Alternative Technology Association

Alternative Technology Assn Forums

Sustainable living: making it happen

Sanctuary Magazine Renew Magazine

Alternative Technology Assn Forums » Sustainable Building

Low-energy houses

(298 posts) (50 voices)
  • Started 14 years ago by GarrySpeight
  • Latest reply from Catopsilia

Tags:

  • double glazing
  • Embodied Energy
  • fans
  • heat bank
  • houses
  • Hydronic
  • indoor climate
  • insulation
  • low energy house
  • low energy houses
  • motorised curtains
  • night purge cooling
  • passive home
  • poem
  • renovation
  • shading
  • solar-passive
  • stack effect
  • Strawbale
  • temperature
  • thermal mass
  • tiny house
12…10Next »
  1. GarrySpeight

    GarrySpeight
    Member

    I am very happy to see this forum up and running. I have been frustrated for years by not having a place to discuss low-energy houses.
    My house, on the north-west slopes in NSW, is solar-passive, high-mass, and well insulated. I have been monitoring temperatures indoors and outdoors for over nine years.
    One interesting (disappointing) result is that this cool wet summer did not make the house very cool. Days were cool, but nights were not. The night air was simply too warm to do much cooling, and the heat bank carried too much heat over from the spring.

    I would really like to swap notes with other low-energy house enthusiasts.

    Posted Friday 11 Apr 2008 @ 4:01:01 am from IP #
  2. Alister1

    Alister1
    Member

    Hi Garry
    What are you using as a heat bank, I am currently preparin to embark on a ESD project and I am tossing up between under floor Rock or Insulated water tank Heat Bank.

    We are looking at a reverse veneer construction

    Thank you for your time

    Alister

    Posted Monday 14 Apr 2008 @ 11:43:14 pm from IP #
  3. GarrySpeight

    GarrySpeight
    Member

    Hi Alister
    I was planning to use reverse brick veneer, but used several double-brick internal walls instead. There was still one external wall that could have been RBV but it was clearly not worth the expense. Basically, brick veneer is just to impress the neighbours, which it doesn't do with the bricks inside.
    My internal brick walls weigh 25 tonnes, and the floor slab 30 tonnes. I think of these as the radiating and absorbing surfaces of the heat bank. The bank itself is the mass of concrete, bricks and compacted soil under the floor slab, which weighs about 150 tonnes. Heat transfer is simply by conduction, and takes days or months. There is perimeter insulation to about half a metre depth to stop heat flow to and from the soil outside. Any heat flow to or from the deep sub-soil is of no concern, because it is at 21 degrees: close to ideal.
    From the embodied energy point of view, concrete bricks would be better than fired clay bricks.

    Posted Tuesday 15 Apr 2008 @ 3:44:10 am from IP #
  4. Gregl

    Gregl
    Member

    Hi Gents

    I am looking at building a house where heating will be the priority. A possibility is to have a suspended slab floor with a large reservoir of water below the slab heated by solar energy. This reservoir of water would hopefully transfer the heat up into the slab. Do you think this is possible/viable?
    Cheers
    Greg

    Posted Saturday 5 Jul 2008 @ 2:19:01 am from IP #
  5. mrampant

    mrampant
    Member

    Hi all,
    I was planning to build a place soon and looking for heating ideas that are longterm cost effective. I thought of underfloor heating by using latent ground heat and piping it under the flooring.
    Has anyonyone got ideas on this or info to sites which would give more data for this sort of thing?
    Mark

    Posted Friday 11 Jul 2008 @ 2:52:26 pm from IP #
  6. cjenn

    cjenn
    Member

    Hey all,

    I"m just after some advice about floors!

    I'm involved in a community project in Tassie, constructing a straw-bale building to act as an example of sustainable design and to house an organic food co-op.

    We have a concrete slab and need to do put something on that to make it non-slip for safety regulations and also able to deal with spills of oil, tahini, honey and the like. It's 54 square metres. Environmentally sustainable and as affordable as possible are the priorities!

    Does anyone have any ideas?

    Thanks!!!

    Posted Monday 13 Oct 2008 @ 8:51:42 am from IP #
  7. greenbizcheck

    greenbizcheck
    Member

    Hi everyone

    We have developed a free home checklist at http://www.greenbizcheck.com/files/home-checklist.pdf which is very useful for overall energy use reduction - please feel free to use and circulate. Feedback is very welcome.

    All the best.

    Nicholas Bernhardt

    Posted Wednesday 22 Oct 2008 @ 6:27:30 am from IP #
  8. Catopsilia

    Catopsilia
    Member

    The house mentioned in the opening post of this thread now has more than eleven years of daily temperature data. Under another pseudonym, I have been posting updated results of the performance of the house in a forum thread on another site:
    http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=42304&page=all

    Posted Friday 11 Jun 2010 @ 1:02:14 am from IP #
  9. IAEA

    IAEA
    Member

    GarrySpeight writes...

