Dear Florence,
That strikes me as something the EnergyPlus developers never envisioned and it won't be a simple modeling procedure!
If I were to attempt it, I would do something like:
- Determine the schedule for fireplace operation, including frequency and duration of use.
- Determine how to represent the intensity of the fire (e.g., starts slowly, builds and then tapers)
- Determine the predominant type of wood (hardwoods like oak have more energy content than softwoods like pine, but burn more slowly)
- If it's an open fireplace, determine whether there is a flue damper and if it gets closed in between fires - that will affect infiltration.
- Infiltration probably increases during a fire, so consider how to represent that in your model
- Determine the portion of the fire's energy which reaches the occupied space. This is often very small (perhaps 15-20% for an open fireplace), but is dependent on the design of the fireplace. The remainder of the heat goes up the chimney.
I wish you success!