MRT with UTCI (HB)_Materials impact

Hi all,
We’ve been testing CoolSeal product, trying to compare temperatures with BAU dark asphalt. But after a large number of different tests we get to the same strange or minimal differneces. There’s a number of papers showing significant temp drops (up to 10-30! degrees) with cool surfaces, but we get 0.2 degrees at best.

Then we tried the basic script from the tutorials, with the basic materials. And the results are questionable as well. Here the left surface is set to Asphalt material (cooler) and the right one Concerete pavement (hotter).

While judging on the constraction break down - concrete suppose to absorb less heat.

Any ideas, comments?


1 Like

Hi @ale.bog,

Are you looking at point in time results or average results over a period?

And are you looking at the surface temperature of the material or at the UTCI / MRT?

I’d recommend looking at a point in time for the surface temperature to start (LB Apply Analysis Period, with the period set to a single hour using LB Analysis Period).

Hopefully that’s a good place to start.


1 Like

Thanks, @charlie.brooker.
I’ve reviewed individual hours across summer, as well as average over a month for all hours or 1 specific hour, across the whole summer. The results obviously vary, but still sit within the same range.

For the analysis, we use environmental conditions output from the HB UTCI component, and read MRTs.

The grid we tried both, not elevated and sligtly elevated from the surface (0.01m) to ensure that the points are not inside the road but on the top surface.

When you asking ‘surface temperature of th material or MRT’ - what other methods are there to review it apart from the one i shown above?
Many thanks,

Have an update. We looked at .idf file and surface temperatures, just by loading it manually, cause UTCI component doesn’t let you review it. And they look okay.

So could it be the MRT is higher for light surfaces due to the reflection, that is not absorbed by the material, while the surface temp is actually cooler?

Just to quickly respond to this:

It seems like you already found a decent way to check the surface temperatures but running a plain old energy simulation with your model using the “Model to OSM” component and then using the HB Color Faces component to check the surface temperatures will go a long way to helping you understand what’s happening in the simulation. Also note that the comfort maps show you both the impact of surrounding surface temperatures AND the impact of solar that’s reflected off the ground towards the human subject. So, during sunny hours, a more reflective surface is likely to look hotter to a human subject an a dark one just because of the shortwave reflection.

Also note tha solar reflectance is important but you’ll often find that things like heat capacity matter a surprising amount when you look at thermal effects overr time.


Thanks, @chris! That make sense.

I’ve also had a chat with a specialist in the topic and here’s some feedback on materials (which we all pretty much descibed above).

High albedo paving surfaces result in lower surface temperatures. However, they do not necessarily lead to lower MRT. Although increased albedo increases the reflection of sunlight from high albedo surfaces, due to canyon geometry and complex light reflection-absorption behaviour of different urban surfaces, the reflected sunlight may not escape the built environment immediately. The reflected radiation from a high albedo surface can be absorbed and stored in other urban materials and cause extra heat load elsewhere in the built environment. Also, excessively bright materials can cause glare problems. MRT may adversely affect pedestrians in the daytime resulting from the added reflection of solar radiation towards people.

The recent development of materials with very high solar reflectance permits to reduce the magnitude of urban overheating. However, technical issues related to the optical ageing of the materials have to be solved, while issues related to glare have to be confronted. Recent research has succeeded in developing the so-called super cool materials presenting a very high reflectance in the solar spectrum and a high emissivity value in the atmospheric window wavelengths. Emissivity and albedo have the greatest effect on determining how and to what extent paving materials and roofs exchange heat and contribute to the UHI effect. Depending on the material properties, location, and canyon geometry you may have different levels of reductions in both ambient and surface temperatures. When it comes to thermal comfort, there are other environmental factors to be considered as well as other mitigation strategies or combinations with other strategies (cool roofs, shading etc).

Please check this paper which may help. It addresses some of your concerns:


Not related to the topic, but don’t forget glare issues.

That’s also why even manufactures don’t go for more that 50% reflectance. Which can already lead to glare risks btw
Thanks for the comment