A Green Retrofit on a Modular Home
The Heating System

For our new heating system, I'm looking at installing a radiant system where heat is stored in and rises from a concrete mass in the floor. The underside of the modular is actually filled with a thick layer of real insulation (R-23 or better), with a sheet of heavy construction plastic sealing that in. I don't want to rip all that out to place heating hose up against the bottom of the flooring material, and then find a way to insulate that so the heat is reflected up and doesn't just drop down, so I'm better off (I think, anyway) to place the heating hose on top of the existing hard flooring and then pour a layer of concrete over that to give the heating system some body-mass to properly store and disperse the heat delivered through the fluids being pumped through the heating hose. All around the exterior walls in the modular the ceiling height is 7'6" so I have a couple inches to work with. All my additions have an exterior height of 8' so I'm good there, too (although when I go into the great room, I'm going to run the heating hose underneath that floor with an aluminum sheet below it to reflect the heat back up, and R-30 insulation below that).

Pex (which is what I'm thinking to go with for heating hose) has a diameter of 1/2" so a concrete layer 1-1/2" thick will cover what I need covered and give me some heat retaining mass so that temperature fluctuations are evened out and a steady heat can be maintained. That will leave me the room I need for whatever surface treatment I choose to cover that concrete "slab" with.

As far as the primary heating source goes, I'm looking at installing a series of solar heat "concentrators" with filled water pipe running through them along the edge of the hill to the south of the great room. That way, I can set the panels up to get maximum sun at the time of year when I'll need it most, and all my water connections can be buried in the ground to reduce heat loss in transport.

Now here's where I'm still doing some research. I can get a wood-fired boiler and install it in the same area as the solar collectors for those days when I need the extra oomph. Or, I can install an on-demand propane-fired water heater in a closed-off section of the mud room. If I go for the wood-fired boiler system, I can bring the heated water into the crawl space under the great room and immediately separate the flow into zones for regulated distribution through the house. An advantage to this is the close proximity to a 12-volt power system that can be used for the pumps necessary to feed the various zones. If I go with the on-demand heater, I'll have to run my hoses back under the great room and still do the zonal division there. There's good and bad about both. However, the general shift from propane-fired, electrically forced air to solar-electric, 12-volt pumped, solar-boosted hot water radiant heat is a definite "good," and not just from the healthful aspect. Couple that with real insulation in the ceilings of the house and I should be well ahead of where I am now in attaining my objective of reducing the utility bill.