A high-efficiency gas furnace, also called a 90%+ AFUE or condensing furnace, captures heat that an older 80% AFUE unit sends straight up the flue. The result is that 90% to 96% of the gas you pay for becomes heat in your house, instead of 80%. In Pittsburgh, where winter gas bills run from November through March, that efficiency difference shows up on the utility statement every month.

Wahl installs Rheem high-efficiency gas furnaces as our primary line (Rheem Pro Partner, top dealer tier), with Trane available for customers who prefer that brand. Every install includes proper PVC venting, condensate drain routing, Manual J sizing, and a commissioning checklist.

How a 96% AFUE furnace works differently

The technology change is straightforward. A standard 80% furnace burns gas, sends the hot combustion gases through a heat exchanger, and exhausts them through a metal flue at roughly 350 to 400 degrees. The heat in those exhaust gases is lost.

A 96% AFUE condensing furnace adds a second heat exchanger. The hot gases pass through that secondary heat exchanger and give up most of their remaining heat to the airstream. The exhaust gases cool low enough that water vapor in them condenses to liquid water. That water drains out through a condensate line. The exhaust temperature is low enough (often 110 to 130 degrees) that it can be vented through PVC instead of metal.

What this means in practice:

• Lower gas bills (the savings are the whole point)
• Sealed combustion (the burner pulls combustion air from outside, not from your basement)
• PVC vent piping (lower cost, easier to route, often vents directly out a side wall)
• Required condensate drain to a floor drain, sump, or condensate pump
• Slightly more complex commissioning and maintenance

When high-efficiency is the right call

The 90%+ tier pencils best for:

• Homeowners staying in the house seven to ten years or longer
• Homes with high winter gas usage (older homes, larger homes, multi-story)
• Locations where a condensate drain run is practical
• Houses with chimney problems that would otherwise need a chimney liner for a metal-flue 80% furnace (the PVC vent often skips the chimney entirely)
• Anyone replacing an old 60% or 70% AFUE furnace (the efficiency jump is dramatic)

Where 80% AFUE often still wins:

• Rental properties and short-term holdings
• Homes with no practical condensate drain route
• Homes where the existing chimney is in good condition and the upcharge does not pencil

We will quote both tiers when we visit. You see the math, you decide.

What we install

• Rheem 96% AFUE single-stage condensing furnaces
• Rheem 96% AFUE two-stage condensing furnaces
• Rheem 97%+ AFUE variable-speed modulating condensing furnaces (top tier)
• Trane high-efficiency models
• PVC vent and combustion air piping
• Condensate drain runs and condensate pumps where gravity drainage is not available
• Matched coils and AC condensers for full system replacement
• Smart and programmable thermostats

What goes into a high-efficiency furnace install

A high-efficiency install is more involved than swapping an 80% AFUE in place. There is real venting work, condensate work, and combustion air work that has to be done right.

1. Manual J load calculation
2. Vent route planning, sealed combustion air and exhaust both routed (typically two pipes out the side wall)
3. Condensate route planning, gravity drain or pump
4. Combustion analyzer reading at startup
5. Temperature rise verification across both heat exchangers
6. Gas pressure check at the manifold under firing conditions
7. Confirm condensate drainage and trap fill
8. Walk-through with the homeowner on filter, condensate, vent inspection, and warranty

What about the chimney

This is a Pittsburgh-specific consideration. Many older Pittsburgh homes have a shared masonry chimney that vents the furnace and the water heater. When you switch from 80% AFUE (metal flue, hot exhaust) to 96% AFUE (PVC vent, no chimney), the water heater is suddenly venting alone into an oversized chimney. That can cause draft problems, moisture problems, and in worst cases, backdrafting carbon monoxide.

Two solutions exist and we will quote whichever fits the home:

• Reline the chimney with a properly sized aluminum or stainless liner for the water heater
• Replace the water heater with a tankless or power-vented model that does not need the chimney at all

If your installer does not address this when they quote a 96% furnace, that is a problem. We address it on every quote.

Common questions about high-efficiency before buying

Will my gas bill actually drop? Yes, and the drop is bigger when you are replacing an older furnace. A 1995 furnace at 78% AFUE replaced with a modern 96% AFUE is a meaningful Pittsburgh utility-bill change every winter month.

Do I have to use PVC venting? In nearly all installs, yes. PVC is the standard for condensing furnaces. We size and route the vent according to manufacturer specs and local code.

What happens to the chimney? We address it during the quote. See the section above.

Schedule a quote

Call 1-855-GET-WAHL (1-855-438-9245) or schedule online. We walk the house, calculate the load, address chimney and condensate, and quote two or three real options on paper.