Solar-passive House Testimonials

Photo of a birthday party in the solar-passive house

Birthday Group

Family members visited the solar-passive house in Monash Street, Manilla, NSW, in Mid-winter 2016. The date of their visit is shown on the graph in this earlier post. This photo shows us dressed for comfort at 17 degrees indoors.

Interviewer:
What do you think of Grandpa’s house in winter?

Grand-son (10):
I like Grandpa’s house. It’s nice. Except there’s no wifi. But apart from that, it’s good.

Grand-daughter (13):
Grandpa’s house? It’s cool. It’s interesting. Awesome curtains – I get a shock when they move because I’m not used to it. The garden is cool too – it’s pretty.

Daughter:
I love winter. And I love visiting my Dad. He built this really great house in Manilla nearly twenty years ago. Prior to that, he was tenanted in an old office space above the newsagent. I loved visiting him back then as well, even if his flat was super hot in summer and not at all cosy in winter. The house he built is wonderful all year round.

Even if there are only a few hours of sun each day in the depths of a NSW winter, that is all you need to warm my dad’s house. You can find yourself a chair in the sun, sit for a while and imagine you’re on vacation in Hawaii. Only with much better coffee. As the sun goes down, the sound of noisy birds settling in for the night comes through from outside.

Kitchen view SW

Kitchen view SW

The kitchen is well-stocked for preparing dinner (especially after we restock it) and, once the stove is on, it’s toasty warm in there. There is a curtain that closes the kitchen off from the rest of the house, but cooking time is social time for us, so we leave it open – which also helps flood the house with the delicious smells of curry. The house finally gets coolish sometime after dinner. That’s when we don the cardies and fluffy slippers and pre-heat the beds. The electric blankets, even on low, manage to warm the bedrooms all night.

Next morning, on a strict schedule, the automatic curtains fly open to announce the new day. Not being an early-morning person, I make good use of the curtain override button. At least, until I get the first whiff of toast.

Son-in-law:
Having grown up in India, I find summer is a breeze and cold weather is a challenge. After a couple of decades in Canberra and almost a decade in Switzerland, I have finally realised that dealing with winter boils down to managing the environment in the house and wearing the right gear.

I have stayed in my father-in-law’s house in Manilla several times, in summer and in winter, most recently in the winter of 2016. The house is comfortable in both summer and winter. I remember feeling colder in winter when I first stayed there compared with now – I am not sure whether the house is warmer, or I have more layers of fat to protect me as I get older. Maybe I just dress more appropriately now for winter thanks to my time in Switzerland.

The place where we hang out the most is the kitchen, and around the kitchen table, over cups of coffee or improvised meals, catching up on left and right leaning newspapers. The kitchen is very cozy in winter, especially when there are multiple dishes cooking away on the stove.

A memorable feature of my father-in-law’s house is the automated curtains which felt space-age when I first experienced them, but now I am used to them. They are like a bell-less morning alarm. Being a morning person, I beat them to it, and am awake before they start moving and letting in light.

Photos of porch awnings adjusted for outdoor living in winter and in summerI love the balcony on the first floor. It is well protected and I can sit there for hours with a cup of coffee and a book, and listen to cockatoos and other birds, and watch the paragliders in the distance when they are out. In winters the mid to late afternoons are the most comfortable.

Photo of a path between trees

In the garden

As the trees and shrubs in the evolving garden have grown and the paths have become more structured it has become a wonderful place to walk around and to relax. The garden bench is particularly inviting. This man is as passionate about his garden as he is about his house. The guided tour of his garden is one of the highlights of our stay there.

Interviewer:
Thank you all for your answers.
Goodnight, everyone.


Recent photos of the house and garden are here.

Hard Winter for Solar-passive

Graphical log of daily indoor and outdoor temperatures for winter 2016.

Temperature log: main features

This graph, for 2016, shows a winter pattern of indoor and outdoor temperatures that is typical for this house. Indoor temperatures vary much less than outdoor temperatures, they rise and fall with them, and they are higher nearly all the time.
While the outdoor temperatures shown go as low as minus three degrees, those indoors lie within the winter “comfort zone” from 17° to 24° (see this post) nearly all the time.

Weather this winter

This winter was harsh for a solar-passive house. Near-record rainfall (227 mm) came with the greatest number of cloudy days of any winter in the new century. There were 53 mornings with more than four octas of cloud, when the average is 33.

