This time nothing about props or sabers. I keep going with the house renovation & improval. Among the silly stupid things you find in 20 years old houses, there's the electric ventilation system.

It's ON all the time, and of course it refreshes the air in the house (great to keep it sain) however it brings in cold air during the winter and hot air during the summer.
In the kitchen, we do have a air exhaust connected to the outside of the house, so we don't need a permanent ventilation in there. And we of course occasionnally open the windows.
After reading some book about that topic, a simple improvement is to install a programmer/timer on the ventilation.

I found a nice wall-mount programmer that doesn't need any removable battery. It has a micro ni-mh internal battery that stores the programs, so you don't loose your data when the mains are down. Found at our local Brico-Dépot hardware store, 9.90€ 

The device is really simple to disassemble. It's composed of a power board with a relay and the circuit to recharge the tiny battery and an control panel handling the timer/programmer. Wiring is trivial, phase in, phase out, common neutral.

No need to keep the outlet section. Cut with a hand saw, filing/sanding a bit, then cleaning edges with my mill. Some white plasticard will close the box later.

Ready to install the device

To allow and easy disassembling process, back holes were filled with epoxy bondo, then drilled and taped in M3 for frontal screws. 

Installed. Et voila ! (yada yada ^^)

This timer doesn't have programs you can enable or disable (or swap / switch).
So I have an "all season" program for the bathroom usage time, splitted between 6:30-8:00 AM during work day and 9:00-10:00 AM during the week-end.
Then during the winter, 2h in the middle of the day, everyday, when the outside air is the "warmest", and during the summer, at night like 11PM to 6AM for instance.
The timer also has a Force ON / Force OFF key when needed (when you mess up a meal in the kitchen for instance ^^).

We will see the impact of this improvement on the electricity (we have electric heater) bill next winter !