What More Can We Do?

This brick veneer single storey residence in town was built in 1990. 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. The next investment in energy efficiency must be optimally cost effective. Increasingly frequent power outages have prompted the owners to consider the value of battery storage.


The assessment confirmed the owners’ assessment of a notable level of energy efficiency achieved with a 20 panel 5kW solar system, adding 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 assessor discussed some areas of likely heat leakage such as no pelmets over the curtains, insulation of only 50% of the ceiling, draught amplification around slow combustion wood heater, downlights and skylights and some ineffective door seals. Inspection of the solar system, powerboard and gas Hot Water System lead to discussion of converting the current Hot Water System to a solar heat pump.


In terms of appliances, the gas cooktop/electric oven has recently been replaced but the split system is relatively old.


Recommendations:

  1. Save money by improving the thermal envelope of the building:

  2. Heat leaks and draughts:

  3. Replace exhaust fans in bathrooms with back-draught protected extraction fans.

  4. Replace downlights with sealed IC rated LED units that allow insulation cover.

  5. Replace both skylights with a solar powered ceiling light; see example at "Kimberley Illume" https://illumeskylights.com.au

  6. Fit 'Ecomaster Draught Dodgers' to all exterior doors and include at floor level a Raven R3P Door Seal.

  7. Insulation: install insulation to 100% of living room and ensure independent verification of the installation; also, the assessor explained a technique used for insulating a brick veneer home.

  8. Windows: the window style is not suitable for secondary glazing and the return on investment on full double-glazing is debatable. ‘Closing’ the tops of windows with pelmets would be an effective way to achieve a better thermal blanket.

  9. Solar opportunities:

  10. 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 (electric stovetop, HWS heat pump, update 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 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).

  11. Finally, to generate more power in winter, the tilt angle of the current panels could be increased.

Richard Keech casts an analytical eye over the household power bills to see where the main household electricity use is going

An external blind keeps this home cooler in summer by keeping direct sun off the glass. Internally, to reduce heat loss in winter, make sure window coverings are sealed at the top (the drapes in this case are open at the top) to stop thermal convection passing over the window

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