[Bldg-sim] Query on Night Flushing: Approaches for quantifying savings

[Timothy Moore]

Jeetendra,

I would suggest that you actually model the night flushing (whether this is flushing the occupied space or a thermal mass like TermoDeck hollow-core slab), as the performance and limits to this approach will be specific to the climate and the particulars of the design, including thermal mass, airflow rates, control strategies, etc.  In doing so, you'll want to use thermal comfort requirements, such as operative temperature at the beginning of the occupied hours, to limit the night flushing. In other words, it's important to avoid overcooling the space or taking credit for night flushing that does so, as this will tend to be offset by heating (in the model, actual use, or both). Also, be sure to fully account for fan energy in your model. If the night flushing must drive air through a convoluted path, you will need to account for the pressure the fan needs to overcome in doing so. If, on the other hand, you're using natural ventilation for night flushing, then you'll need to prepare an appropriate model of that using a bulk-airflow network or similar approach with suitable wind pressure coefficients,  description of operable openings, control of those openings, and pressure/buoyancy driven inter-zonal airflows. If mixed-mode, you really need to include both in the same model to understand the interactions.

Cheers,
Timothy

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Timothy Moore
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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Greentech Partners
Sent: Thursday, March 20, 2014 11:10 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Query on Night Flushing: Approaches for quantifying savings

Hi All,

Could someone share an understanding on the commonly used approaches for quantifying the savings from night flushing.

Hope it's also possible to connect with members who have worked on night flushing based opportunities. If possible, please share any examples/details.

Regards,

Jeetendra.
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