OpenStudio Tips - Natural Ventilation-Windows

We discuss how to download and implement the OpenStudio measure "Add Wind and Stack Open Area". This measure simulates opening a casement or door type window for natural ventilation. It takes into account wind driven air exchange and thermal bouyancy "stack" effect air exchange. Transcript: I get a lot of questions about how to do natural ventilation. There is a number of ways that you can approach natural ventilation. We will focus on one of them in this episode; adding a natural ventilation object to your windows on the building. That object is called ZoneVentilation:WindandStackOpenArea. This is a download that you can get from the Building Component Library. If we go to the BCL and we search for "stack"... Here it is. It is called Add Wind and Stack Open Area. You can download this measure and put it into your my measures directory. I discussed this in some of my other videos. Unfortunately this version in the building component library, at the moment, is an older version. It is not compatible with the most recent version of OpenStudio. What can we do? We can go to GitHub.com. Search for Building Performance Simulation. One of their repositories, OpenStudio Measures, has...they are updating many of the EnergyPlus measures to be OpenStudio measures. We can go into their Library, measures, and then add_wind_and_stack_open_area here. You would have to download all these folders and files and place them inside your my measures folder. I discussed this in my previous video, but you can go to the measures Tab and easily open up your My Measures folder with this button down here. So, that is where you would place these downloaded files. You would place them in their own folder called add_wind_and_stack_open_area. That way you can access those through OpenStudio. So, what does this wind and stack open area measure do? It is based on some ASHRAE research...it is based on a typical door or a casement type window that that swings outward. It has an opening area from the very bottom of the window to the very top. From the very bottom of the door to the very top of the door. If we look at casement windows...and...I am trying to find a good example... A casement window is very similar to a swinging door. It opens very much like a door. We can just take a look at this one right here...just do a Snipping tool...and we will just do this...so we can draw on this. What does this add_wind_and_stack_area measure do? It looks at two different calculations from ASHRAE fundamentals. There is a wind component and it uses this equation here. It is based on open area, the effectiveness, the angle of the window to the wind, the actual open fraction of the window, and the wind speed. That is the wind component of the equation. The other component of the equation is a stack effect. This equation here. It is based on a temperature difference between the outside air and the Zone temperature. It is also based on a height difference between the neutral pressure level and the open area fraction...how open is the window...and then the actual window opening area and there is a discharge coefficient of the opening. What is this stack effect doing? It is modeling a thermal bouyancy stack effect. Basically, when you open the window there is a neutral pressure level here somewhere in the middle of the window. Air is getting sucked in at the bottom portion and air is discharging out the top portion of the window. So, this measure is combining the stack effect and the wind effect as a quadrature sum. It is calculating a ventilation rate for that room. Let us look at our model...we have a typical building. This was generated with the Department of energy prototype measure. It is a typical, standalone, office building. It has a number of Windows and doors located around the building. All of these windows on this model are are called fixed windows. So, the first thing to note with this measure; we have to change these windows to operable windows. You can go to the spaces tab...and go to subsurfaces...we can search by subsurface type...we can look for fixed windows. We want to change all of these to an operable window type. We will change that one and then we will apply to selected. That changes all of our windows in the building to operable windows. You can change whatever windows you want. For this example we are going to assume that all the windows in the building are operable. We will click save. The next step is to go to the measures tab. The measure that we are looking for is located under Library, envelope, fenestration. ... Complete transcript: https: //www.helix-engineers.net/technical-articles