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NC-v4 EAp2:Minimum energy performance

Modeling Proposed DHW with Insulation

Hi I am Modeling a DHW system and most of my savings are coming from Insulation in the heater tank, now the LEED reviewer said that the savings should be modeled with Exceptional Calculation MEthododlogy, How can I do that, what I have done is for the proposed model I included 2inch insulation in the energy model, what can I do?

 

TIA

 

Rajat

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Wed, 01/31/2024 - 19:34

Hard to say without more details. Not sure an exceptional calculation is the right path? Typically the determination of a water heater's efficiency includes the level of insulation for the tank. This gets included in the EF determination and obviously in the standby loss. So are you double counting by adding more insulation in the model or are you actually adding extra insulation to the tank? If you are adding extra insulation then an exceptional calculation should be pretty easy. The baseline remains the same. For the proposed model it with and without the extra insulation so you can isolate the savings associated with the extra insulation only and report that to the reviewer.
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Jamy Bacchus
Associate Principal
ME Engineers
LEEDuser Premium Member
29 thumbs up

Wed, 01/31/2024 - 19:59

...So many relevant related topics here: how to model different premise piping distribution layout types, getting updated usage schedules vs possibly outdated COMNET ones, right-sizing centralized HPWHs. We need better data to do better designs and to create better tools. This will then permit better analyses of things like heat recovery options to cover said loads. 

***END OF RANT***

Wed, 01/31/2024 - 20:04

This is the Comment from the LEED,   
  1. The service water heating savings are attributed to the insulation in the Proposed heater. However, the energy savings due to the insulation on service water heating should be modeled using the Exceptional Calculation methodology.
Now Both Baseline and Proposed have electric water heater and I am using 100% efficiency for both and for proposed I am adding a 2inch insulation which is getting us some savings.
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Wed, 01/31/2024 - 22:32

Electric water heaters are not 100% efficient. You need to use the Energy Factor. Did the project actually add an additional two inches of insulation beyond what came already installed on the tank? Is there any difference in the hot water demand due to low flow fixtures? No other differences beside the insulation? If all of the hot water savings are attributable to the extra insulation then it makes no sense to require an exceptional calculation as everything else is already identical and that is basically already the calculation they need. It only makes sense if they are trying to see the savings of the additional insulation separate from some other EEM.

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