Cost to Add HVAC to An Old House: Real Prices And Retrofit Factors

Adding HVAC to an older home typically costs between about $4,000 for a small ductless install and $60,000+ for a large, complicated retrofit. Most full-house retrofits fall between $12,000 and $28,000 depending on system type, ductwork, electrical/gas upgrades, and envelope work. (Source: ASHRAE Technical Resources) If you are adding or upgrading a system in an older home, our residential HVAC services page explains ducted and ductless options, load calculations, and what a full retrofit typically involves.

Key Takeaways

Expect small ductless installs around $4k–$10k; full forced-air or whole‑house heat pump with new ducts typically $12k–$28k; complex historic retrofits $25k–$60k+.
Require a Manual J load calculation and Manual D duct design, blower door and duct leakage targets to avoid oversizing and comfort issues.
Prioritize air sealing and insulation first; lower loads reduce equipment size and operating cost and expand system choices.
Get 3 itemized bids showing models, efficiencies, duct scope and leakage targets, electrical/gas scope, permits, timeline, and rebates.

How much does adding HVAC typically cost?

Typical national price ranges?

Ductless mini-split (single-zone to small multi-zone): $4,000–$10,000 installed. Central air-source heat pump with new ductwork (about 1,500–2,500 ft², moderate to cold climate): $12,000–$28,000. Furnace + AC with new ducts (gas furnace + central AC): $8,000–$25,000 depending on furnace AFUE, AC SEER, and duct complexity. Full historic/complex retrofit (3,000+ ft², electrical service upgrades, architectural work): $25,000–$60,000+. Ranges reflect equipment, labor, new ductwork, electrical/gas upgrades, permits, and any needed insulation or structural access work. Practical example: a 2,000 ft² bungalow needing new ducts and a 14-SEER heat pump in a moderate climate commonly lands in the $14k–$20k range after permitting and basic electrical work.

Which components drive most cost?

Major cost drivers: Equipment type & efficiency: high-efficiency heat pumps or two-stage gas furnaces can add 10–40% to equipment cost. Ductwork: routing through walls or ceilings in a tight, plaster house is much more labor‑intensive than running ducts in an open attic or crawlspace. Electrical service upgrades: many modern heat pumps need new breakers or a 200A service, which can cost $1,500–$4,000. Gas piping/venting: running new gas lines or adding Category III venting may add $500–$3,000+. Envelope work: air sealing, attic insulation, and window repairs lower loads but add upfront cost. Permits, testing, and commissioning: plan $500–$2,000 for permits and required tests in many jurisdictions.

How expensive is new ductwork?

Typical ductwork costs and examples?

Simple attic or crawlspace run for a modest house: $3,000–$6,000.
Complex multi-level, in-wall, or concealment runs (historic or tight cavities): $6,000–$15,000+.
High-quality sheet-metal mains, sealed and insulated trunks: add $1,000–$3,000 versus basic flex duct.

Practical check: ask contractors to list linear feet of trunk and branch ducts, register counts, and insulation R-value. A 2,000 ft² two-story house with a full new duct layout commonly falls in the $5k–$10k band unless ceilings or floors require significant framing work.

Practical checks for ductwork bids

Request a duct layout with trunk and branch lengths. Ask for register counts and the location of returns. Confirm insulation R-value for ducts in unconditioned spaces. Require sealing method details: mastic, foil tape, or aerosol duct sealing.

Ductless and heat pump options

What does a ductless mini-split cost?

Single‑zone wall-mounted unit: $3,000–$6,000 installed (one outdoor unit, one indoor head).
Multi-zone (2–4 heads): $5,000–$12,000+.
Concealed ducted indoor units, flush-ceilings, or more than four heads increases labor and parts quickly.

Ductless is less invasive and often the fastest option. Consider adding a whole-house ventilation strategy (ERV/HRV) if you install several mini-splits and your home lacks mechanical ventilation. If you are tempted to DIY parts of the install, read DIY HVAC install first so you understand the safety risks and what should be handled by a licensed pro.

How much for heat pump systems?

