Accurate Manual J load calculations are essential in Boise because winter temperature inversions keep furnaces running at high capacity for days rather than short cycles. Oversized units short-cycle, fail to reach steady-state efficiency and leave indoor humidity too low during shoulder seasons when daily temperature swings reach 35–40°F. We measure actual heat loss room by room, including the effects of older single-pane windows common in North End bungalows and the tighter envelopes of 2000s tract homes in Meridian and Kuna.
Existing duct systems often dictate equipment choice. Retrofitted ducts in 1920s East End homes frequently create high static pressure that reduces airflow and stresses the new blower motor. In newer subdivisions we routinely find undersized returns installed with builder-grade 80 % furnaces now at end of life. We test static pressure before and after installation and resize or modify trunks and returns so the replacement furnace operates within manufacturer specifications.
Combustion air, venting and local permitting requirements differ sharply between natural-gas homes in the city and propane properties on the rural edges of Star and Middleton. We verify vent sizing for high-efficiency units, confirm condensate drainage on hard-water lines and pull permits through the appropriate jurisdiction. Final commissioning includes combustion analysis, temperature-rise verification and a full static-pressure report so the system runs reliably through the next inversion period.
Technician insight
In Boise the thing that catches most people out with Furnace Replacement is the duct static pressure in North End bungalows. Those retrofitted runs were never designed for modern blowers, so a new furnace that looks perfect on paper will short-cycle and trip pressure switches unless the ducts are corrected first.
North End Bungalow Furnace Replacement
Homeowner reported short cycling and cold rooms during an inversion. We found the original 80 % furnace oversized for the 1928 home and ducts with 0.8 in. w.c. static. After Manual J calculation we installed a properly sized 95 % unit, enlarged the return trunk and commissioned the system. Static dropped to 0.45 in. w.c. and the furnace now runs steady through cold spells.
Furnace Replacement Services We Offer
✓High-Efficiency Furnace Replacement
Install 95–98 % AFUE furnaces sized to Manual J loads so Boise homes maintain comfort during multi-day inversions without short cycling.
✓Propane Furnace Replacement
Replace propane furnaces on outer Kuna and Middleton properties with correctly orificed units matched to tank pressure and local combustion-air rules.
✓Ductwork Modifications for New Furnaces
Resize or reroute trunks and returns in North End and East End homes to bring static pressure into spec before the new furnace is set.
✓Builder-Grade Furnace Swap in Tract Homes
Direct replacement of aging 80 % furnaces in Meridian, Star and Kuna subdivisions with properly commissioned high-efficiency models.
✓Venting and Combustion-Air Upgrades
Update PVC or metal venting and add combustion-air intakes required when switching to condensing furnaces in tight mechanical closets.
Furnace Replacement Cost in Boise, ID
| Service | Typical Range | What Affects It |
|---|---|---|
| Standard 95 % Furnace Replacement | $5,200–$7,800 | Includes basic venting; rises with duct modifications or propane conversion |
| Ductwork Modifications | $1,100–$2,900 | Common in pre-1950 North End homes; depends on trunk and return resizing |
| Propane Furnace Replacement | $5,800–$8,400 | Includes correct orifices and tank connection; varies by line length |
| Permit And Commissioning Package | $350–$550 | Required for all replacements; covers inspection and combustion report |
Ranges are typical for Boise, ID and confirmed with an exact written quote before any work starts.
How it works
- 1
Site Assessment And Load Calculation
We measure the home, inspect existing ducts, note gas or propane supply and run a room-by-room Manual J calculation.
- 2
Equipment Selection And Duct Review
We choose the furnace that matches the calculated load, then test and correct static pressure issues in the duct system.
- 3
Permit, Removal And Install
Permits are pulled, the old unit is removed, new venting and condensate lines are run, and the furnace is set and connected.
- 4
Commissioning And Handover
Combustion analysis, temperature rise, static pressure and safety checks are completed; the homeowner receives the commissioning report.
Pricing
Pricing varies with efficiency rating, fuel type, required duct changes and whether the home is on natural gas or propane.