A Green Retrofit on a Modular Home
The Hot Water System

The hot water system is a little different to work with, mostly because we are so accustomed to having a steady supply of adjustable temperature hot water immediately on hand. The heating system is a closed system in that the heat-carrying fluid (a 50/50 mix of propylene glycol and water) can stay in the system for years and there's an economy built in to that on-going recycling of the fluid. In a hot water system, we heat the water, use it once and essentially flush it with whatever heat it still retains (this is where the grey water system comes in, but the heat itself is still "flushed," and whatever we have invested in heating that water is flushed, too).

So for this, I'm still doing research into solar-boosted storage coupled with an on-demand propane heater. A couple of the wood-fired boilers that I'm looking at have provisions for heating running hot water, too, but this is one system I don't want to have to do twice to get right. You'll have to come back to see where I get to with this one.