Boilers
Hydronic heating via radiators or radiant floor, sometimes with domestic hot water.
Buyer's guide: Replacing an old boiler: stay hydronic, go ductless, or bothWe hold full sourced data on 9 boilers, each with a specification traced to its source and cross-checked against owner reports.
All the boilers we have data on
Sorted by data completeness.
Lochinvar Knight Fire TubeKHB
Fire-tube condensing boiler with 10:1 turndown, built for the residential and light-commercial hydronic market.
Owners: 1 watch-out 1 report →Navien NFC-175NFC-175 (full designation NFC-250/175H)
High-turndown condensing combi boiler providing both hydronic heat and domestic hot water from one wall-hung unit.
Owners: 2 watch-out1 mixed 3 reports →Viessmann Vitodens 100-WB1KE-120
German-engineered condensing boiler with a stainless Inox-Radial heat exchanger and a 10:1 turndown ratio in line with the rest of this catalog's condensing boilers.
Weil-McLain Evergreen
Stainless condensing boiler from the most established US residential boiler brand.
Rheem PrestigeRCBH199DVLN
199,000 BTU/h condensing combi boiler, a real currently-stocked substitute for the now-defunct Triangle Tube Prestige line this catalog originally targeted.
U.S. AltaALTA-080-1G00
Floor-mount, space-heating-only condensing boiler at the smallest capacity point in this catalog, sold under the well-known Burnham brand name.
Bosch Greenstar 100ZWB-28-3
Compact wall-hung condensing combi boiler, Bosch's current US residential line replacing the discontinued Buderus GB142.
HTP Elite PremierEP-110
Floor-mount, space-heating-only condensing boiler with the highest AFUE in this catalog, paired with a separate indirect tank for domestic hot water.
IBC SL SeriesSL-30-199G3
199,000 BTU/h condensing boiler, the top of IBC's own Residential SL Series G3 lineup — sized for a larger home or a house with a genuinely high design-day load, without stepping into commercial-grade equipment.
What the specifications mean
AFUE (%)
Annual Fuel Utilization Efficiency -- the share of fuel energy that becomes usable heat.
95% AFUE means 95 cents of every fuel dollar reaches the house. The jump from 80% to 95% requires condensing operation and PVC venting, which changes installation cost.
Turndown ratio (:1)
The ratio between a modulating boiler's maximum and minimum firing rate.
A 10:1 boiler can throttle to a tenth of full output on a mild day instead of short-cycling. High turndown is the main reason modulating-condensing boilers outperform their AFUE rating in the real world.
Rated capacity (BTU/h)
Nominal heating or cooling output at the standard rating condition.
Sizing matters more than efficiency. An oversized system short-cycles, fails to dehumidify, and wears out early. Always size from a Manual J load calculation.