Where is the warmth in a house?
People are building houses that should keep warm in winter with little heating.
Some parts of the house will stay warmer than other parts. Which parts? How warm?
Answers are not easily found. I hope this temperature record from a house with only personal heating may be useful. This was a time when the house was under extreme stress due to cold weather.
Over a five-day period in winter 2016, I read thermometers frequently at a number of stations around the house. I have selected those stations that form profiles from top to bottom of two wings of the house: the two-storied west wing, and the east wing that is one-storied with a clearstory.
To find how my house differs from yours, see the note below: “Key features of the house”.
Selected thermometer stations
In the West Wing (two-storied)
OUTDOORS, upstairs veranda (+4.7 metres);
Wall upstairs at head height (+4.2 metres);
Wall downstairs at head height (+1.5 metres);
Floor slab surface downstairs (0.0 metres);
Garden subsoil at -0.75 metres.
In the East Wing (single-storied)
Clearstory space at +3.5 metres;
Wall in the hallway at head height (+1.5 metres);
OUTDOORS, in a Gill Screen (+1.5 metres);
Floor slab surface in the en-suite (0.0 metres);
Solid “heat bank” beneath the floor slab (-0.75 metres).
Part I: Average temperature values
In the ground under the floor slab the temperature would be just warm enough for winter comfort. Above the floor slab, the higher you go, the colder it gets.
The graph above plots mean temperature against height above the floor slab. (The mean temperature is the time-average over the five days.)
Comparing east wing, west wing, and outdoors
The single-storied east wing was several degrees warmer at all heights than the two-storied west wing. The east wing has advantages: thermal mass, perimeter insulation in the footings, less shading, and a more compact shape.
I specified wooden louvre blades
This louvre window installation is described in this earlier post.
Louvre now fitted with glass blades
The automated louvre window that I specified for my system of summer cooling by nocturnal purge had wooden louvre blades of western red cedar 14 mm thick.
I specified wood because I preferred that this louvre should not be transparent, as I did not want to see through it and I did not want it to admit light. I took the risk that wooden blades might not seal as well as advertised.
Other posters on the ATA forum (see link below) doubted that the blades would seal effectively. They were right.
Failure of the wooden blades to seal
When the louvres were closed for the first time, there was clearly no seal at all. The rubber seals fastened to the blades failed to meet the matching blades, leaving gaps of up to 2 mm admitting daylight.
Attempts to rectify
I wrote a letter of complaint on 18/5/2016.
Rectification work on warranty first revealed faults in the gallery of gearing at the side of the window. However, when the gallery was replaced the gaps remained. The photo shows daylight visible on the right side through three of the gaps.
Wooden louvres showing daylight
As the blades did not meet their specification, the company replaced them without charge. When these new blades did not seal any better, the company offered (on 10/10/2016) to replace them with aluminium blades, 6 mm thick. I reviewed the specifications of their blade options, and decided that this was not acceptable. The aluminium blades had little thermal resistance (U-value: 6.55). Glass blades 6 mm thick, with a low-e coating had much higher thermal resistance (U-value: 4.40), almost the same as the wooden blades (U-value: 4.39). The company agreed to provide these low-e glass blades. (In fact, this had been their original suggestion.)
Sealing of glass louvre blade gaps
This October has been very cold. That has kept indoor temperature
in this solar-passive house almost too cool for comfort. I wore warmer clothes and opened windows to admit warm air.
The climate this October
The graph shows (on the x-axis) how cold this October [in red] was: the coldest of the new century.
Here on the North-west Slopes of NSW, October warms and cools more from year to year than other months. It is the month most affected by climate cycles such as the El Nino-Southern Oscillation (ENSO). As shown, October warmed by one degree each year from 2011 to 2015, then cooled by nearly six degrees from 2015 to 2016.
ENSO followed almost the same pattern, but October 2012 was warmer than October 2013.
For five months, world temperature has also been down: much lower than it was in the record-breaking months of February and March 2016. (HadCRUT4 Global monthly near-surface data set (Column 2 in the linked table.))
Indoor climate this October
As shown on this graph beginning 2005, the indoor mean temperature in October months has varied with outdoor mean temperature. This coldest October outdoors (15.9 degrees) was also the coldest indoors (20.8 degrees). (But see Note below.)
October is the final month that I keep the house in its winter warming regimen. In 2014 and 2015 it had been almost ideally warm, but in 2016 it was just above the comfort minimum. Since this figure is just an average, there were times when the house was too cool for comfort, especially in the mornings.
Successive unfavourable months this year
As in other seasons, I intend the indoor climate to be comfortable through each spring season.
As I posted in “Hard Winter for Solar-passive” this very cloudy winter had reduced solar gain, making heaters needed much more than usual. However, the mean indoor temperature at winter’s end (August) was normal, although the heat bank was 0.7 degrees cooler than normal.
In September months, the warmth indoors still depends on solar gain through the north windows. This time,the sky continued very cloudy, and the daytime temperature was a record low value. As a result, the indoor temperature was 0.9 degrees down and the heat bank 0.7 degrees down.
