Browse Forums Windows & Doors Re: Low-E glass and passive solar heating 141Aug 03, 2009 9:09 pm Nice design and an interesting house Dyno - http://www.kingspanlighthouse.com/ But I still think that in Australia with longer daylight hours - which is even around when we get home mid winter - and the benefits of winter warmth and sunlight inside to stimulate seretonin is far more beneficial than a heat bank and PV that blocks the sun out. Call it a desire to be camping indoors if you like - As oppossed to being sheltered from the elements by technology. There is a lot in our triggers with nature that many people still forget we need to live in harmony with the daylight and seasons being part of our lives. Once_artisan Have a read of these two links. The orgin factory is an interesting place to go through - and they are perfecting the cells day by day - test by test. http://www.abc.net.au/catalyst/stories/s1865651.htm And here is another system in the makings - low energy output at present - but they will get there. http://www.ernmag.com/News/2009/040609/Anti-glare_coating_makes_see-through_solar_cell_--_ERN_040609.html Then there are automated system that lower and raise blinds and cells as you desire which I remember seeing many years ago. Re: Low-E glass and passive solar heating 142Aug 03, 2009 9:18 pm Yak_Chat Nice design and an interesting house Dyno - http://www.kingspanlighthouse.com/ But I still think that in Australia with longer daylight hours - which is even around when we get home mid winter - and the benefits of winter warmth and sunlight inside to stimulate seretonin is far more beneficial than a heat bank and PV that blocks the sun out. Personally I thought the idea was a bit kooky. Why convert the sun's energy with at most a 20% efficiency when you could just have it warm your house? Like food, sun is best served up unprocessed. Re: Low-E glass and passive solar heating 143Aug 03, 2009 9:19 pm Yep fantastic technology... wish it was available now I'd happily be a pilot home trialer Seen both before and a few others... the race is on Thanks for posting the links, more time and I'd have gotten around to it ...but there were a few other issues I was dealing with. They should all be resolved now Where you are coming from is where you are going to... Re: Low-E glass and passive solar heating 144Aug 13, 2009 7:10 pm onc_artisan Wow dymo your average indicates 45Kw per day considering we use less than 15Kw/day on average annualized (over a 10 year period) for our TOTAL energy use. BTW where do you get all your info... it seems verbatum, not of the wiki is it? The ABS statistic on total energy use does not just include electricity (it is from all sources including gas and wood). 1 tonne wood = 4500 kWhr Re: Low-E glass and passive solar heating 145Aug 17, 2009 10:09 pm OK .... can I add some value here ... hopefully. I HAVE JUST DONE IT - Retrofit DG that is. I have a 1914 double brick house in Melbourne with a 1996 extension single brick (insulated) but with a lot of glass at the rear (south facing glass!). Timber floor. Good insulation in roof. Some weathersealing. Gas central heating. I replaced 17 windows at the rear (all the fixed pane windows). They are currently covered with holland blinds. The window area was 20m2. I replaced the single glazed with DG IGUs with low-e. It cost $7,500 installed. All of the glass is toughened (kids and building regs). DG (no low-e,only half toughened) would have cost $5,000 installed. While I sure it will take 20 years to get the money back, IT HAS MADE A BIG DIFFERENCE TO COMFORT. The TV room in the rear had glazing on 3 out of 4 walls and it has gone from being the coldest room in the house to the warmest. The baby sitter sat in the room and when I asked her if it made a difference she said she didn't have to put on blanket and wondered why. I think the difference here is in a conditioned house (ie heated) by double glazing a particular room you can make a big difference to what temp you need to set the heater to. Spud I would DG as much glass as you can, subject to budget. If budget is constrained, DG the TV / living area. Re: Low-E glass and passive solar heating 146Aug 17, 2009 10:20 pm dymonite69 ed @ EcoClassic you have argued that I over estimate the effect of double glazing when I use U values (which are empirical and cannot be challenged), then you argue that I have left out the effect of convection... you want it both ways... any discussion is pointless. Unless the AFRC are doing something different in their thermal conductivity test then your U values assume no convective effects. I will stand corrected on this if your AFRC contact can provide their test procedure. 