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#890751 - 13/10/2010 22:36 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Midwinter2010
Modelling indoor temperatures of the Manilla solar-passive house
4b. Modelling max/min temperatures on the surface of the concrete floor slab: Discussion

The relationships in the models are shown in the graphs below. As an example, I have chosen the coldest day and night on the slab surface indoors, and I have marked the weighted inputs to those results.


The general shape of the successful models is similar to those developed for indoor wall temperatures.

1. For slab temperature modelling, outdoor MINIMUM temperatures had no value. Slopes on their regression lines were all less than 0.1, and Coefficients of Determination (R^2) were trivial.

2.While the models for wall temperatures included data lagged up to three days, those for slab temperatures include lags up to five days for maxima and four days for minima. Slab surface temperatures fluctuate less with inputs on the same day; they reflect longer-term re-distribution of heat in the thermal mass of the house.
The excellent fit of these models depended on using Heat Bank values lagged two days; not more and not less. It would take about two days for heat to travel up 750 mm through the thermal mass material.

3. As noted, outdoor temperature variations from day to day are reflected in smaller temperature variations indoors. The damping factor (output/input ratio) for Indoor wall maxima is 0.55, and that for Indoor wall minima is 0.45.
Damping factors for slab temperatures are not much smaller: 0.50 and 0.43. The obviously smaller day-to-day variation in slab temperatures is due to the smoothing effect of inputs from more days, rather than more damping on each day.
Only the smoothing effect of slow heat movement in a very large Heat Bank can account for the persistence of inputs for five days.

4. Indoor slab temperatures are affected by the cloud cover several days earlier. The chosen "Target" data points in these diagrams are minimum points. They are affected by events three or five days earlier, when the night was not only cold but also cloudless.
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#892094 - 19/10/2010 00:35 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
October weather is being unkind.
My models (above) suggest that indoor temperatures respond most to outdoor maximum temperatures. These have been running 4.5 degrees below normal, as part of a cold-wet peak in the climate cycle.
As usual, on the 1st of October I re-set the curtain-timer to close by day to keep solar radiation out and open by night to allow excess heat to radiate out. Last night, following a daily maximum temperature 13 degrees below normal, I had to use a fan heater for an hour, costing me 50 cents.
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#892097 - 19/10/2010 04:58 Re: Indoor Climate [Re: Surly Bond]
Seabreeze Offline
Weatherzone Moderator

Registered: 18/09/2005
Posts: 10670
Loc: SWR
The indoor temperature here since mid September has generally been around 19-22 degrees at its peak and 16-18 degrees at its lowest. I haven't used the heater since late August.
The other night after that big cold front moved through (we had a outdoor max of 8.8 that day), I nearly put the heater on but instead put on a jumper and I was fine. The house was 21 degrees on the morning the cold front moved through and by sunrise it was 2.5-3 degrees outside (the massive temperature difference meant I had alot of condensation on the inside of my windows) and by the end of the day the house had cooled to 16 degrees in response to the wintry blast, and with a below freezing minimum that night fell to 11 degrees. The next day, an outdoor maximum temperature around 15 degrees meant the house warmed up to a comfortable level again, and the indoor temperature did not drop as far that night despite a below freezing minimum again but still felt slightly cool because of the lingering impact from the day before. Yesterday almost got to 20 degrees outdoors, so now the house is back at a completely comfortable level both day and night.
Similarly, in September there were several nights where I thought about turning on the heater but instead opted to put on a jumper, long pants or ugg boots. After a cool August, most September nights felt tropical in comparison and the majority of October nights have felt similar. I'm quite confident that I won't use the heater again until May. You tend to adjust with the increasing (and decreasing) temperatures as the months progress, so by December/January I expect that if we were to experience similar indoor temperatures of low 20s in the day and mid/high teens at night as I currently do, that I would find it cool and perhaps uncomfortable.


Edited by Freeze (19/10/2010 05:06)

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#892242 - 19/10/2010 22:06 Re: Indoor Climate [Re: Seabreeze]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Hi, Freeze

We are talking of the same cold snap, but I think our houses responded differently.
I find it hard to describe the sequence of events, so I'll make a list:

Sat 16th minimum temp (early morning): 7.2 deg (near normal);
Sat 16th maximum temp (before 8 am); 14.2 deg (13 below normal);
Sun 17th minimum temp (early morning): 1.4 deg (10 below normal);
Sun 17th maximum temp (afternoon): 19.1 deg (8 below normal);
Mon 18th minimum temp (early morning): 4.0 deg (7 below normal).

