Browse Forums Heating, Cooling & Insulation 1 Jun 17, 2013 11:11 am In terms of insulation/deflecting heat. I live in Brisbane and am wondering if we can get away with a mid grey colorbond roof or if we really should go lighter for reflection of the summer sun. Does anyone know if this makes a real significant difference or is it an exaggerated thing? Re: Does roof colour really matter? 2Jun 17, 2013 7:57 pm EmyN In terms of insulation/deflecting heat. I live in Brisbane and am wondering if we can get away with a mid grey colorbond roof or if we really should go lighter for reflection of the summer sun. Does anyone know if this makes a real significant difference or is it an exaggerated thing? Not sure on the actual question, however I did come across this when I was researching our colorbond roof - a scale based on the colour and solar absorption. http://www.colorbondcolours.com/commercial/information/thermal-performance/classification-of-colorbond-steel-colours-for-bca-and-basix Carlisle Homes ~ Winslow 33 http://jm-winslow33.blogspot.com.au/ 04/7 - Site cut 22/8 - Base 28/8 - Frame 02/9 - Roof 15/9 Plumbing & Electrical 7/10 - Lockup November - Complete Re: Does roof colour really matter? 3Jun 20, 2013 2:08 am I'm sorry I don't recall the reference, but I did a lot of research on this, and the answer was "No, not much at all" Certain materials have more reflectance but in the end it doesn't make much difference to the internal roof temperature at all. P_D . Block settled 07 June 2011 Our little piece of the Interwebs on HomeOne....... viewtopic.php?f=31&t=48577&start=0 Re: Does roof colour really matter? 4Jun 20, 2013 2:59 am My initial internet based investigations into this topic, double glazing, anticon and differences in R values have been interesting. I'd say pick any colour you like. The differences are most likely to be in the realm of a few cents a day at worst. Mid grey......................sounds pretty light to me. I'd be happy to go with Colorbond "Monument" and have now chosen "Bushland" I'd go for it Saving money on quality stuff done right firstime Our Build Thread https://forum.homeone.com.au/viewtopic.php?f=31&t=66810&p=1094349#p1094349 Re: Does roof colour really matter? 6Jun 20, 2013 9:36 am Danois With proper ventilation and insulation, I'd say pick the one you like.... Just did some research and what Danois says is pretty much spot-on. First thing I found was almost every single Google search result around the terms "roof colour temperature" brought pages of results where the summary was words to the effect "Light coloured roofs are cooler". (Since most (all) of the returned results spoke of white or lighter-coloured roofs, I'll generically use the term "white") Digging into lots of these results it soon became obvious that all of articles Google had found fell into one of three categories .......... 1) We sell something white to put on your roof so it will be cooler 2) Everyone knows white roofs are cooler So we dismiss all these results 3) This group was more interesting, it seems there is a valid scientific theory that white roofs may help with GLOBAL COOLING by reflecting heat back into the earths atmosphere, but that's not the topic here Then I noticed that I had my search engine set to "Google Australia" Setting it to "Google" made life a bit more interesting !! I found that many people were referencing one study conducted in Florida in the early 1990's that did show a decrease in internal roof temperature of just a few of degrees Fahrenheit, which converted to Celsius is of course even less. What did make some difference was the "reflectance" of the roof, which is, surprisingly, not too closely related to the colour ! Seems that the properties of the particular application of that particular roof material mattered more than anything else. Some dark coloured roofs had higher reflectivity than some lighter coloured roofs. Shingles / asphalt / tiles / iron, there was no significant relationship between the colours and the materials, every application was different, some light coloured asphalt had poor reflectivity (the hypothesised that it was not reflecting as much as expected because of the coarser grains some of them had), some darker tiles were quite reflective and so on. There are coatings (paints etc) that are designed with high reflectivity, but while they naturally had a high reflectivity (d'uh) their actual usefulness was not as great as their increased reflectivity might have suggested. The reports (that were factual and not selling anything !! ) said that part of the reason that it is not as intuitive as you may think was that a lot of solar energy hits our roofs but not all of it is in the spectrum we can see. So while we assume that all solar energy must act like the portion we can see (light reflects, dark absorbs) in practice this is not the case for all parts of the solar spectrum. Another aspect that has to be considered, but is less relevant in USA then