring.
4. The Knauf Insulation-lined walls include a thick composite of polyester and recycled plastic, which offers thermal performance and sound control.

The home is orientated on an east-to-west axis to achieve economy of construction, practical vehicle access, outdoor living, and optimization of westerly views. Credit: Margriet Geesink