Dymomite:
Do you mean internal or external window coverings. My experience is that external ones are more effective. BTW speaking about location are you in WA, as well, by any chance?
single or double glazing for new home?
(88 posts) (24 voices)-
Jeffbloggs
MemberPosted Wednesday 4 Aug 2010 @ 3:22:30 pm from IP # -
dymonite69
MemberNo SA but in a slightly cooler district similar to Wagin, WA (midway along the hwy from Perth to Albany)
Posted Wednesday 4 Aug 2010 @ 11:59:58 pm from IP # -
Re: internal or external window coverings
You can just about see my window coverings in this photograph:
http://i188.photobucket.com/albums/z49/Supeito/weatherzone/Manilla%20solar-passive%20house/2007_0911HouseandGarden0073.jpgIn the window on the right you can see the reflective lining of one of the set of five (internal) heavy curtains that are retracted by motors on a time-clock.
(BTW, through the same window you can see part of the central brick wall, lit by sunlight coming through a clear-story window.)
There is an external shutter in the photo, but perhaps you need the eye of faith to see it, as it is in deep shadow. It is on the full-height single-glazed window of the sun-porch at the front door. The shutter is a retractable roller blind with slats like those of a venetian blind. It is rolled up into a housing just below the eaves. By clicking to enlarge the image you can at least see the electrical dome-cover through which it is operated, using the same switching system as the curtains.
The shutter was an expensive afterthought, fitted when I became concerned about big temperature swings in the sunporch due to gains and losses thruogh the tall single-glazed window. I should not have been so much concerned because the inner door of the sunporch is always shut when porch temperatures are very high (mid-summer days)or low (mid-winter nights).
I monitored temperatures in the sun-porch at head-height and floor-level before and after fitting the shutter. I was very disappointed to find that I could not detect any improvement at all to justify the expense.
It impresses visitors, except for the mess the spiders make between the shutter and the window.Posted Thursday 5 Aug 2010 @ 2:37:48 am from IP # -
dymonite69
MemberThere is evidence that wind movement over the external surface of a window can decrease the apparent U value. This is presumably by increasing convective loss. From recollection the difference is around 10% for a moderate breeze.
However, the effect would be true for movement either side of the pane.
The most important thing is to have a radiant barrier outside the window in summer to prevent the sun heating the internal structure of the house.
Posted Thursday 5 Aug 2010 @ 5:05:39 am from IP # -
Jeffbloggs
MemberDymonite
Ok, I know Wagin.Roller shutters, preferably plastic not ally, on the outside of the window generally work fairly well for radiation and convection control. Otherwise old style external louvers can work to. The sun is only our friend if it is managed properly
Does anybody know how effective venetian blinds are that are mounted between the panes of DG? Maybe even with a reflective surface on one side?
Posted Thursday 5 Aug 2010 @ 9:55:36 am from IP # -
dymonite69
MemberYes, the sun is a very powerful energy source. It can both warm a house comfortably in winter or overheat it intolerably.
One can theorize about the effects of glazing, mass, orientation and shading. However, quantifying its proportions is vitally important. Human thermal comfort exists in a very narrow band and the tolerances of human survival is not that much wider. Ideally one can optimise the combination to provide a free running temperature that doesn't vary more than 5 degrees.
Posted Saturday 7 Aug 2010 @ 1:08:08 pm from IP # -
Jeffbloggs
MemberDym
Our temperature tolerance probably came from the time we used to live in caves, they don't change temperature much either, but then we figured out how to wear another creatures skin for climate control, and lost all our fur(most of us anyway!). Since then we've been stuck out in the cold, stark naked, losing our mind about how to get warm again...it's a good job we figured out how to make fire with fossil fuels....;)Posted Saturday 7 Aug 2010 @ 1:37:08 pm from IP # -
dymonite69
MemberGround (and cave) temperatures vary enormously between climates. One near the poles would be different from one at the equator.
Posted Saturday 7 Aug 2010 @ 11:32:00 pm from IP # -
Jeffbloggs
MemberDym
We seem to be cross-threading with the cave theme... Maybe we should start a cave/earthship thread to weave some different environmental thermal discussions to blanket housing vs global warming? :p
Didn't someone already post something about ground temperatures not varying much in Aus? (I agree different continents would cave temperatures would differ greatly)I quite liked the MtBest websites idea for low budget bubble wrap insulation glass. Maybe it would be an option to use this for extra active thermal control and lighting(maybe in the roof even) provided that it could be shaded etc. I still like looking out through clear glass for "room feel".
