LEED review comments for System 5 heating source

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Dear eQuesters,

I just got LEED review comments for my project. Our proposed design is
VRF system with roof top unit providing ventilation air. Roof top unit
is using gas as heating source. There are misc. elec. heaters in the
building for places like entries. I interpreted my building heating
source as "electric hybrid" and used hot water fossil fuel boiler as my
base design. The comments I got read as the follows:

Section 1.1.A of the form indicates that the primary heating source is
fossil fuel. However, the electric heating energy use reported in Table
EAp2-5 for the Proposed Case exceeds the fossil fuel heating energy use.
Please verify that the correct heating source has been selected. If
electric heating is the primary heating source, please change the
Baseline system type accordingly. Provide updated simulation results and
a revised Prerequisite Form as necessary.

I couldn't find an official definition either on LEED reference book or
90.1. What is your take on this?

Your input is highly appreciated! Thank you very much!



Li, Lan's picture
Joined: 2011-09-30
Reputation: 0


90.1-2007 requires a system 5 with a fossil fuel hot water boiler as you have
modeled, but in 90.1-2007 Table G3.1 Number 10 HVAC Systems Base Building
Performance column it states that you need to meet any system-specific
requirements in Section G3.1.3.

In G3.1.3.2, it states that for system 5, the boiler plant shall use the same
fuel as the proposed design, which in your case is electric resistance and
compressor heat pump energy. I would model electric hot water boilers.

Paul Diglio

Paul Diglio's picture
Joined: 2011-09-30
Reputation: 400


Since you said that your rooftop unit which is providing your outside air
uses gas, I think you have modeled it correctly. Something you might want to
do is look at using a different thermostat schedule for your electric
resistance heaters, It sounds like it might be justifiable to set them to
meet a lower heating temperature. As long as you keep the schedule for them
the same between the baseline and the proposed building you should be okay..


cmg750's picture
Joined: 2010-10-05
Reputation: 0