Validated room-by-room against EnergyPlus®

The reference building

The RIME Loads Validation Building (RLVB-2026.01) is a three-story, 45,000 SF office in Seattle: 63 rooms per the published plan set, punched and ribbon glazing on four orientations, steel-stud framed walls, slab on grade, and a full internal-load schedule per space — conference rooms, open offices, a cafeteria, huddle rooms, restrooms, mechanical spaces. The complete definition (plans, constructions, loads) is in the reproduction package below.

The method

The same building was modeled twice: in Revit with RIME HVAC Loads (ASHRAE Heat Balance engine, all twelve monthly design days), and in EnergyPlus 25.1 (ideal loads, one zone per room, the same Seattle-Tacoma design days). Inputs were then audited room-by-room — people counts, people heat rates, lighting and equipment densities, setpoints, infiltration — until the two models were provably identical: 59 rooms, zero discrepancies. Where the engines differ by design (partition conventions, slab methods, film models), each difference is named, quantified, and published — not hidden in the residuals.

What the engines agree on

• Every one of the 43 interior rooms within ±1.4% (−0.1% in aggregate) with conventions matched
• Exterior-wall design heating within 0.01% — two engines, 2 Btu/h apart on a 30,000 Btu/h component
• Roof heating within 1.5%; window totals within single digits on all four orientations
• Peak months and peak hours coincident, room by room
• Building cooling +8.1% and heating +5.9% — every residual a named convention, all conservative

Documented conventions — the honest fine print

Two independent engines never agree to the last Btu, and pretending otherwise is how load tools lose your trust. Every residual difference in this study is a named, deliberate modeling convention:

1. 1

   Inputs verified identical, room by room

   59 rooms audited: seat-count occupancy at 450 Btu/h·person (250 sensible / 200 latent), lighting and equipment W/sf per the published spec, 75/70°F setpoints, infiltration 0.05 cfm/sf of exterior wall in both engines — zero discrepancies.

2. 2

   Interior surfaces adiabatic in both engines

   The standard single-zone loads convention. The E+ reference sets all 408 interzone wall, floor and ceiling faces adiabatic (thermal mass retained). Against the realistic multizone run, RIME reads +8.6% cooling — that sensitivity is published too.

3. 3

   Slab-on-grade heating by the ASHRAE F-factor method

   Q = F·P·(Tin − Tdesign air), the standard sizing convention. E+ drives the slab to winter soil temperature and reports about a third of the loss — RIME is conservative and method-faithful.

4. 4

   Ground-coupled slab cooling

   RIME’s monthly shallow-ground model gives a smaller cooling-side sink than E+’s soil-and-storage model, so Level-1 glazed rooms read higher — the only rooms outside ±15%, all in the conservative direction.

5. 5

   Fixed exterior film

   ASHRAE h₀ = 3.0 sol-air film (the classic ASHRAE design-calculation convention) vs E+’s per-timestep film model — affects the roof/wall attribution split at the peak hour, not zone totals.

6. 6

   Sensible-only infiltration heating

   Standard air density, no humidification credit; E+’s component includes cold-air density and latent effects.

7. 7

   Window gain bookkeeping

   RIME reports full-SHGC solar plus pure UA·ΔT conduction; E+ books the inward-flowing absorbed fraction under conduction. Solar + conduction totals are the like-for-like metric and agree within single digits on all four orientations.