12star ed @ EcoClassic Independent, meaning stand alone... i.e. U values stand alone, uninfluenced by convection... the remainder that you speak of is insignificant compared to heat losses via conduction (U value) which is huge. Since I'm following this discussion, Ed could you let us know how insignificant it is please Ed, you had a post previously where you said that the U values standards would be changing - downwards, probably about a year ago however they hadn't come into effect as yet (then) Found the link - viewtopic.php?f=23&t=10767 Is this why you are saying that the U value is 'independent' 12 star, This is the test protocol for the NFRC / AFRC (it is in the public domain as with all its lab procedures). http://www.afrc.org.au/LiteratureRetrieve.aspx?ID=30091 (see p20) It makes the assumption that wind speed is 5m/s for the purpose of predicting U values. FYI this is about 3 on the Beaufort scale (a gentle breeze). The maths calculations are quite complicated and it involves assumed values of the U-value of the air film next to the window and the emissivity behaviour of the different window components. Suffice to say that the variables are controlled for the purpose of comparing products but the real-life performance will depend on different conditions. Here is a study looking at the effect of air radiant temperature and wind speed on U-values. http://gaia.lbl.gov/btech/papers/25487.pdf (see Table 2) On the limited data there was can be at least a 16% difference in observed U values because of this. (see p 20). This is about a U value of 0.5 difference (SI units). Re: Low-E glass and passive solar heating 147Aug 17, 2009 10:56 pm 12star ed @ EcoClassic Independent, meaning stand alone... i.e. U values stand alone, uninfluenced by convection... the remainder that you speak of is insignificant compared to heat losses via conduction (U value) which is huge. Since I'm following this discussion, Ed could you let us know how insignificant it is please If you use wind chill tables then heat loss (in watts/m2) from a warm person/object/building/window can increase by around 25% when wind speeds move from 5m/s (gentle breeze) to 20 m/s (fresh gale). http://home.iprimus.com.au/foo7/windchi ... tts=1713.1 Re: Low-E glass and passive solar heating 148Aug 18, 2009 11:08 pm 12star ed @ EcoClassic Independent, meaning stand alone... i.e. U values stand alone, uninfluenced by convection... the remainder that you speak of is insignificant compared to heat losses via conduction (U value) which is huge. This is the test protocol for the NFRC / AFRC (it is in the public domain as with all its lab procedures). http://www.afrc.org.au/LiteratureRetrieve.aspx?ID=30091 (see p20) Here is a study looking at the effect of air radiant temperature and wind speed on U-values. http://gaia.lbl.gov/btech/papers/25487.pdf (see Table 2) On the limited data there was can be at least a 16% difference in observed U values because of this. (see p 20). This is about a U value of 0.5 difference (SI units). D69 the conditions they are using have a 39ºC difference, so if those were applied in Aust conditions 'real world' lets say Adl where the real world is mild - eg a difference of 10ºC internal/external then wouldn't that basically make the wind speed to quote Ed "insignificant" ok I know Ed was not moving on his beliefs that the U value was independent, when clearly wind speed is factored in the calculations, but if the temp diff is only 10ºC and not 39ºC then he would be basically right regarding the use of U values in Aust (at 10ºC) I hope that makes sense! NFRC Simulation Conditions: Tin = interior ambient temperature of 21.0ºC (69.8ºF) Tout = exterior ambient temperature of -18.0ºC (-0.4ºF) V = wind speed of 5.5 m/s (12.3 mph) rm,out = Tout Trm,in = Tin Is = 0 W/m2 (0 Btu/h·ft 2 ) Re: Low-E glass and passive solar heating 149Aug 19, 2009 10:36 am 12star D69 the conditions they are using have a 39ºC difference, so if those were applied in Aust conditions 'real world' lets say Adl where the real world is mild - eg a difference of 10ºC internal/external then wouldn't that basically make the wind speed to quote Ed "insignificant" I take your point. The question which I cannot directly answer is how much convective transfer is influenced by the initial temperature gradient. In the wind chill calculator (which assumes human body temp of 37) the % change in heat transfer does not vary significantly for the temperature gradient between 32-79 deg C. I am not sure if how much you can extrapolate this to a gradient of 10-15 deg C as would occur in normal Oz conditions. The other empirical study I referenced, the 16% variance in U value occurred with fairly small changes in wind speed which suggests that the effect is still significant in 'normal' conditions. Having said this, if double glazing is susceptible to this effect then single glazing is even more so. For a 25% increase in U value: single glaze U value 6 deteriorates to 8 in fresh gale versus double glaze 4 deteriorates to 5. In other words, all forms of insulation will be relatively affected by air movement but the absolute change is lessened with good insulation. Finally, there is a warning that is issued by First Rate that instructed AC installers not to point duct outlets towards the window because of the convective heat losses that it would induce. There is still a significant argument to have curtains to prevent the window surface air film being broken by air movement. Re: Low-E glass and passive solar heating 150Aug 19, 2009 8:26 pm dymonite69 The other empirical study I referenced, the 16% variance in U value