here is darker (and heavier mass such as tile) can absorb heat in winter and MAY assist in winter heating. They said that this was generally dismissed and not considered relevant (in USA) as there is not all that much difference generally and specifically in their winters there is a combination of very low ambient temperature and or no solar gain due to excessive cloud cover and or no difference in ANY roof material as they are all equally covered in snow !! (My $0.02 is that in Australia if there is any significant difference in summer, then that would ALSO apply in winter as we generally have some solar gain in winter and almost never have no solar gain due to snow cover !!) Surprisingly though for me, my research found that the USA research DID find that attic spaces could be made significantly cooler by good ventilation, that is, a combination of BOTH eaves vents (to let the (relatively) cooler air in and ridge vents (to let the hotter air escape) ). So, yes while "everyone" knows light-coloured roofs are much cooler, the (independent) research doesn't necessarily bear that out !!! P_D . Block settled 07 June 2011 Our little piece of the Interwebs on HomeOne....... viewtopic.php?f=31&t=48577&start=0 Some selective quoting... 7Jun 20, 2013 10:03 am ...and my interpretation thereof "From the Florida Study" http://www.fsec.ucf.edu/en/publications ... PF-336-98/ "Location 1 ..Data from the second group of four homes suggests that soffit venting only can result in substantially higher temperatures than with soffit and ridge venting. This is likely a result of increased ventilation." Eaves-only venting lets heat in. "....The first is in its initial condition with a black roof and very little ventilation; the second year is with an attic radiant barrier and soffit and ridge venting. The attic to ambient dT is reduced by 16oF (8.9oC)" The sealed black roof was hot, then we added Sisalation and put vents in both the eaves and ridge. That made a big difference ! http://energyoptionsexplained.com/roof- ... mperature/ "Roof color plays some role in attic temperature, but its role isn’t nearly as significant as roof material and attic ventilation. Depending on your climate, a light or dark roof in a residential application may work in favor of or combat your primary conditioning needs (heating or cooling). If its interior comfort you’re most concerned about, then adequate insulation in your roof or attic will have the biggest effect on thermal resistance." Insulation, and lots of it is the answer "Most everybody understands the basic physics behind light and colors. Dark colors absorb more of the light spectrum, while lighter colors reflect more of it. ...Dark colors usually feel hotter to us, so our assumption would be that dark colored roofs would generate much hotter attics. The answer revolves a lot around reflectivity, the amount of energy a material reflects, and emissivity, the amount of absorbed energy re-radiates. Many assume that if something is dark colored, it will be hotter than something that is light colored. This may be true in many cases, but one thing that should also be considered is the material. Different materials have different properties as far as how they hold, disperse, or radiate heat. Studying the combination of both color and material may be a better study than just color alone. " There's more to it than you might think. "Attic ventilation is always important to ensure minimal moisture build up, and it also plays a very large role in cooling attic or roof spaces." That was a surprise to me. "While attic ventilation is always important in minimizing moisture levels, it also plays a major role in keeping attics cooler, more so than color difference between a single type of roofing material. Adequate ridge, soffit, and/or, gable ventilation prevents roof or attic suffocation and allows it to breathe and exchange that warm air from the roof with surrounding outdoor air that isn’t as hot." [My emphasis] Not what the people who sell you white roofs want you to hear "Material can have a greater effect than color on attic temperature as the reflectivity or the emissivity of the material itself can make all the difference. Case in point: A study comparing metal to tile, both of which are white, shows white tile has proven to create a much cooler attic temperature..... [My emphasis] Didn't see that one coming did you ? And much more that shows it's not as simple as white steel is good, dark tiles are bad !! Off to bed, I was night-shift last night P_D . Block settled 07 June 2011 Our little piece of the Interwebs on HomeOne....... viewtopic.php?f=31&t=48577&start=0 do not pay until you are satisfied with workmanship windows require flashing over the head archithrave and up under weatherboards 3 28287 thanks guys! yes this is how I've exactly raised it with the builder. still awaiting response. 12 6052 Thank you so much. We ended going with the terrain that’s part of our brick. 2 2539 |