Jenny's place & the -8 degree start to July
When David and I moved into our new house in February, we decided to go for twelve months with no heating (apart from a 600W infrared panel on the ceiling of each bathroom) or cooling (apart from ceiling fans). The 'no coolers' thing wasn't a big deal as all Light House homes are optimised to stay cool in the Canberra summer without needing more than ceiling fans. But even though our homes are very thermally efficient, they typically require one or more small heaters to the living areas to take the edge off the depths of winter. We, however, wanted to put our house to the test. How well will the great design and science hold up in a Canberra winter without heaters to assist?
People have been keen to know how we've coped in our unheated living rooms and bedrooms so far. The first three nights of July were cold for Canberra, hitting minimums of -8.7, -8.2 and -7.1 respectively. Well... we were fine.
Part of the reason is that our house is designed so it gets plenty of free heat from the sun in the middle of winter through the well positioned and sized windows (and doesn't lose much overnight due to a well-sealed and insulated building envelope). Below is a photo to show you what I'm talk about. This picture was taken at 1pm on July 2. That's my thonged foot in the foreground and the youngest teenager in the background after he had to retreat outside to cool down. Yes, seriously. (Our dog Zac had already sought shelter in the shade of the courtyard wall by this stage.) The sun soaked sections of the slab were at 27 degrees at this time and the areas out of the sun's reach toward the back of the house were between 14 and 17 degrees (compared to the carport slab which was at 2 degrees). According to BOM the air temperature in Canberra reached a maximum of 13.8 around 2:30pm on this day while the inside temperature at our house got to 19.8.
Weather data from the Bureau of Metereology. See minimums and maximums to the left but also note the columns labelled 'Cld'. The 'Cld' columns tell you how many 8ths of the sky were covered by cloud ie. the number 8 means the sky was pretty much completely overcast.
Those first two days of July weren't too bad at all as the very cold early mornings were preceded by days with classic, clear (and oh so crisp!) blue skies. It doesn't take much sunshine to get the temperature in the house rising quickly. The other great thing is that despite the lack of heating the house remained >20 degrees warmer than the external minimum temps. On July 3 the clouds rolled in - that's not so much fun - more on that later.
When we first moved in, I installed data loggers all through the house and the yard so I could collect and track the temperature data for an entire year. These little gadgets send out data packets around the clock, giving me a complete picture of the building's thermal performance over time. I put together a chart to show you how it's going so far.
Here it is!
The daily minimum-maximum temperature ranges in the two living areas of the home (green and black) and the external minimum-maximum inside our front courtyard wall. See below for more info.
The graph above shows the daily minimum to maximum range for our front kitchen/dining/sitting area (in green) and our east/west glazed lounge that sits to the south of this space (in black). The larger blue zone shows the daily external minimum-maximum range inside our front, northern courtyard wall - you can see that the temperatures measured here are generally a few degrees warmer than the air temperature as measured by BOM.
We do start to feel it when the days are cold and overcast and have on occasion imagined turning on our imaginary heater... but surprisingly infrequently and we are still yet to hear the teenagers complain of being cold (not bad for two lads that used to park themselves in front of the heaters during winter at our previous two rental homes).
Daily minimum to maximum temperature ranges in the front kitchen/dining/living area.
The graph above just shows the daily min-max temperature range in our front northern living area (the social hub of the home). You can see a 'nasty' patch on the graph around mid June where the internal temperature range overlaps with the external temperature range (June 17 was particularly horrible!). We are pleased to say this coincided with 4 very overcast days AND with us being away. The lack of sunshine and the lack of human (and hound) generated heat really took its toll on the house temperature. Fortunately, we had one day of sunshine to take the chill off a bit before we came home on the Monday and things picked up again very quickly.
Another big dip around ANZAC day coincided with cloudy days and the family being away. All the maximum temperature dips in the graph correspond to overcast days and/or days when nobody was home.
WILL WE SURVIVE THE REST OF WINTER? Definitely! Having tested and logged temperatures in a range of Canberra homes I know that this house, without heating, is really quite comfortable, healthy and very affordable to run (did I mention the increase in energy prices that also happened on July 1?).
However, I am willing to admit that I reckon we will install a small infrared panel in each living area next year to give things a little boost on the grey days - it won't take much (we know that from the effectiveness of the single 600W infrared panels on the ceilings in the bathroom). I challenge you all to turn your heaters off for the next week and measure the temperatures in your home! If you can't bring yourself to do that, at least promise me you will open up the window dressings on your northern windows on the sunny days to let some free heat in (it still staggers me how many - the VAST majority - of houses in my suburb keep all of their window dressings closed on the days when the sun is blazing through the chilly air).
(You can see earlier posts about the thermal performance of Jenny's house via our main Journal page and more specific info about the house design here).