Central Place AC Installation: 1924 Tudor Revival Ductless Retrofit

Case study summary: 1924 Tudor Revival home in Kirkwood’s Central Place historic district with no existing central AC and original plaster walls throughout; installed Mitsubishi MXZ-5C42NAHZ 5-zone ductless mini-split system with strategic placement to preserve plaster walls and architectural detail; total project cost $19,400; completed in 3 days during June 2025 with full Kirkwood Historic Preservation Commission review and approval. Outcome: complete cooling and supplemental heating coverage of 2,180 sf home; zero modifications to plaster walls or original woodwork; customer satisfaction high with zoned operation flexibility and preservation outcome.

The Home

• Built: 1924
• Style: Tudor Revival with brick first floor, stucco-and-half-timber second floor
• Location: Central Place historic district, Kirkwood, MO 63122
• Size: 2,180 sf across two floors plus partial basement
• Construction: Brick and stucco exterior; original plaster walls throughout interior; original wood floors, trim, baseboards, leaded glass windows
• Existing heating: Gas-fired hydronic boiler (Weil-McLain CGa-5 from 2009, 95% AFUE condensing) serving original cast-iron radiators throughout home; system in good condition with no changes during this project
• Existing cooling: None; home had window AC units that were removed for the new system
• Layout: First floor (living room, dining room, kitchen, half bath, sunroom); Second floor (3 bedrooms, full bath, hallway); attic accessible but unfinished

The Situation

Customer purchased home in spring 2025 and wanted to install central air conditioning before summer 2025 heat. Multiple constraints drove equipment selection:

• Plaster wall preservation: Customer was firm that no significant modifications could be made to original plaster walls; this ruled out ducted forced-air installation which would require substantial wall and ceiling modifications
• Window AC unacceptable: Customer found window units aesthetically inappropriate for the Tudor Revival architecture and physically obstructive to original leaded glass windows
• Hydronic heating preservation: Customer wanted to keep existing hydronic heating system serving cast-iron radiators; this ruled out forced-air conversion that would have required boiler removal
• Zoning flexibility valued: Customer wanted ability to cool occupied rooms while turning off cooling to unused rooms (saving energy and customizing comfort)
• Historic preservation compliance: Kirkwood Historic Preservation Commission approval required for any exterior changes (outdoor unit placement, refrigerant line routing visible from street)
• Budget: Customer’s stated budget range was $18,000-$24,000 for the project

The Equipment Selection

Mitsubishi MXZ-5C42NAHZ Multi-Zone System (Selected)

• Outdoor unit: 5-zone heat pump rated 42,000 BTU/hr cooling, 48,000 BTU/hr heating; Hyper-Heat technology with rated heating capacity down to -13°F outdoor temperature
• SEER2: 19.0
• HSPF2: 10.5
• Indoor units: 5 wall-mounted air handlers placed strategically in: living room (12,000 BTU), dining room (9,000 BTU), kitchen (6,000 BTU), master bedroom (12,000 BTU), second bedroom (6,000 BTU)
• Third bedroom: not directly served by indoor unit; cooling provided by open door to hallway air movement from master bedroom unit
• Sunroom: not served (customer accepted seasonal temperature variation in this room)
• Bathrooms: not directly served; cooling via door to adjacent rooms
• Why selected: Mitsubishi has best preservation-conscious installation track record for historic homes; Hyper-Heat technology provides supplemental heating capability for shoulder seasons reducing boiler operation; 5-zone multi-port outdoor unit allows independent control of each indoor unit

Alternative Equipment Considered

• Daikin VRV multi-zone system: Competitive equipment but premium pricing exceeded customer budget
• Fujitsu Halcyon multi-zone: Competitive equipment; selected against based on dealer support depth for Mitsubishi in our service area
• Single-zone ducted high-velocity system (Unico): Considered but ruled out due to required ceiling chases that would have affected plaster ceiling integrity
• Multiple single-zone window units: Customer’s initial idea but rejected based on aesthetic and architectural considerations

