dymonite69, I don't get that effect of south rooms being cooler, because the clear-story windows send winter sunshine through to them. Where there is a brick wall in the way, the wall has big internal windows to let the sunshine through. (Serendipitously, they let in the summer full moon.)
Apart from direct solar radiation, I am not sure that radiation shifts much heat around indoors, as the temperature differences are small. Certainly my fans in the clear-story space shift a lot of heat by forced convection. They come on when the warmed bricks heat the adjacent air to 26 degrees, and ensure that the upper bricks never get much warmer than that.
Similarly, cooling the exposed surfaces of the heat bank by admitting cool night air and exhausting it by an enhanced stack effect can hardly have much of a radiative component.
Low-energy houses
(298 posts) (50 voices)-
Posted Saturday 3 Jul 2010 @ 12:37:27 pm from IP #
-
dymonite69
MemberI don't have clerestory windows so there is no direct solar gain for the south side. The only way I can heat the south side is to force warmer air from the sunny side of the house. In this situation it does not seem to much purpose in putting to much mass on the non-sunny side. Heating the mass with warm air is much slower than having the sun fall directly on it.
In the US literature they have differing areas of thermal mass depending on whether it is sun-exposed or not. Baggs does not differentiate the two situations. I believe that how much mass you put in a particular room depends on how much sun it gets.
Posted Saturday 3 Jul 2010 @ 1:55:28 pm from IP # -
dymonite69
MemberI had another look at one of Baggs' calculations:
4.5 m2 air to 150mm of 1m2 concrete. The concrete section would hold 52x more energy than that volume of air for a one degree rise.
Volumetric heat capacity:
Air 1.297 KJ/m2/K
Concrete 2060 KJ/m2/KThe magnitude of conducted transfer from air to mass would be comparatively small compared to radiant energy.
On the other hand, direct sunlight would transfer between 0.5-1 kJ/m2 every second (1800-3600 kJ/hr)
Posted Wednesday 7 Jul 2010 @ 1:04:02 pm from IP # -
I have begun a new series of notes and graphs about the temperature response of my solar-passive house during mid-winter 2010:
http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=874144#Post874144Posted Thursday 29 Jul 2010 @ 12:09:53 pm from IP # -
Thanks! For your informative post But I am shocked for low energy house. You can use solar energy for increase energy and use it in proper way.
Posted Monday 2 Aug 2010 @ 6:03:00 am from IP # -
There has been a good deal of discussion that I am sure would interest those reading this thread to be found in the second page of the thread titled: "single or double glazing for new home".
The discussion concerns the role of thermal mass in indoor comfort.How fast does heat travel in thermal mass materials?
Some comments and queries on these forums suggest that people do not have a good grasp of just how slowly heat travels in heavy materials, and how small the temperature differences are likely to be.
Steve Szokolay's book "Introduction to Architectural Science: The Basis of Sustainable Design" is a good source for such information.
Core parts of the book are on the web, at:
http://elsevier.insidethecover.com/searchbook.jsp?isbn=9780750687041
Navigate yourself by some means to Section 1.4.4 on Page 47.
Fig 1.67(a) shows that heat moves about half a metre in 12 hours in bricks or concrete. That is one metre per day. If a patch of floor at one side of a room gets sunlight, the floor on the other side will also warm up about three days later.
Fig 1.67(b) shows that the pulse of heat will be rather less than 5% of its original size by the time it gets there. But it will get there, and dozens of successive daily pulses will have quite a big effect.Posted Wednesday 4 Aug 2010 @ 9:09:00 am from IP # -
Jeffbloggs
MemberCatopsilia
All the more reason to use water as a thermal store and metal radiators to disperse the heat into the rooms. As I posted in 'single or double glazing for new home' thread you mentioned.Posted Wednesday 4 Aug 2010 @ 9:27:54 am from IP # -
dymonite69
MemberThe assumptions here that the thermal energy stays in the slab. Even if the edge is insulated, the heat still inexorably moves downward. There is a continuous loss. Can the solar input completely offset this? Ideally you want just enough mass inside the house to store the day's heat and then superinsulate the envelope - top, sides and bottom. The majority of the heat that is gained during the day is then transferred inward rather than outward.
But let's take the extreme example. Assume you dig a cave into the side of a mountain and put a piece of north facing glass at the mouth. It might take decades (if at all) before you raise the average temperature of your cave to comfortable levels.
Even with JB's isolated gain system you would still need to insulate the mass well.
