Furnace Installation in Hermann, MO

When you need a new furnace installation, not a swap

This page covers heat that does not exist yet. Four situations fit it.

• New construction. A house going up on a Hermann lot, a Gasconade County farm or a Warren County subdivision.
• An addition or finished space. A new wing, garage apartment or basement that the old system cannot reach.
• A second system. An upstairs or far end of a long farmhouse that one furnace has never heated evenly.
• A first furnace. A home leaving baseboard, a boiler or a wood stove, usually with new ductwork.

If a working house simply has a worn-out furnace, read about furnace replacement instead. That job keeps most of what is already there, and this one builds it.

Choosing the fuel for a gas furnace install or an electric one

Settle the fuel first, because it sets the piping, the venting and the running cost for the next 15 to 20 years. Your address usually decides it.

Most gas furnaces ship set up for natural gas. On propane, the manufacturer's kit changes the orifices and regulator spring, and the manifold pressure gets set to spec. That work is done before first fire, not after a complaint. For an all-electric plan, compare a heat pump installation as well, since it can also supply your cooling.

Why furnace sizing comes before the equipment quote

Size it from a calculation, never from square footage or the neighbor's unit. ACCA Manual J works out the heat loss of this house, room by room. Manual S picks the equipment to match that load, and Manual D sizes the ducts to carry the air.

DOE's federal buying guidance names oversizing, poorly designed distribution and leaky ducts as sources of efficiency loss. That is the reason to do the math first. An oversized furnace short cycles, heats unevenly and wears its parts faster. New homes with tight walls and good windows often need far less capacity than people expect, and that sealing can allow a lower-capacity furnace.

Design decisions to make before the walls close

Four choices are cheap on paper and expensive after drywall.

• Mechanical room location. Central placement shortens duct runs. Leave service clearance on the sides that need it.
• Vent route. A condensing furnace vents through PVC, and DOE's Building America guideline says side-wall vents in most areas need at least ten feet between buildings, sometimes more in cold climates. That matters on tight in-town Hermann lots, so check the local code first.
• Condensate drain. The same guideline says cold-climate condensate belongs in the house sanitary drain, never outdoors. It also warns against ventilated attics where freezing can occur. Plan a gravity drain, or a pump if there is none.
• Cooling later. If central AC is coming, pick the blower and coil cabinet now so the ducts are sized for summer airflow too.

Building inside the Hermann Historic District? Whether exterior equipment is reviewed there is unconfirmed, so ask the city before you choose a vent or condenser location.

How does furnace installation in Hermann work on a new build?

A new-construction job comes in stages that follow the other trades, with more than one trip.

1. We review the plans and run the load calculation.
2. We quote the system, ducts, venting and any gas piping before work begins.
3. At rough-in, we hang ducts and set vent and drain routes while the framing is open.
4. We coordinate gas service with the city, gas company or propane supplier.
5. At trim-out, we set the furnace, connect it, and fit registers and the thermostat.
6. We pressure test the gas piping and start the furnace, then check gas pressure, temperature rise and airflow.
7. We walk you or the builder through filters, shutoffs and the first-year checks.

An addition or second system follows the same order, compressed. Timing depends on your builder's schedule, so we set it when we quote.

What the installation package covers

Ask any contractor to put these in writing, so you can compare quotes fairly.

• A Manual J load calculation and the equipment selection that follows from it
• Furnace set, leveled and connected, with a shutoff at the appliance
• Duct design and installation, or a stated reason for reusing ducts
• Vent and combustion air piping to the manufacturer's clearances
• Condensate drain, trap and any pump
• Thermostat, wiring and any new circuit
• Start-up readings recorded and left with you

What does a new furnace cost to install?

The furnace is often not the largest number on a new-system quote. Angi's St. Louis estimate, checked November 2026, runs about $2,605 to $6,142 for a furnace installed, with labor at $1,000 to $4,000 and higher when ducts, wiring or gas lines need major changes. Treat them as regional figures, not our prices.

A first-time install adds what a swap skips: new ductwork, gas piping run length, a new circuit and any permit. Ask us for a clear, upfront quote based on your plans.

Why Brian Grannemann Services for a furnace installation?

• New construction is listed among our trades, alongside heating and cooling, on our Google profile.
• We also do electrical and plumbing, so a new circuit or a drain tie-in can stay with one company.
• Stephanie H. wrote that Brian "shows up when promised," which is what a builder's schedule depends on.
• We have been based in Hermann since 1998, and our office at 124 E 10th St is staffed during office hours.

Your first year with a new furnace

Change the filter often during construction and the first months, since drywall dust loads it fast. Have the first furnace tune-up before your first full freeze season, and keep the start-up readings with the manual. Register the equipment for the manufacturer's warranty as soon as it runs.

We take new installations across our area, including Washington, Warrenton, Owensville and New Haven. Call (209) 563-1270 with your plans.