From experience this is not correct
Browse Forums General Discussion Re: A rant about dark roofs ! 22Dec 24, 2009 11:58 am Hmmmm very interesting read. Our roof colour is "Loft", so a mid dark tone I guess, we have R4.1 insulation in the roof and get quiet a few 40+ degrees days here. We're not worried, will just wait and see I guess. Building Thread viewtopic.php?f=31&t=13002 Site start: 8th July 2009 Handover: 11/12/2009! 5 months total build time. 40 sqs of luxuary...Bliss! Re: A rant about dark roofs ! 23Dec 24, 2009 12:29 pm pinkfairymagic Hmmmm very interesting read. Our roof colour is "Loft", so a mid dark tone I guess, we have R4.1 insulation in the roof and get quiet a few 40+ degrees days here. We're not worried, will just wait and see I guess. With insulation under the roof inside will not be a problem it is just the total heat stored in black roofs over a large area. You seem new suburbs that are just a mass of black or dark roofs. There is also evidence that small areas of hot cities are creating even stronger micro storms because if the convection currents rising off the heat. Re: A rant about dark roofs ! 24Dec 24, 2009 1:42 pm Our last house had roof tiles in a light pinky/creamy colour (gross I know). We had them repainted a dark blue colour and never noticed any difference in the temperature inside. We did have good insulation though. When we chose the roof colour for our house we considered the location of our house in the street. As we are on acreage you can see most of our house roof as you drive up the street. The north facing roof (where we will eventually put solar panels) is the side of the house most clearly seen as you drive up and we didn't want a light coloured roof with really obvious (and potentially ugly) big black solar panel squares on it. We are hoping that the solarpanels won't be so noticable on a darker roof. Building the Pl@ntation Retreat on 4009m2. All moved in!!!!!! Now for the real work https://forum.homeone.com.au/viewtopic.php?f=31&t=20588&p=285640#p285640 Re: A rant about dark roofs ! 25Dec 24, 2009 1:45 pm An interesting thought I just had from your post Seast - would solar panels work better on a darker roof than a lighter roof?? 'A bottle of wine contains more philosophy than all the books in the world.' Louis Pasteur Vegie garden: viewtopic.php?f=19&t=27637&start=0 My Backyard Adventure Re: A rant about dark roofs ! 26Dec 24, 2009 1:57 pm HERE YOU GO Solar Absorptance of Cb colors eg. dark colors have double the solar absorptance of lighter colours. Hotter Roof, hotter house and more power consumption. Of course if you live in Hobart get a dark colour http://www.colorbondcolours.com/index.c ... 970272AA#1 Re: A rant about dark roofs ! 27Dec 24, 2009 2:11 pm lisanne An interesting thought I just had from your post Seast - would solar panels work better on a darker roof than a lighter roof?? No , the panels absorb their own sunlight not what is stored in the roof. If anything they may be a fraction more efficient on a light roof as there would be more reflected light but not enough to notice. Re: A rant about dark roofs ! 28Dec 24, 2009 2:41 pm D200 Doug lisanne An interesting thought I just had from your post Seast - would solar panels work better on a darker roof than a lighter roof?? No , the panels absorb their own sunlight not what is stored in the roof. If anything they may be a fraction more efficient on a light roof as there would be more reflected light but not enough to notice. I would imagine that you would get more efficiecieny on a light coloured roof because it would reduce the heat of the solar panels that are sitting on them, therefore allowing them to run more efficiently due to lower temperatures. Re: A rant about dark roofs ! 29Dec 24, 2009 3:16 pm Sheepdog D200 Doug lisanne An interesting thought I just had from your post Seast - would solar panels work better on a darker roof than a lighter roof?? No , the panels absorb their own sunlight not what is stored in the roof. If anything they may be a fraction more efficient on a light roof as there would be more reflected light but not enough to notice. I would imagine that you would get more efficiecieny on a light coloured roof because it would reduce the heat of the solar panels that are sitting on them, therefore allowing them to run more efficiently due to lower temperatures. I had not thought of that but yes that would be a factor Re: A rant about dark roofs ! 30Dec 24, 2009 3:20 pm A lot of the time it is due the covenant of the estate, as of Jan 1 2010 (in Qld) developers cannot dictate what colour types you can use, as long as it is not reflective. Lots of changes due to sustainability such as house size, energy declarations when selling a house, position of Solar, where garages can be built are some. Re: A rant about dark roofs ! 