This brick veneer single storey residence nestled within a native garden is situated near the centre of the Apollo Bay township. It was built in 1990 and has had a number of energy efficiency upgrades and improvements.
The Owners' Aims
The owners’ interest in the assessment is to reduce energy bills even more than they have already achieved given there are no remaining thermal comfort challenges. Their goal is to find out 'what more can we do?' The next investment in energy efficiency must be optimally cost effective, delivering good 'bang for the bucks'. Increasingly frequent power outages in Apollo Bay also have prompted the owners to consider and explore the value of investing in home battery storage.
The Assessor's Findings
The assessor confirmed the owners’ assessment of a notable level of energy efficiency they have already achieved by installing a 20 panel 5kW solar system, adding exterior film to glass to reduce sun entry, installing full length curtains in most living spaces, and low usage of bottled gas for cooking and the solar/gas boosted hot water system. The home was actually producing more power than what it was using, which supported the consideration of installing a battery.
The assessor identified some areas of inefficiency caused by draughts and likely heat-leakage, such as the absence of pelmets over the curtains. Without pelmets the windows were subject to convection air movement over the glass, reducing the window thermal performance. Other draughts were round the slow combustion wood heater, the ceiling penetrations around downlights and skylights, and some ineffective door seals. In discussion with the owner, the assessor also noted the ceiling insulation was incomplete.
Inspection of the solar system, the household power bills, the electricity power-board and gas hot water system lead to discussion of converting the current hot water system to a solar heatpump.
In terms of appliances, the gas cooktop/electric oven has recently been replaced but the split system was relatively old.
The Assessor's Recommendations
The assessor advised there was money to be saved by improving the thermal envelope of the building through some targeted equipment replacement and treatments.
Recommendations were the replacement of exhaust fans in bathrooms with back-draught protected extraction fans; existing downlights with sealed IC rated LED units that allow insulation cover; the skylights with solar powered ceiling lights such as the"Kimberley Illume".
Treatments suggested included: fitting 'Ecomaster Draught Dodgers' to all exterior doors and include at floor level a Raven R3P Door Seal; installing insulation to 100% of living room and ensure independent verification of the installation; and 'closing’ the tops of windows with pelmets to achieve a better thermal blanket.
Solar opportunities: Given the options available, the assessor suggested that the best investment would be to expand the solar system by 1.6kW and install a battery to make the house more fully electrified (such as a HWS heat pump and an updated split system in place of wood burning).
The assessor noted that the current export is exactly equivalent to a Tesla 13.7 battery. This means that the decision to invest in a battery comes down to a financial cost-benefit analysis: the loss of income from exports (0.6c per kWh) versus savings made by supplying own power rather than buying retail (0.22c per kWh).