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Blueprint MechanicalDenver, Colorado
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BOULDER, CO · 2025

Heat recovery VRF for a laboratory with 19 zones and one budget

Nineteen zones with genuinely opposed loads: instrument rooms rejecting heat year round, perimeter offices calling for heat on the same January morning. Heat recovery VRF plus a dedicated outdoor air unit doing the ventilation properly.

Measured result

Simultaneous heating and cooling handled without a second plant.

Client
Research and light laboratory building
Sector
Laboratory and office, 41,000 ft2
Completed
2025
A row of white modular VRF outdoor condensing units with racked refrigerant line sets on a flat commercial roof

The brief

  • Nineteen zones across laboratory, instrument and office space, with loads that oppose each other for most of the shoulder season.
  • The existing four-pipe fan coil system was fed by a chiller and boiler plant that had eight years left and no budget behind it.
  • Ventilation and space conditioning were tangled together, so any zone that needed air also got conditioning it did not want.
  • Boulder wanted the design to survive a 1 F heating design day without electric resistance carrying the building.

What we did

Zone the loads honestly, then check whether VRF earns its place

A zone-by-zone load calculation showed 5.5 hours a day of genuinely simultaneous heating and cooling across the shoulder seasons. That is the condition heat recovery VRF is built for. Without it we would have recommended something cheaper.

Separate ventilation from conditioning

A dedicated outdoor air unit with energy recovery handles the ASHRAE 62.1 ventilation rate procedure requirement and delivers neutral air. The VRF then does space conditioning only, which is what it is good at, and no zone gets conditioning it did not ask for.

Refrigerant concentration checked room by room

Every occupied space got an ASHRAE 15 refrigerant concentration limit calculation against the system charge for its branch. Two small instrument rooms failed on the first pass, so the branch was resplit rather than the calculation being reinterpreted.

Cold climate capacity, stated at the design temperature

Selection was made on capacity at 1 F ambient, not at the 47 F rating point. The heat pump holds 76 percent of nominal heating capacity at the Boulder 99.6 percent design condition, and the balance point sits at 4 F with a small hydronic assist below that.

The outcome

  • Nineteen zones with individual setpoints, and heat moved from the instrument rooms into the perimeter offices instead of being rejected to the roof and then bought back on the gas bill.
  • Ventilation now metered and verifiable, with the outdoor air rate trended against occupancy rather than assumed.
  • Full BACnet/IP integration to the campus front end, with a written sequence of operation verified point by point at handover.
  • Piping isometrics, the refrigerant charge calculation and every RCL check issued as part of the O and M package.

Other case studies

Denver, CO · 2025Nine rooftop units replaced over four weekendsMeasured fan energy down 31 percent. No tenant lost a working day.Aurora, CO · 2024A warehouse that finally holds 65 F at the floorFloor level temperature swing cut from 14 F to under 3 F.

Tell us what the building is doing wrong.

Send us the building, the equipment and the complaint. You get a written response with the load we would run, what we would measure first, and a range before anyone visits.

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