Heater use

Because cloud limited the the solar gain, I had to use blower heaters far more than in previous winters. My records show that I used 320 kWh ($80) in these heaters this winter, when I normally use about 40 kWh ($10).
Heaters were also used by guests who were present on the six days shown. As well as being unused to the climate, the guests lived in the colder west wing of the house. They may have used 72 kWh ($18). Those guests have kindly written reviews of their visit.
Even using 400 kWh of electricity for personal heating in a winter could not make a detectable change in house temperature. I have found that blower heaters are surprisingly good at making a room in this house comfortable. As the radiant temperature of the walls is only 2° or 3° too low for comfort, it can be compensated by making the air temperature only slightly higher.

The pattern in detail

While cloudy days are not plotted here (Cloud observations for this winter are plotted elsewhere.), cloudy days can be recognised on the graph. In this climate, days with low maximum temperature and high minimum temperature are always due to cloud. Only in fine weather are days warm and nights frosty. The graph shows how the weather goes through a cycle every week or two: sunny days get warmer, then rain sets in. As it clears, the air gets even colder, before warming up again.
Indoor temperatures follow the same cycle, but there are differences. There may be a delay of up to a day, and sometimes longer.

Correlations

I did scatter plots comparing all the variables shown in the first graph and I fitted linear regressions. I present the four scatter-plots that had the highest coefficients of determination (“R-squared”). Continue reading

January “Coolth” in a House without Air-Conditioning

I have now 15 years of January average temperature data for my house at Manilla, North-west Slopes, NSW. These graphs show how the house temperature relates to the outdoor (or ambient) maximum, mean, and minimum temperatures.Regression graphs of indoor on outdoor temp in the hottest month

The house is not too hot and not too cold

Solar-Passive House from the NE.

House at Monash St Manilla from NE

In January (the hottest month) the rooms* in this solar-passive house do not heat up much during the day, nor do they cool down much at night. Since the indoor temperature always rises and falls just one or two degrees from the mean, only the mean is shown. Green lines on the graphs, which are drawn to pass through the middle of each cloud of data points, show by how much (on the average) the indoor temperatures have differed from the outdoor maximum, mean, and minimum temperatures. On the middle graph the green line shows that the rooms have been 0.5° cooler than the mean temperature outdoors. The left graph shows that the rooms have been 8.2° cooler than the daily maximum outdoor temperatures. The right graph shows that the rooms have been 7.3° warmer than the daily minimum overnight temperatures.

The design of the house aimed to protect those living there from excessive summer heat. It may seem that reducing the mean temperature by only half a degree is a failure. Not so! The January mean temperature at this site (26.1°) is near the middle of the adaptive comfort zone for this month, and so is the indoor mean temperature (25.6°). The house succeeds in keeping the indoor temperature comfortable in the heat of the day, when that outdoors is an uncomfortable 34 degrees. The high thermal mass that achieves this has the unfortunate result that the minimum indoor temperature overnight (not shown) is some five degrees warmer than the outdoor minimum. However, on average, it is still a comfortable 23.5 degrees. (Curiously, no-one knows the best room temperature for sleep.) Continue reading

July Warmth in an Unheated House

Solar-Passive House from the NW

House at Monash St Manilla from NW

I have fifteen years of temperature data for my high-mass, solar passive, unheated house at Manilla, NSW, Australia. This article has been posted previously here. These graphs show how July temperatures indoors relate to those outdoors. Indoor maxima and minima are not shown, because they are consistently between one and two degrees above and below the indoor mean.

House and ambient temperatures, 15 July months. The house is much warmer (dashed green lines)

In July, the rooms* in this solar-passive house, heated only by the sun, are much warmer than outdoors. This is shown by the green lines on the graphs, which are drawn to pass through the middle of each cloud of data points. The middle graph shows that, as an average over 15 July months, the rooms have been 8.7 degrees warmer than outdoors. The left graph shows that the rooms have even been 1.4 degrees warmer than the daily maximum outdoor temperatures. The right graph shows that the rooms have been nearly sixteen degrees warmer than the daily minimum overnight temperatures. To stay warm in this way the house must have absorbed many hundreds of kilowatt hours of heat from the sun. I have burned a few kilowatt hours of grid power to maintain my comfort, but this cannot have warmed the house by as much as one tenth of a degree in any month. Continue reading

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.

Continue reading

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.