Air-source and geothermal ranges

Single outdoor + one indoor (small home): $4,500–$9,000.
Whole‑house cold-climate air-source heat pump (including moderate duct retrofits): $12,000–$28,000.
Ground-source (geothermal) heat pumps: $30,000–$60,000+ depending heavily on site geology and loop-field installation. (Source: ASHRAE Technical Resources)

Efficiency and climate notes: look at SEER2/HSPF2 and manufacturer cold-climate ratings. In very cold areas, plan for supplemental heat or a dual-fuel arrangement.

Can a heat pump work in older homes?

Modern cold-climate heat pumps work in many older homes if you:

Do targeted air sealing and insulation to reduce peak load.
Verify electrical service can handle the unit.
Consider a hybrid system pairing the heat pump with a gas furnace for backup in very cold climates.

Example: upgrading attic insulation from R-15 to R-38 and sealing major leaks can drop heating load by 20–30%, enabling a smaller, less costly heat pump.

Retrofitting steam radiators and hydronic systems

Converting steam or old hydronic systems to forced air or direct heat pump solutions is possible but often costly. Alternatives include:

Use ductless heads in rooms served by radiators.
Retrofit boilers to run with a hydronic heat pump if water temperatures are compatible.

Historic properties: consult a preservation specialist. Changes to radiators or visible piping often need approval and careful planning. (Source: ASHRAE Technical Resources)

Ductwork, comfort, and moisture control

Why Manual D duct design matters

Manual D ensures sized ducts deliver correct airflow to each room. Proper design prevents:

Room over- or under-supply, drafts, noise, and imbalanced comfort.
Excessive static pressure that increases energy use and shortens equipment life.

Ask for a written Manual D plan and register layout with airflow CFM per supply/return.

How duct leakage increases bills

Leaky ducts can lose 10–30% or more of conditioned air, especially when ducts run through unconditioned attics. Request a pressure-tested duct leakage target. Many quality installs aim for less than 6–8% of system fan flow or <6 CFM25 per 100 ft² of conditioned floor area, depending on local standards. Practical check: ask contractors if they perform a duct blaster test and will seal ducts with mastic and foil tape rather than plain duct tape.

Can existing ducts be reused?

If existing ducts are properly sized, structurally sound, and can be sealed and insulated, reuse saves money. Expect to replace undersized or damaged flex ducts in many older homes. Have a contractor measure existing trunk and branch sizes against Manual D requirements.

How wall cavities affect runs and cost

Thick plaster walls, lathe, and narrow studs typical of older homes limit in-wall runs. Expect workarounds: soffits, closets, lowered ceilings, or routing through conditioned attic/crawlspace. Each workaround adds labor and finish work.

Crawlspace and attic options

Attic ducts are common but must be well insulated and sealed. Otherwise expect large thermal losses.
Crawlspaces may require encapsulation or insulation to be treated as conditioned space.

Aim to place ducts inside the conditioned envelope where possible.

Getting accurate bids and required tests

What should a Manual J calculation include?

A proper Manual J should list:

Conditioned floor area by space, window types and areas, insulation levels, orientation, and infiltration assumptions.
Heating and cooling loads per zone, expressed in BTU/h and CFM.

Require a printed Manual J (with input assumptions) before accepting a proposal.

Which contractor credentials matter for old homes?

State or local HVAC license and any required mechanical/electrical licenses. NATE-certified technicians and manufacturer training for the proposed equipment. Experience with older homes and historic preservation when applicable. Proof of insurance (general liability and workers’ comp) and local references. Ask for at least two references from projects similar in age and complexity. (Source: ASHRAE Technical Resources) Use our HVAC inspection checklist to verify the quote includes documented testing and commissioning, not just equipment replacement.

How many estimates should I get?

Get at least three itemized bids. To understand what happens during a retrofit from start to finish, read our HVAC installation process guide. Compare make/model numbers, efficiencies (SEER/HSPF/AFUE/COP), Manual J/D included, duct materials and leakage targets, electrical/gas scope, permit fees, startup and commissioning, total price, timeline, and warranty details. Practical tip: create a one-page comparison sheet to force an apples-to-apples review.

