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Mechanical Ventilation is not being optimized - BEopt

asked 2020-11-18 23:59:23 -0600

EnergyModeller gravatar image

updated 2020-11-19 12:57:19 -0600

Hi,

I am developing a retrofit strategy for poorly built homes from 1960s to be Passive House ready. I have developed a series of assemblies (Figure 1) to be optimized in my house (Figure 2). However when I run my simulation the mechanical ventilation always sticks at "none" regardless of the price the efficiency and energy consumption. I have even tried dropping the price to $0 for equipment and made the HRV/ERV super energy efficient while still having a high SRE. Figure 3 is the inputs I currently have for my BEopt Model. Please let me know what you think.

Thanks!

image description Figure 1: Optimization Levels

image description Figure 2: Geometry

image description image description Figure 3: Imputs

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answered 2020-11-19 09:31:17 -0600

updated 2020-11-19 13:53:09 -0600

Whole house continuous mechanical ventilation nearly always result in higher energy use than having no such system. After all, you are bringing in outdoor air that needs to be conditioned to the thermostat setpoint (plus using fan energy to do it). Mechanical ventilation systems are designed to improve indoor air quality, not save energy. Even systems with heat recovery will result in higher energy use than no system, though "less high" than systems without heat recovery.

In general, it only makes sense to optimize across mechanical ventilation systems that provide the same level of indoor air quality. In your example above, that would mean deselecting the None option, so that the optimization is evaluating different HRVs/ERVs that all provide the same amount of airflow (100% of ASHRAE 2010 requirement).

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Asked: 2020-11-18 23:59:23 -0600

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Last updated: Nov 19