Cooking pot with lid for saving gas but that doesn't overflow? I care about gas saving and for that I want to cook with the lid covering the pot. This allows me to reduce the fire power of the stove top (then using less gas).

I need to cook foods in cooking pots such as rice, noodle, etc. Everyone that cooks these foods know they tend to overflow and (also look at this for the why) if the lid is over, except if the fire is really low, (wich is indeed a possible solution to my problem, but read below).

Idea 1: Is there some ingredient (like salt) that reduces a lot the bubbles that overflow and doesn't affect compromise the food?

Idea 2 (I want this one): Is there a device that releases the pressure automatically when the pot is trying to overflow?

Edit clarification: It's unfortunate that I referred to the pressure associated with the heating boiling food inside the pot (wich is extremely small, but still enought to lift the lid (Is it or I'm wrong?) and pressure cookers in the same 
post, wich have a HUGE pressure. This realization is important for me!

PD: Are we sure that my idea of releasing vapour periodically doesn't save more than just open? To me is not so cutting obvious, it needs a proof (sorry if it's basic thermodinamics, I'm ignorant on that).

PD2: This got all really good answers! I hope you don't get put off that Im not accepting right away, but I can tell you the discussion was very good!.

Is this device what I'm looking?
The device which "releases the pressure automatically" is a normal pot. You don't put the lid fully on, you leave a small gap on the side. It is sufficient for practically all cooking. 

And yes, if it is still overflowing, you should reduce your temperature. Not only don't you win anything by cooking it at such a high flame that it boils over even with a gap, you are also wasting gas - which you said you care about. 

As for the device you linked, it is a very different thing. It cooks food faster because at higher pressures, it can be heated to over 100 Celsius. Cooking with it is very different from cooking with a normal pot, and it is up to you if you want to get into it - but not having to leave the air gap is not a typical reason for it. 



Trying to clear this thing up after some discussion with Jefromi: 

You are pumping more energy into the system than it can hold. You have a few possible solutions: 


Stop pumping that much energy into it (reduce the heat). It is wasted anyway. 
Have an open system - one which can't withstand pressure and bleeds it off as soon as it starts rising. This is the "pot with a gap in the lid" method, no matter if you are using a standard lid or one with the gap and catch lip built in like suggested in the other answer. 
Have a closed system which can keep in the energy (it will produce pressure higher than atmospheric pressure) and release it after you are done cooking. This is what a real pressure cooker is for. It does come with some advantages, I've also seen claims that it is more energy efficient (I don't know if it is, really), but it is really a completely different mode of cooking. 


What you are proposing is a mixture of 2 and 3. Now, if you make it very close to 2, such that minute amounts of pressure are built up before venting, you are still expelling that same energy from the system, and haven't saved it in any way. You just have created a more complex (and so more expensive less failsafe) device, there is no reason to not stay with solution 2. If you make it very close to 3, in that you hold in a lot of pressure before releasing, you automatically make it almost the same as pressure cooking, only with some useless venting of energy, so there is no reason to not build a real pressure cooker. Basically, anything in between 2 and 3 is going to be worse than both 2 and 3. 

The most practical solution, used by countless cooks over the world, is a combination of 1 and 2.