Browse Forums Building A New House 1 Dec 05, 2008 5:57 pm Just wondering if a black roof (tiled) makes the house harder to cool by retaining and radiating more heat due to it's colour?
Any input would be appreciated. I have heard mixed results so far. Thanks themax wanting to build Cl@rendOn B@lm@ain Soil Report done Survey next week Tender week after. [/quote] Re: Does a black roof make the house hotter? 2Dec 05, 2008 6:29 pm Put in some whirlybirds and soffit vents and all will be fine. Lock the whirlybirds in winter and things will be even better. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Does a black roof make the house hotter? 3Dec 05, 2008 7:11 pm Our builder said that the whirly bird helps get the moisture out of the roof in Winter...? We've gone a black (nightsky) colorbond roof which for some reason appears it will be hotter than black tiles which are almost standard across the suburbs. Fi has moved in!! Re: Does a black roof make the house hotter? 5Dec 06, 2008 10:48 am From what I have read on this site Whirlybirds have questionable benefit. Like most things unless they are installed correctly, they have very little benefit. As with most things opinions differ greatly.
From what I can tell upgrading your insulation is the way to go. FD2 www.thebedbug.com.au Children's Licenced and Treehouse Manchester for all of those new rooms! Fringe Dwellers - Building Urbanedge Homes Larne 002 www.devohosting.com.au/fringedwellers Re: Does a black roof make the house hotter? 7Dec 06, 2008 11:12 am Do black tiles make a house hotter? Abso - bloody - lootly...
Is a black car hotter? (put your hand on one). Is a black dog hotter (put your hand on one)? (got 2). And it is not just the hot air in the roof space - it's the heat radiated from the super hot tiles. He says sitting next to tinted windows exposed to the sun radiating into the office. Black absorbs radiant energy and it is a radiator... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Does a black roof make the house hotter? 8Dec 06, 2008 11:14 am Casa2 Put in some whirlybirds and soffit vents and all will be fine. Lock the whirlybirds in winter and things will be even better. Whirlybirds will only work if you draw hot air out of the conditioned space via a ceiling vent. Cooling the roof space in isolation has neglible effect on the living areas below. This has been modelled by the Florida Solar Energy Centre. It may reduce cooling requirements by about 6% The first solution is to block solar radiant heat in the first place with reflective foil under the roof or painting the roof white. http://forums.envirotalk.com.au/Whirlyb ... entry26656 Re: Does a black roof make the house hotter? 9Dec 06, 2008 11:17 am MBBN Yes it does. Probably not so much that you will really notice it but the lighter you go the better your energy rating is. On the contrary the FSEC demonstrates roof colour is a strong determinant of cooling load. (Later edit: i.e. a white roof makes a BIG difference not just a small difference) http://www.fsec.ucf.edu/en/publications ... PF-337-98/ They show a 19% reduction in cooling load compared to a dark tiled roof. Their findings confirms this practice employed in the vernacular architecture of typically hot climates around the world. Re: Does a black roof make the house hotter? 10Dec 06, 2008 11:21 am dymonite69 MBBN Yes it does. Probably not so much that you will really notice it but the lighter you go the better your energy rating is. On the contrary the FSEC demonstrates roof colours is a strong determinant of cooling load. http://www.fsec.ucf.edu/en/publications ... PF-337-98/ They show a 19% reduction in cooling load compared to a dark tiled roof. Their findings confirms this practice employed in the vernacular architecture of typically hot climates around the world. I think you contradicted yourself - MBBN says "yes" dark colour affects energy rating negatively... you say "on the contrary..." and then you seem to be agreeing with MBBN. Clarification might be in order... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Does a black roof make the house hotter? 11Dec 06, 2008 11:26 am EcoClassic Do black tiles make a house hotter? Abso - bloody - lootly... Is a black car hotter? (put your hand on one). Is a black dog hotter (put your hand on one)? (got 2). And it is not just the hot air in the roof space - it's the heat radiated from the super hot tiles. He says sitting next to tinted windows exposed to the sun radiating into the office. Black absorbs radiant energy and it is a radiator... Ed For those who like the geeky science this property is called the emissivity of the surface. This describes the amount of electromagnetic radiation that emanates from a heated surface (specifically infra-red thermal radiation). Shiny metals or light colours have low emissivity e.g. put you hand near (not touching) a stainless steel teapot filled with boiling water - it feels cool). he same principle seen when covering food sitting out of the oven with foil. Low emissivity surfaces have correspondingly low absorptivity and high reflectivity - and vice verse. Dark matte finishes have high absorptivity and emissivty - and low reflectivity. EcoClassic touches on a separate subject of thermal mass. These are substances which can hold high amounts of heating energy with only small changes in temperature. Similarly they can release this energy with only a small fall in temperature. The energy released is what you experience below a heated tile roof or next to a brick wall. Re: Does a black roof make the house hotter? 