    "My internal brick walls weigh 25 tonnes, and the floor slab 30 tonnes."

    What would be the embodied energy stored in the total tonnage of the home that you have built? What is the payback time against a build like this?

    Cheers,
    IAEA

    Posted Friday 11 Jun 2010 @ 1:53:35 am from IP #
  10. dymonite69

    dymonite69
    Member

    0.6-1 GJ/tonne

    Average embodied energy in house 1000 GJ (= 15-20 years of operational energy)

    About 1/4 embodied energy in the slab.

    Adding 25 tonne wall = 25 GJ (= 6 months of operational energy)

    If it reduced the energy use by 25% (excluding other interventions) it would payback in 5 years.

    Posted Friday 11 Jun 2010 @ 2:22:19 am from IP #
  11. Catopsilia

    Catopsilia
    Member

    Hi IAEA
    I don't have good answers for you. I have concentrated on temperature records.

    As for mass materials, I tried to limit transport costs by buying local. Much of the effective mass of the house is existing material in place in the footings, simply isolated from environmental temperature swings by perimeter insulation. I know that earth bricks would have had less embodied energy than fired bricks, but I aimed as conventionally as I could to get the job done.

    Real payback times are hard to judge. I estimated $15,000 worth of costs of energy-efficient measures. If I were to sell now, after 12 years, it would be in the lap of the gods whether I could find a buyer who appreciates the values built into the house. I suspect that today's house-buyers are even more wilfully pig-ignorant about low-energy living than those buying 12 years ago.

    A savvy estate agent would install superfluous air conditioners to ensure a sale, I am sure.

    Posted Friday 11 Jun 2010 @ 2:31:43 am from IP #
  12. Eco

    Eco
    Member

    Hello Catopsilia
    Can't believe Renew would have rejected an article on your house. Perhaps they thought the paper was too technical? I for one would be interested in reading about it.

    Posted Friday 11 Jun 2010 @ 5:21:42 am from IP #
  13. Catopsilia

    Catopsilia
    Member

    Hi Eco

    I put this link up on another thread in answer to a question. It covers some of the stuff I have prepared:
    http://www.cyberspeights.com/index.php/en/sustainable-living/housing/13-comfort-in-an-unheated-solar-passive-house

    Posted Friday 11 Jun 2010 @ 8:42:50 am from IP #
  14. dymonite69

    dymonite69
    Member

    Figure 2 looks interesting. Outdoors 0-40 but indoors 15-30. Have you got scatter graphs by month or season?

    What is your temperature trigger for turning on heating?

    Would you have done anything differently? More insulation? More mass? More shading?

    Posted Friday 11 Jun 2010 @ 9:55:32 am from IP #
  15. Catopsilia

    Catopsilia
    Member

    Not yet, dymonite69 and thanks for asking. I plan to do summer and winter scatter plots, with standard deviations on each axis.
    Have you looked at my more detailed recent whole-year plots, with discussions, in the last page of the forum that I linked to 5 posts earlier?

    I feel I need the blower heater on in the kitchen or study for an hour or so on a few winter evenings. It does not warm the house. I seem to need it at about 19 degrees sometimes, but other times I don't need it at 15 degrees. I hardly ever feel I need it in the mornings, although the temperature is usually lower then.

    Do it differently? No, not for the main part of the house. The lower floor at the west is not well insulated in the footings, and is partly shaded by a step in the line of the long north wall. (North walls MUST be in one line!) The upstairs bedroom in the west is a failure. It cannot be protected from extreme heat or cold. I would never again build a second floor at an inland site. However, I enjoy the view from the upstairs veranda. In general, the house could have been both cheaper and more efficient if it had been built on a flat site with no views to admire, or gum trees to avoid.
    A neighbour's iron-bark, which had been stunted by a lightning strike, has now grown back to limit my winter solar gain.

    Posted Friday 11 Jun 2010 @ 1:24:05 pm from IP #
  16. dymonite69

    dymonite69
    Member

    Hi Catopsilia,

    I have been trying to analyse your data to understand the implications of the slab mass. It is interesting to compare the mean march of indoor air temperatures compared to thermal mass temperatures.

    I notice that the mean indoor air temperatures is always warmer than the heat bank during winter. This indicates there must be some degree of heat loss from slab floor.

    Perhaps the wall mass has a greater impact on maintaining air temperatures? Have you got sensors embedded in the brick walls?

