A talk about work so far on OpenTRV. OpenTRV sets out to make it easy to save lots of energy by not heating rooms that you're not in, and by no longer trying to use a single thermostat to get your whole house comfortable. OpenTRV also allows a simple schedule to be set (no complex displays though!) and tries to anticipate when you'll need heating to improve comfort while boosting efficiency. OpenTRV is designed to be simple to (retro-)fit to existing UK housing stock with radiator central heating. OpenTRV runs on PICAXE and AVR/ATMega microcontrollers drawing micro-watts to run for a year or two on AA cells while saving you kilowatts in space heating and is completely open source (Apache/SolderPad), software and hardware. We like to call it FOSSH - "free open source software and hardware". We've been working on a combination of open hardware and software projects this year to prove the concept that retrofitted programmable thermostatic radiator valves can reduce the energy required to heat a house and thereby reduce carbon emissions. Along the way we've encountered and solved problems with developing open hardware and software devices and commenced testing in conjunction with a local university. The talk highlights the lessons learned and maps out the current state and future plans. We've designed a PCB, got it manufactured, populated it ourselves and via a manufacturer, sourced components, 3D printed boxes, written software, entered competitions, are in the process of testing it with real end users in conjunction with a local university and generally sweated, got frustrated and elated at various times. Now we'd like to share the lessons learned, let people know what the project is about, outline the future plans and hopefully inspire some talented people to help the project out with reducing carbon emissions significantly.