House June warmth profiles: IV

Part IV: Solar gain in the clear-story


In a solar-passive house, do clear-story windows trap much heat?
How about overcast days?

Graph of clear-story temps, 2 days

[This post repeats some data of an earlier post, headed  “Part III: Daily temperature cycles, east wing”. Please refer to that post for more details.]

The graph above shows records of temperature for two days in mid-winter. Records of cloud cover (plotted in purple) show that the first day was overcast and the second mainly sunny.
Through the sunny second day, the temperature readings taken just inside the clear-story windows (black) rose and fell just like the outdoor temperature (red), but they were much higher. I have drawn a dotted red line at a temperature 13.5° higher than outdoors. It fits well to the clear-story temperature (black) on that day. During the previous day, which was overcast, the dotted red line does not fit. It is about 6° higher than the actual clear-story temperature.
By experiment, I found that I could make a model (plotted in green) that would match the actual clear-story temperature as the cloud cover changed. As well as adding 13.5° to the outdoor temperature, I subtracted two thirds of the cloud cover measured in octas. As plotted (green), this model matches the clear-story temperature through both days. At two data points there was a mis-match: those points have not been plotted.

 Graph of clear-story temps, 5 days

The second graph shows all five days of the experiment. My model of temperature in the clear-story space (plotted green), fits the actual readings (black) on all days.
The model includes one other feature: the maximum temperature that I allow is 26°. That also matches. As mentioned in Part III, a thermostat turns on fans at 26°. That prevented the temperature from rising higher.

Comment

A solar passive house is likely to gain more winter heat if it has north-facing windows in a clear-story above room level. It may also lose more heat. If so, the cost of the clear-story design may not be justified.
This experiment shows that, in this particular house during one harsh winter, the clear-story performed very well.

People may be as surprised as I was at the closely-matching pattern of outdoor and clear-story temperatures in mid-winter, and at how very much warmer the clearstory was: more than thirteen degrees warmer in fine weather.
It may also provoke some thought that the match persisted in overcast weather, but with the clearstory being only eight degrees warmer than outdoors in that case.

Back to Part I: Average temperature values.
Back to Part II: The two-storied west wing’s daily temperature cycles
Back to Part III: the single-storied east wing’s daily temperature cycles

Advertisements

Adaptive Comfort

The Adaptive Comfort Standard of ASHRAE

Adaptive Comfort Zone graph

You need to know what range of temperature you are likely to find comfortable when you are planning a house or its heating and cooling. This graph is a guide to the temperature range for comfort.

The graph explains itself. People are comfortable at rather higher temperatures in places, or at times of year, when the climate is warmer. They are comfortable at lower temperatures if the climate is cooler.
For any month in any place, you must simply look up the mean temperature for that month. Then 90% of all people will feel comfortable at temperatures in the five-degree range between the magenta line and the green line. At temperatures in the seven-degree range between the red and blue lines, 80% of people will feel comfortable.

Generally, using the local mean temperatures for January and July will give enough information for your planning. Sydney provides an example:

Because the Sydney mean temperature in the coldest month, July, is 13°, 80% of people will remain comfortable if a house gets no colder than 18°.

Because the Sydney mean temperature in the hottest month, January, is 23°, 80% of people will remain comfortable if a house gets no hotter than 29°.

The adaptive comfort zone shown on the graph was proposed by Richard de Dear and Gail Schiller Brager (2001).
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, the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) recognised publicly that full climate control of buildings at one “ideal” temperature and humidity may not be the way of the future.

I have used this Adaptive Comfort Standard in many of my posts, notably the one showing how my house maintained a temperature almost completely within the Comfort Zone through a whole year.


This material, with its graph, was posted originally to a “weatherzone” forum more than seven years ago. Unfortunately, the photo-hosting website “Photobucket” has now withdrawn the image from public use. This post is to make it available again.

House June warmth profiles: III

Part III: Daily temperature cycles, east wing

Graph showing the daily temperature cycles for five days at mid-winter

This five-day period was a testing time for the unheated solar-passive house. Days were at their shortest, some nights were frosty, and overcast persisted for two days. It fell within a cold, wet, and cloudy winter.

This post is about the single-storied east wing of the house. It is the main part of the house, with most of the clearstory windows.

Back to Part I: Average temperature values.

Back to Part II: Daily temperature cycles, west wing

Observations

View of the house from the street

House From the Street

In this wing, seen on the left in the photo, five thermometer stations define a profile in height. They are:

Subsoil in the heat bank beneath the house;
On the floor slab;
On the room wall;
In the clearstory space;
OUTDOORS, in a Gill Screen, 1.5 metres above the ground and eight metres from the house.

During the five days I made 84 observations at each station at intervals as shown. They define the daily temperature cycles. I observed the amount of cloud in Octas (eighths of the sky) at the same intervals.

Table of east wing temperatures.This table lists for each thermometer station the five-day values of the average, maximum, and minimum temperatures, and the temperature range.

The daily cycles

Subsoil

Continue reading

House June warmth profiles: II

Part II: Daily temperature cycles, west wing

Graph of temperatures in the house west wing in mid-winter

I report here on the thermal performance of a solar-passive house in Manilla, NSW, during five days at the winter solstice of 2016. The house is described briefly in a Note below.
This post is about the 2-storied west wing of the house, which is less successful. The more successful east wing will be considered later. An earlier post showed that average temperatures decreased with height. Go to Part I.

This five-day period was a testing time for the unheated solar-passive house. Days were at their shortest, some nights were frosty, and overcast persisted for two days. It fell within a cold, wet, and cloudy winter.

Observations

View of the house from the street

House From the Street

In this wing, seen on the right in the photo, five thermometer stations define a profile in height. They are:

Subsoil in the garden near the house;
On the downstairs floor slab;
On the downstairs wall;
On the upstairs wall;
OUTDOORS, on the wall of the upstairs veranda.

During the five days I made 84 observations at each station at intervals as shown. They define the daily temperature cycles. I observed the amount of cloud in Octas (eighths of the sky) at the same intervals.

Table of west wing temperaturesThis table lists for each thermometer station the five-day values of the average, maximum, and minimum temperatures, and the temperature range.

The daily cycles

Subsoil

Continue reading

House June warmth profiles: I

Graph of house temperatures versus height

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

SUMMARY RESULT
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.

Results

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.
Continue reading

Ventilation louvre hassles

I specified wooden louvre blades

This louvre window installation is described in this earlier post.

Photo of louvre for night purge

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.

Photo evidence that louvre does not seal

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

Continue reading

House in a cold October

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.

Indoor/outdoor temperature scatter-plot.

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

Continue reading