Heating Services in Kirkwood and West St. Louis County

Heating design in Climate Zone 4A is governed by a specific number: 3°F. That’s the ASHRAE 99% winter design temperature for St. Louis Lambert, the temperature that the heating system must reliably meet on the coldest 1% of winter hours. A furnace sized for 35°F average January conditions but unable to maintain interior temperature at 3°F is a furnace that fails its customer during Polar Vortex events — the January 2019, February 2021, and December 2022 stretches that dropped St. Louis into single-digit and below-zero territory for days at a time. Heating equipment selection for our service area must accommodate the design condition, not the average condition, while not being so dramatically oversized that the equipment short-cycles during the 35°F operating reality of most of the heating season. Six service categories address every heating need across our Kirkwood, Affton, Sappington, Webster Groves, Crestwood, and Town and Country service area.

Heating Equipment Categories in Our Service Area

Gas-Fired Forced-Air Furnaces

The dominant residential heating equipment across our six-city service area. Approximately 85% of homes in Kirkwood, Webster Groves, Crestwood, Affton, Sappington, and Town and Country use natural gas forced-air heating through Spire Missouri natural gas service. Equipment ranges from 60,000–120,000 BTU/hr input capacity for typical residential applications, with three primary efficiency tiers:

80% AFUE single-stage furnaces — entry-level non-condensing equipment. Vents through traditional masonry chimney or B-vent. Used in budget retrofits and rental properties.
92–96% AFUE condensing single-stage and two-stage furnaces — mid-tier efficiency. Sidewall PVC venting. Standard recommendation for most residential replacements in our service area.
97%+ AFUE modulating variable-speed furnaces — top-tier efficiency with communicating controls. Carrier Infinity 98, Trane S9V2, Lennox SLP99V. Higher upfront cost, lower operating cost, longest equipment service life.

Cold-Climate Heat Pumps

Heat pumps for Climate Zone 4A heating require AHRI-rated 100% capacity at 5°F outdoor temperature — called “cold-climate” heat pumps in industry terminology. Standard heat pumps derate sharply below 35°F outdoor, requiring auxiliary electric resistance backup that drives up utility bills during Polar Vortex stretches. Cold-climate variable-capacity units from Mitsubishi Hyper-Heat M-Series, Daikin Aurora, and Bosch IDS Premium 2.0 carry the design heating load to 5°F without auxiliary backup, with reduced capacity below that point (the 3°F design temperature requires a small amount of auxiliary backup on most cold-climate equipment).

Heat pump applications in our service area:

Homes without natural gas service (limited to specific areas where Spire Missouri service hasn’t been extended)
Homes with electric utility-rebate qualification through Ameren Missouri’s heat pump rebate program
Homes pursuing electrification or solar-pairing strategies
Homes where ductless mini-split retrofit makes more sense than ductwork retrofit (typically historic district homes in Meramec Highlands, Central Place, Jefferson-Argonne)

Hydronic Boilers

Hydronic boiler heating dominates historic district homes built before the forced-air ductwork era. Common in Kirkwood’s Meramec Highlands (1890s housing), Central Place (1920s), and Jefferson-Argonne (1850s–1950s), plus equivalent-era housing in Webster Groves. Equipment includes:

Cast iron sectional boilers — traditional 70–85% AFUE equipment from Burnham, Weil-McLain, Peerless. Very long service life (40–60 years on properly maintained units).
Modulating-condensing wall-hung boilers — 92–98% AFUE equipment from Buderus, Viessmann, Weil-McLain Ultra, Burnham Alpine. Smaller footprint, higher efficiency, more sophisticated controls.
Combination boilers (combi-boilers) — integrated heating and domestic hot water. Less common in our service area but increasing in retrofit applications.

Gas-Line Service

Gas line installation tied to HVAC equipment includes new gas line runs for furnace or boiler installations, gas pressure verification through Spire Missouri shut-off coordination, and CSST (Corrugated Stainless Steel Tubing) installation where appropriate per local code.

The Six Heating Service Categories We Operate

Furnace Installation

Complete gas furnace replacement with ACCA Manual J load calculation, Manual S equipment selection (within 0–15% of calculated heating load), and Manual D duct verification on the existing duct system. Brand options across Carrier, Trane, Lennox, Bryant, Rheem, Goodman, and American Standard residential lines. Furnace Installation details →

Furnace Repair

Diagnostic-driven repair with Bacharach Fyrite Insight Plus combustion analysis (target under 100 ppm CO air-free), Testo 510i digital manometer gas pressure verification (Spire Missouri 7" WC nominal at meter, 3.5" WC at manifold post-regulator on single-stage natural gas), ignition system diagnostics, inducer motor service, blower wheel and motor service. Common repairs include hot surface igniter replacement ($48–$140 parts), flame sensor cleaning ($25–$50 service), inducer motor replacement ($240–$680 parts), and pressure switch replacement. Furnace Repair details →

