A High-Performance House of the Future
This 198 sq/m family home represents an example of the how our future dwellings might be designed and constructed. It contains a number of innovative features to improve quality and buildability, increase resilience and ensure the occupants are warm, dry and comfortable all year round – without having to spend vast amounts on their energy requirements.
The north-south orientation of the site is not ideal, therefore we could not rely on a passive solar solution to provide adequate thermal comfort. Instead, a high performance low energy model was adopted. It is a model that will become increasingly important as our cities become denser and therefore the competition for space, light and sun will increase.
LOW ENERGY HOME
When analysed, this design was shown to use only 28% of the annual energy requirements of the same design built to current code minimum standards. In other words, the house is 3.5 times better at saving energy when compared to a new home built to code. No solar panels or wind generation was used, so how was this amazing result achieved?
-Multi-layered insulation with minimal thermal bridging. 190mm thick wall insulation and 230mm thick ceiling insulation using Christchurch-made Terra Lana wool-blend batts.
-Airtight envelope using Intello membrane fitted behind the linings to eliminate infiltration and manage moisture vapour transfer through the building envelope.
-High quality Thermadura laminated timber windows, double-glazed using soft coat low E glass, argon gas and warm edge spacers. These windows achieve much higher insulation and airtightness levels compared to standard double-glazed aluminium windows.
-Wolf ducted mechanical heat recovery ventilation system for continuous fresh air supply, even temperature distribution and moisture extraction from wet areas.
-Cost-effective thermostatically-controlled electric panel heating. Analysis indicated less than 4.0 kW of heating was required for the entire home.
-Heat pump hot water delivered from an internal storage cylinder.
SITE CHALLENGES
There were a number of challenges to be overcome with the design. The site is a modest 506 sq/m and is only 15m wide. The ground comprises low-lying sandy soils of poor bearing capacity and is subject to earthquake-induced liquefaction. The site is also subject to surface flooding and inundation due to predicted sea level rise.
DESIGN SOLUTION
Considering the potential for inundation led to a design solution that positioned the floor level about 1.1m above natural ground. A lightweight construction system was employed that would allow the building to be relocated with relative ease, should predicted sea level rise occur within the lifetime of the building. A simple 2 storey gable form was used with the upper bedroom spaces contained within the roof space to help keep the total building height within limits. Timber decks, steps and ramps are used to facilitate indoor-outdoor connections and provide easy access for elderly or wheelchair-bound people. These can be easily dismantled in-future, should relocation prove necessary.
PREFABRICATION
The house is to be built using panellised pre-fabrication, a method of construction that is common in Europe and Scandinavia. Floor, wall and roof panels are fabricated in a factory then delivered to site, craned into position and fixed in-place. Exterior cladding and interior linings and services are then site fixed in the usual manner.
Wall & roof panels typically include framing, insulation, building wrap, ply bracing, and cavity battens and may also have windows fitted. Floor panels utilize factory-made structural cross-laminated timber slabs (or CLT). These slabs eliminate the need for floor framing and are able to span considerable distances, depending on thickness. They provide an ideal structure should the home require relocation in future.
Advantages of prefab construction include:
-Improved build quality due to factory-based controlled assembly.
-Less affected by inclement weather on site.
-Reduced build time due to off-site construction happening in tandem with site based work.
-Capitalises on modular construction methods and reduces construction waste.
-Improved health & safety outcomes.
-Is able to utilize a shared digital model during the design and documentation phases.
Talk to us at Chaplin Crooks Architects about designing your house of the future.
