The first year or two after a new or retrofit building has been lived-in can be critical to an energy performance plan. Collecting data during this 'post occupancy' period is helpful to Energy Advisors and Contractors alike.

This may be a difficult data collection to organize unless the preliminary planning stages included consultation with the client to agree upon the intrusion. In a normal building or retrofit situation, this time period is usually when problems and deficiencies show up, and so the relationship with a client may be strained.

Call-backs and client issues aside, the importance of collecting performance data post-occupancy is a valuable part of the overall plan for energy efficient builds and retrofits. It allows the design and energy advising team to see how well their modelling is holding up during a fully operational and occupied space, and provides an opportunity to identify areas where more careful attention may be required in future projects.

The types of data that may be collected post-occupancy will often include:

• Power consumption on a monthly or seasonal basis - power demand of appliances and systems vs. the modelled projections.
• Water usage and hot water heater power / fuel consumption.
• Wear and tear on ventilation systems and HVAC - accumulation in filters, fuel use efficiency, etc..
• Temperature and relative humidity variations throughout the year, along with identification of cold spots or drafts.
• Power usage and efficiency of renewable systems vs. modelled projections.