New types of low-cost sensors have the potential to replace existing sensor networks in buildings, which have high cost and low flexibility in terms of monitoring local indoor environmental quality (IEQ) close to the occupants. The objective of this study is to (i) investigate the reliability, accuracy, robustness, and communication capabilities of low-cost sensor networks and (ii) develop and implement an overall framework of monitoring and control of indoor environmental conditions, embedded in existing control infrastructures or using new system typologies. Different low-cost temperature, humidity, and light sensors, wired and wireless, were tested. The sensors can communicate with a single-board computer, and with the building monitoring and control system, providing flexibility in monitoring IEQ (local sensing), communication (networking) with other devices, as well as in developing new control frameworks. We present results for monitoring and control of indoor thermal conditions using low-cost local sensing with a flexible scheme embedded in existing thermal control infrastructures.