80% direct replacement
A metal-flue system may have a more direct replacement path, subject to venting and chimney condition.
FURNACE REPLACEMENT / GREATER BOSTON
Furnace replacement starts with venting and condensate.
A direct 80% replacement and a 90%+ condensing furnace are not the same installation. New PVC intake and exhaust, drain routing, neutralization, freeze risk, and a shared chimney can change the project even at the same input BTU.
NO SIGN-INRESULTS BEFORE CONTACT DETAILS“NOT SURE” IS OKAY
01 / THE USEFUL PART
What matters before anyone quotes the work.
90%+ conversion
A condensing furnace needs approved intake/exhaust and condensate handling; those are part of the installation scope.
Shared chimney check
If a water heater shares the chimney, removing the furnace from that vent can require a separate orphaned-appliance review.
02 / SYSTEM BRIEF
The furnace details that change the quote
A few photographs and observations can distinguish a direct replacement from a real efficiency conversion.
Open the free System Check →- 01Current input BTU or model number
- 02Natural gas, propane, oil, or other fuel
- 03Metal flue or PVC venting
- 04Whether a water heater shares the chimney
- 05Nearby drain, pump, or no drain
- 06Basement, attic, closet, or crawlspace access
03 / COST & SCOPE
Why a responsible price is a range first.
Efficiency path
AFUE changes equipment and can change venting, drainage, electrical, and control details.
Cabinet and duct transitions
Capacity, cabinet width, orientation, return-air configuration, and supply transition must fit the installation.
Condensate protection
Drain route, pump, neutralizer, safety switch, and freezing exposure are verified where a condensing appliance is proposed.
A complete proposal accounts for equipment, standard materials, labor, installation configuration, access, required accessories, allowances, disposal and permit assumptions. A site review confirms the final scope.
04 / STRAIGHT ANSWERS
Before you decide.
No contact form is required to read these answers or use the System Check.
01Can a metal-flue furnace be changed to 90%+?+
Often, but it is a conversion—not a like-for-like swap. Approved PVC venting, condensate, and shared-chimney conditions must be scoped.
02Is the existing furnace BTU automatically reused?+
No. It is a starting point. Final sizing and duct compatibility are verified before installation.
03Can the Builder compare 80% and 90%+?+
Yes. Choose “Show Me Both” so the installed ranges can reflect the different venting and condensate requirements.
USE THE SITE AS A TOOL
Get the plan first. Decide what to send second.
The System Check can return a broad result early, then narrow it with equipment, installation, venting, condensate, access, and optional photos.