Wednesday, March 17, 2010

Our Eco House - the Inner Workings

Our home is a solar passive design which means by the careful placement and quantity of windows we use the sun to help heat our home in winter. On the north side there is only 4% of the total square footage of the house devoted to windows. On the south side there is 12% of the total square footage devoted to windows.

The sun is lower in the sky during the winter and enters 20’ into the house bathing the black concrete floors with sunlight. On sunny winter days the inside temperature is a cozy 23C° – 25C° with no additional heat source required. We use a high efficiency wood stove for cloudy days and nights and there is radiant in-floor tubing as additional backup. To heat with wood (the only renewable resource) usually costs about $500 if we have to pay for it.

In the summer the sun is higher in the sky and the wider 2’ overhang on the house keeps the sun from entering the house, the concrete floors stay nice and cool so that we require no air conditioning. We have three ceiling fans that see occasional use.

The building shell is Nudura insulated concrete forms – big Lego block Styrofoam forms that are joined together and then concrete is poured into the middle. The walls are 2” of Styrofoam on the outside, 6” of concrete and then another 2” of Styrofoam on the inside for an R value of 50+. The ceiling insulation is R40. This helps keep the house cool in summer and warm in winter. Our basement floor is insulated with 2” Styrofoam and this combined with the Nudura walls keeps the basement at 18-19C with no heating. There is radiant in-floor heating if we want to use it.

We produce most of our electricity from the 1740Watts of solar panels. During the day when we are producing more than we need the “green” energy flows out to the grid. At night when we are using more than we are producing we use energy from the grid. The dual meter tracks both inputs and outputs and we pay the difference. Our hydro bills average about $30 a month, most of which is service charges. We have an integrated battery backup which allows us to still have power in the event of a blackout for all critical appliances.

The average Canadian home uses 35Kw per day of electricity – we use between 5-10Kw – all CFL’s, Energystar appliances, 3 computers, two televisions, DVD players all on power bar. We have no dishwasher, clothes dryer, air conditioner.

We pre-heat our water with ten Thermomax solar collectors on the roof. The water is pumped from the well using a solar panel to power the pump into a 5,000 Litre cistern located under the porch, then is preheated from the Thermomax and topped up with a propane in-line water heater as needed. In the summer we often shower with water heated solely by the sun. Our propane for heating water and cooking averages about $75 per month.

The septic system is a gravity fed Ecoflow system using peat moss to filter the waste.
The metal roof allows us to collect cleaner rainwater into the rain barrels and we also have the ability, should it be required, to direct one of the downspouts into the cistern.
We further conserve water with dual-flush toilets, low-flow shower heads and a front-load washing machine.

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