Efficiency on a budget: Easy, low-cost retrofitting

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Alan Cotterill takes us on his journey retrofitting a standard brick-veneer home for energy savings.

Eleven years ago we bought a near-new four-bedroom brick-veneer house in Wagga Wagga, an inland town in NSW, in an area that experiences hot summers and cold winters.

It’s a fairly standard house for the area, set on a concrete slab, with a verandah running the length of the eastern side. The house is long and narrow, on a north–south axis, with only the double garage facing north. Excluding the double garage and verandah, the house size is 183 m2 and the window area is 19% of the floor area.

R3.3 batts were already installed in the ceiling, along with reflective foil in the walls and under the colorbond roof. We found that an evaporative cooler provided effective summer cooling on most days and later-fitted gas central heating provided winter heating, albeit at a cost.

There were several areas, however, where we found we could significantly increase comfort and decrease bills, through simple retrofits. Some of these are detailed below, including information on any issues we encountered and how we overcame them. Hopefully this will be of assistance to others planning similar retrofits.

Downlight gaps

The house’s original lights were 12 V, 20 W halogen downlights. A 30 cm clearance without insulation batts is required around each downlight to guard against overheating and fire. There were 18 halogen downlights, meaning 18 gaps in the insulation. Thus, there was about 6 m2 of ceiling without insulation.

So, four years ago I did a simple changeover from 20 W halogen globes to 3 W LEDs ($15 each at the time), using the existing fittings and transformers. I later covered each downlight with a downlight mitt ($18 each) and, ensuring that all transformers were held above any insulation to prevent overheating, I filled in the insulation gaps up to the mitts.

Each mitt comes with a wire support to secure it to the plasterboard and a wire tower to secure each transformer above the mitt and batts. Installation of the mitts was easily done from below, standing on a ladder. Because they are soft, you can simply collapse them, insert them through the hole for the light fitting, and open them up inside the roof cavity and position them over the hole. Then you just push the light fitting back in place, as they are held in the ceiling with spring clips.

The main energy saving wasn’t from the significantly lower wattage for lighting, but from the improved ceiling insulation, which reduced energy costs, especially from winter heating.

There were some problems, however. The original transformers were designed to run with a higher wattage than the 3 W LED globes I used, resulting in some flickering and some transformers failing. With what is available today, I would, instead, plug in an entire new 12V LED downlight unit, which includes a matched transformer ($28 from a specialist electrical trade/retail outlet).

Also, the 3W LED bulbs were bright enough for general socialising, but a little dim for reading. We’ve since added newer 8 W LED bulbs selectively, such as over a chair used for reading or over a work area in the kitchen. Not only is there now plenty of light, but the beam angle of 95 degrees (rather than a narrow 33 degrees) gives wider and more even illumination.

The choice of downlight mitt also needs to be considered carefully. Mitts need to be matched to the type of light fitting and may need a ventilation hole. Mitts without ventilation holes can be used with fittings of the gimble type, where the light can be tilted in its fitting. This tilting action requires a small circular air gap, flush with the ceiling, and this allows some ventilation around the bulb. But, where fixed fittings are used, mitts with ventilation holes are required. We used mitts with ventilation holes to avoid any risk in the future; for example, a new homeowner could unwittingly replace a gimble fitting with a fixed fitting.

Read the full article in ReNew 130.

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