Exterior insulation
Insulation is placed on the outside to retain energy in the thermal mass.
THE BIG IDEA
The building becomes the heating, cooling, and thermal-storage system.
Water carries energy into tubing embedded in the concrete walls and floor. The structure stores that energy and gradually exchanges it with the room. Exterior-only insulation keeps the concrete connected to the interior while limiting energy loss.
01 · WHAT TWT PHYSICALLY IS
Four elements. One integrated assembly.
Continuous concrete thermal mass
Walls and floor store energy across a vast, accessible surface.
Embedded hydronic tubing
Tubing is embedded in the concrete to charge or cool the mass efficiently.
Thermally conductive interior surface
Interior surfaces naturally exchange energy with the room through radiant comfort.
02 · WHY IT WORKS
More surface. Lower temperature.
Using the entire building as the emitting and receiving surface, TWT can operate at lower water temperatures while delivering the same comfort.
See surface-area detailTraditional systems
Small surface. Higher temperature.
110–120°FTypical emitter temperatureTWT walls & floor
Building-scale surface. Lower temperature.
65–75°FModeled operating range03 · HOW ENERGY MOVES
From the energy source to the room.
Generate or collect
Solar, heat pump, ground loop, or grid
Route the fluid
Controls send water where it is needed
Charge the mass
Concrete walls and floors store energy
Retain energy
Exterior insulation protects the charge
Release comfort
Interior surfaces exchange energy slowly
04 · HOW IT WORKS THROUGH THE SEASONS
One system. Three operating modes.
Heating
Charge the mass during off-peak periods, then release steady radiant warmth.
- Lower operating temperatures
- High efficiency
- Comfort without drafts
Passive solar
Capture solar gains in the mass and redistribute energy when it is needed.
- Collects earlier and later
- Works on cloudy days
- Reduces conventional heating
Cooling
Remove heat from the mass or reject it outside while protecting indoor comfort.
- Passive & mechanical cooling
- Draws heat from the structure
- Dew-point-safe operation
Dew-point control is integrated into cooling operation to prevent condensation and protect indoor air quality.
05 / THE FULL SYSTEM
One closed loop.
Every part working
together.
TWT connects the energy source, heat exchanger, controls, thermal storage, and building zones into one coordinated hydronic system.
Energy can be directed where it is most useful—immediately to the building, into reserve storage, or through individually controlled zones.
Supply flow (energy delivered) Return flow (fluid returning) Control signal (information)
TWT is not one device added to a building.It is a coordinated hydronic system that uses the concrete structure to receive, store, distribute, and release thermal energy.
Continuous circulationA closed loop supports stable operation and efficient energy use.
Directed where it's usefulEnergy is sent to building zones or storage according to need.
Built-in stabilityThe concrete mass provides steady comfort and reduces temperature swings.
See the data behind the system.Explore the evidence, modeling, and research program.