In the last month, you have received several complaints from building occupants about the indoor air quality (IAQ). Additionally, you notice an unanticipated upward trend in the electric bill over the last 12 months. What is the most likely cause?

The most likely cause of the complaints regarding indoor air quality (IAQ) alongside the upward trend in the electric bill can be attributed to deterioration and unwanted openings around windows or doors. When windows and doors are not sealed properly due to wear and tear, they can allow outside air to infiltrate the building. This influx of unfiltered outdoor air can lead to poor indoor air quality, as it may bring in pollutants, allergens, and increased humidity levels.

Additionally, if the building's heating and cooling systems must work harder to maintain a comfortable temperature due to drafts from these openings, energy consumption will consequently increase, leading to higher electric bills. This means that not only does the integrity of the air quality suffer, but the efficiency of the HVAC system is compromised, directly affecting energy use.

The other options present scenarios that might have various impacts on the building environment, but they do not directly correlate with both the IAQ complaints and the rising electric costs. For example, cracks in the foundation or decaying wood posts may have structural implications but are less likely to affect air quality or electric usage in such a significant way compared to the effects of deteriorated seals around windows and doors. Similarly, standing water in the basement could lead to mold and water damage over time