Everything is going very well with the Greeny Flat experiment after seven months of testing. If you look at the Results table you’ll see that in total we have now exported 2252kWh of electricity which is almost three times as much energy as we’ve imported (764kWh). It’s been another very dry month so our town water usage (27018 lt) has crept up over our tank water usage (22910 lt). And the indoor temperature has stayed relatively comfortable (between 16.6 and 28.0 degC) compared to the outdoor temp which has ranged from 4.9 to 37.7 degC.
Most people would probably say that 28 degrees is a bit too warm for comfort and generally I would agree. But in this case the 28 degree indoor temperature occurred on a day when it really didn’t get that hot outside (about 32 degrees) so, at that time, we weren’t making any efforts to keep the house cool. In the last few days though it has really started to heat up outside and the forecast is for it to get much hotter in the days to come.
So how can we keep the Greeny Flat cool inside?
The first thing is to keep the sun from coming in any more than necessary and the great thing about Passive Solar Design is that the sun itself does most of that work for us. This is because the sun travels high in the sky in summer which allows the eave overhang on the north side of the Greeny Flat to do its job of stopping the sun from coming in during the hottest part of the day.
The photo above was taken today at 1pm which, during daylight savings time is when the sun is highest in the sky. As you can see, the windows are almost completely shaded by the roof overhang. In fact, if you look at the next photo taken from inside, you’ll see that the sun is not coming in at all. And that will remain the case until about the end of January.
The other thing you’ll notice is that we have now (just this morning) put up a gazebo to shade the patio on the north side of the house. This will help a lot with keeping the place cool through the summer because it will prevent the brick paving from heating up and holding the heat until late into the night.
The other thing we need to do is to use the windows and blinds to allow the thermal mass of the concrete floor to do its job. Basically we just need to open the blinds and windows at night to allow the house and the slab to cool down. Then, during the hot days, we need to keep the windows and blinds closed to stop the heat from coming in. The slab floor will, in effect, store the coolness that it absorbs during the night and work to keep the inside cool throughout the day.
So it will take a few minutes in the evening to open all the blinds and windows and a few more in the morning to close them again and we should stay nice and comfortable through the rest of what is shaping up to be a scorching hot summer.
We’ll let you know how it all goes.