Case Study: Central AC Installation Near Lake Manawa, Council Bluffs
This case study documents a central AC installation for a home in the residential area near Lake Manawa, the 660-acre lake in Council Bluffs that’s the centerpiece of Lake Manawa State Park (Iowa’s first state park, established 1922). The property had previously relied on window AC units; the customer chose central AC installation with particular attention to humidity management given the lake-adjacent location’s higher ambient humidity. The work included addition of central AC to a home with existing forced-air furnace, with ductwork modifications for proper AC airflow integration.
Customer Situation
The property is a 1978 ranch home in the residential area west of Lake Manawa, 1,850 sq ft on a 9,800 sq ft lot. The customers (couple in their early 60s with adult children no longer at home, husband retired construction superintendent, wife retired healthcare administrator) had purchased the home 8 years earlier (2017). The home had original 1978 forced-air heating (replaced 2019 with modern condensing furnace) but had never had central AC installed.
Existing equipment:
- 2019 Lennox EL296V 96% AFUE two-stage furnace, 6 years old, operating well
- No central AC; window units in living room and master bedroom during summer
- Builder-installed ductwork from 1978 original construction
- 200-amp electrical service updated 2012 (previous owner improvement)
Motivations for central AC installation:
- Eliminate seasonal window unit installation, removal, and storage burden
- Whole-home cooling vs limited two-room coverage with window units
- Particular concern about humidity management given lake-adjacent location
- Customer experience with lake-effect humidity making summer indoor comfort difficult
- Retirement-budget consideration with appropriate equipment tier
Diagnostic Assessment
Consultation by Krystal Bauer (IAQ Lead with substantial cooling and humidity expertise). Assessment time approximately 2 hours including detailed ductwork inspection and humidity assessment.
Ductwork Assessment
- 1978 original builder-installed ductwork: adequate for furnace operation but never sized for AC airflow
- Supply trunk in basement: adequate cross-section for AC operation
- Branch ductwork to rooms: minor adjustments needed for AC humidity removal capacity
- Return air: 1 return only (typical 1978 construction); additional return location recommended for AC effectiveness
- Existing ductwork sealing: substantial leakage at joints; ductwork sealing recommended
Humidity Management Considerations
- Lake Manawa proximity creates higher ambient humidity than typical Omaha metro location
- Indoor humidity goal: 45-55% during cooling season (vs typical Omaha summer indoor humidity often 55-65% with average AC equipment)
- Two-stage AC operation produces longer steady-state cycles with substantially better humidity removal vs single-stage
- Right-sized equipment (avoiding oversize) supports longer cycles for humidity management
- Existing two-stage furnace will pair particularly well with two-stage AC for matched system operation
Equipment and Ductwork Selection
- Lennox EL18XCV two-stage AC — 18 SEER2 R-454B, 2.5 ton size (right-sized to actual cooling load via Manual J)
- New evaporator coil — A2L-compatible matched to AC
- New refrigerant line set — A2L-compatible
- Additional return air location — new return added in master bedroom area for improved AC effectiveness
- Ductwork sealing — mastic sealing of accessible joints to reduce leakage
- Aprilaire 1830 dehumidifier (optional, declined by customer) — presented as supplemental humidity management option; customer chose to defer dehumidifier decision until evaluating AC humidity performance first
- Smart thermostat with humidity sensor — ecobee Smart Thermostat Premium for humidity monitoring and control
Project Execution
Two-day project given ductwork modifications and AC installation:
Day 1 (8 hours) — Ductwork modifications: install additional return air location and ductwork to master bedroom area, mastic sealing of accessible joints throughout supply and return systems, ductwork pressure testing.
Day 2 (6 hours) — AC installation: outdoor unit positioning on new concrete pad with vibration isolation, refrigerant line set installation, new evaporator coil installation in existing air handler, electrical work, R-454B refrigerant charging, smart thermostat installation and commissioning, customer walkthrough including humidity monitoring explanation.
Results
- Whole-home central AC capability — first time the 1978 home has had central air conditioning
- Window unit elimination — seasonal aesthetic, noise, and operational burden eliminated
- Two-stage humidity management — longer steady-state cycles produce substantially better humidity removal than single-stage equipment would
- Indoor humidity achievement — first cooling season indoor humidity 45-52% (within customer target range)
- Matched system operation — two-stage AC paired with existing two-stage furnace produces integrated matched system
- Additional return air benefit — master bedroom AC effectiveness substantially improved with dedicated return
- Ductwork sealing improvement — reduced ductwork leakage produces approximately 8-12% efficiency improvement on entire system
- Modern A2L refrigerant — R-454B compliance for 15-20 year equipment lifespan
- OPPD/MidAmerican rebate — $400 for qualifying SEER2 16+ equipment (Iowa MidAmerican Energy customer)
Pricing
Total project cost: $7,400
- Lennox EL18XCV AC (2.5 ton, 18 SEER2, R-454B): $4,500
- A2L-compatible evaporator coil: $785
- A2L-compatible refrigerant line set: $385
- Additional return air installation (ductwork + grille): $585
- Ductwork mastic sealing: $385
- ecobee Smart Thermostat Premium with humidity sensor: $485
- R-454B refrigerant charge: $185
- Concrete pad installation: $185
- Installation labor (14 hours over 2 days): $1,485
- Materials and supplies: $185
- Day 1 / Day 2 coordination: included
Net cost after rebate:
- Project cost: $7,400
- MidAmerican Energy rebate: -$400
- Net cost: $7,000
Federal tax credit not applicable for AC-only installation (federal Section 25C focuses on furnaces and heat pumps; standard AC doesn’t qualify).
First-Year Humidity Performance
Customer feedback during first cooling season:
- Indoor humidity maintained 45-52% throughout summer (substantial improvement over window unit operation which typically produced 60-70% indoor humidity)
- Two-stage operation handles approximately 80% of cooling hours at reduced first-stage capacity
- Longer steady-state cycles produce substantially better moisture removal vs short single-stage cycling
- Customer specifically noted reduced sticky/clammy feeling in lake-adjacent humid conditions
- Additional return in master bedroom produced excellent AC effectiveness in that space (which had been particularly affected by humidity)
- Dehumidifier addition deferred (and ultimately not needed) given AC humidity management adequacy
Lessons from This Project
- Lake-adjacent properties benefit substantially from humidity-focused AC equipment selection and installation
- Two-stage AC produces substantially better humidity management than single-stage; particularly important for humid environments
- Right-sized equipment is essential for humidity management; oversized equipment produces short cycles inadequate for moisture removal
- Ductwork modifications during AC installation (additional returns, sealing) substantially improve outcomes vs simple equipment installation in existing ductwork
- Smart thermostat humidity monitoring enables customer to verify performance against humidity targets
- Iowa MidAmerican Energy customer rebates for qualifying equipment provide modest incentive comparable to OPPD Nebraska rebates
Contact Omaha Heating and Air Conditioning
For Council Bluffs Lake Manawa area central AC installation, humidity management consultation, ductwork modification with AC addition, or two-stage matched system installation, call our 24/7 line.
- Emergency Line (24/7): (402) 258-6703
- MidAmerican Energy Emergency: 800-595-5325 (Iowa gas/electric)
- 911: for CO detector alarms or fire/smoke situations
- Address: Lake Regency Building, 450 Regency Pkwy #370, Omaha, NE 68114
- Email: info@omahaheatingairconditioning.xyz
- Iowa Plumbing & Mechanical Systems Board License: #B-027841
- EPA Section 608 Universal: #608U-2014-227841