One year of House Performance: II

Graphical 1-year record of outdoor and indoor mean temperatures, subsoil and heat bank.

See also “One Year of House Performance: I”.

Like the graph in the post linked above, this is a log of indoor and outdoor 7-day mean temperatures at my low-energy solar-passive house at Manilla, NSW.
In place of the curves for normal air temperature and comfort zone limits, this graph includes two (raw value) logs of subsoil temperature at 750 mm below the surface. The green trace is the subsoil temperature outdoors in the garden. The orange trace is that below the middle of the main floor slab. The mass of material below the slab is surrounded by insulation at the edge so as to form a “heat bank”.

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One year of House Performance: I

Graphical 1-year record of outdoor and indoor mean temperatures with the comfort zone

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.

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Indoor/Outdoor Regressions for Maxima and Minima

Regressions for maximum and minimum temperatures compared

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.

Adaptive Comfort

[I have re-posted the lost graph of the Adaptive Comfort Zone here.]

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.