Thermostat

Sometimes I wonder why the temperature control in our lives isn't better.  For years I've wondered about the hot water in the shower.  It doesn't make sense to me why we can't set a temperature so that you turn on the tap and then nothing comes out until the water is at the temperature you want.  This seems to be well inside the capabilities of our technology.  Mostly it just seems like this doesn't happen because it doesn't happen.

But it could happen, yes?  If it did happen it would seem like many houses would waste a lot less water.  Right now you turn on the tap and then the cold water in the line has to run out the faucet and down the drain until you gauge the warmth - by touching the water - and then you get in the shower.  Alternately I imagine that sometimes people crank up the temp to try to make this happen faster and then wind up getting scalded when they check the temp on their hand.  That's an unfortunate result.

To fix this there would need to be a doubled set of pipes.  You'd need a return from behind the tap that ran back to the hot water heater.  Then there would need to be a thermostatic sensor and a diverter valve right at the tap.  The temp would be set on the sensor and until the water reached the desired temp the water would flow through the diverter and back to the tank.  Once the proper temperature is reached the valve opens and the water comes out the tap, with the first drop being the temp you are looking for.  The system could also have an envelope such that if the temperature got too high the valve would swap again and the overtemp water would recirculate to the tank.

So obviously there's more dollars here in the initial installation.  There's an extra sensor and a valve, and there's an extra run of tubing for every length of hot water tubing.  That's like a 50%+ increase in initial outlay.  With the price of water being where it is right now that is probably a fairly long ROI before you get to a break even.  But you get the convenience, and you waste less water.  It seems like something worth offering as an option anyway.  I don't think I have ever been in a home that works this way.

Lately I've been wondering the same kind of thing about my HVAC system.  The sensor package and the air sources don't seem to be the most efficient here either.  Often, because of the way our house is built we wind up running the air conditioning even though the outside temperature is lower than the inside.  Why does the system have to create cold air when there is available cold air outside?

Couldn't a system be built with inside and outside theremostats?  Something that combines traditional air conditioning with exhaust fans and exterior air inputs.  So if the desired temp inside is below the actual temp inside and it is also below the outside temp the traditional air conditioning runs.  If the desired temp inside is lower than the actual temp inside but it is higher than the outside air, then instead of running the traditional system the unit would draw in outside air and exhaust the warmer air from inside.

This seems like it ought to be less electricity.  You don't have to run the exterior chiller unit in some of the cases.  There is probably a humidity benefit from running the air conditioning that you wouldn't get just using exhaust fans.  The existing system would have a way to dry the air that the other wouldn't.  And there are probably extra mechanical dampers to facilitate bringing in outside air that would be vulnerable to maintenance problems, that's a downside.  But again, this seems to be well inside the capability of our technology - and in this case, doesn't feel a whole lot more expensive at the installation stage - and yet I can't recall ever being in a home that had such technology available.

It would seem like there are environmental reasons to develop both of these systems.  I wonder why it hasn't happened.