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A description of the floor system at the Green Garage

A cross-section of the floor system in the historic side of the building.

In addition to being a component of the super insulation strategy, the floor of our building will house the tubing for the radiant heating and cooling system we are installing. This system may require maintenance and tuning, so our floor system allows easy access and still provides insulation value.

  • Floor layers on historic side
Existing 4" concrete slab
1" polyiso foam
1" polyiso foam
2 x wood sleepers for floor leveling
1/2" layer of plywood
1/2" layer of Uponor Quik-Trak (carries pex tubing)
electrical distribution
Storm or disease-damaged red oak and ash as finish floor
Total thermal resistance for the floor is R-14
  • Floor layers on annex side
1" pex tubing for cooling
4" polystyrene foam
Pex tubing for heating system poured into 4" concrete
Total thermal resistance for the floor is R-20

How does the floor system help heat the building?

Radiant floor design calculations
Diagram of the floor loops in the historic side of the building.

Because of the ceiling height in our building, we decided on a radiant heating system. The system fundamentally works this way: Solar thermal collectors on the roof of the annex heat 5,000 gallons of water in 2 tanks in the annex. The tanks are made of stainless steel and are insulated with cork. They are located in an insulated room in the annex. Nine pumps next to the tanks push water out to the historic side of the building. The water travels to one of 12 manifolds located at various points throughout the building, which distribute it out to the floor sections.

An Altherma Heat Pump is our back-up when conditions do not allow enough sunlight to heat the water in the tanks.

A little more about the wood used for the floors

  • The wood was supplied by Lon Ullman, a wood processor from Troy, MI. Lon has connections with urban foresters, who obtain fallen wood in the southeast Michigan area. He has a solar kiln on his property to dry the wood and has a sawmill on his property in addition to a portable mill.
  • The wood for the floor of the Green Garage came from fallen and diseased ash and red oak trees. You may recall that the emerald ash borer devastated Michigan ash trees in the early 2000's. Much of our wood came from borer-infected trees.
  • Instead of using uniform-sized boards, we used 3 - 7" wide boards so whole tree could be used, which minimized waste. We also kept boards with knots.
  • We did not sand the floors, knowing that paths will naturally form. While you may not do this at your home, it is perfectly acceptable in this setting, where we will always have shoes on.
  • Instead of sealing the floors, we oiled them with Bioshield Hard Oil.

Why is the floor screwed in instead of nailed down?

Working on manifold dampers in our floor subsystem during construction.

  • It provided easy access to plumbing and electrical and to hot water manifolds.
  • It allowed us to better reuse flooring material if necessary.
  • In addition to being screwed down, the edges of the hardwood are ship-lapped, as opposed to traditional tongue and groove. This means that the edges overlap instead of being connected in a tongue and groove style, allowing for easier disassembly.


For more floor photos, please see our Flooring and Radiant Tubing Flickr set.


See Also