    I estimate that your 25 tonnes of internal brickwork is about 50 lineal metres of a 2.7m high wall?

    Posted Saturday 12 Jun 2010 @ 11:40:25 am from IP #
  17. Catopsilia

    Catopsilia
    Member

    Hi dymonite69

    I think we both take the floor temperature to be close to the indoor air temperature so far as mean monthly values go. (I do have floor temps if needed.)
    The mean indoor temp is warmer than the heat bank temp (at 750 mm) in every month except for June and July, when it is a little cooler. Thus there are no losses from the house to the subsoil in June and July. As you say, heat must be flowing downwards in other months. This is desirable in months when the outdoor air is too hot.
    In April, May, August and September there are downward flows that are undesirable, but they are into a mass that is at a comfortable temperature, reaching a minimum of 18 deg in September. By contrast, the thermometer at 750 mm out in the garden reaches a chilly minimum of 13.7 deg in July. This shows that, without perimeter insulation a great deal more heat would be lost downwards. With no mass at all in or under the floor slab the indoor temperature would not differ much from that outdoors.

    No, I have no sensors inside the brickwork. Given the small daily temperature range of the indoor air, I am fairly sure that the temperature of the bricks is much the same.

    My thermal mass walls of pressed clay bricks are Flemish bonded double brick walls 225 mm thick. Several walls 3.7 m high total 13 m length, and another 2.4 m high is 4 m long. I estimate 13 cubic metres which, at a density of 2000 kg/m3 totals 26 tonnes.

    Posted Saturday 12 Jun 2010 @ 1:46:02 pm from IP #
  18. dymonite69

    dymonite69
    Member

    Hi Catopsilia,

    My thoughts were running in a different direction. In winter, indoor temps fall because the heat bank is transferring more heat down and out than up and in.

    By using mass in the walls, I wonder if you have more dynamic control of the heat flows. Heat transfer would be predominantly be inward during winter. Following the summer regime, you could flush the stored heat each day because of a greater exposed surface area for both convective and radiative transfer.

    Posted Saturday 12 Jun 2010 @ 11:58:32 pm from IP #
  19. dymonite69

    dymonite69
    Member

    WRT to the added benefit perimeter slab insulation, the actual cross sectional area of the slab edge in contact with the first few feet of cold ground is relatively small.

    I would not expect the entire slab to cool down to garden soil temperature if it wasn't present.

    Posted Sunday 13 Jun 2010 @ 12:08:56 am from IP #
  20. Catopsilia

    Catopsilia
    Member

    It's food for thought dymonite69. I have collected a quantity of house temperature data that is seldom to be found. However, I am weak in physics, so the modelling of the heat flows awaits someone with the skills. (Or perhaps I will come to grips with it in time.)
    I visualise the main function of the brick walls as re-distributing the heat on a daily basis. Weekly, monthly, and seasonal heat storage is achieved by the larger underground mass, I think. That was what I wanted to show in my graph of the annual march of monthly mean temperatures.
    I take it as a rule-of-thumb that the movement of heat in the thermal mass is so slow that the sun's heat on the top of my taller brick wall would take about a week to reach the floor slab.

    Re: "I would not expect the entire slab to cool down to garden soil temperature if (perimeter slab insulation) wasn't present." I may be able to work up comparative data for my neighbour's house. I have a year of slab-surface temperatures for both houses, I think. As I recall, the neighbour's house behaves as if there is very little heat storage in the soil under the slab.

    Posted Sunday 13 Jun 2010 @ 1:26:51 am from IP #
  21. Catopsilia

    Catopsilia
    Member

    I have posted some new graphs, comparing my house temperatures in mid-winter with those in a neighbouring conventional house in another forum, which allows images:
    http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=868562#Post868562

    Posted Wednesday 16 Jun 2010 @ 3:01:31 am from IP #
  22. dymonite69

    dymonite69
    Member

    Wouldn't it depend on how much internal solar gain the houses get. No energy in = No energy out.

    Posted Wednesday 16 Jun 2010 @ 8:22:20 am from IP #
  23. Froglips

    Froglips
    Member

    We have a perfectly good house on a few acres of land and would like to build a straw bale studio (girls shed) for all my hobby stuff. I have bought 2 American DVD's on the subject and the information is quite good. Just wondering if there is anyone around the Central Coast of Tasmania that has done or interested in doing this.

    Posted Saturday 19 Jun 2010 @ 3:07:29 am from IP #
  24. Frateco

    Frateco
    Member

    Froglips, can't help you with strawbale but if you're interested, we are going to be starting a hempcrete house next month. The framing is going up and in August, we will be pouring the hempcrete. If interested, I wrote a bit on hempcrete in another forum post, just do a search.

