EcoDesigner STAR – Thermal Bridging Simulation Part 2
Now that the geometry is ready (discussed here), we can actually launch the Thermal Bridging Simulation. Go to the Design/Energy Evaluation Menu and then select Thermal Bridge Simulation. If your active window is a detail, that window will be the one selected. If you’re in another view, you’ll be prompted to select which detail you want to analyze.
Boundary Condition – External Air
First we designate the external air by selecting the representative fill. We can then either go with the defaults for external air temperature and external heat transfer coefficient or customize them. For our first explorations, I’d suggest going with the defaults.
Boundary Condition – Internal Air
Designating the internal air is no different. Likewise we have internal air temperature and internal heat transfer coefficient that can be tweaked or ignored. When selecting air, remember to hold down shift if you need to designate multiple fills. In this scenario, I have two fills for interior air. I think one of them probably could be ignored, considered airspace, or just modeled in a way that it doesn’t exist. What’s nice is that already the Thermal Bridging Simulation is making me think about the design of my detail.
By now you’re a pro at selecting fills and designating them as Boundary Conditions. You’ll notice on the left is the soil type, which by default is set to Gravel. On one hand, that’s fine if you don’t know what the soil is. For my purposes not stressing about the soil type seems wise. I’m sure I could dig through some reports and easily find the correct soil conditions. In the future, when I look at data from the surveyor or civil engineer, I will make sure to make a note of soil descriptions. That is a simple tweak of my process.
Default settings are okay for some things. BUT… not for everything. Click on the Change button next to soil type. We’re not going to worry about the soil, but clicking this button will bring up the Environment Settings. We’ll return to the Environment Settings again and again as we learn EcoDesigner STAR, so we don’t have to learn everything right now. In fact, we can ignore almost all of it, for the moment. Click on Project Location.
The first two lines of Project Location are the Project Name and Project Address from the Project Info. For other reasons you should have these filled out, but for Thermal Bridging Simulation this is just fluff. Instead we want to make sure the Latitude and Longitude is correct. The easiest way to do this is to pick a city from the list. If you want to be more specific or you’re not working in one of the default cities, you can manually put in the coordinates. Using various sources on the internet, it should be quite simple to know the exact location of any project you are working on. Once we have the coordinates, we can input the altitude, time zone, and make sure north is in the right direction. Whether or not Thermal Bridging Simulation needs all of that doesn’t matter, it’s easy to input, so we might as well do it now.
I’m not sure how Surface Heat Transfer affects our exploration, so I’ll ignore it for now. Hopefully later research or the eventual help documentation that will come with EcoDesigner STAR will shed some light on those variables.
In the next post we’ll assign thermal properties to our fills and finally be ready to hit the Start Simulation Button!
Until then, think about this:
What if you want to do an analysis of an internal wall and its relationship to the ground? In this scenario there is no external air, but EcoDesigner STAR demands that you select both internal and external air. Here’s a potential solution: set the internal and external air temperature and heat transfer coefficients to be identical. Then select one side of the wall as ‘external’ and one as ‘internal’. It doesn’t matter which is which. That theoretically should mean the air on both sides of the wall are the same, thus mimicking an all conditioned space. Anyone from Graphisoft HQ reading this want to confirm or refute that guess?