IanVG
Mechanical
- Jan 21, 2022
- 76
I am tasked with designing a two AHU replacement system for one floor of a five story university building built in the 1960's (includes mostly offices, small classrooms, computer labs, and a research laboratory (exhaust required)). I was told to consider infiltration to determine how positive my building should be. Air is currently returned to the AHU via the hallways. There is no return air moving in the plenum space. All rooms have ~8 drop ceiling (2x2 ceiling grid system). The construction below the ceiling grid is different from above. There are large windows on each face of the building and the building is a rectangular shape. The windows are known to be leaky (allows water and spiders in). I have been reading through some ASHRAE handbooks, articles and journals but feel no closer to an answer. I feel like a lot of words have been spilled over how to perform tests to determine how leaky a building is - that is not useful for me, as I will in no way have the money or the will of the owner to perform that test.
I am looking to estimate how positive (OA CFM - Exhaust CFM) I need my entire floor to be to prevent infiltration of outside air into the building. I also have a lab space that includes these leaky windows, so maybe estimating the amount of OA coming in through the window would be nice.
I am getting too far into the weeds, and I believe I am looking for simplified plug-n-play values here. E.g. cfm/sf, turnover, etc. Does anybody have recommendations on how to proceed? No one in my office has done a calculation like this, and I honestly don't know where to begin. Does anyone have any recommendations? I am attaching a floor plan of the fourth floor (where I plan to do my work).
I am looking to estimate how positive (OA CFM - Exhaust CFM) I need my entire floor to be to prevent infiltration of outside air into the building. I also have a lab space that includes these leaky windows, so maybe estimating the amount of OA coming in through the window would be nice.
I am getting too far into the weeds, and I believe I am looking for simplified plug-n-play values here. E.g. cfm/sf, turnover, etc. Does anybody have recommendations on how to proceed? No one in my office has done a calculation like this, and I honestly don't know where to begin. Does anyone have any recommendations? I am attaching a floor plan of the fourth floor (where I plan to do my work).