31Dec 24, 2009 6:06 pm dadandsue HERE YOU GO Solar Absorptance of Cb colors eg. dark colors have double the solar absorptance of lighter colours. Hotter Roof, hotter house and more power consumption. Of course if you live in Hobart get a dark colour http://www.colorbondcolours.com/index.c ... 970272AA#1 Hmm very interesting. We were originally going to have a Jasper roof, but ended up with Woodland Grey as per our developers requirements. I figured it'd be a much bigger difference. Stefan Building the M3tr!con Liberty 42 at Stonecutters Ridge. The New Build Blog - "Life, In Progress." Stonecutters Ridge Community Website | My photos Re: A rant about dark roofs ! 32Dec 24, 2009 6:28 pm deletedpenguin dadandsue HERE YOU GO Solar Absorptance of Cb colors eg. dark colors have double the solar absorptance of lighter colours. Hotter Roof, hotter house and more power consumption. Of course if you live in Hobart get a dark colour http://www.colorbondcolours.com/index.c ... 970272AA#1 Hmm very interesting. We were originally going to have a Jasper roof, but ended up with Woodland Grey as per our developers requirements. I figured it'd be a much bigger difference. I wanted Deep Ocean (I am in love with it) but when I saw a 235% heat increase I went back to Surfmist. Certainly location will dicate how critical the solar reflection is Re: A rant about dark roofs ! 33Dec 24, 2009 6:45 pm D200 Doug If anything they may be a fraction more efficient on a light roof as there would be more reflected light but not enough to notice. How does light reflected from a roof manage to bend and then reflect off the solar panels? SheepDog I would imagine that you would get more efficiecieny on a light coloured roof because it would reduce the heat of the solar panels that are sitting on them, therefore allowing them to run more efficiently due to lower temperatures. How is this possible when the roof under the solar panels are not even under direct sunlight? Transparent solar panels? A lot of missinformation in here. My 2c is that the higher thermal mass of roof tiles would lead to a slightly cooler house (and roof to walk on). The much lower thermal mass of colorbond would lead to a cooler house to a much lesser degree. I would say insulation plays a MUCH greater role in keeping your house cool, or not. Re: A rant about dark roofs ! 34Dec 24, 2009 7:05 pm Rex D200 Doug If anything they may be a fraction more efficient on a light roof as there would be more reflected light but not enough to notice. How does light reflected from a roof manage to bend and then reflect off the solar panels? SheepDog I would imagine that you would get more efficiecieny on a light coloured roof because it would reduce the heat of the solar panels that are sitting on them, therefore allowing them to run more efficiently due to lower temperatures. How is this possible when the roof under the solar panels are not even under direct sunlight? Transparent solar panels? A lot of missinformation in here. My 2c is that the higher thermal mass of roof tiles would lead to a slightly cooler house (and roof to walk on). The much lower thermal mass of colorbond would lead to a cooler house to a much lesser degree. I would say insulation plays a MUCH greater role in keeping your house cool, or not. Like I said "A fraction" that indicates a very small amount there would be a fraction more light scatter off a light coloured roof but as I said "Not enough to notice" heat rises a black roof absorbs heat so becomes hotter That heat rises off the black surface and would affect anything above that surface, usually solar collectors do not cover the whole roof space. AN increase in heat = a decrease in efficiency of solar cells Before answering it may help if you read what others have said and think about what you are suggesting. Re: A rant about dark roofs ! 35Dec 27, 2009 8:32 am I think this dark roof tile attributing to hot houses is a bit of a myth. A friend of mine has Bristile Onyx (Black gloss) roof tiles. And when I recently house sat, I didn't notice anything unusal heat wise on hot days. In fact, even one of the days it was 38C outside and even though I used the ceiling fan, I still slept with the covers on. Even now, he needs a string of very hot days before he needs the aircon on. And he has the blow in insulation. Which he hates. I was scared of getting a dark roof tile before, because of what I had been told. Even thought I prefered the look of them. But after experiencing first hand how much it doesn't affect the air temp in his house. I went on and chose Graphite (Black) from bristile, with R3.0 insulation. And believe me I have experienced both sides of this argument. My parents have a cream colored Colorbond roof, and they do actually have heat issues with interior temps in summer. But they also were given R2.5 Bats, instead of R3.0. Remember, the air gaps between roof tiles and roof cavity on a tiled rood does let the heat out somewhat. Especially in a breeze. Re: A rant about dark roofs ! 