In this field observational study, 3 types of laying-hen houses, namely, high-rise (HR), manure-belt (MB), and cage-free floor-raised (FR), were monitored for air temperature, RH, CO2 , and atmospheric NH3 under winter and summer conditions in Iowa. Under winter conditions, the HR and MB houses had more comfortable temperature and NH3 levels (mean 24.6 and 20.6°C, and maximum 9 to 24 ppm of NH3 , respectively) than the FR houses (mean 15.5°C and maximum 85 to 89 ppm of NH3 , respectively), and house temperature varied more with outside conditions. Under summer conditions, house temperature showed the least increase above ambient in the FR houses (mean 0.3°C vs. 4.7 and 1.2°C for the MB and HR houses, respectively), and NH3 levels were similar for all housing types (mean 3 to 9 ppm). Examination of the hen health status revealed differences in pathogen prevalence between housing systems for winter and summer, but not conclusively in favor of one system over another. Results of this study indicate that the benefits of each system were season dependent. Further monitoring of the environment, bird health, and production performance over an extended period (e.g., 1 yr) to quantify the benefits and limitations of each system is warranted. Information of this nature will aid in optimizing hen housing systems for enhanced bird welfare and sustained production efficiency for the egg industry