District heating/cooling and On-site renewables

Colin Day

Sustainable Building Associate, LEED GA

The Institute for the Built Environment

LEEDuser Basic Member

0 thumbs up

September 27, 2013

Hello Eliot, The project I am working on is a mixed-use (mostly residential) neighborhood. There will be solar PV on every home as well as ground source heat pumps. The client and achitects are aiming for net-zero. They seem very confident that all exemplary performance points dealing with energy will be achieved. However, they also plan on having a district heating and cooling system. The on-site renewables and ground source pumps will acount for much of the energy and heat needed. Where does this leave the points for GIBc12? The credit language states that district heating and cooling must account for 80% of the project's annual heating and cooling. If the majority of that is already accounted for through other measures, and it is not necessary that the district heating and cooling system supply 80%, does that mean that the credits are rendered unachievable? Thanks in advance! Colin Day

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Eliot Allen

LEED AP-ND, Principal

Criterion Planners

LEEDuser Expert

231 thumbs up

Fri, 09/27/2013 - 21:56

Colin, you raise an interesting point. First, the project's thermal demand should be calculated after GIBp2 and c2 have been taken into account. The solar PV isn't relevant to thermal supplies, so you're left with determining how much of the thermal load will be met by the ground-source heat pumps. If that share exceeds 20%, you've got a problem meeting the required DHC 80%. But you might have a good argument for a CIR if a lesser DHC share is being offset by an equal or better efficiency alternative. The bottom line for GIBc12 is delivering thermal Btus more efficiently that baseline conditions. Eliot

Colin Day

Sustainable Building Associate, LEED GA

The Institute for the Built Environment

LEEDuser Basic Member

0 thumbs up

Mon, 09/30/2013 - 16:10

Great, thanks Eliot. That makes a good deal of sense and confirms what my thinking has been about this issue. You say the PV isn't rlevent to thermal supplies, which I do understand, but what if the PV is linked to HVAC systems? Thanks again!

Eliot Allen

LEED AP-ND, Principal

Criterion Planners

LEEDuser Expert

231 thumbs up

Mon, 09/30/2013 - 16:23

Power for HVAC fans/controls falls outside of the credit's thermal production scope that's limited to "heating and/or cooling consumption." So it's the production of the thermal Btu, not ancillary power to distribute it.

Colin Day

Sustainable Building Associate, LEED GA

The Institute for the Built Environment

LEEDuser Basic Member

0 thumbs up

Mon, 09/30/2013 - 16:38

Crytal clear, thanks Eliot!