A mania for monitoring

Sensors

When you build a high-performance house, you want to know that it’s performing as expected. Cameron Munro has monitoring in place to do that—and he’s producing some lovely graphs in the process!

We moved into our renovated home in Melbourne in November 2016, having undertaken an extensive renovation with a focus on massively improving the energy efficiency of the building fabric (for more, see ‘All-electric and hydronic’ in ReNew 141).

Our approach was driven by a desire to produce a comfortable home no matter how hot or cold it was outside and to reduce our operating costs to as close to zero as possible. To do this we used the Passive House approach, a scientific method incorporating extensive modelling and verification. This required very high levels of insulation (including high-performance windows), avoidance of thermal bridges and a building wrap that reduces the air infiltration to about 1/15th that of a normal home. We also opted to remove the gas service; instead, we use heat pumps to provide hot water and space heating. We also installed a 6.4 kW solar PV system.

Having gone to what is, by Australian standards, extreme lengths to improve the thermal performance of our home, we were keen to understand exactly how well it performed against our expectations and modelling. Knowledge is power—we want to be able to run our home in the most energy-efficient way and to do this we need to have a good understanding of how it functions. Thus we decided to install monitoring that is well beyond the norm.

The big picture
First up, we’ve kept track of our electricity bills. Over the most recent 12 months we have exported 20% more power to the grid than we have consumed and our net electricity bill was $627, of which two-thirds was the fixed supply charge. This bill includes cooking, hot water, heating and cooling as well as our plug-in hybrid car. The car accounts for about a third of our electricity consumption and this bill of $627 contributed to driving around 9000 km over the year in all-electric mode. If we were to exclude the car we’d have earned about $520 over the year.

Over the 12 months we exported 6071 kWh to the grid and imported 5135 kWh. Our consumption of around 19 kWh/day is high compared to many households, but bear in mind that about 7 kWh/day is used by the car, 2.5 kWh/day for hot water and in winter we’re using about 8–15 kWh/day for heating. Figure 8 shows our month-by-month consumption and export.

Read the full article in ReNew 144.

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