Posted on another web-site, the graph on the next post up attracted a query from a resident of Bulleen, near Latrobe University in Melbourne. I was able to show him a graph of the 30-year sequence of October outdoor temperatures in that area. Given how many people live there, there may be readers here thinking of building solar-passive in that area.
I was quite surprised at how much colder October is there than at my place, and how much narrower the daily temperature range is.
It changes the parameters, to coin a buzzword.
http://forum.weatherzone.com.au/ubbthreads.php/topics/1025940/Re_Observations_of_climate_var#Post1025940
Low-energy houses
(167 posts) (33 voices)-
Catopsilia
MemberPosted Monday 31 Oct 2011 @ 8:42:05 am from IP # -
Catopsilia
MemberHouse Doesn't Warm Much with the Climate
In the twelve years I have lived in my solar-passive house at Manilla, NSW, the climate has changed. The mean temperature for each year has varied. The low extremes were 2001 and 2008, 0.70 and 0.75 degrees low, and the high extreme 2009, 0.95 degrees high. Elsewhere, I have plotted this temperature variation as smoothed monthly values on a graph, which shows how global mean temperatures also varied in the same sense during this time:
http://www.ata.org.au/forums/topic/2190/page/2#post-21029This data set misses the fact that the house operates in distinct regimens in summer and winter: it includes only annual averages.
Here, I have simply plotted each year's mean indoor temperature against that year's mean outdoor temperature. The indoor temperature is much more comfortable:
http://forum.weatherzone.com.au/ubbthreads.php/topics/864290/Re_Indoor_Climate#Post864290
For a climate with that mean outdoor temperature (18 degrees) the corresponding "neutrality temperature" giving best comfort is 23.4 degrees. While this falls above the top of the graph, all plotted points have indoor temperatures within the 90% satisfaction comfort zone, which extends down to 20.9 degrees.
The data points match a second-degree curve. At the coldest temperature (2008) each degree of climatic cooling brings a degree of cooling in the house. However, at the warmest temperature (2009) each degree of climatic warming brings only half a degree of warming in the house.
If the relation changes little for higher (or lower) temperatures, this house is likely to perform even better in a warmer climate. The mean temperature indoors will reach the ideal "neutrality temperature" when the climate is about two degrees warmer than in 2009.Posted Wednesday 14 Dec 2011 @ 1:34:38 pm from IP # -
PeterReefman
MemberA 2011 update on our 8 Star all-electric house in Portland on the balmy* SW coast of Victoria.
First off - we have a strict rule of putting the heater on if the living room temp drops below 20c. There were four nights that we needed to do that this year. No artificial cooling has been required ever.
Each of those "heating nights" consumed an average of 1.25kWh from our heat pump (which is a 2.5kW Mitsubishi reverse cycle air-con), giving us a total heating/cooling energy consumption of 5kWh for 2011.
To widen that to total energy use (projecting a little for the next 2 weeks), the house
* Consumed 2,740kWh **
* Produced 4,570kWh with solar PV ***
* And again, used 5kWh for all the heating/cooling requirements.And yes we have a Victorian pFiT contract so our family of four are doing well financially from our sustainability "investment".
I'm looking forward to fitting more energy monitoring/publishing equipment to be able to see and publish online which appliances are doing what. I've got an ENVI and are in the middle of our Bridge being expanded to the 10-channel version.
Cheers,
Peter* That's a joke. But we do love the nine months of cold wet windy weather here.
** And "Consumed" means actually consumed - not just imported from the grid.
*** Actually the PV system was only recently expanded from 1.44kW to 3.34kW, so the 4,570kWh is an accurate estimation of what it WILL produce in a year, rather than what was produced in 2011 which was more like 2,000kWh...
Posted Thursday 15 Dec 2011 @ 10:20:51 am from IP # -
Catopsilia
MemberThis December has been by far the coldest of the last thirteen. Daily maxima of 26.9 degrees are 4.7 degrees below average, and daily minima of 13.9 are 2.5 below.
The mean temperature is 3.6 degrees down. In my solar-passive house, designed to limit excess heat in summer, the indoor temperature is 2.2 degrees lower than usual. Instead of 23.9, which is near the ideal, it is 21.7, near the lower limit for comfort.
A low-energy house must be designed for the climate. To design for possible deviations from the climate is another layer of difficulty. How often should we expect months with temperatures nearly five degrees different from normal?Posted Thursday 29 Dec 2011 @ 10:35:55 pm from IP # -
KimW
MemberQuestion for all,
What do you consider a reasonable usage of electricity for one person in an average house (4 bed, 2 bath)?
I am currently using about 5kW/day - a bit more in summer with a bore pump running.
Heating in winter is gas, HWS is solar with gas boost. Have an induction cooktop, but don't do that much cooking.cheers Kim
Posted Friday 30 Dec 2011 @ 3:29:05 pm from IP # -
KimW
MemberHi Macklinvinger,
It would help me if you could please indicate some quantitative values for average and low-energy homes?
For example - Peter's figures (above) come to 7.5 kW/day. Not sure of the size of family.
Anybody else interested in comparing electricity usage?
cheers KimPosted Saturday 31 Dec 2011 @ 10:47:02 am from IP # -
Catopsilia
MemberThat seems to be a fairly acceptable definition macklinvinger, though one could quibble (How about the heat of the sun?).
Are you offering it as a topic for debate?Sorry, KimW, I don't have much to say on your question. I once filled in an energy-saving questionnaire from a power company and was told I got a low score. I guess I may have been competing with other bachelors who don't live in houses but in small flats in the city, where they do no cooking, washing up or laundry and are seldom home. All their energy costs are externalised and don't count.
