Cost-effective night purging techniques
We're experiencing an unusual weather espisode in Melbourne. In March it's now autumn (southern hemisphere) but we're on track to have the longest period on record with maximum temperatures above 30C. This started a few days ago and is forecast to last for around 10 days. As an interesting aside, one should always be careful not to confuse weather with climate but this kind of anomaly is bang on the money for what the climate modellers have been forecasting for SE Australia for some time under anthropogenic global warming scenarios.
Our double-brick house stays reasonably cool for about 3 days when temperatures get above 30C. (Forecast for Wednesday is 37C and today it hit 36C in the CBD; we're about 12km from the CBD; our summer temps are often a bit hotter and our winter temps a bit cooler.) After 3 days or so of elevated temps the thermal pulse has made it's way through the walls and starts to seriously heat up the interior. As I write it's 29C inside.
So to night purging.
There were some great posts a while ago on GBA about installing an attic fan to bring cooler air from the outside through the house into the attic. Appealing idea but this depends on the house either being leaky (which is something we're addressing) or opening windows. We've been experiencing night-time temperatures in the mid to high 20C's until the wee hours of the morning during this period. To get best benefit from the attic fan I guess we would need it to be thermostatically controlled driven by the difference between inside and outside temperatures. We would face the issue of having windows open to allow cooler air to be drawn in.
The manual night purging process at the moment is largely based around me getting up in a not particularly cheerful mood at about 6am and opening all the windows and doors. With a bit of a breeze - also something of a rarity at the moment with this persistent atmospheric high sitting to the south - this can cool the house 3 degrees Celsius or so fairly quickly. Of course, given the thermal mass of the house the interior temperature can rise once the windows are shut.
Another possibility would be some thermostatically controlled automatic windows which opened and closed by a controller driven by actual interior temperature, desired interior temperature and outside temperature. To make a significant difference as things stand we would need a number of such windows but I'm hoping that as we get some aspects of out house thermal performance a bit more under control even one or two such windows would be useful. This would help us either avoid installing an AC unit or at least getting a smaller unit than otherwise.
So does anyone have some recommendations or experiences to share about such windows? I understand they are available commercially
Posted Sat, 03/09/2013 - 08:32
Edited Sun, 03/10/2013 - 06:48
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