Material Properties for accurate MRT calculation (UTCI component)

ladybug-tools
, ,
1

Hi all,
I have a HB problem- Outdoor thermal comfort related.

I’ve been working on comparing MRT field measurements with the outputs from the HB UTCI component but am having trouble getting results close to my measurements. I THINK because I don’t have the correct material properties set for the model’s ground/floor so I’m wondering if anyone can help my finetune the material properties? - The ground is a kind of pebble dash roofing tile which i’ve currently set based off a mix of the properties from Solid rock & Dry Dust because Solid Rock was giving me close LW MRT and Dry Dust close SW MRT. But that isnt really working out :smile:
Images of experimental set up and HB model below. (Basically the roof tiles are the roof of the ground zone with an ‘orphan’ shade connected to the model as the textile)

IMG-5120
IMG-51201920×2560 928 KB

ViewCapture20230912_204635
ViewCapture20230912_2046353072×2304 175 KB

Material Properties:

Shadematerial
Shadematerial1145×687 61.6 KB

Ground Material
Ground Material1302×582 70.1 KB

Here are the current results with red as the simulated values and blue as the measured values. First pic is: MRT, longwave MRT and MRT shortwave delta

MRTresults
MRTresults1245×1447 143 KB

Second pic is: air temp under the shade, and ground surface temp

EPresults
EPresults1710×1157 145 KB

And here are the direct and diffuse rad values for the same period if anyone is wondering about that weird peak mid morning. Wouldn’t mind an explanation for that too?

RAd values
RAd values1917×1015 139 KB

Also the EPW values have been replaced with local weather data collected on the analysis day including air temp, rh, wind speed and direction and radiation values.

Thank you!

2

Hi @sineadn, sounds like you’re well across what you’re doing, but I ask a primitive question - where did you get material properties from? Solar and visaul absorbtance in particular. It loooks a bit high at the first glance.

We did a study comparing reflectance parameters and it’s very critical for MRT results, more than surface temperature outcomes. May check out the discussion here MRT with UTCI (HB)_Materials impact - grasshopper / honeybee - Ladybug Tools | Forum

Is the grid set up at the same height with the site measurements?

As an idea, could cloud cover create the spike in the air temp observations?