Posted Sunday 8 Aug 2010 @ 3:18:29 am from IP # -
dubbo teacher
MemberCatopsilia I've been checking your figures on your other posts. They certainly represent a lot of work and suggest that you are evening out temps very well but no doubt this is due in some part to your clerestory glazing - which I would like to use but prefer to keep the roof as cheap and simple as possible - 9 metre span of trusses with gable ends that allow for future extension east or west.
You say 'My temperature measurements on the surface of my floor slab ARE in the bathroom, and the floor does not get any direct sun.'
I still can't stand on MY bathroom floor these nights barefeet but I'll take your word for it where you are.
Re your offer 'Why don't you come over and look at the set-up some time? '
I might take you up on that when(January next year) I go through to Grafton to visit my brother. Naturally I'd like to check out any place at the hottest or coldest time of the year
Posted Sunday 15 Aug 2010 @ 11:03:19 am from IP # -
Lumbuck Thornton
MemberI live in a very unsustainable house because that was all we could find in the market place when we moved here. I am interested in how double glazing would go on enclosed passive solar outdoor furniture that could be moved around to aim at the sun, away from the sun or when you were not home, stored in the shed. All I want is a comfortable place to read or play on the laptop and know that I am not having to heat or cool the whole house. I would also like to appreciate the garden more and might even rearrange it so there are approriate points for certain seasons and climatic conditions. I am sick of the compromises that have to be constructed into fixed buildings and think there must be better combinations of sheds, garden and things we move in between in that might be cheaper, more comfortable, healthier and smarter. I have called it the "Revalator" that has absolutely no religious aspects, just smart adjustments in a shelter that allows for the revolution of the earth on its axis and around the sun. Have not built one yet but I reckon it could be quite an interesting competition. My question is should my double glazed window be at a fixed angle of about 45% or should I have the whole piece of furniture capable of swinging inside an insulated box so I can target sunrise with the aid of side mirrors/shutters also sending light into the thermal mass on the side walls. I envisage it not being that much wider or longer than a wheel barrow. In cold winter mid day I might also want the double glazing to swing up to the sun at mid day. Don't need to worry about water proofing, security etc - just retreat to shed. When too hot then retreat to various graduate shades and ultimately total shade tunnels in the summer half of a circuit though a specially structured garden. I am keen on use of double glazing to generate energy I need to drive the passive ventilation and reheat the new air.
Posted Wednesday 29 Dec 2010 @ 12:23:43 pm from IP # -
Hi Dubbo Teacher
I just found your latest post.
You would be very welcome to visit. You don't need to be much of a detective to track me down!Posted Friday 31 Dec 2010 @ 10:47:04 am from IP # -
brentus
MemberI have specced double glazing for my new house but was thinking of evaporative cooling. I am led to believe for this to run efficiently windows need to be left open. Would this defeat the object (of the double glazing) and would sealing the envelope and using refrigerative be more effective?
Posted Thursday 27 Jan 2011 @ 7:38:03 am from IP # -
brentus, You have hit the nail on the head.
In non-tropical, non-coastal Australia, I believe that double-glazing is an essential part of the insulating shell of a house. Yes, a basic evaporative cooler must by-pass that insulation, so is not compatible.
Since a well-sealed house may need air conditioning in some rooms for a few hours per year, we need honest air-conditioner salesmen to advise on suitable CHEAP units. Note that they do not need to meet stringent efficiency standards as they are so seldom used.Posted Thursday 27 Jan 2011 @ 8:31:56 am from IP # -
dymonite69
MemberBrentus,
You can have a DG unit that opens. Close it for winter heating. Open it for summer cooling.
"Build tight, ventilate right"
Posted Thursday 27 Jan 2011 @ 9:35:07 am from IP # -
Benny
MemberBrentus. The answer depends critically on your local climate. If you are in the tropics evaporative won't work even with open windows. If you need significant winter heating (and most houses in Australia use more energy for heating than cooling) then DG is appropriate to keep that heat in and reduce energy loss. If you live in a hot dry climate, like Perth, then evaporative cooling will work and uses less energy than reverse cycle, BUT as you say, it is essential to open the windows and let the humid cooled air flow through. The closed DG windows will still help to keep out the heat until its time to turn on the evap AC. In fact even without evap AC I'd always want opening windows to take advantage of free sea breezes and cool night time air.
I don't really agree with Catsopilia's comments that because you don't use something often it can be cheap and inefficient. I think we should always strive to use devices that are as efficient as possible and that we can afford.
