IECC C505 Energy Use definition

[lessthantag]

Hello all - I have a project within a small portion of an existing building that is undergoing a change in occupancy and it is assumed to increase energy usage (going from a retail store to a restaurant). As such, we will need to bring our space up to the current version of the code, no issues understanding that.

My question is, what defines the prior and new energy uses that you are comparing to determine you will in fact use more energy? I do not have energy/utility data from the prior tenant to understand what it used to be, and my project will be done prescriptively (no energy modeling). What if it was a horribly old and inefficient office space, but the intended new program is a highly efficient library, how does one prove they will be using less energy with the new project? Should you use the median Energy Star EUI metrics? Or are there other EUI databases that folks have referenced before?

Thanks!

 

[Mr. Inspector]

just guessing. service upgrade, larger breakers, new or enlarged gas lines, longer open hours, appliances added, air conditioning added.

 

[steveray]

Put an engineers seal on it.....I am a little confused as you mention a new restaurant and a new library?

 

[Paul Sweet]

HVAC envelope heat losses & gains probably won't increase, unless you're adding windows. People and ventilation loads will increase because you're going from one person per 60 SF (Mercantile) to one per 15 (Assembly). A lot of new energy will be used for cooking, makeup air for the hood, and hot water for dishwashing. Lighting energy probably won't change much, and may even decrease, especially if you change to LEDs.

 

[lessthantag]

Thanks for the replies all. I certainly agree that the new restaurant will be using significantly more energy than the prior occupancy.

But I guess what I'm getting at is, is there are hard and fast database or something to point to that says "this type of occupancy uses X kbtu/sf/yr and this other type uses Y kbtu/sf/yr, therefore we expect the new space to use more energy"? Even if one does an energy model of the new space, what do you do about comparing it to the existing space type (since you presumably don't have utility data from the prior tenant)? Or as Steveray alluded to, is it simply up to the engineer's discretion and to convince the AHJ?

Steveray - the library and office were a hypothetical in my case; I was attempting to identify two space types that use similar amounts of energy, specifically because in my mind it would be difficult to state unequivocally that one would use more energy than the other.

Rick - those certainly could be used in a pinch to try to justify reduced or increased energy consumption.