Posted Wednesday 4 Aug 2010 @ 10:37:03 am from IP # -
dymonite69, Re: caves
Australia has some of the most desirable dwellings in the world for troglodytes. My data at Manilla NSW show a mean ground temperature at an outdoor site of 20.16 degrees at 0.75 metres. At that depth there is less than 0.3 degrees of daily variation and 12 degrees of annual variation. At a depth of five metres even the annual variation should disappear, leaving the temperature constant at 20 degrees. If the cave you propose was about five metres deep the air in it would have that temperature, which would be comfortable for most people when dressed normally for winter.
Without attempting an analysis, I believe the proposed solar gain window would work well (just as they do in my house). The air temperature need not be raised many degrees to make the cave comfortable in summer attire. The losses to the rock walls would not be very great because rock is such a very poor conductor.
If twenty degrees was considered too cool by the occupants, they could set the solar gain window to operate all year round. There is everywhere an interchange of solar energy from the sun to soils and rocks metres below the earth's surface. A dwelling, whether a house or a cave, can be heated by catching some of that energy as it passes through.Posted Wednesday 4 Aug 2010 @ 1:21:15 pm from IP # -
Jeffbloggs
MemberCatopsilia
Caves make sense. I just don't believe we have enough of them for everyone, or that anyone wants to live underground
However energy wise caves work well, another reason why I suggest to install a hydronic water thermal store system with heat-pump and a shallow geo-thermal collector. The geo-thermal collector can take full advantage of the ground temperature constant if it is sized correctly. Its called shallow geo-thermal because it is only between 1-20m in depth. Some might suggest such a system is not cost effective in Australia but given the overall effect on living quality and reduction in energy demand I beg to differ.
Posted Wednesday 4 Aug 2010 @ 2:11:44 pm from IP # -
dymonite69
MemberA free running range of 18-23 degrees all year round would be ideal.
Posted Wednesday 4 Aug 2010 @ 3:32:20 pm from IP # -
In the thread "Does Solar Help Sell a House" there is some discussion around the following topic:
A winter house-heating system based on a large underground water tank described in the link posted by dymonite69
http://mtbest.net/heat_pump.htmlPosted Sunday 8 Aug 2010 @ 4:44:40 am from IP # -
Jeffbloggs
Memberoldfossil
Sorry I missed your post. It would be a heat pump-hydronic interconnected system, however depending on your climate it would need to operate with a larger (possibly lower temperature) system for climate control and another for HWS. The reason is so that you can cool with the climate system and still continue to use hot water from a smaller system at the same time in summer. In winter this will allow you to use the climate hydronic system to a lower level in the winter with out the discomfort of luke warm water out of the HWS.The key to making a dual mode heating/cooling system is to decouple demand from supply in a efficient/effective manner. As Catopsilia posted, theres some further explanations also about the system i proposed, on the "Does Solar Help Sell a House" and "single or double glazing for new home". BTW I don't take the credit for this, most of it is already in use in europe, especially Germany, and has been for years.
Anybody use Google Wave before?? I really wished we could migrate the forum to that, it is tons better than hacking around in this DOS type environment, and only being able to share text. Plus it notifies you about any post addressed to you as well, that way you don't have to monitor any threads to stay involved in a discussion.
Posted Sunday 8 Aug 2010 @ 6:57:15 am from IP # -
What makes a solar-passive house warmer or cooler as the weather changes in winter?
I have posted an analysis, with graphs, showing how the indoor maximum temperature in my house varied during this mid-winter depending on outdoor max and min temperatures, Heat Bank temperature, and cloudiness:
http://forum.weatherzone.com.au/ubbthreads.php/topics/877256/Re_Indoor_Climate#Post877256Posted Sunday 15 Aug 2010 @ 10:19:30 am from IP # -
I have just posted details of how wall temperatures in my solar-passive house in mid-winter respond to outdoor temperatures, cloud, and the long-term storage of heat under the slab.
Outdoor temperature and cloud up to three days earlier are reflected in indoor wall temperatures. This shows that heat is still moving in the near-surface parts of the thermal mass of the house for days after it is first absorbed.
http://forum.weatherzone.com.au/ubbthreads.php/topics/882793/Re_Indoor_Climate#Post882793Posted Sunday 12 Sep 2010 @ 12:58:57 pm from IP # -
dymonite69
MemberHello Catopsilia,
Lots of useful data here which I still chewing over.
I note that the drop in wall temperature occurs at the maximum cloud cover despite rising overnight temperatures.
Another conclusion: solar gain has a more dominant effect on internal fabric temperatures than ambient air temperature?
