Goldilocks in Witchcliffe

It has been a year since we were handed the key to our new Econest home in the Witchcliffe Ecovillage. How well did the house live up to its energy-efficiency promise?

“The energy efficiency is clearly illustrated by the comfortable indoor temperatures no matter the weather outside. Our home is exceptionally easy to live in with the spacious feel of the rooms highlighted by the high ceilings and wide doorways.”

The expectation

Our home is a 3x2 RETREAT design and is certified as NatHERS 9.1 Stars with thermal performance of 4.3 MJ/m2 for heating and 11.2 MJ/m2 for cooling per year.

Note the disclaimer:

“The predicted annual energy load in this NatHERS Certificate is an estimate based on an assessment of the building by the assessor. It is not a prediction of actual energy use, but may be used to compare how other buildings are likely to perform when used in a similar way. Information presented in this report relies on a range of standard assumptions (both embedded in NatHERS accredited software and made by the assessor who prepared this report), including assumptions about occupancy, indoor air temperature and local climate.”

In other words – it is a benchmark, not a guarantee.

This means we expected to spend more energy cooling the house in summer than heating it in winter.

Despite the expected low energy requirement for heating, we were cautious, having spent winter holidays in the Margaret River area and associating winter in the southwest with grey skies, strong wind, and frequent rain. Winters in the southwest meant cosy log fires, granny blankets at outdoor restaurants, puffer jackets, boots, beanies and scarves.

When the opportunity presented itself, we had underfloor heating installed, just in case a prolonged spell of overcast days prevented the distant winter sun from warming our little Econest.

The underfloor heating is electric and intended to be run from solar panels during day-time – bumping up the heat of the floor, the only significant thermal mass in the house. Upon commissioning the underfloor heating, the installer informed us the soil temperature does not go below 16oC in winter.

Living in an Econest

The first sensation is the silence. The double-glazing blocks most sounds from outside and one can feel the change in air pressure when opening a door. This was unexpected but welcome.

At night the ecovillage is a very quiet place, which took a while to get used to. The absence of strong street lighting makes the stars appear bright and plentiful. The Southern Cross, Orion and the Milky Way are constant companions.

It is also really impressive how well the home keeps temperature, compared to the house we rented nearby, which is constructed from clay bricks and single pane glass windows.

Summer

Our first summer arrived late – only in October. By January we started to experience day-time temperatures in the 30s and in February there were 38-degree days without a breeze. How did the house perform?

We soon learnt to actively manage the internal climate. A typical day would start with ambient temperatures ion the high teens or low twenties. Open the windows and let the cool air in. When the day warms up, close the windows to keep the warm air out, usually by about 10am. Close the curtains to keep the sun out, first the east-facing windows then the north-facing windows and doors. Turn on the Big Ass fans to move the air around for comfort.

By late afternoon the sea breeze kicks in and the ambient temperature drops. Now open the windows (and close the fly screens) and turn off the fans. The sea breeze cools the house wonderfully and we had many pleasant evenings on the veranda.

At night we only needed sheets, no doona. The breeze at night was pleasant, maintaining a south-to-north ventilation. Sometimes the breeze was slight and we kept a ceiling fan on its lowest setting instead.

Winter

The winters were true to form – cold, grey and wet. July and August had stretches of overcast days with little or no sun. We were really glad for the underfloor heating.

Again, we learnt to actively manage the indoor climate – almost exactly the opposite to summertime.

Letting the sun warm the house is important. As soon as the sun rises we open the curtains to let the warmth in. Some mornings will have no breeze and lots of morning mist. The outside temperature warms up in the late morning, sometimes only at noon. Afternoons can be sunny but as soon as the sun sets the temperature drops markedly. That is the time to close the curtains to help keep the heat in the house.

One can feel where the sunlight touched the floor and where it doesn’t. The floors of the southernmost rooms are much cooler than those of the northern sun-facing rooms.

Cooking also helps to add heat to the kitchen area by an extra degree or two even the dishwasher contributes. The heat pump dryer doesn’t add much heat to the laundry, a testament to its energy-efficient design.

Overcast days are usually also windy days, when the ambient temperature will hardly reach 14oC. That is when the underfloor heating makes a big difference. We have it set to come on when the sun is strong, at 9am, to take advantage of the solar energy. It bumps up the floor temperature to 20oC in half an hour, which results in a nice cosy indoor temperature throughout the living area. The bedroom gets morning sun only and the bathroom gets none – so we set the underfloor heating at 22oC from 5am (we’re early risers).

Goldilocks in Witchcliffe

One of the pleasures of living in an Econest home is how cosy the home is when one enters. Nice and toasty in winter, lovely cool in summer. We still forget that it may be cold outside and step out in a t-shirt, just to find a bracing wind in the face. The house keeps its temperature for much longer than the traditional brick house we rented in Witchcliffe the year before.

The Details

Design

RETREAT 3x2 Econest™ by Arcologic Design

Build

Tallwood Custom Built Homes

Construction

9.1-Star all-electric family home of 129 square metres

Burnished concrete floors for thermal mass

Climateframe double glazed windows and doors

Built to Livable Housing Australia Silver guidelines for accessibility

Hot Water : 250 litre Reclaim heat pump hot water system

Renewable Energy : 10.6 kW solar PV system with 8.2 kW Fronius Symo inverter

Solar system connected to the strata cluster microgrid, enabling access to 232 kWh Tesla battery storage and trading of solar power between neighbours

Water Saving : 60,000 litre Pioneer rainwater tank plumbed to whole house; overflow runs to a swale which leads back to the ecovillage dams

Water Wally Greyflow greywater system supplied from the laundry and showers.