12Dec 06, 2008 11:34 am dymonite69 EcoClassic Do black tiles make a house hotter? Abso - bloody - lootly... Is a black car hotter? (put your hand on one). Is a black dog hotter (put your hand on one)? (got 2). And it is not just the hot air in the roof space - it's the heat radiated from the super hot tiles. He says sitting next to tinted windows exposed to the sun radiating into the office. Black absorbs radiant energy and it is a radiator... Ed For those who like the geeky science this property is called the emissivity of the surface. This describes the amount of electromagnetic radiation that emanates from a heated surface (specifically infra-red thermal radiation). Shiny metals or light colours have low emissivity e.g. put you hand near (not touching) a stainless steel teapot filled with boiling water - it feels cool). he same principle seen when covering food sitting out of the oven with foil. Low emissivity surfaces have correspondingly low absorptivity and high reflectivity - and vice verse. Dark matte finishes have high absorptivity and emissivty - and low reflectivity. EcoClassic touches on a separate subject of thermal mass. These are substances which can hold high amounts of heating energy with only small changes in temperature. Similarly they can release this energy with only a small fall in temperature. The energy released is what you experience below a heated tile roof or next to a brick wall. No I am not discussing thermal mass I am talking about radiation from a black radiator. Black tiles continuously absorb heat and reradiate (if they did not they would just get hotter and hotter). If you put a black tile out in the sun it will heat up very quickly - a large thermal mass would take longer to heat up and would radiate depending on its colour. The hot tile radiates like a bar heater, except in every direction. Incidentally, Colorbond claims their new dark colours are very energy friendly - I have no idea if it is true or how they do it. The reason that a stainless steel teapot does not feel so hot up close is that it is not a black radiator and stainless is one of the lowest heat conductive metals, ideal for making windows except it must be fabricated from flat sheet and is not easily worked. Your car radiator is effective because it is made of copper (very good conductor) and it is painted black (very good radiator). Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Does a black roof make the house hotter? 13Dec 06, 2008 12:13 pm EcoClassic No I am not discussing thermal mass I am talking about radiation from a black radiator. Black tiles continuously absorb heat and reradiate (if they did not they would just get hotter and hotter). If you put a black tile out in the sun it will heat up very quickly - a large thermal mass would take longer to heat up and would radiate depending on its colour. The hot tile radiates like a bar heater, except in every direction. Incidentally, Colorbond claims their new dark colours are very energy friendly - I have no idea if it is true or how they do it. The reason that a stainless steel teapot does not feel so hot up close is that it is not a black radiator and stainless is one of the lowest heat conductive metals, ideal for making windows except it must be fabricated from flat sheet and is not easily worked. Your car radiator is effective because it is made of copper (very good conductor) and it is painted black (very good radiator). Ed As regards to thermal mass, I am talking in relative terms. A low-mass metal roof holds much less heating energy and will cool down faster (by radiation and convection). Your tile can release heat for quite a while. Unless they have changed the coating forumation, the Colourbond colours aren't that cool. However, there is paint technology which is spectrally selective and can reflect infa-red more than visible light. It allows you a darker roof with less heat absorptio. Highly conductive materials like metal will transfer heat by conduction readily when they are touched. However, metal surfaces also transfer radiation poorly. This is why they do not recommend allowing the shiny side of the Sisalation to touch the building fabric. Thermal conductivity should not be confused with emissivity. They are independent parameters. The emissivity is a surface property and not one related to the material under the surface. If you paint a stainless steel teapot black it will have a higher emissivity. It is not a given that a substance with low emissivity had high conductivity but this is generally true. Re: Does a black roof make the house hotter? 14Dec 06, 2008 12:20 pm Lol that's all confusing. Pretty much, the closer to white the roof colour is, the cooler the house will be.
We really like black/charcoal roofs, but after seeing how much of an effect it can have on house temperature, we are looking at very light colours such as surf mist. We've looked at display homes with light coloured roofs to work out how to do it. Colorbond has an link on their site classifying the colours: http://www.colorbond.com/index.cfm?objectid=8B47C5CE-A52F-FE7E-1932836BE38355FB Aim for very light or light. Also, the lighter to roof is, the slower it will fade. Black fades very quickly, as do other bright or dark colours, so the very light and light colours will last longest, if that helps the decision. Re: Does a black roof make the house hotter? 15Dec 06, 2008 12:26 pm Actually black does not fade so much - it's the primary colours like red that fade. "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Black roof? 16Dec 06, 2008 12:33 pm In these days of saving energy and environmental issues, why is everyone choosing dark roof colours? It must purely be because of the aesthetic look? I also had a black roof in my mind for our new house (aesthetic look, once again) but I am now reconsidering. I wonder what other colours look nice besides the terracotta? Thanks for all the input to my original question. It has made for interesting conversation and something to consider. mmmm...i also wonder if the outside render colour has the same effect, I would think so, but only minimal? mmmmmm...
