Use the slab that was being replaced anyway
Radiant in a warehouse is usually ruled out by the cost of the slab. Here the assembly bays were being cut and repoured for a new racking layout, so the tubing went in during work that was already funded.
AURORA, CO · 2024
A warehouse that finally holds 65 F at the floor
Twelve gas unit heaters that heated the roof structure beautifully and the working floor barely at all. Replaced with a condensing boiler plant and in-slab radiant across the assembly bays.
Measured result
Floor level temperature swing cut from 14 F to under 3 F.
- Client
- Distribution and light assembly warehouse
- Sector
- Industrial, 62,000 ft2
- Completed
- 2024
The brief
- Twelve suspended gas unit heaters in a 32 ft clear-height warehouse, producing a 14 F vertical stratification and a floor that never got warm.
- Assembly staff working at floor level for full shifts through a Denver winter with a 30 F to 40 F diurnal swing outside.
- Dock doors cycling all day, which no ceiling-mounted convective system recovers from quickly.
- A concrete slab replacement already scheduled for the assembly bays, which was the only window this was ever going to be affordable in.
What we did
Design around return water temperature
A radiant slab at 105 F supply and a 20 F drop returns water at 85 F, which keeps a condensing boiler in condensing mode for essentially the whole season. The plant was sized for a 95 percent thermal efficiency operating point rather than a nameplate one.
Zoned to how the building is actually used
Six slab zones matched to the assembly cells and the pick faces, plus destratification fans and two retained unit heaters covering the high-turnover dock area where radiant response is too slow for a door that opens 90 times a shift.
Gas equipment derated for altitude, properly
Above 2,000 ft, gas input has to come down and the orifices have to change. The boilers were ordered with the high-altitude kit, commissioned with a combustion analyser, and the printout is in the handover file.
The outcome
- Floor level temperature holds within 3 F across a shift, against 14 F of stratification before.
- Gas consumption down 24 percent against the previous two heating seasons, degree-day normalised.
- The slab carries the load, so the destratification fans run far less than the previous unit heaters did.
- Combustion analysis, the reset curve as programmed, and the loop layout drawing all issued at handover.
Other case studies
Denver, CO · 2025Nine rooftop units replaced over four weekendsMeasured fan energy down 31 percent. No tenant lost a working day.Boulder, CO · 2025Heat recovery VRF for a laboratory with 19 zones and one budgetSimultaneous heating and cooling handled without a second plant.
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