Saturday was the extremely cold day, leading to a very cold night. However, my house did not cool that day. It was the evening of Sunday that I needed the heater, and I added a second blanket that night (the bedroom minimum went down to 17.4).
Mind you, if I had simply delayed resetting the house for summer cooling, I might not have needed either the heater or the second blanket.
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#896808 - 09/11/2010 18:05 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Compared to what has been normal since the house was built in 1999, this spring season is lagging by several weeks.
For example, today is the first day to exceed 30 degrees, when the median date for that to happen has been 23 September, 47 days earlier!
As shown by Bureau of Meteorology Temperature Anomaly maps large areas, extending from Central Australia into populated inland areas of eastern and southern states, have had low temperatures this spring.

Solar-passive houses need to be managed appropriately. I normally open my house for night-time ventilation from the beginning of November. This month, with night-time indoor minimum temperatures still only 20 to 21 degrees, I kept it closed up for an extra nine days. Only now have I opened up the clear-story windows and re-set the fans to blow warm air out from 1 am to 5 am, assisting the stack-effect ventilation. I plan to open doors and windows before I go to bed to let cool air in.
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#896880 - 09/11/2010 23:14 Re: Indoor Climate [Re: Surly Bond]
Seabreeze Offline
Weatherzone Moderator

Registered: 18/09/2005
Posts: 10670
Loc: SWR
Could be a bit uncomfortable for a sleep tonight, at least for next few hours. 15 degrees outside but still sitting on 26 degrees in my room.

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#896913 - 10/11/2010 10:02 Re: Indoor Climate [Re: Seabreeze]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Interesting, Freeze. I did get a warm night, the warmest this month. The min in the screen was 16.6, but Tamworth was not nearly so high, at 13.7.
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#902382 - 30/11/2010 21:47 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Midwinter2010
Modelling indoor temperatures of the Manilla solar-passive house
3a. Improving the models for indoor wall max and min temperatures

The great thing about models is you can tweak them!

In Post #882793, the final models for indoor max and min wall temperatures for the midwinter data set had rather large residual errors:

Indoor wall max temp:
Y = 0.55*(0.6*(OutMax(--)) + 0.1*(OutMax(-1)) + 0.1*(OutMax(-2)) + 0.1*(Outmax(-3)) + 0.1*(OutMin(-2))) + (Heat Bank temp) - 0.12*(Cloud(--)) + 0.10*(Cloud(-3))- 6.8
Standard Deviation of residual error: 0.83 degrees.

Indoor wall min temp:
Y = 0.45*(0.35*(OutMax(-1)) + 0.55*(OutMax(-2)) + 0.1*(OutMax(-3))) + (Heat Bank temp) + 0.07*(Cloud(-2))- 9.1
Standard Deviation of residual error: 0.44 degrees.

(Key: "(OutMax(--))" means the value of the Outdoor maximum temperature of the same day; "(OutMax(-1))" means the value of the Outdoor maximum temperature one day earlier; etc.)

Models for the indoor slab surface temperatures had much smaller residual errors of 0.25 and 0.34 degrees.

I have managed to improve the fit to wall temperatures by adjusting the constants in the models, and using the Heat Bank temperature from the previous day rather than the current one.

Improved model for indoor wall maximum temperature:
Y = 0.62*(0.25*(OutMax(--)) + 0.17*(OutMax(-1)) + 0.17*(OutMax(-2)) + 0.25*(Outmax(-3)) + 0.16*(OutMin(-2))) + (Heat Bank temp(-1)) - 0.12*(Cloud(--)) + 0.12*(Cloud(-3))- 7.5
Standard Deviation of residual error: 0.68 degrees (a 20% reduction).

Improved model for indoor wall minimum temperature:
Y = 0.54*(0.35*(OutMax(-1)) + 0.55*(OutMax(-2)) + 0.1*(OutMax(-3))) + (Heat Bank temp(-1)) + 0.07*(Cloud(-2))- 10.6
Standard Deviation of residual error: 0.36 degrees (a 20% reduction).

To summarise: the residual errors for the four models are now as follows:
Indoor wall maximum temperature: SD = 0.68 degrees;
Indoor wall minimum temperature: SD = 0.36 degrees;
Indoor slab maximum temperature: SD = 0.25 degrees;
Indoor slab minimum temperature: SD = 0.34 degrees.

