[Greenbuilding] radiant floor matrix and sunspace

[Ken Beiser]

We are adding a bedroom suite to our home and like the rest of our home, I am using mostly salvaged and recycled materials and straw bale walls.  I will still have to buy about 10 yards of concrete, some PEX tubing, some plywood, a toilet, and the roof covering.  We have the salvaged timbers, some salvaged foam panels, earth plaster on site, and insulated glass units stored in my barn.

The floor system will be tongue and groove wood floor over sleepers laid on salvaged EPS foam panels with OSB on one side.  Under the foam with be compacted gravel on undisturbed soil to eliminate a crawlspace.  John from Duncan, BC has used this approach for floor systems with good success.

Between the sleepers I plan to run 1/2" PEX for radiant heat.  I was hoping for an alternative to concrete or gypcrete to help pull heat from the tubing.  In other areas of my house the staple up approach in a joist cavity with insulation below does not pull as much heat from the tubing as I would have liked.  I have heard that an earthen or sand mix is not considered to be as good as concrete.  Are there some other alternatives.

I also liked the advice given to John from Kalispell, Montana to try a sunspace in front of his south windows and dump heat to the living area when the solar heat is available.  I am his neighbor and have lived here about 20 years.  Just when we need the solar heat (Nov to Feb), there is very little.  I was hoping the 2 foot wide sunspace would also provide another layer between me and the outdoors.  I have some Heat Mirror glass units for the fixed windows between the living space and the sun space but plan to use single pane clear glass on the sun space to maximize solar gain to the space.  With all that in mind, I was considering minimizing the mass in the sun space so it heats up quickly.  I was also visualizing some sort of duct fan with automatic dampers that would open when the sunspace temperature exceeds the living area by a few degrees.  Does anyone have any experience with something like this and know what I might be able to use for fans and dampers?  Solar powered??  Grainger lists some that might work.  Any input would be appreciated.

Thanks,

Ken
Western Woodwrights
Whitefish, Montana