Existing Building Constructions modeled for LEED

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Greetings everyone,

I am going to be modeling an existing building as a "major renovation" under LEED NC 2009. Per the App G Guidelines, I will be using all of the constructions that exist in the existing building as opposed to creating constructions as per 90.1 for the baseline model. However, I have come across an interesting situation that I have not dealt with previously. We will be adding a large data center to an interior space on the top floor, which is currently just office space. Currently there is no insulation in the walls and floors surrounding this new data center and it is throwing the HVAC systems assigned to adjacent spaces way out of whack. Though I would like to be able to take some credit for properly insulating the interior constructions surrounding the new data center, it doesn't seem appropriate to leave the baseline with completely uninsulated interior walls and floors.

I am wondering if anyone has come across this issue in the past and how you may have handled it. Please feel free to contact me directly if you need more information or have any questions. Thanks in advance for your comments.

Cheers,

Ross Farris, CEPE

Ross Farris's picture
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Ross,

I've always modeled partitions identically for the baseline and proposed models, even for existing buildings. The wording in Appendix G is "For existing building envelopes, the baseline building design shall reflect existing conditions..." Interior partitions are not part of the building envelope, and are not covered in the Building Envelope Requirements Tables 5.5 in ASHRAE 90.1. If you are insulating the walls around the data center, I would do the same in both the baseline and proposed models.

You didn't elaborate on what "out of whack" means for the HVAC systems. In case you are not already doing it, the data center should be modeled in the baseline with its own single-zone system per G3.1.1. If the concern is that the data center is so cold that it is causing heating in adjacent spaces, you could use this opportunity to educate the design team/client regarding recent research that shows data centers don't have to be kept as cold as conventional wisdom has dictated. Don't forget that the data center constitutes a large process load that should be modeled identically in the baseline and proposed models, and that this offers an opportunity for energy savings through heat recovery, efficient cooling, etc.

Regards,
Bill

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Bill Bishop's picture
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Bill,

Thanks for the response. For now I am going to leave the walls insulated in both models. I may keep digging a bit further to see if anyone has taken credit for interior construction insulation in the past.

As for the systems. Yes, I have the Data Centers on PSZ systems. The "out of whack" that I was referring to was too much heat being transmitted through the slab to the floors below and that heat wasn't being accounted for when the system for the floor below was sized based on the loads within its assigned spaces. Therefore, the systems for the adjacent spaces to the data center (both below and beside) had cooling hours out of range. Some spaces were never going below 85 degrees so I had to force up to 5 CFM/sf(min design flow) into some of the spaces to make the system autosize properly. Inputting the proper insulation eliminates these issues.

As for your points regarding both educating the client about the design conditions acceptable for a data center and regarding energy savings from the heat recovery and conditioning for the data center, yes definitely. I couldn't agree more.

Thanks again for the insight!

Regards,
Ross

Ross Farris

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