Furnace Tune-Up

Fall preventive service in September or October with combustion analysis verification (under 100 ppm CO air-free target), gas pressure measurement at the meter and manifold, heat exchanger borescope inspection using Hawkeye inspection scope, ignition sequence verification, blower motor amperage check, and filter replacement. Standard fall tune-up is $129. Furnace Tune-Up details →

Heat Pumps

Cold-climate heat pump installation and service for Climate Zone 4A applications. Mitsubishi Hyper-Heat M-Series, Daikin Aurora, and Bosch IDS Premium 2.0 carry AHRI-rated 100% capacity at 5°F outdoor. Diamond Contractor status for Mitsubishi extends parts warranty to 12 years. Heat pump installations include Manual J load calculation, Manual S equipment selection with attention to the heating capacity curve at design temperatures, and auxiliary backup sizing for the 3°F design condition. Heat Pump details →

Heat Exchanger Repair

Heat exchanger inspection uses the Hawkeye inspection borescope to visually verify cracks, carbon scoring, condensate damage, and structural integrity. Cracked heat exchangers are a serious safety issue — cracks allow combustion products including carbon monoxide to mix with the supply air, posing health and life-safety risk. Heat exchanger replacement is typically a warranty-claim process (most residential equipment carries 20-year heat exchanger warranty on top-tier units, 10-year on mid-tier). On equipment outside heat exchanger warranty, replacement frequently doesn’t make economic sense compared to complete furnace replacement. Heat Exchanger Repair details →

Boiler Installation and Boiler Repair

Hydronic boiler service across cast iron sectional, monobloc, and modulating-condensing equipment. Brand coverage includes Burnham, Weil-McLain, Peerless, Buderus, and Viessmann. Service work includes circulator pump replacement, expansion tank service, pressure relief valve replacement, water feed valve service, and full system flushing. Installation work includes new boiler installation in historic district homes where retrofit forced-air would require extensive ductwork through finished walls. Boiler Installation details → | Boiler Repair details →

Gas Line Installation

Gas line installation tied to HVAC equipment. New equipment installations occasionally require new gas line runs (relocating furnace from interior to closet location, adding gas service to a previously electric heat home, etc.). Gas line work requires Spire Missouri coordination for shut-off and meter verification, CSST or black iron piping per local code, pressure testing to manufacturer and code specifications, and final permit inspection through Kirkwood Public Works, St. Louis County DPW, or applicable municipal authority. Gas Line Installation details →

Why the 3°F Design Temperature Matters

The ASHRAE 99% winter design temperature represents the temperature that’s only exceeded (on the cold side) 1% of all heating hours over the climatological record. For St. Louis Lambert, that’s 3°F. Heating equipment sized to the 3°F design load reliably maintains interior temperature during the coldest stretches of winter. Equipment sized to average January conditions (typically 25–30°F outdoor) leaves the homeowner cold during Polar Vortex events.

Recent Polar Vortex events in our service area:

January 29–31, 2019 — St. Louis Lambert recorded -6°F low temperature, with wind chills to -25°F. Heating systems in our service area ran continuously for 60+ hours.
February 14–20, 2021 — A six-day stretch of single-digit and below-zero temperatures, with -10°F low on February 16. Notable for the Texas grid failure that month; St. Louis utility infrastructure held but residential heating equipment ran at design conditions for extended periods.
December 22–25, 2022 — Pre-Christmas blizzard with -8°F low and 36 consecutive hours below 0°F. Coincided with widespread power outages from ice damage.

Each of these events tested heating equipment at or near design conditions. Properly sized equipment ran continuously without falling behind interior temperature setpoint. Undersized or marginal equipment couldn’t maintain setpoint, and homes saw interior temperatures drop into the 50s and 60s during the worst stretches.

Spire Missouri Natural Gas Service

Most residential heating in our service area runs on natural gas delivered through Spire Missouri (formerly Laclede Gas Company, rebranded 2018). Service infrastructure considerations:

Delivery pressure: 7" WC nominal at the residential meter, 11" WC maximum. Gas pressure verification at the meter and at the manifold post-regulator (3.5" WC for single-stage natural gas burners) is part of every gas-fired equipment install and diagnostic.
Service shut-offs: Spire Missouri coordinates gas service shut-offs for HVAC work that requires it. Homeowner can request shut-off through Spire’s customer service line; we typically handle the coordination as part of installation scope.
Meter location: Most residential service has the meter outside the home with a service entry point through the wall to the interior gas distribution. Older homes occasionally have meters in basements or utility rooms.
Service interruption events: Spire Missouri natural gas service has high reliability, but interruption events do occur (utility-side maintenance, infrastructure damage from severe weather). Heat pump systems provide an electrification alternative that’s resilient to natural gas interruption (vulnerable to electrical service interruption instead).

