Steam vs Hot Water In New Construction

It's funny how we accept that steam system leak a little, so it's too challenging to build a deep vacum system, but hot water may be under an even higher 15-20psi and MUST be leak free.

A steam system with a deep vacuum and a modulating boiler, plus zone controls, could be very, very impressive in efficiency and overall performance.

Steam, when it's temperature is controlled with a vacuum, had the added ability of not only a wide range of heat outputs but can also heat only part of the radiator. On hot water, it's all or nothing.

At work, large vacuum pumps pull down to 27" without a problem. Steam is only 115F at that level of vacuum. You are getting into a range at that point where you could even use geothermal for steam generation.

You could even take it one strep farther and at very high vacuum levels, you utilize steam line a refrigerant and the vacuum pump becomes a centralized component.

Actually, you could at that point just to direct exchange for geothermal or air to vapor heat exchanger to boil the water. Really, there's a whole untapped level of technology using R718.

In reverse, you could even use steam to cool buildings as well. You might be able to use the steam condensate in a closed loop as seal water for the vacuum pump and recover that heat energy as well.