occurred with fairly small changes in wind speed which suggests that the effect is still significant in 'normal' conditions. Having said this, if double glazing is susceptible to this effect then single glazing is even more so. For a 25% increase in U value: single glaze U value 6 deteriorates to 8 in fresh gale versus double glaze 4 deteriorates to 5. In other words, all forms of insulation will be relatively affected by air movement but the absolute change is lessened with good insulation. Finally, there is a warning that is issued by First Rate that instructed AC installers not to point duct outlets towards the window because of the convective heat losses that it would induce. There is still a significant argument to have curtains to prevent the window surface air film being broken by air movement. Makes plenty of sense I asked about the A/C duct vent outlets on another forum, the A/C guy's who answered said they always point them in all direction when installing them, not one said not to point the outlets towards the windows! I guess they just throw them in and say cya call me if you want to spend some more money So I wonder how the wind would affect a S/G window with curtains? Last year I added a large number of roller shutters to my windows, (we already had roman blinds fitted inside the window frame), and this made a huge difference to the heating of the home (this was before I found this forum & another), but not to much on the cooling which was the original problem. (So I learnt the hard way that the heat is due to the thermal overload coming from my roof though I still have west wall & window issues & all-round wall insulation issues still to sort out I'm currently on the look out for a blow-in product that will insulate & thermally reflect to put in my walls. Re: Low-E glass and passive solar heating 151Aug 22, 2009 11:58 am 12star - What sort of walls do you have? Dyno said Quote: The other empirical study I referenced, the 16% variance in U value occurred with fairly small changes in wind speed which suggests that the effect is still significant in 'normal' conditions. Having said this, if double glazing is susceptible to this effect then single glazing is even more so. Suppose that explains why it's colder on windy days As per the above post - I am sure it all has an effect, but IMO it's really case of how much in real terms of heat loss or temperature gains does that impact on the windows overall performance - and short of external shutters to stop the wind movement there is not a lot you can do about it. Re: Low-E glass and passive solar heating 152Aug 22, 2009 12:09 pm Yak_Chat 12star - What sort of walls do you have? Dyno said Quote: The other empirical study I referenced, the 16% variance in U value occurred with fairly small changes in wind speed which suggests that the effect is still significant in 'normal' conditions. Having said this, if double glazing is susceptible to this effect then single glazing is even more so. Suppose that explains why it's colder on windy days As per the above post - I am sure it all has an effect, but IMO it's really case of how much in real terms of heat loss or temperature gains does that impact on the windows overall performance - and short of external shutters to stop the wind movement there is not a lot you can do about it. In a built up area, it will be probably not as significant but landscaping does provide significant changes in microclimate around the garden and house. If I was out bush, I'd know where I'd be heading for if the cold wind picks up. Re: Low-E glass and passive solar heating 153Aug 22, 2009 2:21 pm Yak_Chat 12star - What sort of walls do you have? bog std brick veneer upstairs, dbl brick lower1/2, built into a hill so only have a half house on the bottom...basically a garage & a rumpus room; the rest of the house (upstairs) has all the living area (bed rms, ktn, lounge & wet areas) Have a nth facing house with majority of windows facing nth (living areas), & a couple of Lg west windows (street views) Re: Low-E glass and passive solar heating 154Aug 22, 2009 2:56 pm The best prooduct is rockwool treated with a moisture repelent - it's certified as suitable for inside brick / briock veneer walls when a vapour barrier isn't present and has been tested in a NZ facility. Not sure that a silver foil mixed in with it would make much difference as it would not be reflecting in the same direction so would degrade it's performance I'd think. And getting a flat sheet of foil in there is not possible due to the brick ties etc. dyno - Quote: If I was out bush, I'd know where I'd be heading for if the cold wind picks up. Can't be done when there is fencing to be done - it's a case of the drizabone, (wind barrier/shutters) gloves (draft protectors) and a nice hat (thermal curtains for the head) and lots of thermal gear (part of the double glazing) But it sure is nice when you have a hot bath and sit by the fire afterwards Steve 0 4982 4 6201 If you can calculate the reasonable charged head from let's say 100mm below the gutter to the top of where the vertical riser's horizontal discharge pipe will be, that… 11 17530 |