It all really comes back to your priorities - saving money, reducing energy use/GHG ? Paying whatever is necessary to minimise use ? The most "effective" system would probably be fully automated, computerised, reverse cycle AC with individual room controls, but then I was just in an office where this was being used and because adjacent rooms had different set temps, one AC kept going on to the heating cycle because the cold air from the adjacent room kept leaking in and dropping the temp below its set point.Posted Thursday 27 Jan 2011 @ 10:26:05 am from IP # -
dubbo teacher
MemberCatopsilia
My plans to get up your way (on my way to see my brother in Grafton and also check out permaculture farms up on the coast) were thwarted as you could imagine by the flooding and road closures earlier this month. Maybe next time.
Regarding effective cooling this time of year. What about the use of water?
I used to have a fernery with a misty spray system just outside the lounge room in a house in Bendigo (yes it could get hot there too)and the cooling effect was fantastic.
The same effect can be achieved (theoretically) by having a strategically placed pond between the room you want to cool and the prevailing wind.
Every bit helps.Posted Thursday 27 Jan 2011 @ 10:47:00 am from IP # -
Jeffbloggs
MemberBrentus
If your going for DG make sure you get not-metallic (ie aluminium) and non-conducting frames. The frames themselves can conduct more heat than a single pane glass itself, with DG the difference would be even worse.On evaporative AC:
Human temperature comfort levels are actually linked to the dew point of water in the atmosphere. By adding moisture to the atmosphere, especially when it is already saturated (humid), will only make it feel even more uncomfortable. Evaporative cooling works by "absorbing" heat from the surrounding air, by warming the evaporated water up to produce more humidity, and by depositing "cooler" humidity on your body. Likewise if you continuously increase the dew point with evaporative AC in a closed house without sufficient ventilation, or reintroduction of dry air to be humidified, it will become uncomfortable. http://en.wikipedia.org/wiki/Dew_pointIf you look at the graph and table down that page, you will see that you are just as comfortable with the dew point temperature at 12'C: at 37'C @ 20% humidity (Hot by dry, with possible respiration/skin drying problems though!) also at 11'C @ 100% humidity (Cold but muggy), or the more ideal 25'C @ 40% humidity. You could say that the perceived comfort level is the the point at which the body can regulate perspiration/evaporation against ambient temperature by itself, for it to maintain the body core at 37'C. This is what your artificial AC climate control should allow.
A refrigerated AC actually dries the air and reduces the dew point. If you recycle that air (which is standard in most split and ducted AC systems) the dehumidifying is actually increasing its own cooling efficiency, and at the same time increasing your bodies sweat evaporation rate, that cools you even further. The water in the air is also the best conductor for heat from the humid air to your body, dry air is much better, and allows natural body perspiration/evaporation to function effectively.
If you are concerned about cost and energy consumption, the best way is to limit the areas you climatise to areas of high traffic, insulate and seal these areas as best as possible, (even 2-3x better than the rest of the house, that is if you have doors to separate the zones!) and regulate according to the weather conditions effectively. This way you can get away with installing just a few split system reverse-cycle ACs, and still be comfortable when switching off those not in use. BTW seeing that you said "new house", I can only recommend to get the design spot on before you build. The more effort you put into planning (including getting professional help!) the more cost effective it will be. To design in our minds and on paper costs less than in brick, mortar and tears.
BTW welcome to the ATA forum.
Posted Thursday 27 Jan 2011 @ 4:27:44 pm from IP # -
brentus
MemberThanks for the replies guys,
I am at Aldinga Beach about 40km south of Adelaide about 1km inland.
Jeff, we have placed a door in the corridor between the bed/bathroom area and the living/cooking area to enable 'zoning'
With any luck we have designed intelligently and won't need too much heating/cooling, but coming from Northern England 15 months ago we are still not used to 40c and like you say it must be easier to get it right before we start building.
The windows will be openable (is that a word)
We were thinking evap to reduce running costs but I'm new to all this aircon malarchy.
Posted Friday 28 Jan 2011 @ 9:07:18 am from IP # -
dymonite69
MemberInvoking dew point as a means of measuring human thermal comfort is awkward, confusing and unnecessary. You also have omitted the important point that evap AC lowers the air temperature (sensible heat).
Dew point is essentially the temperature at which the moisture in the air will condense i.e. reach 100% relative humidity.
It depends on the initial dry bulb temperature and relative humidity of the air.
Cold dry air has a low dew point. Hot humid air has a high dew point.
Evaporative AC works really well in dry conditions. With very low humidity e.g. desert air the AC can drop temps up to 20 degree.
Human comfort levels are best described with psychometric charts. Empiric studies demonstrate most people can tolerate a certain range of dry bulb temperatures and relative humidity. By superimposing before and after conditions with different cooling systems it is then possible to determine whether the evap or refrigerative AC is required.
