Worked cases · Denver
Four rooms on one three-pipe VRF: on 2 300 hours a year the glazed south suites shed sun while the north waiting rooms ask for heat, and moving that heat sideways is 2 400 kWh and 370 hours of waiting.
Open the building in the Simulate tabLookout Ridge is a single-storey 480 m² clinic: two glazed consulting suites on the south façade — 10 m² of aperture each, lightweight fit-out — and two waiting rooms on the north, block walls and strip windows with a crowd in them by day. Each room has its own 14 kW VRF indoor unit and all four hang on one outdoor unit, a 30 HP frame. It is in Denver on purpose: of every city in the TMY list it has the most cold-and-sunny hours — 579 an hour under 12 °C with more than 400 W/m² on the ground — which is the climate where one façade cooks while the other freezes.
The Tokyo office showed what three-pipe heat recovery buys a building whose rooms disagree by trickles: the hour, not the kilowatt-hour. Here they disagree by kilowatts. On a −5 °C morning at 900 W/m² each suite wants well over 8 kW of cooling — a south wall under a low sun sees more than the ground does — while each waiting room wants 4–5 kW of heat, and a two-pipe unit follows the larger call: the waiting rooms go cold on 422 hours a year, and the suites lose the vote the other way on 257. Declared three-pipe, the same unit serves both directions on 2 300 hours, moves 2 374 kWh from the suites into the waiting rooms instead of rejecting it to the weather and pumping it back in, and the waiting rooms wait on 53 hours, the suites on none. The outdoor unit draws 25.2 against 26.5 MWh; the building 29.4 against 30.6 — 4 % of its electricity, with a comfort figure attached to it.
Two things sized it, both measured. The first draft glazed the suites at 15 m², and they sat at their indoor unit's 14 kW ceiling on 836 hours a year — the two-pipe baseline read 1 018 unmet cooling hours, a badly designed clinic rather than a fair comparison. Ten square metres was the most one 14 kW indoor unit carried on that model, and the ceiling that decides a VRF design turned out to be the box in the room, not the machine outside. Since the rooms declare which way they face, the suites read the sun a south wall actually sees — the low winter sun in full, the summer noon glancing off — and ten square metres holds them with no unmet cooling hour on three-pipe. The second was thermal mass: at ISO 13790's medium class the suites climbed 20 → 24 °C over seven sunny hours and touched their band only at noon, the mass eating the very peak recovery exists for; the light class — a raised floor, a suspended ceiling, stud partitions — is what a fitted-out consulting suite is.
| Cooling / heating | 25.2 MWh cooling and 78.8 MWh heating at the indoor coils |
| Electricity | 29.4 MWh — 25.2 at the outdoor unit, 4.2 in the indoor fans; 30.6 with the same unit declared two-pipe |
| Recovered | 2 374 kWh moved from the suites to the waiting rooms on the 2 300 hours both directions ran |
| Comfort | waiting rooms 53 unmet heating hours each against 422 on two-pipe; suites no unmet cooling hour against 257 |
| Rooms | 17.7–24.0 °C over the year |
Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.