Posted Monday 13 Sep 2010 @ 1:16:33 am from IP # -
>>Another conclusion: solar gain has a more dominant effect on internal fabric temperatures than ambient air temperature?
I don't have the radiation data to prove that, dymonite69.
The fact that indoor maxima are nearly always higher (sometimes much higher) than outdoor maxima in mid-winter suggests to me that heat leaking in from warm outdoor air is not very important. In mid-winter the uninsulated house next door had almost identical indoor and outdoor maxima as heat leaked freely in and out:
http://forum.weatherzone.com.au/ubbthreads.php/topics/868562/Re_Indoor_Climate#Post868562Posted Monday 13 Sep 2010 @ 12:29:30 pm from IP # -
dymonite69
MemberWinter solar radiation inward heat flux is around 500W/m2 of solar exposed glazing. However, conductive heat loss through the fabric is about between 25-150 W/m2 depending on how well insulated the house is.
If you can store the gain and you have reasonable insulation then the house is always warmer than outside.
Posted Monday 13 Sep 2010 @ 12:39:54 pm from IP # -
Climate swings affect a solar-passive house
The seasonal shading of north-facing windows on a solar-passive house results in the house having two distinct regimens: winter heating by solar gain and summer cooling by shading and ventilation. The effects can be enhanced by adjusting devices such as curtains and awnings to suit twice a year, roughly at the equinoxes, or the beginning of October and April, or Easter and Labour Day. I like to work to such a rule, which can become a ritual, as practiced since agriculture was invented.
Unfortunately, climate swings are upsetting my routine. In inland north-eastern NSW and adjacent regions temperatures have been rapidly cooling ever since the extreme heat of November 2009. Daily maximum temperatures are now several degrees below normal. Daily minimum temperatures are still above normal.
The temperature trends are shown here:
http://forum.weatherzone.com.au/ubbthreads.php/topics/887038/Re_Observations_of_climate_var#Post887038At least for the cooler part of the year, my data suggest that it is the outdoor maxima that dominate the indoor temperatures of my solar-passive house:
http://forum.weatherzone.com.au/ubbthreads.php/topics/882793/Re_Indoor_Climate#Post882793A very large area of inland NSW and Victoria is now experiencing these very low daily maximum temperatures, as shown on maps of maximum temperature anomaly, monthly for August and September 2010, and weekly during October:
http://www.bom.gov.au/jsp/awap/temp/index.jsp?colour=colour&time=history/nat/2010070120100731&step=1&map=maxanom&period=month&area=natThe fact that outdoor maximum temperatures this month are running at least three degrees lower than normal means that the change-over from trying to warm the house to trying to cool it ought logically to be delayed by about a month.
As to day-to-day comfort, the extreme cold front of the 16th of October brought a daily maximum (14.2 degrees) that was 13 degrees below normal. My house did not cool until the evening of the following day, but then I needed to turn on a heater for an hour and add a second blanket to the bed, as the bedroom temperature fell to 17.4 degrees.Posted Wednesday 20 Oct 2010 @ 11:17:21 am from IP # -
Appropriate desert homes: Ghadames
For years I have been looking for information and images about traditional houses suited to hot dry climates. Finally, I have found a wonderful World Heritage listed city full of them: Ghadames, Libya
This is about the best photo gallery I found:
http://www.darsahara.com/view_foto.asp?id=127&gal=8&sh=768&sw=1366&slide=onTo see the structure of the town, look for Gadamis on Google Maps, or Ghudamis (30 deg 8 min N; 9 deg 30 min E) on Google Earth.
Ironically, given that the houses yield almost perfect comfort in the sahara by natural means, the old city was virtually abandoned in the 1980's, in favour of generic houses in a modern new city. Search the web to see if you can make sense of this. It is not clear whether people moved willingly. Reasons cited for the move included the difficulty of updating the old houses with running water and other services, and failure of the adjacent gardens due to a falling water table.
There is a scrappy paper that has sketches of old city houses and new city houses and some indoor and outdoor climate data:
http://research.ncl.ac.uk/forum/v2i1/The%20Impact%20of%20Hot-Dry%20Climate%20on%20Housing.pdfPosted Sunday 23 Jan 2011 @ 8:42:08 am from IP # -
I have posted graphs of measured mid-winter daily cycles of temperature in my solar-passive house:
http://forum.weatherzone.com.au/ubbthreads.php/topics/943353/Re_Indoor_Climate#Post943353Posted Sunday 30 Jan 2011 @ 3:34:40 am from IP # -
Frateco
MemberCatopsilia, what sensors/logging system are you using? Did you make it or if bought, where? Cost?