Tests and permits required

Manual J is the standard for sizing. Oversized equipment wastes energy and underperforms on humidity control. A blower door test quantifies whole-house air leakage and identifies priority air-sealing locations. Sealing can cut required capacity by 10–30%. A duct blaster test provides cfm leakage numbers or a percentage of fan flow. Include target numbers in the contract. Use ASHRAE 62.2 for ventilation rates. The continuous ventilation rate formula: Qf (cfm) = 0.03 × floor area (ft²) + 7.5 × (bedrooms + 1). Most work requires mechanical, electrical, and sometimes building permits. Expect inspections at rough-in and final stages. Allow 1–2 weeks for permit scheduling in many areas. Ensure an electrician or licensed plumber performs service changes and gas piping. They must provide inspection signoffs.

Electrical, gas, and insulation impacts

Typical electrical and gas upgrade costs and checks

Electrical service upgrade to 200A: $1,500–$4,000 depending on meter location and utility coordination.
New dedicated circuits, disconnects, and minor wiring: $300–$1,500.
Gas line installation or extension: $500–$3,000+ depending on distance and trenching needs.

Practical check: if the main panel is 100A, with old wiring and few spare breakers, plan for a potential panel upgrade. Ask the contractor to list required breaker sizes and any utility coordination fees.

How does insulation affect system size and cost?

Sealing air leaks and adding insulation reduce heating and cooling loads. They can let you choose a smaller, less expensive system. Example: increasing attic insulation from R-19 to R-38 and sealing attic-to-house penetrations can lower peak heating load by 10–25% depending on climate and leakage. Homeowner checks: measure attic insulation depth, inspect for daylight at sill plates, and note recessed lights and wiring that may need sealing.

Action checklist for homeowners

How to compare bids side by side

Create a spreadsheet with columns for: equipment make/model and serials, SEER/HSPF/AFUE/COP, Manual J/D included, duct materials and leakage target, electrical/gas upgrades, permit fees, pre- and post-testing (blower door/duct blaster), total price, startup/commissioning visit, labor warranty and equipment warranty, timeline, and rebate assistance. Ask contractors to justify differences in labor scope and material quality. Sample email checklist to request bids from contractors Use this text to request comparable bids (edit fields in brackets): Hello [Contractor name], Please provide an itemized proposal to serve my house at [address]. Include the following: A printed Manual J load calculation and Manual D duct layout if ducts are required. Equipment make/model, SEER/HSPF/AFUE ratings, and estimated capacity in BTU/h. Detailed duct scope: trunk length, branch layout, register counts, insulation R-value, and proposed sealing method (mastic, foil tape). Duct leakage target and confirmation that a duct blaster test will be performed. Electrical panel and circuit requirements and estimated cost for any panel upgrade. Any gas piping or venting work and associated costs. Permit fees, inspections, and expected timeline from start to final inspection. Start-up and commissioning visit included in price and written equipment warranty information. Any available rebates you will assist with and an estimate of net cost after rebates. Please include at least two references for recent jobs on older homes and a copy of your insurance certificate. I plan to collect three bids and will schedule site visits the week of [date]. Thank you, [Your name, phone number, email] Sample three-bid comparison (hypothetical house: 2,000 ft², northern climate)

Bid A (Heat pump + new ducts): $18,500 total. Equipment: 15-SEER/8-HSPF inverter heat pump, new sheet-metal trunks and insulated flex branches, duct leakage target <6% fan flow, panel upgrade to 200A included, blower door pre/post testing not included, 10-year compressor warranty. Timeline: 10 working days.
Bid B (Ductless 3-zone): $9,800 total. Equipment: 3 indoor heads, 20-SEER equivalents in heating mode, minimal drywall work, no changes to electrical service, no blower door test, optional ERV for $3,200. Timeline: 3 days.
Bid C (Furnace + AC + ducts): $14,200 total. Equipment: 95% AFUE gas furnace + 14-SEER AC, new ducts run in attic, duct leakage target 10% (lower price quoted), gas line run 40 ft included, panel upgrade not included ($2,100 if needed). Timeline: 7 working days.