See Givoni bioclimatic chart:
http://nceub.commoncense.info/uploads//Saberi.pdf
Fig 6.1.4.
Posted Friday 28 Jan 2011 @ 10:51:47 am from IP # -
Jeffbloggs
MemberD69
I don't think that introducing a dew point temperate is confusing and unnecessary, the "real feel" temperates given by weather presenters are based on this. In fact I always use this dew point calculation from the int/ext to decide if I should turn on the AC or just a fan. It's not hard at all, and both humidity and temperate need to be realised to control comfort. Even air pressure plays a role....
I think that if households would use commercial size AC with HRV and de-humidification, with dew point oriented temp control, then household energy consumption would decrease significantly in comparison, and comfort level would increase.BTW I did say: "Evaporative cooling works by "absorbing" heat from the surrounding air", this is otherwise known as "cooling". I try to refrain from using the "cooling" terminology, simply because most people think that you can "make cold", which you cannot, you can only make "less heat", by making something else even warmer.
Also Thx for the link, adds some other factors to human comfort perception.
Posted Saturday 29 Jan 2011 @ 6:37:31 am from IP # -
dymonite69
MemberNow I see what you mean. Dew point is a convenient parameter that encompasses both terms. < 13C and evap will work well. > 18 and it will struggle.
Posted Saturday 29 Jan 2011 @ 9:44:59 am from IP # -
ghostgum
MemberA better estimate of the evaporative cooler temperature is the wet bulb temperature, which is the dry bulb temperature minus Delta-T. The following are the weather observations about 10km from me
http://www.bom.gov.au/products/IDV60901/IDV60901.95867.shtml
The wet bulb temperature is warmer than the dew point.
For explanation of the BoM observations, see the "About weather observations" link on the web page.It's going to be warm in Melbourne tomorrow, so if you want to see how an evaporative cooler works in Melbourne on a hot but dry 40C day, have a look at the BoM observations tomorrow night.
Posted Saturday 29 Jan 2011 @ 10:03:09 am from IP # -
dymonite69
MemberI think point that JB is making is not what temperature is reached with the evap cooler (which is usually about 2/3rd the way between dry bulb temp and dew point) but the potential to bring it into the the thermal comfort range of < 18C dew point.
You can pretty much look at the historical BOM data and if your climate is normal > 16 dew point then an evap probably won't be adequate to stay comfortable.
Posted Saturday 29 Jan 2011 @ 11:00:39 am from IP # -
Desert Boots
Memberthanks for kicking off discussion thread regarding double glazing - we're effectively working through the list: "draughtproofing, ceiling insulation, slab edge insulation, wall insulation and lastly double glazing" as per Dymonite69 posting some time ago. Just did a posting in another forum regarding underfloor insulation, as have been putting in foilboard under the floor. Was wondering if any can relate experiences with insulation and/or double glazing suppliers. We're in Orange (no evaporative cooling in our house!) - looking at DG Window options. If it can make it work, will order recycled polyester insulation from outside the CW region, and then overlay over current insufficiently thick (about 4 cm) mineral fibre batts.
cheers
Posted Sunday 25 Sep 2011 @ 5:58:51 am from IP # -
fireflies
MemberAn interesting benefit of sliding security screens is the reduction in heat through the covered half of the door. I've noticed our west facing glass doors where we recently put aluminium security screens are signficantly cooler than the other panes of glass. I don't have a thermometer to measure but the covered door is 'cool' perhaps 25deg to the exposed pane's 'hot' 45 deg perhaps. Interestingly the aluminium security mesh though black and in full exposure to afternoon sun remains cool as well - perhaps re-radiating and diffusing as quickly as it absorbs heat.
Posted Thursday 6 Oct 2011 @ 2:17:38 pm from IP # -
ghostgum
MemberIt depends on how much glass and how long you run the air-conditioning.
Assuming 20m2 of glass, with single glazed aluminium frame with U=6, temperature inside 25, outside 30 (temperature difference = 5). The rate of heat gain through the windows is area * U value * temperature difference = 20 * 6 * 5 = 600W.
If your air-conditioner has an energy efficiency ratio of 3, then that is 200W of electrical power. If you run the air-conditioner for 5 hours a day, that's 1kWh per day.
If you convert to double glazed windows with U=3, then you halve the energy requirements.Insert your own numbers in the above.
I expect you to get more return for your money with external blinds on the windows.
Posted Sunday 23 Oct 2011 @ 9:31:20 am from IP #