Frequently Asked Questions

What heating equipment is typical in Kirkwood homes?: Gas-fired forced-air furnaces dominate, representing approximately 85% of residential heating in our six-city service area. Equipment ranges from 80% AFUE single-stage non-condensing furnaces (budget retrofits and rental properties) through 92–96% AFUE condensing furnaces (most common new installations) to 97%+ AFUE modulating variable-speed equipment (Carrier Infinity 98, Trane S9V2, Lennox SLP99V) in top-tier installations. Hydronic boiler heating dominates historic district homes built before the forced-air era — Meramec Highlands, Central Place, Jefferson-Argonne neighborhoods in Kirkwood and equivalent-era housing in Webster Groves. Heat pump installations are increasing but still represent a minority of total heating equipment.
What’s the 3°F design temperature and why does it matter?: The ASHRAE 99% winter design temperature for St. Louis Lambert is 3°F — the temperature exceeded on the cold side only 1% of all heating hours over the climatological record. Heating equipment sized to the 3°F design load reliably maintains interior temperature during the coldest winter stretches, including the Polar Vortex events of January 2019 (-6°F), February 2021 (-10°F), and December 2022 (-8°F). Equipment sized to average January conditions (25–30°F outdoor) cannot maintain interior setpoint during these events, leading to interior temperatures dropping into the 50s and 60s. ACCA Manual J load calculations use the 3°F design temperature for equipment sizing.
Should I install a heat pump or a gas furnace in Kirkwood?: Depends on several factors. Gas furnace advantages: lower operating cost when natural gas prices are low relative to electricity, no auxiliary backup heat required at design conditions, reliable operation independent of electrical service. Heat pump advantages: single equipment handles both heating and cooling, potential Ameren Missouri rebate qualification on cold-climate equipment (Mitsubishi Hyper-Heat, Daikin Aurora, Bosch IDS Premium 2.0), reduced carbon footprint, immunity to natural gas service interruptions. For homes with existing Spire Missouri natural gas service and standard cooling needs, gas furnace plus separate AC remains the most common recommendation. For homes pursuing electrification, qualifying for utility rebates, or without natural gas service, cold-climate heat pumps are the right choice. We provide both quote options on installation requests so customers can compare upfront cost and 15-year operating cost trajectories.
How does Spire Missouri gas service affect my furnace?: Spire Missouri delivers natural gas at 7″ WC nominal pressure (11″ WC maximum) at the residential meter. Gas pressure verification at the meter and at the manifold post-regulator (3.5″ WC for single-stage natural gas burners) is part of every gas-fired equipment install and diagnostic. Spire Missouri coordinates gas service shut-offs for HVAC work that requires it. Service infrastructure is generally reliable, but interruption events do occur from utility-side maintenance or infrastructure damage from severe weather. Heat pump systems provide an electrification alternative resilient to natural gas interruption (though vulnerable to electrical service interruption instead).
What’s the highest-priority heating service for a Kirkwood homeowner?: Annual fall furnace tune-up, scheduled in September or October before peak heating demand. Tune-up includes combustion analysis verification (target under 100 ppm CO air-free), gas pressure measurement, heat exchanger borescope inspection, ignition sequence verification, blower motor amperage check, and filter replacement. The combustion analysis component is particularly important — it verifies safe combustion (no excess carbon monoxide production) before the equipment runs continuously through winter. Cracked heat exchangers are a serious safety issue, and annual borescope inspection catches them before they become health hazards. Standard fall tune-up cost is $129; combined fall furnace and spring AC tune-up is $219 (saves $39 vs. separate visits).

Contact Purisync Heating and Air

For heating service across any of the six categories — furnace installation or repair, heat pump installation, boiler service, heat exchanger inspection, gas line work — contact our 325 N Kirkwood Road office at (314) 338-5111. Emergency no-heat calls during winter (October through April) get same-day response with dispatch following geographic proximity from our Kirkwood location.

Emergency Line (24/7): (314) 338-5111
Address: 325 N Kirkwood Rd #245, Kirkwood, MO 63122
Email: info@purisyncheatingairconditioning.xyz
St. Louis County Mechanical Contractor License: #MC-2014-08439-STL
Kirkwood Business Registration: #BL-2014-1187
EPA Section 608 Universal: #608U-2014-385721

Office Hours

Emergency Service: 24 hours a day, 7 days a week
Office Staff: Monday – Saturday, 9:00 AM – 5:00 PM
Closed: Sundays and State/Federal Holidays (emergency line always active)

3°F Winter Design & Spire 7″ WC Gas | Purisync Kirkwood