Surface Temperature under reflected solar heat gain

HI there guys.

Our studio is working on a large scale project. A university pavilion. Right now we are at the design development phase and since the begging we are using LB and HB for daylight analysis. One special condition of the project is a concave south west glass façade (north America) that will, for sure, create some solar heat gain because its concentrating solar light on a specific area on the ground.

Using LB we are able to pin point the location of the sunrays hitting the ground after being reflected by the facade and with HB we can spot potential glare areas. But Now we need to know if this solar heat gain concentrated by the concave facade will create uncomfortable areas on the ground.

Is there a way that I can measure temperature on a given surface that is heated by reflected solar rays or simulate (using LB comfort components) if a person standing on the sunlit area will suffer from the solar heat gain because of that façade.

Please see image bellow for graphical explanation

Thank you all

cheers

Replies are closed for this discussion.

Replies to This Discussion

Permalink Reply by Chris Mackey on October 16, 2016 at 11:11am

Ernesto,

The reason for the different results with the the same simulation is Radiance's stoichastic way of ray-tracing. It's still accurate and see these other discussions.

2C seems pretty reasonable when talking about MRT differences from the sun. In many cases you can get MRT differences as large as 20 C between sitting in the sun and sitting in the shade. This is the consensus of many experts like those at the thermal comfort research group at the Berkeley Center for the Built Environment, who established the method used here and published to a peer-reviewed scientific journal:

http://www.sciencedirect.com/science/article/pii/S0360132314002960

-Chris

Permalink Reply by Arie-Willem de Jongh on August 21, 2015 at 12:56pm

Chris, Claudio, Abraham,

Thank you all for your swift responses!

@ Chris, thanks for your very extensive explanation, I'm about to tryout what you described above and let you know how it turned out. What I figured yesterday is that the increase in radiation because of the reflective facade for the 'worst' month is only about 2-3 kWh/m2 as your looking at a value of 80 without and 82-83 kWh/m2 with reflection.

So my assumption is that the glare factor will play a much bigger role instead of intensity of the sun, looking at comfortable levels. So I'm looking in this as well. It's very cool to play around with these plugins and see the outcome. I'll keep you guys posted.

@ Claudio, that was exactly my problem as well. I presented a direct sunlight hour analysis, to show the increase in direct sunlight hours because of the mirrored facade and at what times of the day the reflections occurred. But it is hard to asses if this is 'bad' or 'good'. The restaurant in question receives more or less 130 direct sunlight hours 'naturally' in the worst month and because of the reflection the result was 161 direct sunlight hours, but the client was like okay..... and is this a problem? So we decided to look at sun intensity but I didn't want to fall into the trap of in the end presenting kWh/m2 and having the same problem not knowing if this is 'comfortable' or 'annoying' etc. Good luck with your study, I'll post my findings

Thanks again guys

Permalink Reply by Chris Mackey on August 23, 2015 at 1:46pm

Arie,

Glad to be of help and keep us posted.

I will say that, from my own experience (both in simulation and in the real-world), it is very difficult to be comfortable when sitting in direct sun. If you are indoors, direct sun will almost certainly make you feel too hot and it is really only in cold outdoor conditions that the sun really starts to become desirable. The only times that I have ever seen direct sun making the indoors comfortable is around sunrise on winter mornings, when the solar radiation is not too intense and the indoor temperature tends to be cold enough to make the sun seem desirable.

The other major reason why direct sun is usually uncomfortable is glare, which you will (almost certainly) have in any case of direct sun unless you are wearing sun glasses or keeping your head down looking at a (non-reflective) ground. It may be worthwhile to run some Honeybee glare simulations in order to understand how this will affect your specific case.

-Chris

Permalink Reply by Arie-Willem de Jongh on August 25, 2015 at 4:57pm

I've run some tests and everything seems like the way it should behave in real life =) There is one thing that I could not quite make it work and that is the honeybee convert hdr to gif component.

If I switch the option to false it works, but if I switch the option to true (which is what I want in the end) the image being generated has a file size of 0 kb. I looked in the code and found the rad_gif.exe from radiance is doing the converting(?). Maybe the issues lies there I'm not sure.

The weird thing is that sometimes it works and I get an adjusted exposure image, but for the majority it fails.

We should have the analysis within the next two weeks, I'll post some findings here.

Cheers!

Permalink Reply by Chris Mackey on September 6, 2015 at 9:51am

Arie,

I feel like I have encountered this error myself, although the last time it happened to me, I was working to a deadline and did not have the time to debug it. It may just be that some images are not able to handle an adjusted exposure. If you upload a GH file with the error, I can look into it for you. Mostapha might also have some input as the creator of the component.

Cheers,

-Chris

Permalink Reply by Mostapha Sadeghipour Roudsari on September 6, 2015 at 3:17pm

I'm almost sure this is because you have an old version of Radiance which has a bug in "pcond". Update Radiance on your machine and the error will be solved: https://github.com/NREL/Radiance/releases/tag/5.0.a.4

Permalink Reply by Chris Mackey on September 8, 2015 at 10:33pm

Thanks, Mostapha. Good to know.

Permalink Reply by Arie-Willem de Jongh on September 21, 2015 at 10:50am

Hi Chris, Mostapha,

Updating my Radiance did the trick! Thanks a lot!

Cheers!

Permalink Reply by Dennis Goff on May 18, 2017 at 9:03am

Hi Chris,

I realize this is an old thread, but this is exactly the problem I am currently working on, and I came across this file and have run into some issues. I've been testing this out and it works well on certain days, but others it seems to return no data. I've attached an image of December and March 21. December works correctly, but March is returning all 0s for cumulative radiation out of the honeybee daylight analysis.

Attachments:

December.jpg, 1.4 MB
March.jpg, 1.4 MB

Permalink Reply by Chris Mackey on May 18, 2017 at 4:10pm

Dennis,

March 21 is working fine for me (see attached GH file).

-Chris

Attachments:

ComfortableAnalysis_v1_CWM.gh, 559 KB

Permalink Reply by Claudio on May 18, 2017 at 7:55pm

Hello Everyone,

I know this is an out of date post. But I'll like to thank everyone for your interest in this thread. It really helped me a lot. The project went well and its now under construction. I'll be able to post some images as it gets build. I'm proud to say that HB-LB where part of our design toolbox.

Thank you

Cheers

Permalink Reply by Dennis Goff on May 19, 2017 at 10:41am

Thanks Chris,

I have figured out my issue was in my weather file. The days I was testing had little to no radiation for most hours, so by tweaking to a day close to the desired date, I got it to work.