This graph shows the two regression lines for Indoor versus Outdoor daily maximum temperature (purple) and daily minimum temperature (green), taken from separate scatter-plots for maxima and minima. I have marked three points on each line: the mean temperature point and points at the extreme ends of the lines, one for a very hot day and one for a very cold day.
The interest of this graph is in the space between the regression lines. It represents the daily temperature range. I have linked each pair of points by two lines like the tread and riser of a stair. The tread (red) is the outdoor daily temperature range; the riser (blue) is the indoor daily temperature range.
The mean outdoor temperature range here is 15.4° and the mean indoor temperature range of the house is 3.1°. By this measure, the indoor temperature range is one fifth of that outdoors.
It happens that, in Manilla, the outdoor temperature ranges in the hottest and coldest parts of the year are, as shown, slightly less than for the year as a whole. Indoor temperature ranges show a clear gradient, from as much as 3.7° on a very hot day through 3.1° at the mean, to only 2.3° on a very cold day.
These very narrow temperature ranges result from the way the high thermal mass dispersed within the house allows heat to be absorbed and radiated at room temperature, eliminating extremes. Hot spots and cold spots are few and do not last long.
For comfort, we do not need indoor temperature ranges as narrow as these. Using the Adaptive Comfort Zone model we find that the neutrality temperature (for best comfort) based on Manilla’s January mean temperature of 26° is also 26°, and the neutrality temperature based on Manilla’s July mean temperature of 10° is 21°.
According to the model, 80% of the population feel comfortable when the temperature is within 3.5° of the neutrality temperature: in January at Manilla they are comfortable up to 29.5°, and in July they are comfortable down to 17.5°.
My graph shows that the maximum indoor temperature of this house on a very hot day (29.9°)is only 0.4° above the January comfort limit, and the minimum indoor temperature on a very cold day (15.8°) is just 1.7° below the July comfort limit.
On this model, most people could live comfortably in this house using heating or cooling for only a few days in a year.
This post is one of a set of four back-dated to June 2010:
Indoor versus Outdoor Temperatures (1096 days)
Indoor versus Outdoor Minima (1096 days)
Indoor versus Outdoor Maxima (1096 days)
Indoor/Outdoor Regressions for Maxima and Minima (This post.)
This article was originally posted in the weatherzone forum thread “Indoor Climate” on 9th June 2010. It is backdated here to 19th June 2010.