By October, there is no solar gain through the north windows: warmth is gained from the surroundings in daytime by conduction, convection and radiation and retained by closed curtains at night. This time, both day and night temperatures were three degrees below normal, reducing daily heat gain and increasing nightly loss. As a result, the indoor temperature was 1.2 degrees down and the heat bank 0.9 degrees down.
What I did
Porch Awnings in Summer and Winter
This porch, which is a sun-trap in winter, is converted simply to a shaded breezeway for summer.
The porch is an upstairs outdoor room, open on three sides, at the west end of my house. With a Tallowwood deck and steel balustrade, it could be called a verandah or a balcony. I like to call it a talar, although it is not as grand as the talar of the Ali Qapu Palace, Isfahan.
For the colder part of the year, from March to October, the talar awnings are arranged as in the right photo. I fasten down the canvas awning on the south side to stop drafts, and I roll up the awning on the west side so I can enjoy the views. On sunny winter afternoons it is pleasant to have a late lunch there, with temperatures in the high twenties, several degrees warmer than the maximum in the thermometer screen.
For the warmer part of the year, from November to February, the awnings are arranged as in the left photo. The awning on the west side is fastened down against the intolerable heat of the afternoon sun. That also keeps the heat off the west wall of the house. The south awning is raised, to allow air to flow through, from south to north. When there is a breeze, it can be comfortable to sit on this porch even on very hot days.
By the use of cheap canvas awnings, this porch can make outdoor living pleasant in months when the climate here is too cold or too hot for it.
The louvre opened
A daily chore in summer
My high-mass solar-passive house keeps me comfortable through the year with very little attention. I have detailed the actions I must take in this post. Being in BCA Climate Zone 4 “Hot dry summer, cool winter”, I have a summer regimen to keep the house cool, and a winter regimen to keep it warm. Most actions are required only twice a year: to change over from one regimen to the other. However, one action is required daily throughout the hot season: I must open doors each evening to admit cool air, then close them again in the morning. At night, air is drawn through the house and out the clearstory windows by the stack effect, assisted by fans at the windows. Warm air in the house is purged by the flow of cold night air, which continues to cool the mass of the house until sunrise.
My louvre vent project
[Photos, with descriptions, may be seen in carousel view here.]
Subsequently, I had to have the wooden louvre blades replaced with glass ones, as I describe in a later post.
I have put into effect a long-standing project to avoid the daily chore of opening and closing doors. I bought a motorized louvre window (Breezway Altair Powerlouvre Innoscreen) to let in the night air.
Louvre Time Clock
It is controlled by a programmable electric time clock (Hager EG203E) that will open the louvre at 21:00 and close it at 07:00 daily through the hot season. In the cold season the louvre will remain closed, with the motor control turned off.
The louvre closed
The louvre is installed low in a wall on the colder south side of the house. It is near the back door that I have been opening and closing up to now. It was difficult to find a place to fit it.
I thought of fitting a motorized louvre in the back door itself. This would have been awkward and expensive. Doubly so, because the back door opens into the laundry, which forms an air-lock, and the inner laundry door would also have needed a motorized louvre.
The kitchen was the only suitable room to admit the cooling air. Of course, it is almost completely lined with benches and cupboards. Eventually, I found a place for the louvre, and had a hole cut in the wall for it.
Louvre aperture from outdoors
Louvre aperture from indoors
The place I chose is partly behind the refrigerator. Continue reading
One Brick Thermal Mass
The “Indoor climate” posts on this blog relate to the particular house that I live in. Mainly by luck, it has proved to need very little energy indeed to remain comfortable in all seasons.
Recently, I have collected and arranged photos of the house so that people can see what kind of a house it is.
These photos are accessed by way of “My House Page”.
Footings View East
In the last few days I have uploaded photos of the stages in the building of the house. They are in two galleries. The first, “Building Photos: Start” covers from preparation for building up to the erection of timber frames. The photo on the left, showing some of the footings, is an example.
The second new gallery, “Building Photos: Finishing” covers from laying bricks for thermal mass walls (as in the photo at the top) to the completion of an acrylic textured coating on the walls.
Photos of the completed house, inside and out, had been posted already, in “Award photos 1999”.
Once an “Indoor Climate” post or page has been accessed on this web-site, links to all others appear. A post such as this one, when accessed through “Home” will not link to the others until it is selected positively by clicking its title line.
Monash Street House Plan
Distant view from the south-east
Posts on “Indoor Climate” in this blog come from my experience living in my solar-passive house from 1999, and monitoring its performance.
Until now, I have not given readers a clear idea of what the house is like. I have now set up a special page called “My House Page” where details can be found. So far, there are two sub-pages, both referring to the time when the house was new:
- A gallery of photos called “Award photos 1999”, and a house plan, which were submitted in an entry for the Housing Industry Association (NSW) awards for 1999.
- An essay “House Profile 1999” that sets out the principles that I thought important then, and the features that I had built in to the house. I added a reading list of books available at that time, and a list of Credits to those people who built the house.
The “My House Page” is not directly indexed in the main menu on the banner, but it appears with a hover over “Indoor Climate”.
Posts and Pages on Indoor Climate have links to each other in the side-bar on the right, in the panel “Indoor Climate Blog and Pages”. This panel does not appear on the Home Page, but only when an “Indoor Climate” blog post (or Category of posts) is selected.
I intend to add more pages in time.