The poorer fit to the wall maximum temperatures could be due to highly variable daytime environmental inputs defeating the wall and roof insulation.
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#912485 - 21/12/2010 14:42 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
This house is designed to mitigate the extreme summer climate of northern inland NSW. December days usually have temperature peaks around 32 degrees and a daily temperature range about 15 degrees.
So far this December, daily maxima have run about 27 degrees, and the daily temperature range only 11 degrees.
This month provides no return on the investment in the house. A tent would provide equally satisfactory shelter and comfort. cry
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#943353 - 30/01/2011 14:13 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Modelling temperatures of the Manilla Solar-Passive House
Midwinter daily cycles (2003)

1. Observations

The two graphs shown are logs of the temperatures observed during 51 hours from 13th to 15th July in midwinter 2003.

Weather
Although there had been rain on the 12th, these were calm sunny days without cloud, except for morning fog on the 13th, becoming low cloud which cleared at noon. On the other mornings there was fog in the river valley below.
Mean of daily minima: 2.9 degrees; mean of daily maxima: 15.4 degrees; mean daily temperature range: 12.5 degrees.

House regimen (winter)
The northern curtains were set to open at 06:40 and close at 17:20. Doors and windows were kept closed all night and most of the day. Clear-story windows were closed and fans in the clear-story space were set to blow warmed air down when it reached 26 degrees.

Comfort
No heating was required. Clothing included a flannelette long-sleeved shirt, jumper, singlet, trousers, socks and slippers. Bedding was sheets and one blanket the first night, two blankets the second.


The first graph shows that indoor temperatures are all higher than the highest outdoor temperatures, and vary much less, remaining close to 20 degrees day and night.
Sunrise normally fixes the time of daily minimum outdoor temperature. The fastest temperature rise of the day comes one or two hours later. The maximum temperature comes about 14:00. At sunset the outdoor temperature is only about three degrees below the maximum for the day, but the rate of fall is at a maximum. During the fourteen hours from sunset to sunrise the temperature falls by eleven degrees at a reducing rate.


For clarity, the second graph uses an expanded temperature scale and a shifted zero for indoor temperatures.

Wall temperature. Mean of daily minima: 18.35 degrees; mean of daily maxima: 21.95 degrees; mean daily temperature range: 3.60 degrees.
Again, the minima came at sunrise and the maxima near 14:00, but the graph was saw-toothed, rising and falling at steady rates of about +0.70 degrees per hour and -0.25 degrees per hour.
Ventilation
Some north-facing windows were opened for ventilation at times marked in blue on the graph. The outdoor temperature was about seven degrees cooler than indoors, and too cool for comfort. However, sunshine had heated the outer surface of the wall to about 30 degrees, and warmed air was rising. Since the windows are awning style, warm air was diverted into the room when they were opened.
The slope of the blue lines suggests that this trick is not a complete success: ventilation comes at a cost in lost warmth.


Floor temperature. Mean of daily minima: 18.65 degrees; mean of daily maxima: 19.85 degrees; mean daily temperature range: 1.20 degrees (barely noticeable).
Minima again came at sunrise, but maxima at 15:00. The minimum value persisted for two hours, and the maximum value for six hours, putting flats on the saw-tooth pattern.

Heat bank (750 mm below floor). The temperature was 19.1 degrees, rising at a rate that can hardly be detected.


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#966562 - 27/02/2011 10:33 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
There is a lot of discussion on the climate of particular kinds of houses in the new thread "Hobbit houses, ultimate weather proof house?" led by swamp-lady.
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#975535 - 16/03/2011 23:16 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Midsummer 2010-2011
Modelling indoor temperatures of the house

A series of posts with graphs modelling midwinter performance of my solar-passive house at Manilla, NSW, began with Post #874144.
This post is the first of a planned second series that model the performance in midsummer.
The house is managed in summer as described in Post #42328

1. Weather and house temperature logs

The first graph is the weather log for Manilla NSW in the midsummer period from 15th January 2010 to 14th February 2011. It shows daily 9 am readings of rainfall in mm, and cloud amount in Octas, using the scale on the right. Temperatures, to be read on the left scale, include the daily maximum, mean and minimum, and the mean temperatures (at a depth of 750 mm) of the outdoor subsoil and the heat-bank under the house. Dashed lines mark the normal maximum, mean and minimum temperatures for the time of year.
Very hot weather prevailed from January 24th to February 6th. The maximum of 42 degrees on January 26th was 8 degrees above normal, making it the second hottest day of the 12-year record. The final week was cloudy, with some heavy rain.