How to read this: Bid A costs more but includes a panel upgrade, tighter duct leakage target, and a longer warranty on the heat-pump compressor. Bid B is the least invasive but may need supplemental ventilation (ERV). Bid C is lower price but calls out looser duct leakage and excludes electrical work. Ask follow-up questions and request changes to make the scope comparable.

Final practical checks before signing

Verify Manual J/D documents and blower door/duct blaster reports will be provided. Confirm who pulls permits and that the price includes permit fees. Get the exact equipment models and written warranty terms. Request startup, system balancing, and thermostat programming as part of the contract. Require written change-order procedures and lien releases for major material purchases. Making the system choice for an older house depends on your budget, access for ducts, desire to preserve original finishes, and long-term energy goals. Prioritize a proper load calculation, air sealing, and clear, itemized bids to avoid surprises and get a comfortable, efficient result. (Source: ASHRAE Technical Resources)

Key Takeaways

Expect small ductless installs around $4k–$10k; full forced-air or whole‑house heat pump with new ducts typically $12k–$28k; complex historic retrofits $25k–$60k+.
Require a Manual J load calculation and Manual D duct design, blower door and duct leakage targets to avoid oversizing and comfort issues.
Prioritize air sealing and insulation first; lower loads reduce equipment size and operating cost and expand system choices.
Get 3 itemized bids showing models, efficiencies, duct scope and leakage targets, electrical/gas scope, permits, timeline, and rebates.

How much does adding HVAC typically cost?

Typical national price ranges?

Which components drive most cost?

How expensive is new ductwork?

Typical ductwork costs and examples?

Simple attic or crawlspace run for a modest house: $3,000–$6,000.
Complex multi-level, in-wall, or concealment runs (historic or tight cavities): $6,000–$15,000+.
High-quality sheet-metal mains, sealed and insulated trunks: add $1,000–$3,000 versus basic flex duct.

Practical checks for ductwork bids

Ductless and heat pump options

What does a ductless mini-split cost?

Single‑zone wall-mounted unit: $3,000–$6,000 installed (one outdoor unit, one indoor head).
Multi-zone (2–4 heads): $5,000–$12,000+.
Concealed ducted indoor units, flush-ceilings, or more than four heads increases labor and parts quickly.

How much for heat pump systems?

Air-source and geothermal ranges

Single outdoor + one indoor (small home): $4,500–$9,000.
Whole‑house cold-climate air-source heat pump (including moderate duct retrofits): $12,000–$28,000.
Ground-source (geothermal) heat pumps: $30,000–$60,000+ depending heavily on site geology and loop-field installation. (Source: ASHRAE Technical Resources)

Efficiency and climate notes: look at SEER2/HSPF2 and manufacturer cold-climate ratings. In very cold areas, plan for supplemental heat or a dual-fuel arrangement.

Can a heat pump work in older homes?

Modern cold-climate heat pumps work in many older homes if you:

Do targeted air sealing and insulation to reduce peak load.
Verify electrical service can handle the unit.
Consider a hybrid system pairing the heat pump with a gas furnace for backup in very cold climates.

Example: upgrading attic insulation from R-15 to R-38 and sealing major leaks can drop heating load by 20–30%, enabling a smaller, less costly heat pump.

Retrofitting steam radiators and hydronic systems

Converting steam or old hydronic systems to forced air or direct heat pump solutions is possible but often costly. Alternatives include:

Use ductless heads in rooms served by radiators.
Retrofit boilers to run with a hydronic heat pump if water temperatures are compatible.

Historic properties: consult a preservation specialist. Changes to radiators or visible piping often need approval and careful planning. (Source: ASHRAE Technical Resources)

Ductwork, comfort, and moisture control

Why Manual D duct design matters

Manual D ensures sized ducts deliver correct airflow to each room. Proper design prevents:

Room over- or under-supply, drafts, noise, and imbalanced comfort.
Excessive static pressure that increases energy use and shortens equipment life.

Ask for a written Manual D plan and register layout with airflow CFM per supply/return.

How duct leakage increases bills

Can existing ducts be reused?

How wall cavities affect runs and cost

Crawlspace and attic options

Attic ducts are common but must be well insulated and sealed. Otherwise expect large thermal losses.
Crawlspaces may require encapsulation or insulation to be treated as conditioned space.

