Exceptional Energy Efficiency
Black Barn House was computer modelled at design stage to ensure the house would maintain a comfortable temperature year round and be exceptionally energy efficient.
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Once the site and solar orientation was optimised the following six factors were incorporated into the build to ensure the energy and comfort goals were met.
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1 SIP's
By using Structural Insulated Panels (SIP's) in the construction the house envelop is super insulated. Wall panels are 165mm (6 1/2") thick and the roof panels are 210mm (8 1/4"). The cores are closed cell expanded polystyrene.
With R-values of 4.4 for wall panels and 5.6 for roof panels they are more than double the NZ Building code requirement for climate area 3.
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To further reduce heat loss through thermal bridging the panels were joined using insulated splines.
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Note: R-value is a measure of resistance to heat flow through a thickness of material such as a wall, window or roof. The higher the factor the better. R-value can be expressed in metric (above) or in imperial units as used in the US. The US R-factor is 25 and 32 for walls and roof panels respectively.
2 Insulated Foundation
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Fully insulated MAXRaft foundation system was used minimize heat loss through the concrete foundation slab.
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This system provided two critical functions:
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It is insulating the slab from the ground to a) minimise heat loss through the slab and b) maximise the efficiency of the underfloor hydronic heating. For this 250 mm thick Expanded Polystyrene panels were used.
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By Insulating the edge of the slab the perimeter heat loss is minimised. This is illustrated in the diagram.
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3 Hydronic Underfloor Heating
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Underfloor heating is exceptionally energy efficient when the insulated slab is powered by an air to water heat pump.
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Installed is a 8kW heat pump which provides more than sufficient capability to heat the home even on coldest Central Otago Days
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The zone controls allows fine tuning or to turn off a room or zone if desired.
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Extra water loops were installed in the hallway to assist heating by capturing solar gain.
4 Wooden Doors and Windows
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'The Andersen 400 series joinery range provided the perfect solution to ensure that the house's windows and doors met the design specification for thermal performance. The windows and doors are double glazed, argon gas filled and Low-E. Both have mechanisms to seal air- tight.
Timber joinery is twice as efficient for limiting cold from the outside when compared with aluminium. In fact aluminium is second only to copper for thermal conductivity.
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The garage doors are a five layer Clopay Canyon Ridge Series. These have a Intellicore polyurethane core with a thermal break . They have a R-value of 3.6 (US = 20.4)
5 Continous Flow Hot Water and Gas Fire
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Hot water heating is a major energy cost component. Continuous flow water heating is efficient because it only heats water when needed on demand. There is no hot water storage. And reticulated gas is a lower energy cost per kw than electricity.
Installed is a 6 star energy rated Rheem continous flow water heater delivering 27 litres per minute.
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Additional heating and ambience is provided by a Escea DL1100 gas fire in the lounge. This unit has a 5 star energy efficiency rating and incorporates powered direct vent flue technology. It has a heat output of 10.4kW.
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6 LED Lighting
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LED (light emitting diode) lighting has been used throughout the house. LED's use only 10% of the power of incadesent lighting. With a large house the saving per annum is surprisingly large.