Blower-door pre and post on a Clintonville 1925 Tudor: the real ACH50 numbers

The starting point

A 1925 Tudor in Clintonville near the Olentangy. 2,400 sqft, full basement, 1.5-story design with a finished attic-converted second floor. Owner had bought the home in 2022 and lived through three winters with the original 1925-spec envelope. Symptoms: cold upstairs (the converted second floor consistently ran 12-15 degrees below the thermostat setting in winter), drafty exterior outlets in the first-floor living room, ice damming on the front-facing roof gable every winter.

The owner had read about foam-versus-cellulose decision frameworks and called us in March 2026 for a quote.

The on-site assessment

The pre-spray thermal imaging walkthrough identified six specific heat-loss surfaces.

1. Wall cavities (empty). Original 1925 plaster walls with no insulation. Thermal imaging showed exterior walls running 14-20 degrees below the conditioned space temperature during the winter pre-assessment, a wide delta driven by the cold Zone 5A outdoor temperatures. 2. Attic floor (R-11 batts, 1980s retrofit). Settled and incomplete coverage. Edges along soffit areas showed no insulation at all. 3. Knee walls (back side of finished second-floor walls). No insulation. Major heat-loss source explaining the cold upstairs. 4. Rim joist (basement). Original 1925 construction, no insulation. Stack-effect chimney for the entire envelope. 5. Bonus-room cold spots over an attached garage addition (1962). Insulation in the floor cavity between the garage ceiling and the bonus room above had compressed and degraded. 6. Roof deck along the front gable. No insulation between rafters; original board sheathing with shingles directly attached.

Quote: $19,600 fixed for whole-home foam package plus a Panasonic ERV pairing. 3 days of install plus 1 day of ERV ductwork.

The blower-door numbers

Three blower-door readings: pre-spray, mid-install, and 60-day post-spray verification.

Pre-spray (Day 1, 7:30 AM, before any work): 11.8 ACH50. This is typical for pre-1950 Columbus housing with empty wall cavities and incomplete attic insulation. Anything over 10 ACH50 is "very leaky" in the BPI classification.

Mid-install (Day 2, 5 PM, after Day 1 rim-joist closed-cell + Day 2 wall drill-and-fill): 6.4 ACH50. A 46 percent reduction from baseline just from sealing the basement perimeter and filling the wall cavities. The wall drill-and-fill was 47 cavities; the crew used hybrid foam (closed-cell base layer plus open-cell top-up) to reduce blowout risk on the lath-and-plaster substrate.

Post-install (Day 4, 4 PM, after all 4 days of work): 3.6 ACH50. A 69 percent total reduction from baseline. This is in the "tight" category and meaningfully tighter than typical Columbus post-foam homes (post-foam installs on similar pre-1950 stock usually land in the 4 to 5 ACH50 range).

60-day verification (June 2026, same protocol): 3.8 ACH50. Slight loosening as the foam settles and the home reaches new equilibrium. Still in the tight range.

The comfort outcomes (owner-reported, 60 days post-install)

Two months of summer use with the new envelope.

Temperature stability. First-to-second-floor delta dropped from 12-15 degrees winter, 6-8 degrees summer to 1-2 degrees year-round.

Humidity. Indoor RH in summer (typical Columbus July, dew points in the mid-to-high 60s) holds at 48-52 percent on the ERV running continuous-low mode. Pre-foam, indoor RH would run 63-68 percent during humid weeks with the AC fighting it.

Quiet. Significantly reduced exterior noise through walls. Owner specifically called out being able to nap with the bedroom window facing the street, which was not possible pre-foam.

Drafts. Exterior outlets on the first floor no longer have the wintertime cold-draft sensation. The rim-joist closed-cell continuous bead is the main reason.

The HVAC equipment downsize

The home had an 80,000 BTU gas furnace (oversized even pre-foam, common for older Columbus homes) and a 3-ton AC (also oversized). After 60 days of post-foam HVAC operation, the homeowner's HVAC contractor recommended a downsize at next equipment replacement.

Updated load calculation post-foam: - Heating load: 40,000 BTU/hr - Cooling load: 1.75 tons

The new equipment will be roughly half the capacity of the original. Equipment cost savings at replacement: roughly $3,500 (smaller furnace + AC + properly-sized ductwork modifications). The replacement isn't urgent (the existing equipment will work fine, just oversized), but when it eventually goes, the right replacement is much smaller.

The radon system follow-up

The home had a radon mitigation system installed in 2018 by a different contractor. Pre-foam reading on the homeowner's annual short-term test (January 2026): 1.8 pCi/L. We flagged the post-foam radon retest during the install and recommended a 60-day window.

Post-foam radon retest (June 2026): 3.1 pCi/L. The tighter envelope amplified stack-effect pull on the basement, increasing soil-gas entry beyond what the existing fan could handle. Coordinated with Columbus Radon Experts for a fan upsize and additional sealing; post-adjustment retest came back at 1.2 pCi/L.

This is the kind of follow-up that every Columbus post-foam home with an existing radon system needs. We coordinate directly with the radon contractor and budget the homeowner for a possible $200-$600 adjustment cost in the original quote conversation.

The total cost vs benefit summary

| Item | Cost | |---|---| | Whole-home foam package | $19,600 | | Panasonic ERV with installed ductwork | $3,700 | | Post-foam radon system adjustment | $425 | | Total project cost | $23,725 |

Annualized savings (utility bills, comparing 12 months pre-install to 12 months post-install once that data exists): - Heating cost reduction (projected from blower-door math): about 35-45 percent, or $950-$1,300/year on Columbus AEP Ohio electric and Columbia Gas of Ohio gas rates given the long Zone 5A heating season - Cooling cost reduction: about 25-35 percent, or $230-$380/year

Total projected annual utility savings: roughly $1,180-$1,680.

Payback on utility savings alone: roughly 14-20 years.

The comfort, humidity, and resale-value benefits exceed the utility-savings math by a wide margin. Columbus MLS comparables show documented foam-insulated pre-war homes selling at $8,000-$15,000 premiums over unimproved comparable homes. Plus the eventual HVAC equipment downsize ($3,500 savings at next replacement) effectively reduces the net project cost.

What this case shows for other Clintonville, Worthington, German Village, and Bexley pre-war homeowners

Three takeaways from this case.

1. The blower-door numbers on pre-1950 Columbus housing are predictably bad. 11.8 ACH50 is normal for empty-wall-cavity pre-war stock. Owners who think their 100-year-old home is just inherently cold are typically right about the cause but wrong about whether it can be fixed. A whole-home foam package can take a 1925 Tudor from 12 ACH50 to 3.6 ACH50 in 3 days.

2. The HVAC equipment downsize is real money you can plan for. Don't replace your furnace or AC right before a planned foam install. Wait until after, run the load calculation against the new envelope, and buy the right-sized equipment instead of the original 80,000 BTU monster.

3. Coordinate the post-foam radon retest from day one. If your home has a radon mitigation system already, plan for the 60-day post-foam retest and budget $200-$600 for possible adjustment. We coordinate directly with the team at Columbus Radon Experts when the homeowner wants the bundle scheduled together.

Free phone consultations include thermal-imaging walkthrough scoping for any Greater Columbus pre-1950 home. We book most Clintonville, Worthington, German Village, and Upper Arlington whole-home assessments within the same week.