The Project Scope

Pre-Installation Coordination

• Kirkwood Historic Preservation Commission review: Submitted equipment specifications, photographs of proposed outdoor unit location (rear yard, screened from street by existing landscaping), refrigerant line routing plan (interior wall chases between floors and exterior penetrations through brick at non-visible locations), and proposed exterior color matching for line set covers; approval received in 22 days with one minor modification (relocation of one refrigerant line termination from front-yard visible location to side-yard concealed location)
• Kirkwood Public Works permit: Pulled within 4 business days of preservation approval
• Equipment ordering: 12 business days for the multi-zone system (5 indoor heads with specific configurations have longer lead time than single-zone equipment)

Installation Day 1 (June 18, 2025)

• Customer pre-installation walk-through confirming indoor unit placement decisions
• Outdoor unit placement on concrete pad in rear yard, 36" from house foundation, on existing landscaped area cleared by customer in preparation
• Electrical service: dedicated 240V circuit installed from main panel (existing panel had adequate capacity); electrical inspector visit scheduled for end of installation
• Refrigerant line set runs: 5 separate line sets routing through interior wall chases (existing chases used for original gas piping and electrical, with line sets running parallel) to exterior penetrations at second-floor exterior wall
• Exterior line set covers: paintable PVC line set covers installed on exterior walls; color-matched to existing stucco and brick during finishing
• Indoor unit bracketing and mounting: wall brackets attached to wall studs (not plaster) using stud-finder verification; plaster integrity maintained throughout
• End of Day 1: outdoor unit set, 3 of 5 indoor units mounted, refrigerant line sets routed but not connected, no operating equipment yet

Installation Day 2 (June 19, 2025)

• Remaining 2 indoor units mounted (master bedroom and second bedroom)
• Refrigerant line connections at each indoor unit and outdoor unit
• Refrigerant system evacuation: nitrogen pressure test followed by vacuum pull to 500 microns or below verifying system integrity
• Refrigerant charge: factory R-454B charge in outdoor unit; additional charge added per line set length calculations
• Condensate routing: condensate lines from each indoor unit gravity drained to nearest accessible drain location (kitchen sink drain, bathroom drain, exterior drain through wall for living room and dining room units)
• Initial system startup: outdoor unit and indoor units commissioned individually; communication verified between outdoor and each indoor unit
• End of Day 2: all equipment installed and connected, system pressurized and charged, initial commissioning complete

Installation Day 3 (June 20, 2025)

• Performance verification: each indoor unit operated in cooling mode with delta-T measurement (supply vs return air temperature) verifying 16-20°F cooling delta-T across all units
• Heat pump heating mode verification: brief testing of heating mode operation on each unit
• Refrigerant charge fine-tuning: subcooling and superheat verified at outdoor unit; minor charge adjustment made
• Wireless thermostat setup: each indoor unit configured with Mitsubishi Kumo Cloud app integration for remote control and zone scheduling
• Customer walk-through: explained operation, app setup, maintenance schedule (filter cleaning monthly, professional cleaning annually), and warranty registration
• Exterior line set covers painted to match adjacent stucco and brick
• Final cleanup and customer sign-off

Inspection (June 25, 2025)

• Kirkwood Public Works inspector visit 5 business days after installation completion
• Installation passed inspection with no modifications required
• Electrical inspector visit same day verified dedicated circuit installation

The Pricing

• Mitsubishi MXZ-5C42NAHZ outdoor unit: $5,800 equipment cost
• 5 indoor wall-mounted units (varied capacities): $5,400 equipment cost
• Refrigerant line sets (5 separate runs, total 180′ linear): $1,800
• Line set covers (paintable PVC, exterior runs): $480
• Concrete pad for outdoor unit: $240
• Electrical service (dedicated 240V circuit, new breaker): $640
• Installation labor (3 days, 2 technicians): $4,200
• Permit fee through Kirkwood Public Works: $220
• Kirkwood Historic Preservation Commission review fee: $100
• Refrigerant charge and commissioning materials: $280
• Exterior paint matching for line set covers: $80
• Miscellaneous fittings, hardware, and consumables: $160
• Total project cost: $19,400

This pricing fell within our standard range for historic home multi-zone ductless installations ($14,000–$26,000 for residential preservation-conscious 4-6 zone installations).

