Audit Home Energy Efficiency

---
name: audit-home-energy-efficiency
description: Use when assessing a home's energy performance, identifying efficiency upgrades, or preparing for weatherization improvements
source: DOE "Home Energy Score Methodology" (2023); ENERGY STAR "Home Energy Audit Standards" (2023); RESNET "HERS Index Technical Standards" (2023)
tags: [energy-efficiency, home-audit, weatherization, sustainability]
verified: true
---

# Audit Home Energy Efficiency

Systematically evaluate a home's energy performance and produce a prioritized upgrade roadmap with payback estimates.

## Why This Is Best Practice

**Adopted by:** DOE, ENERGY STAR program partners, RESNET-certified raters, utility companies in 50 states
**Impact:** Homes audited and upgraded per DOE methodology reduce energy bills by 15–30%; proper air sealing alone saves average $300/year; HERS-rated homes sell for 2.7% premium
**Why best:** Systematic assessment catches the highest-ROI improvements (air sealing, insulation) that owners miss when focusing on visible upgrades like new windows

Sources: DOE Home Energy Score Methodology (2023); ENERGY STAR Home Energy Audit Standards (2023); RESNET HERS Index (2023)

## Steps

1. **Gather 12 months of utility data** — Collect electricity and gas bills; calculate energy use intensity (EUI = total BTU / conditioned sq ft). Establish baseline before any changes.

2. **Conduct a visual envelope inspection** — Inspect attic insulation depth (R-value), wall insulation type, basement/crawlspace conditions, window age and glazing type, and door weatherstripping.

3. **Perform blower door test (or estimate air leakage)** — A certified rater uses a blower door to measure ACH50 (air changes per hour at 50 pascals). Target: <7 ACH50 for existing homes, <3 for new construction. Without equipment, check for drafts at outlets, switches, and penetrations.

4. **Inspect HVAC system** — Note equipment age, SEER/AFUE ratings, filter condition, duct location (conditioned vs. unconditioned space), and duct sealing quality. Check thermostat type.

5. **Assess water heating** — Record water heater age, fuel type, and EF/UEF rating. Check pipe insulation on first 6 feet of hot and cold lines.

6. **Evaluate lighting and appliances** — Inventory incandescent vs. LED fixtures; note major appliance energy ratings (refrigerator, washer/dryer, dishwasher).

7. **Calculate HERS index score** — Use RESNET methodology or a certified rater: 100 = 2006 IECC reference home; 0 = net-zero. Scores below 70 indicate significant upgrade opportunity.

8. **Prioritize by payback period** — Rank improvements: air sealing (1–3 yr payback), attic insulation (3–7 yr), HVAC replacement (7–12 yr), windows (15–25 yr). Lead with highest ROI.

9. **Identify available incentives** — Check federal tax credits (IRA 2022: up to $3,200/yr for efficiency upgrades), state rebates, and utility programs. Incentives can cut payback periods by 30–50%.

10. **Produce written audit report** — Document findings, recommended measures, estimated costs, annual savings, simple payback, and incentive eligibility for each measure.

## Rules

- Always establish a pre-retrofit energy baseline before recommending improvements.
- Never recommend window replacement before addressing air sealing and insulation — windows have the worst payback of common upgrades.
- Combustion safety testing (CO and spillage) must accompany any air-sealing work in homes with gas appliances.
- Report HERS index relative to local climate zone for accurate benchmarking.

## Common Mistakes

- **Replacing windows first** — costs $10,000–$20,000 with 20+ year payback while air sealing costs $500–$2,000 with 1–3 year payback.
- **Ignoring duct leakage** — ducts in unconditioned attics can lose 20–30% of conditioned air; duct sealing often has better ROI than equipment upgrades.
- **Oversizing replacement HVAC** — bigger is not better; oversized systems short-cycle, reduce comfort, and increase humidity. Use Manual J load calculation.
- **Missing combustion safety** — tightening a home with gas appliances without testing can cause backdrafting and CO poisoning risk.

## When NOT to Use

- When a certified energy auditor has already produced a recent report (within 2 years)
- When the home is already net-zero or HERS-rated below 50
- When the goal is purely cosmetic renovation with no systems changes