Understanding the outputs of the Read Room Energy Result Component

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Hello Ladybug Tools Community,

I have run an energy simulation for a building with 21 zones on 3 levels, and am using the Read Room Energy Result component to analyse the results of the simulation.

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I am using the IdealAir component to set up the HVAC system.

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My main reason for doing this in the first place was to understand how much energy is being used by the building HVAC system to mechanically ventilate the spaces. The building has no natural ventilation.

On closer inspection of the tool tips explanation text for each of these ouputs…

For mechanical ventilation:

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And for cooling:

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So this raises a question:

Since I am using the IdealAir component, does this mean that the cooling loads are the heat being removed? Will I need a different Honeybee HVAC component to determine the energy spent on cooling? Or does this come from the HB End Use Intensity component?

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Finally, the mechanical ventilation load output, based on the tool tip text, indicates that this is the net heat gain/loss (in this case a loss because it is negative) due to mechanical ventilation. But how can I determine how much energy is spent on running the mechanical ventilation system? That is, how much energy does the building demand to move fresh air to the rooms, and how can you determine this? Is the calculation of energy use for mechanical ventilation a much more complicated process?

Apologies for the number of questions scattered within a single post, but please let me know if you have any insights on any of these questions, looking forward to seeing your responses :slight_smile:

Cheers,
Anthony

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Hi @anthony.schneider,

An IdealAir system will tell you how much energy the system needs to deliver to meet the room set points - not how much energy the system uses to deliver it. And so the EUI for an IdealAir system is pretty meaningless.

Full details of IdealAir system here:

The other HVAC system options are intended to calculate the energy that the system uses, including fan energy for mechanical ventilation, and the system efficiencies to that convert energy delivered to energy input.

For heating and cooling you could roughly apply system seasonal coefficients of performance on the IdealAir outputs to give the annual energy those systems consume. Likewise for mechanical ventilation, if you get the air volume you could apply an indicative fan power used to move it to give the annual energy associated.

Cheers,
Charlie

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Hi @charlie.brooker ,

Thanks for getting back to me, much appreciated!

In this case I will need to change to one of the All-Air or DOAS components instead of the IdealAir component, since the outputs I would like to determine in my energy model is the EUI, the cooling energy demand, the heating energy demand, and the carbon emitted by the grid to supply the building.

Cheers,

Anthony

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