So since there still seems to be no definitive answer, I tested it myself in single player on PS4 with default settings. I tested several things and I will provide the findings first, and the methodology second.
Finding 1
Building materials do have an effect on temperature of your character. BUT, they seem to only have a positive effect. By this I mean that a heat building (ex: Aquilonian) can help push your temp down in hot areas, but a cool building (ex: Black Ice) won’t push your temp up in hot areas.
Implications: This means that you don’t need to worry too much about which building type you use in any area unless you want a bonus to dealing with that area’s temperature. So if you want to build a Black Ice building in the volcano, you can, it won’t push your temp any higher than it would be with no building. But if you want a temp bonus from your building, that is still also possible: building an Aquilonian building in the volcano will help lower your temperature.
Comments: I actually like this. It feels like getting the best of both worlds and doesn’t penalize you too much for creating a building with the style you like best.
Finding 2
Only walls and ceilings (above you) seem to affect the character’s temp. Floors (aka what you are standing on), whether it is foundations or ceilings do not seem to have any effect on the character’s temp. Interestingly, you only need one, either walls or ceilings, to have the same effect on the character’s temp. If you have both, they do not seem to have more of an effect (check images 3 & 4 for the reasoning).
Implications: You only need to have either the walls or the ceilings have the desired temp effect to get that effect, for example you could have Black Ice foundations and walls, but Aquilonian ceilings in the volcano to get the same level of heat reduction as an entirely Aquilonian building.
Comments: This makes sense because otherwise there would probably have to be some complicated formula to determine how much temp effect you would get from each building piece which would be hard to build around.
Finding 3
Since I was already doing temperature experiments, I tested normal, glow, witchfire, and radium standing torches. Normal torches have a heating effect, glow torches have a cooling effect, and both witchfire and radium torches did not seem to have any temp effect. I did this by spawning in some after my initial tests and seeing what they did.
Methodology
In single-player on PS4, I went to the structure housing the obelisk in the Volcano region. I put enough heat reduction armor on to get my default temp as “Very Hot” so that any changes in temp would be visible. I then built separate, non-attached, 3x3 square buildings with 4 high walls and flat ceilings along with a doorframe and closed door. I varied which pieces were Black Ice, and which were Aquilonian to see their effect on character temp when inside and under full “Sheltered” condition. I would then walk into each structure, close the door, get full “Sheltered”, then wait several minutes for the character temp to change and stabilize. No torches were in the buildings at all (that would have tainted the results). Below are the results, and form the reasoning behind my above conclusions.
Image 0 – Outside
This is just the default temp with the gear I have on showing I am next to the obelisk in the Volcano for this experiment.
Image 1 – Black Ice Foundations, Walls, and Ceilings
There was absolutely no change in character temp upon entering as compared to outside.
Image 2 – Aquilonian Foundations, Walls, and Ceilings
There was a noticeable change to character temp as it went down to “Soothing” purely by being inside the structure.
Image 3 – Black Ice Foundations with Aquilonian Walls and Ceilings
Notice that the character temp also went down to “Soothing”, and to the same level as with all Aquilonian building pieces. 1st part of the reasoning behind Finding 2.
Image 4 – Black Ice Foundations and Walls with Aquilonian Ceilings
Again, notice that the character temp also went down to “Soothing”, and to the same level as with all Aquilonian building pieces. 2nd part of the reasoning behind Finding 2. I couldn’t figure out an angle that would show there are Aquilonian ceilings along with the Black Ice Foundations, but the fact that is looks exactly like Image 1 yet the temp is “Soothing” should tell you there obviously is something different going on in this image.
Image 5 – Aquilonian Foundations with Black Ice Walls and Ceilings
Notice that there was no change whatsoever from the temp outside just as in Image 1. Again, along with Image 3, this proves the floor has no effect.
I also did 2 more tests. One with Black Ice Foundations and Ceilings with Aquilonian Walls which again had the same cooling effect as Images 2, 3, and 4. Another with Aquilonian Ceilings tiles as floors with Black Ice Walls and Ceilings which again had no effect like in Image 5. I did not add these as images because they would look exactly the same as Image 3 and Image 5 respectively, so you’ll just have to take my word on those (I swear I’m not lying!).
Limitations
Again, this was done in single-player on PS4 with default server settings. It was done only in the Volcano region with Black Ice and Aquilonian structures. Therefore it is possible that these results may vary in different conditions. This would indicate different game mechanics though which seems unlikely, but I wanted to make sure you knew the full scope of the testing I implemented.
Final Word: I wasn’t initially going to write basically a research paper on this, but I ended up typing it up and saying, “Ah what the heck, might as well make it as accurate as possible”. So hopefully this helps anyone else searching for the same answers. Also, Funcom, please keep these settings the same. I like how they are now, and I don’t want this post to become obsolete with some random patch in the future lol. Have a good one exiles!
. For more intel communicate with Wak4863, i am sure he will have something good to add.