36Dec 27, 2009 9:23 am I've discussed this before on the forum and I'll go through it again. I think the best roof colour to keep your house at the best temperature all year round is ... black. Yes, a black roof is best. However, you can't just stop at the roof colour. You need to do a couple of other things. During winter days, the dark roof will heat the roof space. What is then needed is some "reverse" exhaust fans to bring the warm air into the house. The fans should be such that when the are not in use they block air flow. In the past, there have been those that have been concerned about roof dust. If you put sarking in (an essential ingredient) then the amount of dust is minimal. In summer, turn on the whirlybirds (with soffit vents of course). This will keep the roof space temperature down to just a little over the outside temperature. R3 roof insulation will ensue that the outside heat doesn't come in through the ceilings. And as a final twist, the roof space temperature on a summer's night actually get lower than the outside temperature (google "night sky radiation"). This is particularly true for metal roofs. So that same fan that was used during winter days can be used on summer nights. So there you have it, with whirlybirds that can be locked in winter and some "reverse" exhaust fans a dark roof can outperform a light roof. (Don;t forget the sarking and R3 ceiling insulation.) Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: A rant about dark roofs ! 37Dec 30, 2009 2:58 pm Casa2 Yes, a black roof is best. However, you can't just stop at the roof colour. You need to do a couple of other things. The problem is the second part of the equation. People have the dark roof but then don't do the other things you suggest so any benefit can be realised. So they get all the disbenefits of the dark roof but none of the potential benefits. A dark roof, even with sarking and ventilation, can never match the hot day summer performance of the light roof with sarking. So it is always a compromise of summer performance for any potential winter gains - if these are even realised. Dark roofs also impact the urban heat island effect - making it hotter for everyone. Your comment of the night sky radiation cooling black roofing is also interesting. I understand this is not quite as effective in high overnight humidity climates. The other question I have about this is, is a black roof significantly better than a white roof for this purpose as the emissivity of both is about 0.9 so should therefore cool the same amount to night sky radiation? Re: A rant about dark roofs ! 38Dec 30, 2009 3:26 pm We're going with surfmist roof, for this very reason, along with foil under the tin and ceiling insulation. Do some developers not allow surfmist because of the glare?? or some other reason? If it's glare, then I'm sure the people on the hill above our house are not going to be happy Re: A rant about dark roofs ! 39Dec 30, 2009 5:27 pm Eccles Casa2 Yes, a black roof is best. However, you can't just stop at the roof colour. You need to do a couple of other things. The problem is the second part of the equation. People have the dark roof but then don't do the other things you suggest so any benefit can be realised. So they get all the disbenefits of the dark roof but none of the potential benefits. A dark roof, even with sarking and ventilation, can never match the hot day summer performance of the light roof with sarking. So it is always a compromise of summer performance for any potential winter gains - if these are even realised. Dark roofs also impact the urban heat island effect - making it hotter for everyone. Your comment of the night sky radiation cooling black roofing is also interesting. I understand this is not quite as effective in high overnight humidity climates. The other question I have about this is, is a black roof significantly better than a white roof for this purpose as the emissivity of both is about 0.9 so should therefore cool the same amount to night sky radiation? Yes, clear low humidity nights work best for night sky radiation (up to 5 degrees lower than ambient). Cloud cover and humidity reduce this. So you only get the benefit some nights (any are a bonus). I thought the emissivity of a dark roof is higher than that of a light roof. What makes you think otherwise? Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: A black tiled roof does not make the house hotter 40Dec 30, 2009 6:06 pm I wrote a response but have erased it. I'm over it. Hi, We have warm light throughout our house and it sort of makes are already dark stained floor more darker. 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