The Outcome

Cooling Performance

• First-summer operation (June-September 2025): System handled all summer cooling without supplemental window units or other measures
• Hot weather performance: System maintained comfortable temperatures during heat dome conditions (5+ consecutive days over 95°F) with all zones operating
• Bedroom not directly served: Third bedroom (without dedicated indoor unit) reached comfortable temperature with master bedroom unit running and door open between rooms; customer reports satisfactory comfort even on hottest days
• Sunroom operation: Sunroom reaches uncomfortable temperatures (95-105°F) during peak afternoon sun even with adjacent units operating; customer accepted this seasonal limitation as expected at quote time

Supplemental Heating

• Shoulder season operation (October 2025, April 2026): System operated in heat pump mode for supplemental heating during shoulder weather, reducing hydronic boiler runtime
• Mid-winter operation: Customer kept hydronic heating as primary heat source during cold weather (more even heat distribution from cast-iron radiators); used heat pump heating only in selectively occupied rooms
• Hyper-Heat capability validation: Equipment operated normally during Polar Vortex stretches in January 2026 with outdoor temperatures reaching -2°F; not used as primary heat but demonstrated capability

Energy Performance

• Summer 2025 electricity consumption: Approximately $180-$240 monthly for cooling (typical residential air conditioning electricity usage for home of this size)
• Winter 2025-2026 gas consumption: Reduced approximately 12-18% versus prior winter due to shoulder-season heat pump heating reducing boiler runtime

Customer Feedback

Customer reported high satisfaction with several aspects: complete preservation of plaster walls and original architectural detail throughout home; outdoor unit visually screened from street by existing landscaping; refrigerant line covers nearly invisible after painting; zoned operation flexibility allows precise comfort control room-by-room; remote app control valuable for pre-cooling before arrival home; system operation quiet enough to be unnoticeable in adjacent rooms.

Ongoing Service

Customer enrolled in our maintenance plan covering both the new Mitsubishi system and existing Weil-McLain boiler; annual maintenance scheduled spring (for cooling system) and fall (for boiler).

Frequently Asked Questions

Couldn’t you have installed central AC ductwork without major plaster damage?

Honest answer: probably not without modifications the customer wasn’t willing to accept. Central AC ductwork in a 1924 Tudor Revival typically requires: substantial wall openings for vertical ductwork chases (typically 10-14" wide with framing modifications); ceiling soffits or dropped ceilings for horizontal ductwork distribution to upstairs bedrooms (typically 8-12" reduction in ceiling height in affected areas); plaster cuts and patches at each supply register and return grille location (5-15 supply and return locations typical for adequate distribution in 2,180 sf home); air handler installation in attic with substantial structural access modifications. Even with extensive contractor skill, this work results in visible modifications throughout the home — plaster patches that don’t perfectly match original texture, ceiling height reductions in affected rooms, structural modifications visible in attic and basement, and substantial finish disturbance during installation. For some historic home customers, this is acceptable when they prioritize central AC over preservation purity; for this customer who prioritized preservation purity, ductless was clearly the better choice. We had honest conversation about these tradeoffs during quote development; customer’s decision for ductless was informed by full understanding of what central ducted installation would have required.

What about high-velocity small-duct systems like Unico?

Unico and similar high-velocity systems were considered and we discussed them with the customer during quote development. High-velocity systems use 2-3" diameter flexible ducts in modular chases routed through walls, ceilings, and floor cavities, with small (2") supply outlets in ceilings or walls — substantially less installation impact than conventional ductwork. Pros: closer to plaster preservation than conventional ducted installation; centralized air handler can be hidden in attic or basement; works well with existing finished spaces; can use existing chases for some routing. Cons specific to this home: ceiling chases still required for second-floor distribution requiring plaster ceiling penetrations at supply outlets (typically 2" round holes with finished trim, but still visible modifications); air handler installation required structural modifications for unit support and refrigerant connections; equipment costs higher than conventional ductwork (offset somewhat by lower installation complexity); cooling output less than conventional ducted systems for given space (high-velocity is better for cooling than heating). Final decision: customer was firm on plaster preservation including avoiding any visible ceiling modifications; ductless mini-split could be installed with zero modifications to walls or ceilings (only stud-mounted wall units), making it the only solution meeting customer’s preservation priorities. For some homes where customers are willing to accept the modest installation impact of high-velocity systems, Unico is excellent middle ground between conventional ducted and ductless — but for absolute preservation priorities, ductless is the path.

