Today’s data centers (DCs) consume up to 3% of the energy produced worldwide, much of which is wasted due to over-cooling and underutilization of IT equipment. This wastage in part stems from the lack of real-time visibility of fine-grained thermal distribution in DCs. Wireless sensing is an ideal candidate for DC monitoring as it is cost-effective, facility-friendly, and can be easily re-purposed. In this thesis, we develop LEMoNet, a novel low-energy wireless sensor network design for monitoring co-location DCs. It employs a two-tier network architecture and a multi-mode data exchange protocol to balance the trade-offs between low power consumption and high data reliability. We have evaluated the performance of LEMoNet by deploying custom-designed sensor and gateway nodes in a SHARCNET DC at A.N. Bourns Science Building. We show experimentally that LEMoNet achieves an average data yield of over 98%. Under normal operations with one temperature and one humidity reading every thirty seconds, the battery lifetime of LEMoNet sensor nodes is projected to be 14.9 years on a single lithium coin battery. / Thesis / Master of Science (MSc)