The second graph logs the indoor maximum and minimum temperatures, using an expanded scale. Temperatures are taken both at head-height on an interior framed wall and on the concrete slab floor. Mean temperatures of the subsoil and the heat-bank under the house are shown again. Purple curves show the 80% limits for adaptive comfort.

The only indoor temperatures plotting outside the comfort zone were the wall maxima for January 27, 28, and 29 and February 3, 4, 5, 6, and 7. These eight days plotted as too hot for comfort. The wall minimum also plotted at the upper limit for comfort on February 6. (Note there is no temperature standard for comfort while sleeping.)
In daytime, I wore only shorts and T-shirt through this period. I used fans for cooling most days. On the days that plotted as too hot for comfort I felt the fans were not adequate.
I slept in comfort by using only a sheet most nights, no sheet on 26, 27, and 28 January and 4, 5, and 6 February, and running a fan all night on 27 January and 6 February.

These readings provide data for study of how indoor climate relates to that outdoors.
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#975647 - 17/03/2011 11:10 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Midsummer 2010-2011
Modelling indoor temperatures of the house

2. Seven-day mean temperatures, outdoor and indoor


This graph makes clear the broad changes in indoor and outdoor climates in the period plotted in Post #975535 (above). Each data point is a seven-day mean temperature, centred on that day. Only the slowly-changing subsoil and heat bank points are raw data.
These data show a two week heat wave, with outdoor mean temperatures mainly about two degrees above normal, and a late peak nearly five degrees above normal. Subsoil temperature (outdoors) is carried up to a lower peak five days later.
As plotted, both indoor temperatures lag the outdoor temperature by about three days and they vary much less. Values for the floor are about a degree cooler than those for the wall.
The heat bank, measured 750 mm below the floor, is about four degrees cooler still.
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#978808 - 25/03/2011 13:54 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Modelling temperatures of the Manilla Solar-Passive House
Midsummer daily cycles

The two graphs shown are logs of the temperatures observed during 59 hours from 8th to 10th February in midsummer 2011. Times are Eastern Standard Time, although Eastern Daylight-saving Time was in force.

Weather
The first graph includes a record of the amount of cloud in oktas.The first day was overcast with some rain. The second day was mainly fine, and the third partly cloudy. There was little wind: the times marked "Breeze" had an easterly wind of up to seven knots.
Mean of daily minima: 17.1 degrees; mean of daily maxima: 30.6 degrees; mean daily temperature range: 13.5 degrees.

House regimen (summer)
Where the line for indoor temperature on the first graph is coloured blue, it shows how doors and windows were kept open when the indoor temperature was higher than outdoors. They were kept closed when it was not.
As noted in the second graph, the northern curtains were set to open at 18:00 EST and close at 06:00 EST. Fans in the clear-story space were set to blow warm air out the high windows from midnight to 05:00.


Comfort
Fan were used most of each day in occupied rooms. Clothing was only a T-shirt and shorts. Bedding was just a sheet. The Adaptive Comfort Zone for Manilla at this date is from 22.2 to 29.2 degrees. It is clear that indoor temperatures remain within this zone on these days, but some outdoor temperatures reach several degrees too hot or too cold for comfort.

Graphs for daily temperature cycles in midwinter showed that indoor temperatures at that time were all higher than the highest outdoor temperatures. During these midsummer days indoor temperatures lay near the middle of the range of outdoor temperatures.
Again sunrise normally fixes the time of daily minimum outdoor temperature, and at sunset the outdoor temperature is falling at its maximum rate. The temperature peak is sharp, and comes at about 15:00 EST.


For clarity, the second graph uses an expanded temperature scale and a shifted zero for indoor temperatures.

Wall temperature. Mean of daily minima: 23.4 degrees; mean of daily maxima: 27.0 degrees; mean daily temperature range: 3.6 degrees.
Indoor wall minima came about an hour after sunrise. After the outdoor maximum at 15:00, indoor temperatures continued to rise, at a slower rate, to peak after sunset.

Floor temperature.Mean of daily minima: 23.8 degrees; mean of daily maxima: 26.0 degrees; mean daily temperature range: 2.2 degrees.
The pattern of temperature change of the floor was like that of the wall. but without getting so warm or so cool.

