Building Envelope Comparison

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Hi all,

I am trying to compare a mixed use building type for its building envelope ( for roof, exterior walls and windows with ASHRAE 90.1 -2007 baseline). I have maintained HVAC , Lighting and misc loads as default in eQUEST.

The proposed roof, walls and windows R and U values are fairly good.

Can anyone throw some light on range of percentage savings on should expect?

I have run the eQUEST program by maintaining two files to compare the envelope. I have never tried parametric runs so far. Do you think parametric runs should be a better option here?

Your responses will be appreciated.

Thanks,

Sunayana Jain

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Sunayana,

The savings from envelope "upgrades" can vary depending on the building characteristics. If the building has low internal loads (like a house), then envelope upgrades help quite a bit. If the building has high internal loads (like most commercial buildings) then the savings from envelope upgrades are often minimal and can be net negative over the year, especially if there is no airside economizer. With a mixed use building, additional insulation may be beneficial for part of the building but not for other parts!

I often use parametric runs when the change is relatively simple, like changing a number or just selecting a different option from a dropdown menu. Global parameters help simplify making changes with parametric runs. I create a separate file only if the changes are too complex to easily manage with parametric runs. Keeping the change in the same file using parametric runs makes comparisons easier.

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Keith Swartz, P.E., LEED AP

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