Emissivity is about far more than just visible whiteness. IR emissions aren't even in the visible spectrum. They're in the infrared, beyond colours that you can see. You can have materials that are easily 10C cooler than common commercial white paints, yet still appear the same bright white. So, no, I don't think that video was a great explanation. Passive radiative cooling materials that get down to sub-ambient temperatures (by using atmospheric IR window emissions), do exist. Despite the impressions this video will give people. See TechIngredient's video "Revolutionary Paint" for an explanation and demonstration.
@@dlmetcalf1the target of this video is mainly non-engineer , non scientist background audiences. I try to give a very brief and simplified description of emissivity. We are planing to make a video on the use of IR imaging in construction. Hopefully we can do a more detailed explanation on emissivity in the coming video.
For cool climate i always go for or recommended to friends and family to go for darker colours for everything exterior. And we also have ventilated everything here (Norway, cold and wet climate). Any house with light colour turns green from algae since it's always cold and wet. One black can be cooler than a different black just from the thermal emissivity, but that is usually a more expensive specially formulated paint. Most paint are just colours and no thought about it's emissivity, but generally any bare metal or bright white reflects better
Awesome video! Thanks for sharing. It would be good if you could post up the data from this test of all the different colors. My key takeaway here is that going for a medium grey like wallaby (my roof) instead of monument yields very little benefit - 1 degree cooler. So you really need to go for surfmist or dover white to get the full benefit of the light coloured roof.
Excellent video. Every question I had answered. Would be great if you could now compare colours on cement tiles. Looking to get my roof painted so I’d be interested to know how the colour impacts the tiles.
According to the laws of physics (optics). Light colors reflect more photons from light, so they heat up less, while dark colors reflect fewer photons, so they heat up much more. The material only affects heat dissipation (thermal conductivity).
Good vid guys, it is worth mentioning, if you detail the roof correctly the roof could be black and it wouldnt matter. ie passive house roof build up with ventilated cavity and insulation up in the rafters.
If your house is in the middle of nowhere, a well insulated roof can minimize the impact of dark roof. However, in urban settings, dark roofs enhance the urban heat island effect. Which can increases the air temperature of the suburb if all roofs were dark. This in turns can reduces the usefulness of natural ventilation in warm weather and it also makes the heat rejection of air conditioners less effective.
Loving your channel. Is there an argument for darker coloured roof in cooler areas where more energy is spent on heating a house rather than cooling it?
Particularly in homes where it's occupied 24/7, the majority of the heating requirements are at night when solar gain is zero. The insulation is the primary defence against heat loss (the cold) the benefit from dark colour roof is minimal. Potentially, the designer can include features such as a winter garden (greenhouse) with an uninsulated dark roof may be useful.
@josephcheung8311 the same argument about no solar load at night could be given when considering passive solar - its not effective at night. The reality is, the thermal lag from passive solar and from dark colored roofs in cooler climates are more beneficial across a 12month period than not. What we have in cooler climates like Melbourne is two conflicting challenges. The micro effect on individual houses pushing for dark colours vs the macro effects on suburbs
@@nathanwooldridge85the main difference is that the heat from dark roof is generally dampen by the ceiling/ roof insulation where most of the passive solar design features allow some level of direct heating of the thermal mass indoor. Unless the designer implementing more complex strategies similar to a tromp wall which directing the heated air in the roof cavity to warm up indoor thermal mass during the day. These scenarios are far from common volume homes that we are talking about.
Your insulation should be perfect, so no there isn’t. But there is an argument for the potential drying effect that darker roofs have. If water gets inside roof/wall systems.
Energy requirements for Melbourne often relies upon many months of heating with only a few months requiring cooling. Is it still a net benefit to have a light coloured roof in cooler climates when solar production is low thus making energy costs high during cold months?
@@ecoevo Haha I just watched that one too! I'm so sad I found these only after I just got a new colourbond roof put on in monument... considering painting white now.
@@DATApush3r Monumental! Having a warmer roof allows for better drying of condensation that can form in your roof too. So it’s not all bad. Make sure to focus on good coverage of the insulation being abutted to your ceiling. m.czcams.com/video/uLs1eHbOmn0/video.html
@@danielszuba2123 I have no evidence but I'd imagine there would be a difference considering the difference in thermal properties of metal vs ceramic. Metal probably heats and cools faster than ceramic.
How does the roof getting "dirty" impact on heat? How about solar panels on top? Does it matter whats underneath if the roof is mostly black solar panels?
If the entire roof is covered with solar panels, then the effect is negligible. However for most of the common installation in Australia. The dark roof still elevates the roof temperature and reduces the efficiency of the solar panels. The dirt on white roof will gradually darken the colour of the roof - hance the solar reflectance.
I feel like you have miss-labelled your Wallaby sample, or missed it out entirely. The CB Wallaby colour is similar to monument, but lighter and slightly warmer. What you have labelled as Wallaby looks to me to be actually Evening Haze. I was interested in the information because of the Wallaby sample vs the Monument, but this is not an accurate comparison. Can you please confirm this?
Awesome work gents. Science prevails. Love it.
Engineer here - well done, excellent rig and explanation of emissivity.
Emissivity is about far more than just visible whiteness. IR emissions aren't even in the visible spectrum. They're in the infrared, beyond colours that you can see. You can have materials that are easily 10C cooler than common commercial white paints, yet still appear the same bright white. So, no, I don't think that video was a great explanation. Passive radiative cooling materials that get down to sub-ambient temperatures (by using atmospheric IR window emissions), do exist. Despite the impressions this video will give people. See TechIngredient's video "Revolutionary Paint" for an explanation and demonstration.