Aim to place ducts inside the conditioned envelope where possible.

Getting accurate bids and required tests

What should a Manual J calculation include?

A proper Manual J should list:

Conditioned floor area by space, window types and areas, insulation levels, orientation, and infiltration assumptions.
Heating and cooling loads per zone, expressed in BTU/h and CFM.

Require a printed Manual J (with input assumptions) before accepting a proposal.

Which contractor credentials matter for old homes?

How many estimates should I get?

Tests and permits required

Electrical, gas, and insulation impacts

Typical electrical and gas upgrade costs and checks

Electrical service upgrade to 200A: $1,500–$4,000 depending on meter location and utility coordination.
New dedicated circuits, disconnects, and minor wiring: $300–$1,500.
Gas line installation or extension: $500–$3,000+ depending on distance and trenching needs.

How does insulation affect system size and cost?

Action checklist for homeowners

How to compare bids side by side

Bid A (Heat pump + new ducts): $18,500 total. Equipment: 15-SEER/8-HSPF inverter heat pump, new sheet-metal trunks and insulated flex branches, duct leakage target <6% fan flow, panel upgrade to 200A included, blower door pre/post testing not included, 10-year compressor warranty. Timeline: 10 working days.
Bid B (Ductless 3-zone): $9,800 total. Equipment: 3 indoor heads, 20-SEER equivalents in heating mode, minimal drywall work, no changes to electrical service, no blower door test, optional ERV for $3,200. Timeline: 3 days.
Bid C (Furnace + AC + ducts): $14,200 total. Equipment: 95% AFUE gas furnace + 14-SEER AC, new ducts run in attic, duct leakage target 10% (lower price quoted), gas line run 40 ft included, panel upgrade not included ($2,100 if needed). Timeline: 7 working days.

Cost to Add HVAC to An Old House: Real Prices And Retrofit Factors

Key Takeaways

How much does adding HVAC typically cost?

Typical national price ranges?

Which components drive most cost?

How expensive is new ductwork?

Typical ductwork costs and examples?

Practical checks for ductwork bids

Ductless and heat pump options

What does a ductless mini-split cost?

How much for heat pump systems?

Air-source and geothermal ranges

Can a heat pump work in older homes?

Retrofitting steam radiators and hydronic systems

Ductwork, comfort, and moisture control

Why Manual D duct design matters

How duct leakage increases bills

Can existing ducts be reused?

How wall cavities affect runs and cost

Crawlspace and attic options

Getting accurate bids and required tests

What should a Manual J calculation include?

Which contractor credentials matter for old homes?

How many estimates should I get?

Tests and permits required

Electrical, gas, and insulation impacts

Typical electrical and gas upgrade costs and checks

How does insulation affect system size and cost?

Action checklist for homeowners

How to compare bids side by side

Final practical checks before signing

Related reading: what to explore next?

Explore Local HVAC & Plumbing Services

Related Articles

Need HVAC Help?

Cost to Add HVAC to An Old House: Real Prices And Retrofit Factors

Key Takeaways

How much does adding HVAC typically cost?

Typical national price ranges?

Which components drive most cost?

How expensive is new ductwork?

Typical ductwork costs and examples?

Practical checks for ductwork bids

Ductless and heat pump options

What does a ductless mini-split cost?

How much for heat pump systems?

Air-source and geothermal ranges

Can a heat pump work in older homes?

Retrofitting steam radiators and hydronic systems

Ductwork, comfort, and moisture control

Why Manual D duct design matters

How duct leakage increases bills

Can existing ducts be reused?

How wall cavities affect runs and cost

Crawlspace and attic options

Getting accurate bids and required tests

What should a Manual J calculation include?

Which contractor credentials matter for old homes?

How many estimates should I get?

Tests and permits required

Electrical, gas, and insulation impacts

Typical electrical and gas upgrade costs and checks

How does insulation affect system size and cost?

Action checklist for homeowners

How to compare bids side by side

Final practical checks before signing

Related reading: what to explore next?

Explore Local HVAC & Plumbing Services

Related Articles

Need HVAC Help?