How disruptive was 3 days of installation work?

Manageable but more disruptive than a single-day equipment replacement project. The work was distributed across the home rather than concentrated in mechanical room: outdoor unit placement in rear yard (Day 1, no home interior impact); indoor unit mounting in 5 rooms across two floors (Days 1-2, room-by-room access during work); refrigerant line set routing through interior wall chases between floors (Days 1-2, requires access through wall and ceiling cavity locations); electrical work for dedicated circuit (Day 1, basement to second-floor wall routing); commissioning and verification work at outdoor unit and all 5 indoor units (Day 3, throughout home). Customer-side impact during installation: 1-2 rooms not accessible at any given time during installation day work; some construction noise during line set routing through chases; protective coverings throughout home limiting normal use; outdoor unit pad work in rear yard. We maintained protective coverings and daily cleanup throughout, minimizing finish protection issues; family was able to continue normal home function in non-affected rooms during installation days; bedrooms were prioritized for completion before nighttime occupancy on Day 1-2. Customer reported that disruption was manageable and worth the final result; preparation by customer (cleared rear yard area, moved furniture away from indoor unit placement locations, planned around installation days for important appointments) helped manage disruption during work.

What’s the maintenance like on a 5-zone ductless system?

More involved than a single central system but manageable with proper schedule. Routine homeowner maintenance: filter cleaning monthly on each indoor unit during cooling and heating season (filters are washable, no replacement parts needed for routine maintenance); visual inspection of indoor units for blockage or unusual sounds; condensate drain verification (water reaching expected drain locations, not collecting in unit). Annual professional maintenance: thorough cleaning of each indoor unit (evaporator coil, drain pan, blower wheel); refrigerant charge verification at outdoor unit; electrical connection verification; outdoor unit coil cleaning and inspection; condensate drain clearing; communication verification between outdoor and indoor units. Maintenance plan economics: our maintenance plan for 5-zone ductless system runs $340-$480 annually depending on plan tier (more expensive than single-system maintenance plans reflecting the more substantial annual work); covers all routine professional maintenance plus priority dispatch for emergency calls plus 15-20% discount on repair work plus 2 free after-hours diagnostic visits. For this customer with substantial investment in the new system and preservation-conscious approach to home maintenance generally, the maintenance plan economics were favorable; routine maintenance protects warranty registration and extends equipment service life from baseline 15-20 years to 20-25+ years with proper care.

What if the customer hadn’t been firm on plaster preservation?

The quote development conversation and equipment recommendation would have been different. We always honor customer-stated priorities during quote development rather than overriding with our preferences. If this customer had been more flexible on plaster preservation, we would have presented additional options including: full central ducted system installation with managed plaster impact ($14,000-$18,000 typical for similar-size historic home conventional installation with quality plaster restoration; significantly cheaper than ductless multi-zone but with visible installation impact); Unico high-velocity ducted installation ($16,000-$20,000 typical; middle ground on both cost and preservation impact); hybrid approach with central ducted for first floor public spaces plus ductless for upstairs bedrooms ($18,000-$22,000 typical; addresses different rooms with different approaches). The customer’s firm preservation priority eliminated these options and made ductless multi-zone the clear best fit; for customers with different priorities, the recommended approach could be very different. The key is that customer priorities drive equipment selection — we don’t have a default recommendation that gets applied regardless of what the customer values. Our job during quote development is to present options that match customer priorities and explain tradeoffs honestly so the customer can make informed decisions.

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Contact Purisync Heating and Air

For your historic home AC installation or ductless mini-split retrofit, contact our 325 N Kirkwood Road office at (314) 338-5111. Initial consultation includes equipment options across ducted, ductless, and high-velocity systems, preservation review planning for historic district homes, and written quote with itemized pricing across multiple manufacturers and configurations.

• 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

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