Posted Saturday 31 Dec 2011 @ 11:20:42 am from IP # -
dymonite69
MemberKimW said:
Hi Macklinvinger,
It would help me if you could please indicate some quantitative values for average and low-energy homes?
For example - Peter's figures (above) come to 7.5 kW/day. Not sure of the size of family.
Anybody else interested in comparing electricity usage?
cheers KimThere are a few definitions of 'low energy'. German Passivhaus standard and our house energy star rating.
Any definition should include some reference to the type of appliances used e.g. heat pump vs gas and the indoor conditions of the house without artificial heating or cooling inputs.
50% of home energy use is not related to its intrinsic 'efficiency' but due to occupant behaviour. For instance when you go camping you might have to endure temperature ranges from freezing to boiling but given that you have no access to an air conditioner, your actual energy use is close to zero.
Posted Saturday 31 Dec 2011 @ 1:29:41 pm from IP # -
PeterReefman
MemberWe had a great test day here today - the hottest day since moving into our 8 Star house in 2009.
Outside reached a maximum of 41.4c, while inside the maximum temp was 25.9c. There was no artificial cooling used. No Air-con or even a fan.
The day's stats can be viewed at http://www.energised.com.au/8Aquarius_temps.asp
Posted Monday 2 Jan 2012 @ 4:34:36 am from IP # -
dubbo teacher
MemberA build I'm looking at on a 20 acre hill block - sloping down to north with views 270 degrees from E to S - is to construct walls of straw bale with clerestory gable roof, corrugated iron on north side with solar panels and south side a green roof. Because of slope to north thinking of digging into slope on south side and having south wall only 600mm - 1m high.
East and west walls straw bale but not normal bales. Have resources and capacity - crop/front end loader tractor - to use large squares - 8'x4'x3'. Three or 4 bales high would give 9 or 12 foot ceilings on north rooms. Normal restricions like lack of space on block and/or expense of handling/transporting large bales not an issue. Bales could come from 1km away.
Believe such a wall could be load bearing but not to put up a roof first on straw bale risks getting bales wet if it rains so that requires a bit more planning.
Bottom line is that such a dwelling could be low energy + low embodied energy.
Overriding principle in any dwelling is surely to build within our financial and practical means...and that boils down to playing to our strengths...yes?
Mine are those outlined above plus a willingness to source and use recycled materials.Posted Thursday 5 Jan 2012 @ 12:53:55 pm from IP # -
Catopsilia
MemberRecent climate change is bad for solar-passive houses
I am working up performance data for 12 years in my high-mass solar-passive house on the N W Slopes of NSW.
Summer data seem to show that the house is becoming less effective at rejecting summer heat. I think this is a result of recent climate change rather than faults developing in the house.In summer the cooling of the house is done mainly by flooding it with cold air at night. Data show that summer temperature in the house responds to ambient minimum temperature and not to ambient maximum temperature. Thus, summer heat, felt as high daily maxima or daily means, is countered by cooler air that is near the daily minima.
In the 12 years, the summer daily maximum temperature has fallen by nearly half a degree, leading one to suppose that a well-designed house should also have cooled slightly. This has not happened. In the same period, the summer daily minimum temperature has risen by one whole degree, raising the house temperature with it. The night air cannot cool as effectively as it could in 1999.
Solar-passive houses work best in climates with a high daily temperature range. Here, the daily temperature range has fallen dramatically, by about 1.5 degrees in a decade. (By 2112, nights will be warmer than days!)Mid-winter performance of the house is discussed above:
http://www.ata.org.au/forums/topic/3/page/4#post-20805
I show there (and more explicitly in a link) that mid-winter also has decreasing daily maxima and increasing daily minima through these 12 years. These also degrade the house performance. In winter the house is warmed by the sun at mid-day, which is now not as warm as it was. The warmer winter nights give no warmth, as so little heat is exchanged at night.Posted Sunday 8 Jan 2012 @ 5:32:44 am from IP # -
Catopsilia
MemberA cold day in summer
My solar-passive house was not designed to deal with a summer day eleven degrees below normal.
With today the coldest January day in a decade (max 23 degrees) the house is also below 23 degrees. It is doing its best to keep me cool!
I have rugged up. From shorts and bare feet yesterday, I have changed to longs, jumper, socks and slippers. That's from 0.18 clo to 0.72 clo!
Here is a good link to clo units, units of thermal insulation for clothing:
http://www.engineeringtoolbox.com/clo-clothing-thermal-insulation-d_732.html
Posted Sunday 15 Jan 2012 @ 7:57:00 am from IP # -
dymonite69
MemberCatopsilia said:
A cold day in summerMy solar-passive house was not designed to deal with a summer day eleven degrees below normal.
With today the coldest January day in a decade (max 23 degrees) the house is also below 23 degrees. It is doing its best to keep me cool!
It would be interesting to see how hard it would be to design and build a solar-active house that would allow complete flexibility in shading, insulation and window treatment such that you could control sunlight, ventilation or heat loss at any time of the year.
Posted Sunday 15 Jan 2012 @ 1:41:54 pm from IP # -
Catopsilia
MemberIt would be interesting to see how hard it would be to design and build a solar-active house that would allow complete flexibility in shading, insulation and window treatment such that you could control sunlight, ventilation or heat loss at any time of the year.
There are horror stories about people who bought clever houses without the least understanding of how they should work. Even my house needs adjustments twice a year. I intend to leave instructions for future tenants, but they will probably get them wrong if they even care.
Posted Sunday 15 Jan 2012 @ 10:51:49 pm from IP #
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