Heat bank (750 mm below floor). The temperature of the heat bank cooled from 23.2 degrees to 22.6 degrees during this time. Due to being shaded by the house, it was five degrees cooler than the subsoil at the same depth outdoors.
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#983578 - 11/04/2011 21:12 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Modelling temperatures of the Manilla Solar-passive house
Daily cycles in midwinter and midsummer compared

Posts #867857 and #869629 compared the performance of this solar-passive house in midsummer and in midwinter. They used only daily maximum and minimum temperature values. This post, based on recent posts #943353 and #978808 (above) shows details of the daily cycles. These are affected by the different lengths of day and night, and by the use of daytime solar gain in winter and night-time ventilation (night purge) in summer. Some features are unexplained.
[All times are Eastern Standard Time.]


1. Outdoor cycles
The daily temperature range is similar, with the midwinter range a little less.
In both seasons, the morning warming is up to three degrees per hour. The midwinter temperature peak is broader and comes at 14:00, while the narrower midsummer peak comes near 15:00. The late afternoon to evening cooling is just under two degrees per hour. A slower rate of cooling of half a degree per hour prevails from 22:00 to sunrise in winter, but begins much later, if at all, in summer.


2. Indoor (Wall) cycles
Due to solar gain, the rate of temperature rise after sunrise in midwinter is much faster (0.8 degrees per hour) than in midsummer (0.3 degrees per hour). However, in midwinter the temperature falls after the peak at 14:00. After 14:00 in midsummer, the temperature continues to rise slowly for another six hours. This extra warming occurs despite the house being designed to suppress daytime heating in summer and enhance it in winter.
Due to night-time ventilation the rate of temperature fall is much faster in midsummer (0.5 degrees per hour) than in midwinter (0.25 degrees per hour). However, the short summer night makes the time for cooling much shorter.


3. Indoor (Floor) cycles
In midsummer, the night purge causes a sustained cooling of the floor, more than half that of the wall. A draft of cool night air creeps along the floor. The daytime recovery is slower but also rather steady.
In midwinter, the floor temperature varies less. Maximum rates of warming and cooling are much the same but cooling is slow after midnight because doors, windows and curtains are closed. Daily temperature peaks and troughs are both flattened. The floor temperature does not begin to rise for two or three hours after sunrise, then it ceases to rise for about six hours after 15:00 (unexplained).
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#989756 - 16/05/2011 08:52 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
On Sunday morning my house showed how well it can perform.
After days of cold winds, Saturday night was calm, and a black frost developed. The morning minimum of -2.8 degrees was a thirteen-year record for May.
The indoor minimum (no heating) was 18.0 degrees, that is, 20.8 degrees warmer.
Such large over-temperatures can come with very dry air in autumn. This graph shows that indoor minimums twenty degrees above outdoor temperatures have happened before.
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#993387 - 05/06/2011 00:46 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Manilla Low-Energy House: Last year's temperature logs. 1.

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 about three weeks. Indoor cyles have a much smaller amplitude.
The smooth, thinner black line is the normal mean temperature at Manilla. Normal temperatures range through 17 degrees: from 9 degrees in mid-winter to 26 degrees in mid-summer. It is clear that this year's October, November and December were much cooler than normal. For some days in mid-December, the seven-day mean was six degrees below normal.
Indoors, mid-winter temperatures were about 8 degrees warmer than outdoors, and mid-summer temperatures were about one degree cooler than outdoors. These figures are for averages only. This house reduces daily extremes also, as shown in earlier posts.

Curves in purple are the limits of the adaptive comfort zone. The house succeeds remarkably well in keeping indoor temperature within the comfort zone in all seasons. The cold snap in mid-December was one of the few occasions when indoor temperatures were not comfortable, according to this comfort model. High indoor temperatures in April show the effect of changing to the winter regimen.


Adaptive Comfort
The adaptive comfort Zone shown on this graph is based on that proposed by Richard de Dear and Gail Schiller Brager (2001). A graph defining this comfort zone was posted earlier in this thread.
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, ASHRAE recognised that full climate control of buildings may not be the way of the future.
As defined, the zone is calculated from mean monthly temperature (the arithmetic average of mean monthly minimum and maximum air temperature) a number "that can be found easily by examining readily available climatic data" (Brager and de Dear, 2000 ).
Mean monthly temperature has the defect that there is a step between the last day of one month and the first day of the next. At Manilla, the mean monthly temperature increases by four degrees from August to September. This implies the neutrality temperature for comfort would rise by more than one degree overnight.