@@dlmetcalf1the target of this video is mainly non-engineer , non scientist background audiences. I try to give a very brief and simplified description of emissivity. We are planing to make a video on the use of IR imaging in construction. Hopefully we can do a more detailed explanation on emissivity in the coming video.
best video I have seen so far about color temperature.
What a fantastic video, thanks for taking the time to share your experiment.
For cool climate i always go for or recommended to friends and family to go for darker colours for everything exterior. And we also have ventilated everything here (Norway, cold and wet climate).
Any house with light colour turns green from algae since it's always cold and wet.
One black can be cooler than a different black just from the thermal emissivity, but that is usually a more expensive specially formulated paint. Most paint are just colours and no thought about it's emissivity, but generally any bare metal or bright white reflects better
Great video
Excellent video. Thanks
Awesome video! Thanks for sharing. It would be good if you could post up the data from this test of all the different colors. My key takeaway here is that going for a medium grey like wallaby (my roof) instead of monument yields very little benefit - 1 degree cooler. So you really need to go for surfmist or dover white to get the full benefit of the light coloured roof.
Amazing video!
Excellent video. Every question I had answered. Would be great if you could now compare colours on cement tiles. Looking to get my roof painted so I’d be interested to know how the colour impacts the tiles.
According to the laws of physics (optics). Light colors reflect more photons from light, so they heat up less, while dark colors reflect fewer photons, so they heat up much more. The material only affects heat dissipation (thermal conductivity).
Amazing content..
👉Gray and silver color are the best, next is white 👈
Good vid guys, it is worth mentioning, if you detail the roof correctly the roof could be black and it wouldnt matter. ie passive house roof build up with ventilated cavity and insulation up in the rafters.
If your house is in the middle of nowhere, a well insulated roof can minimize the impact of dark roof. However, in urban settings, dark roofs enhance the urban heat island effect. Which can increases the air temperature of the suburb if all roofs were dark. This in turns can reduces the usefulness of natural ventilation in warm weather and it also makes the heat rejection of air conditioners less effective.
@@josephcheung8311 I agree 👍🏼.
Loving your channel. Is there an argument for darker coloured roof in cooler areas where more energy is spent on heating a house rather than cooling it?
Particularly in homes where it's occupied 24/7, the majority of the heating requirements are at night when solar gain is zero. The insulation is the primary defence against heat loss (the cold) the benefit from dark colour roof is minimal. Potentially, the designer can include features such as a winter garden (greenhouse) with an uninsulated dark roof may be useful.
It is advised in cooler regions to choose a darker colour.
@josephcheung8311 the same argument about no solar load at night could be given when considering passive solar - its not effective at night.
The reality is, the thermal lag from passive solar and from dark colored roofs in cooler climates are more beneficial across a 12month period than not.
What we have in cooler climates like Melbourne is two conflicting challenges. The micro effect on individual houses pushing for dark colours vs the macro effects on suburbs
@@nathanwooldridge85the main difference is that the heat from dark roof is generally dampen by the ceiling/ roof insulation where most of the passive solar design features allow some level of direct heating of the thermal mass indoor. Unless the designer implementing more complex strategies similar to a tromp wall which directing the heated air in the roof cavity to warm up indoor thermal mass during the day. These scenarios are far from common volume homes that we are talking about.
Your insulation should be perfect, so no there isn’t. But there is an argument for the potential drying effect that darker roofs have. If water gets inside roof/wall systems.
Energy requirements for Melbourne often relies upon many months of heating with only a few months requiring cooling. Is it still a net benefit to have a light coloured roof in cooler climates when solar production is low thus making energy costs high during cold months?
This video is epic!
Surely this one is more EPIC with the NASA space shuttle launch? czcams.com/video/V8dg1ePdJ68/video.htmlsi=CsQfaYUwxwBlqEv_
@@ecoevo Haha I just watched that one too! I'm so sad I found these only after I just got a new colourbond roof put on in monument... considering painting white now.
@@DATApush3r Monumental! Having a warmer roof allows for better drying of condensation that can form in your roof too. So it’s not all bad. Make sure to focus on good coverage of the insulation being abutted to your ceiling.
m.czcams.com/video/uLs1eHbOmn0/video.html
Loved the video again guys thank you!
Is there any difference between ceramic tiles and colourbond roofing of the same colour?
@@danielszuba2123 I have no evidence but I'd imagine there would be a difference considering the difference in thermal properties of metal vs ceramic. Metal probably heats and cools faster than ceramic.
How does the roof getting "dirty" impact on heat? How about solar panels on top? Does it matter whats underneath if the roof is mostly black solar panels?
If the entire roof is covered with solar panels, then the effect is negligible. However for most of the common installation in Australia. The dark roof still elevates the roof temperature and reduces the efficiency of the solar panels. The dirt on white roof will gradually darken the colour of the roof - hance the solar reflectance.
I feel like you have miss-labelled your Wallaby sample, or missed it out entirely. The CB Wallaby colour is similar to monument, but lighter and slightly warmer. What you have labelled as Wallaby looks to me to be actually Evening Haze.
I was interested in the information because of the Wallaby sample vs the Monument, but this is not an accurate comparison. Can you please confirm this?
Yes it looks like wallaby and evening haze are switched around definetly!
yes, thank for picking it up. As these two colours are not the focus of the discussion, we overlooked the labelling.
You're right!
What about a fully reflective metal roof surface?
We covered zinc alum? White kills it.
🤯 This video is AMAZING!
I can’t believe you only have only 1.8k views 😒
Thank you so much for your videos 🙏🏻
It has helped so much 🥲