This graph is a log of indoor and outdoor 7-day mean temperatures at my low-energy solar-passive house at Manilla, NSW. Indoor mean temperatures are in red, and outdoor mean temperatures in black. Both logs show the same cycles of temperature with a period of two to three weeks. Indoor cycles have a much smaller amplitude.
The smooth, thinner black line is the normal mean daily temperature at Manilla. Normal temperatures range through 17 degrees: from 9°C in mid-winter to 26°C in mid-summer. It is clear that this year’s October, November and December were much cooler than normal. For some days in mid-December, the seven-day mean was six degrees below normal!
Indoors, mid-winter mean temperatures were about 8° warmer than outdoors, and mid-summer temperatures were about 1° cooler than outdoors. These are averages only. This house also reduces the extremes of temperature within each day, as shown in another post.
Curves in purple are the limits of the Adaptive Comfort Zone (see below). The house succeeds remarkably well in keeping indoor temperature within the adaptive comfort zone in all seasons. The cold snap in mid-December was one of the few occasions when indoor temperatures were not comfortable, in terms of this model.
High indoor temperatures in April show the warming effect of changing to the winter regimen. I have given details of my “winter regimen” and “summer regimen” of house management here.
The adaptive comfort Zone shown on this graph is based on that proposed by Richard de Dear and Gail Schiller Brager (2001). I have recently re-posted a graph defining this comfort zone here. This adaptive comfort zone has been incorporated in the de facto international standard: ANSI/ASHRAE Standard 55-2004, Section 5.3,, as summarised here. By this innovation, ASHRAE recognised that full climate control of buildings may not be the way of the future.
As defined, the comfort zone is calculated from mean monthly temperature (the arithmetic average of mean monthly minimum and maximum air temperature) a number “that can be found easily by examining readily available climatic data” (Brager and de Dear, 2000).
Mean monthly temperature has the defect that there is a step between the last day of one month and the first day of the next. At Manilla, the mean monthly temperature increases by four degrees from August to September. This implies the neutrality temperature for comfort would rise by more than one degree overnight. Since I have already estimated the normal mean temperature for each day of the year, it seems logical to calculate the adaptive comfort zone temperatures from these daily values, as shown.
See also “One Year of House Performance: II”.
This material was posted in a weatherzone forum on 5th June 2011. It is posted here and made sticky on 29th July 2014, but back-dated to 20th July 2011.