Since I have already estimated the normal mean temperature for each day of the year at Manilla, it seems logical to calculate the adaptive comfort zone temperatures from these values, as shown.
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#993733 - 06/06/2011 22:49 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Manilla Low-Energy House: Last year's temperature logs. 2.

Like the graph in the post 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, which is surrounded by insulation so as to form a "heat bank".

Outdoor subsoil temperature
For most of the year, the outdoor subsoil temperature (green) closely followed the outdoor 7-day average temperature, with fluctuations reduced to less than one degree, and lagged about four days. It peaked at 27.7 degrees just after the outdoor averaged air temperature peaked at 30.6 degrees.
Subsoil temperature was several degrees warmer than averaged air temperature from mid-March to mid-August, as seems normal in this climate.
Consequently, outdoor subsoil temperature reached a minimum of 13.3 degrees about a month after the averaged outdoor air temperature minimum of 6.7 degrees. This year, the subsoil temperature range at 750 mm was (27.7 - 13.3 = 14.4) degrees.

Heat bank temperature
The temperature of the heat bank (orange) followed a cycle like that of the outdoor subsoil, but with a much reduced range, (23.0 - 17.0 = 6.0) degrees, that is mainly within the comfort zone. One notable difference is that, due to solar heating of the interior brick walls and the tiled concrete floor slab, the heat bank warmed slightly during April, while the outdoor subsoil cooled by three degrees.

Influence on house temperature
Through winter, it seems clear that the heat bank temperature has a very strong effect on temperature in the (unheated) house, or that heat is shared between the two. Both hold temperatures very much higher than either outdoor subsoil or outdoor air.
In summer the heat bank, due to the shading and insulation provided by the house, remains much cooler than the house or the air or the outdoor subsoil. It must be feeding back "coolth" into the house, but the house is not very cool.
I suggest that, despite extremely effective shading, the heat load on this house in summer is so high it defeats the heat bank.
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#993736 - 06/06/2011 23:13 Re: Indoor Climate [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2193
Loc: Manilla, near Tamworth NSW
Manilla Low-Energy House On Show

The two graphs above were prepared for display as part of an event : "Sustainable Namoi Living" sponsored by Tamworth Regional Landcare Association and Namoi Catchment Management Authority, among others.
There was a news video about the Manilla house .
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#994426 - 09/06/2011 22:59 Re: Indoor Climate [Re: Surly Bond]
Vinnie Offline
Meteorological Motor Mouth

Registered: 17/05/2006
Posts: 6821
Loc: Mulambin , Yeppoon Central Qld
The highest temperature my east facing double brick home gets to in summer with all the windows closed during the day and opened late evening and all night is 29 deg. Though we always put the evap air con on if it gets to 26 deg . The coolest it ever has dropped to is 14 deg, though it was -1 outside and from the morning onwards it warmed up. I wonder how much difference the tinting on the massive east window makes ? Because in summer the temp in that room still goes up. It is not black dark tinting , it is a purple colour but you still cannot see in.

Lately the weather in Perth has been average with 19 deg most days some days 20 deg. The house temp is usually 16 deg in the morning and from 7am to 3pm it rises to 18 deg. The past nights have been warmer , 12 deg , compared to 5 deg so it was 17 deg inside this morning rising to 19 deg by the end of the day. It seems to be a slow rise and slow drop. It doesn't seem to drop till after midnight (the temp inside).

It becomes cold inside when it is 16 deg or less. So far this year the coldest temp has been 15 deg (it got to that early one morning). To get to that it was 1 deg outside. It was short lived because as soon as the sun rose in 30 mins it went ot 16 deg and then slowly during the day it got back up to 18 deg again.

In May the house was more in the low 20's hovering between 20-22.

In March it was always 24 deg inside in the morning after opening everything inside overnight, though we have had a lack of cooling breezes this year so the bricks can't really cool down also if you have 30+ everyday and 20+ everynight that didn't help either. Evap air con kept it more bearable.

Haven't used the portable gas heater since August last year, hasn't really been that magical 16 deg or below inside yet to justify putting it on, also we have invested in more lambs wool jumpers. The gas heater works out at 1 dollar 55 a day to run.

I know I am going off topic a bit, but does keeping blinds closed make any difference really to indoor temperatures ? I have started closing blinds etc , it seems to still drop 2 deg inside overnight and rise 2 deg inside during the day regardless !


Edited by vinny06 (09/06/2011 23:08)
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