Passive House Renovation — 1960s Ranch
Converting a 1,800 sq ft single-story ranch to near-Passive House standards. The goal is 90% energy reduction while keeping the original character.
Current Performance
- Blower door test: 12 ACH50 (leaky)
- Heating load: 45 kBTU/hr
- Annual energy: ~$3,200/year
- Insulation: R-11 walls, R-19 attic, single-pane windows
Proposed Envelope Upgrades
Walls
Exterior rigid foam wrap (4" polyiso, R-26) over existing framing. Furring strips + new siding. Total wall R-value: R-37.
Attic
Blow 16" cellulose over existing. Target R-60. Air seal all penetrations first.
Windows
Triple-pane, European tilt-turn. U-value 0.14. Solar heat gain coefficient 0.50 on south, 0.25 on east/west.
Foundation
2" XPS on interior basement walls + sealed crawlspace with vapor barrier.
Mechanical
- ERV: Zehnder ComfoAir Q450 (93% heat recovery)
- Heating/Cooling: Mitsubishi cold-climate mini-split, 2-zone
- Hot water: Heat pump water heater in conditioned space
Budget Estimate
| Item | Cost |
|---|---|
| Exterior insulation + siding | $28,000 |
| Windows (12 units) | $18,000 |
| Attic insulation + air sealing | $4,500 |
| ERV system | $8,000 |
| Mini-split (2 zones) | $7,500 |
| HPWH | $2,500 |
| Total | $68,500 |
Expected Results
- Target ACH50: <1.5
- Heating load: <12 kBTU/hr
- Annual energy cost: ~$400/year
- Simple payback: ~24 years (but comfort improvement is immediate)