I am not an electronics guy so I feel to make something is going to be hard. I looked at Futurelec and can get sensors for temp & humidity but how it all goes together will be beyond me. Suggestions??
Posted Wednesday 2 Feb 2011 @ 4:00:34 am from IP # -
Frateco
I am sure I will disappoint you, but I have no logging system. I have a variety of electronic thermometer/hygrometers. Most of them I read daily and then reset the max/min memories. From time to time I have a "blitz" and read them all every hour or two to get the daily cycle details.
Some of the thermometers have radio transmitters, most of which are "as silly as a two-bob watch".
My best instrument is an Oregon Scientific "Weather Forecaster" (so called) Remote Thermo-Hygrometer Model BAR182HG. For the price, this is pretty good. (They now advertise their BAR208HG at $99.99.) I have put the sensor in a home-made Gill-type thermometer screen, and I fitted lithium AAA batteries to ensure it operates at zero degrees.
I enter data manually into Excel for analysis.
I feel that if I invested in a logging system that I could set and forget, I would lose interest in the project.Posted Wednesday 2 Feb 2011 @ 12:52:50 pm from IP # -
chameleon
MemberI dont have any experience with ibutton loggers... But I do have experience with cave houses, in my opinion the most efficient house system! Except for natural light..
http://www.homeownersinsurance.org/cave-houses/Posted Monday 14 Mar 2011 @ 4:06:12 pm from IP # -
I posted before about my series of graphs that model the midwinter performance of my solar-passive house at Manilla, NSW.
I have just begun a series for midsummer, based on figures from late January and early February this year.
http://forum.weatherzone.com.au/ubbthreads.php/topics/975535/Re_Indoor_Climate#Post975535This period included a fortnight of heat wave. Fans were not really adequate to keep cool during eight of the days.
I have still not found an air-conditioning salesman that I trust to advise me on a unit that is
very cheap;
very reliable;
to be used for less than 100 hours per summer in some of the summers;
to reduce the temperature by no more than five degrees when used;
to cool two or three rooms only when they are occupied.Posted Thursday 17 Mar 2011 @ 3:00:35 am from IP # -
Catospilia, I'm not sure that very cheap AND very reliable are typically used in the same sentence when discussing air-conditioning:) Nevertheless, you may like to read this link, as well as some of the links provided there.
I trust the writers judgement, & they do mention the Homemaker brand as a low cost good value option, so that may be worth exploring.
http://whirlpool.net.au/wiki/aircon_faq
I've now had a MHI (Mitsubishi Heavy Industries) r/c unit for nearly 2 years. It operates superbly for my requirements - last summer I used it for approx 180 hours & last winter approx 150 hrs.
One selection criteria I learnt from previous bitter experience is to buy a brand where, should repairs, particularly during warranty be required, then choose one where local authorised repairers are available. This can be a major issue in some rural/regional areas. (a 2 weeks plus wait for servicemen in peak periods either mid winter or mid summer without a functioning unit is not fun - I've experienced both!!)
In 2 previous homes I had Fujitsu units, both good. The first unit at my current home was a Mitsubishi Electric - which I wouldn't touch again with a 10' barge pole - just my experience. (Interestingly it was the same person who sold me all 3 units - I later formed the view that his advice to change to M E. was more based on the size of his commission than the supposed technological superiority of the brand.)
Perhaps talk to electricians that you know & trust. I purchased my current unit from my electrician, whose judgement & work I trust implicitly. As an MHI agent/installer he can also undertake repairs if ever they are needed.
Posted Thursday 17 Mar 2011 @ 4:49:36 am from IP # -
Thanks, cw nsw, for a very helpful post and link.
I wonder whether others have found themselves in the same bind as I have. When a house has been built so that the indoor climate extremes fall only slightly outside the comfort zone, the most popular air conditioners are not appropriate.
First is the high cost. After investing heavily in insulation, thermal mass, shading and draft-proofing, it makes little sense to spend heavily on air-conditioning as well. A quite small improvement in comfort is sought, so it should be at suitably low cost.
Next is reliability. A device that is seldom used tends not to be reliable. You point to the related difficulty of getting service when needed.
Yet makeshift arrangements such as portable or window-mounted units will not do. These compromise details of the original house design.Very little can be said for evaporative coolers, and nothing at all in this particular case.
Posted Thursday 17 Mar 2011 @ 10:21:49 am from IP #
