While it might be possible to see some heat signatures through thin layers, such as curtains, walls give off their own heat signature and hide whatever is behind them.
Can Thermal See Through Walls. Watch this video and you will find the answer. And why you need a thermal camera see through walls?
See Through Walls with This Smart Phone Add-On Camera ... from www.hometips.com
Walls are generally thick enough—and insulated enough—to block any infrared radiation from the other side. Thermal cctv camera that can see through the wall !! But thermal technology has its limitations.
Seeing through walls is easy.
No, thermal cameras can not really look behind walls. A new device turns your iphone into a thermal imaging sensor. You can't press any key or move the mouse while waiting. Watch this video and you will find the answer.