Baseline vs proposed fuel consumption problem

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Here's a question for you equest folks out there!

I'm working on equest modeling for LEED cert. The project is a religious worship building here in Alaska. It was built in 1940's with CMU exterior walls and minimal interior insulation.
The proposed model shows how we added 5" of EIFS along the exterior, new interior wall furring with insulation and we added a substantial foam buildup on the roof.

We also replaced all lighting with LED, along with completely new HVAC and heating systems.

The baseline model shows the lightweight assembly types from ASHRAE Appendix G table 5.5-8 (for our climate zone). All the R values, U values and thermal reflectance are compliant with ASHRAE minimums for Alaska.

Proposed and Baseline building envelopes are accurately modeled.

The fuel type currently in my proposed model is fuel oil (Condensing HW Boiler).
The fuel type currently in my baseline model is natural gas (Packaged VAV/ac system type 3 - required for this climate zone).

My question is: Does the baseline need to show the same fuel type as in the proposed or does ASHRAE Appendix G determine the fuel type as natural gas?

Here's the problem...
My gas consumption is very high in proposed model when compared with the baseline.

My baseline Gas consumption (BtU x000,000): 3044.1
My proposed Gas consumption (BtU x000,000): 4552.3

My baseline Elec consumption (kWh x000): 208.74
My proposed Elec consumption (kWh x000): 147.43

But we don't feel this accurately depicts the annual cost savings we provided. The proposed gas consumption should be less. Not the other way around.

Could something as simple as fuel type be driving this difference?

I should note that FM1 (fuel meter 1) is the same in both models with utility rate at $3.95 per unit (which is from published data for local fuel oil cost).

Chris Baker
CCI CAD Drafter


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Chris Baker2's picture
Joined: 2014-03-25
Reputation: 0

Based on past experience, the increase in gas consumption may be a result of installing LED lighting. The interactive effect of having more efficient lighting is less internal heat gain, which ultimately increases the need for more space heating.

Gregory Stevens's picture
Joined: 2015-03-03
Reputation: 0

Yes, the Baseline System 3 furnaces should use the same fuel as the proposed building. This is explicitly worded in the 90.1-2007 User's Manual, p. G-23 and also in the 2010 User's Manual.
If this is a LEED V3 project, the Baseline envelope should reflect the existing conditions prior to any improvements in the project scope. Looks like you are using ASHRAE minimums instead.
There are many reasons the fuel consumption could be off. Someone might look at your model if you share the files. (Not me today. Trying to get some work done.)

Best of luck,

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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Bill Bishop's picture
Joined: 2012-02-25
Reputation: 7

I agree with Bill. Often, a second pair of eyes can quickly determine something you don't see in the model. I can likely find a bit of time today to look through the model.

Christopher Jones, P.Eng.
Tel: 416.644.4226 * Toll Free: 1.888.425.7255 x 527

Chris Jones
crollinjones's picture
Joined: 2013-12-12
Reputation: 0