    We got a 6.4 star rating using the most basic of window requirements and this place has about 70% windows in the living room! so it'll perform as well if not better than strawbale.

    Posted Tuesday 22 Jun 2010 @ 1:11:44 am from IP #
  25. Catopsilia

    Catopsilia
    Member

    I have just posted the temperature logs of my solar-passive house and the adjacent conventional house for a mid-summer period:
    http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=42304&page=15
    This completes comparisons for all four seasons.
    The solar-passive house temperatures remain within the Adaptive Comfort Zone throughout the year, although it was built before I was aware of the Zone.
    http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=864290#Post864290

    Posted Saturday 26 Jun 2010 @ 9:08:08 am from IP #
  26. Catopsilia

    Catopsilia
    Member

    Here is a recent conference paper "'Passive Building Design and Active Inhabitants: The Potential of Frugal Hedonism?" by Deborah White of The University of Adelaide:
    http://www.plea2009.arc.ulaval.ca/Papers/1.CHALLENGE/1.1%20Occupants/ORAL/1-1-04-PLEA2009Quebec.pdf

    Quoting M. Kordjamshidi, she is scathing about the way a typical house energy rating scheme "under-rates the effectiveness of buildings designed, on ‘passive’ principles, to dispense with energy-consuming heating and cooling plant".

    She mentions a few well-managed solar-passive houses (in Italy) with energy use for heating and cooling as low as 3 kWh/m^2a.
    My House in inland NSW ("Zone 14") was assessed in 1999 by Max Mosher, using NatHERS V2.11 as follows:
    For 127 m^2 of a 147 m^2 house to be heated and cooled: 18 kWh/m^2a.

    In practice, my energy use for heating and cooling during 11 years has been about 10% of the NatHERS assessment.
    I have been living alone in the 100 m^2 part of the house that is most efficient, excluding the 2-storeyed west wing (for visitors).

    Annual energy use for heating and cooling has been:
    Fans for moving warm and cool air: 100W for 1800 hours = 180 kWh;
    Electic blower heaters: 1kW for 20 hours = 20 kWh;
    Total heating and cooling: 200 kWh;
    Total heating and cooling per square metre: 2 kWh/m^2a

    Approximate annual cost of heating and cooling the house (all electric): $40.00.

    Posted Saturday 3 Jul 2010 @ 4:12:33 am from IP #
  27. dymonite69

    dymonite69
    Member

    Similar research here in Adelaide has demonstrated that 50% of energy use in homes is due to the occupancy factors alone. Having said that, they also show that people who build or purchase energy efficient houses tend to alter their lifestyles in sympathy to the philosophy of the building design. Win-win.

    I do know of a family here who built a passive solar house who don't use any artificial heating and only fans in summer. Their bills are trivial. However, their comfort tolerance are a bit wider than mine.

    Posted Saturday 3 Jul 2010 @ 4:27:06 am from IP #
  28. Catopsilia

    Catopsilia
    Member

    I just found this handy technical summary of the use of thermal mass in low-energy buildings.

    I had not met with the TLA (three-letter acronym) "BDP" before. It means the Australian Council of Building Design Professions Ltd, and it is somehow linked to RAIA (the Royal Australian Institute of Architects) who own the copyright.
    http://www.yourbuilding.org/library/DES04.pdf

    There are a lot of useful graphs and tables. My house, mainly by good luck, seems to be close to optimal.

    Posted Saturday 3 Jul 2010 @ 8:51:57 am from IP #
  29. Catopsilia

    Catopsilia
    Member

    The paper I linked above refers to a companion paper that looks interesting:

    Des 12: Perceived Comfort (BDP Environment Design Guide, Volume 2)

    Does anyone know how to access that paper?

    Posted Saturday 3 Jul 2010 @ 9:10:19 am from IP #
  30. dymonite69

    dymonite69
    Member

    I read that paper by Baggs. It is interesting that he relates surface area of mass to volume of heated air. This assumes that heat transfer to the mass is due mainly to convection and conduction. However, it seems to ignore the much higher transfer rates that occur by radiation. I am not sure what your house is like by our passive solar design tends to result in the darker south side rooms being cooler than the sunnier north side ones. In a predominantly heating climate, most of the mass would be better located in areas of solar gain.

    Posted Saturday 3 Jul 2010 @ 12:12:12 pm from IP #

RSS feed for this topic

12…10Next »

The Alternative Technology Association (ATA) is a not-for-profit, organisation that has promoted the use of renewable energy, water conservation and sustainable building since 1980.

Publishers of ReNew: technology for a sustainable future and Sanctuary: sustainable living with style magazines.

Alternative Technology Association Forum is proudly powered by bbPress.