themax Re: Black roof? 17Dec 06, 2008 12:35 pm themax In these days of saving energy and environmental issues, why is everyone choosing dark roof colours? It must purely be because of the aesthetic look? I also had a black roof in my mind for our new house (aesthetic look, once again) but I am now reconsidering. I wonder what other colours look nice besides the terracotta? Thanks for all the input to my original question. It has made for interesting conversation and something to consider. mmmm...i also wonder if the outside render colour has the same effect, I would think so, but only minimal? mmmmmm... themax Render - exactly the same where the sun catches it... just more thermal mass if it's on brick, so it endures after the sun has gone down. Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Does a black roof make the house hotter? 18Dec 06, 2008 12:38 pm dymonite69 EcoClassic No I am not discussing thermal mass I am talking about radiation from a black radiator. Black tiles continuously absorb heat and reradiate (if they did not they would just get hotter and hotter). If you put a black tile out in the sun it will heat up very quickly - a large thermal mass would take longer to heat up and would radiate depending on its colour. The hot tile radiates like a bar heater, except in every direction. Incidentally, Colorbond claims their new dark colours are very energy friendly - I have no idea if it is true or how they do it. The reason that a stainless steel teapot does not feel so hot up close is that it is not a black radiator and stainless is one of the lowest heat conductive metals, ideal for making windows except it must be fabricated from flat sheet and is not easily worked. Your car radiator is effective because it is made of copper (very good conductor) and it is painted black (very good radiator). Ed As regards to thermal mass, I am talking in relative terms. A low-mass metal roof holds much less heating energy and will cool down faster (by radiation and convection). Your tile can release heat for quite a while. Unless they have changed the coating forumation, the Colourbond colours aren't that cool. However, there is paint technology which is spectrally selective and can reflect infa-red more than visible light. It allows you a darker roof with less heat absorptio. Highly conductive materials like metal will transfer heat by conduction readily when they are touched. However, metal surfaces also transfer radiation poorly. This is why they do not recommend allowing the shiny side of the Sisalation to touch the building fabric. The emissivity is a surface property and not one related to the material under the surface. If you paint a stainless steel teapot black it will have a higher emissivity. It is not a given that a substance with low emissivity had high conductivity but this is generally true. Hmmm... I doubt you are trying to confuse but... Quote: Thermal conductivity should not be confused with emissivity. They are independent parameters. Quote: It is not a given that a substance with low emissivity had high conductivity but this is generally true. Quote: I am talking in relative terms. You are a font of information - you just need to get it out more clearly... "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Does a black roof make the house hotter? 19Dec 06, 2008 1:34 pm EcoClassic Hmmm... I doubt you are trying to confuse but... Quote: Thermal conductivity should not be confused with emissivity. They are independent parameters. Quote: It is not a given that a substance with low emissivity had high conductivity but this is generally true. Quote: I am talking in relative terms. You are a font of information - you just need to get it out more clearly... There are tables on the Internet that give materials data for most of these properties. In the context of standard building materials: The best conductor is copper and followed by most of the metals. e.g. copper pipes can cool very quickly or freeze in winter when not lagged, Stainless steel is a mixture (alloy) so it doesn't quite count. When building with steel frames heat can more easily conduct from the outside to inside via the metal work. Similarly aluminium window frames will allow more heat transfer than timber or PVC frames. By inserting a 'thermal break' in between with an insulative material you can eliminate this 'thermal bridge' of heat transfer. Trapped pockets of air is a great insulator. That's what makes it useful in batt insulation, styrofoam and double glazed windows. Once you stir it up then it becomes less useful e.g. a fan forced oven cooks faster than a normal oven. Rubber is also a insulator. Timber, bricks, tiles, concrete and masonry fall somewhere in between. Materials which act as radiant barriers are metal surfaces e.g. aluminium foil or titanium dioxide (found in large quantities of white paint). They reflect the solar radiation away. Materials which have high emissivity are all the masonry products. The heat released by the internal leaf of a double brick wall can add significantly to the cooling load in summer. The same with tiles on the roof that have been heated all day by the sun. Re: Black roof? 20Dec 06, 2008 1:39 pm themax In these days of saving energy and environmental issues, why is everyone choosing dark roof colours? It must purely be because of the aesthetic look? Spot on. Dark roofs look great but are impractical for cooling purposes. You might be able to get away with it in Tasmania. I couldn't convince my wife to have light coloured roof. As you can tell I am the pragmatist. I compromised by making sure I had foil under the roof and painting the Zincalume with heat reflective Woodland Grey paint. BTW Zincalume is shiny and metallic but doesn't keep heat out as much as foil. if i have understood your dimensions correctly my suggestions include using the smallest toilet and wall hung handbasin eg Caroma Urbane with in wall cistern, small wall… 1 8173 I posted the floorplan on Houzz.com forum and got some really good ideas and advice from people there. Then we reached out to a couple of renovation companies and one… 5 10106 The warning is on the sticker on the door too. Second the aluminium powdercoat 6 18204 |