Stop Burning Cash: Guide to Home Energy Audits & Rock‑Solid Foundations (With Specs, Performance & Real Prices)

Key facts

• A professional energy audit typically costs $212–$698 (avg. ~$437) and should include a blower‑door test, duct leakage testing (where applicable), and infrared imaging. Angi
• Blower‑door testing measures airtightness at 50 Pa; 2021 IECC prescriptively targets ≤3.0 ACH50 in climate zones 3–8 (≤5.0 in zones 1–2). Typical standalone test price: $200–$450. Scott Home Inspection
• Duct leakage in many codes/labels is ≤4 CFM25 per 100 ft² of conditioned floor area; typical homes can lose 25–40% of heating/cooling through leaky ducts. Building America Solution Center
• Air sealing delivers quick payback—often ~1 year or less—especially at the attic plane. The Department of Energy’s
• Basement & crawlspace durability starts with water management: perimeter drain tile, capillary breaks, and gasketed sump lids are best practice requirements in ENERGY STAR’s Water Management System. ENERGY STAR
• Slab‑edge insulation requirements increased in the 2021 IECC (e.g., R‑10 to 4 ft in CZ 4–5; CZ 3 now requires R‑10 to 2 ft). Energy Codes
• Heat pump water heaters (HPWHs) commonly achieve UEF ~3–4.5; many 70–80‑gal models post UEF ≥4.0. Installed cost is typically ~$2,800–$8,000 (avg. ~$4,200) before incentives. ENERGY STAR
• Cold‑climate air‑source heat pumps recognized as ENERGY STAR Most Efficient 2025 meet SEER2 ≥16 / HSPF2 ≥8 (≥8.5 for cold‑climate); NEEP’s ccASHP spec calls for COP ≥1.75 at 5°F. ENERGY STAR
• Smart thermostats save ~8% of heating/cooling on average. ENERGY STAR
• Radon mitigation typically costs ~$800–$2,500, and a replacement fan runs ~$200–$350. US EPA

Why start with a real energy audit (and what to ask for)

A professional audit should follow recognized frameworks and include diagnostic testing:

• Standards & scores:
  • RESNET HERS Index (ANSI/RESNET/ICC 301). The HERS standard updated to 301‑2022, mandatory for many new ratings July 1, 2025. RESNET
  • DOE Home Energy Score (1–10 scale) with a standardized methodology. Better Buildings Solution Center
• Core diagnostics:
  • Blower‑door at 50 Pa to report ACH50 and CFM50. Scott Home Inspection
  • Duct leakage (CFM25/100 ft²). ENERGY STAR V3 guidance and many 2021 IECC adoptions set ≤4 CFM25/100 ft² at rough‑in (or ≤8 at final). Building America Solution Center
  • Infrared thermography to find insulation voids and thermal bridges. Typical IR scan add‑on $200–$500 (avg. ~$400). Angi

Typical pricing: Full audit $212–$698 (avg. ~$437); blower‑door $200–$450. Angi

Hire: Ask for BPI or RESNET certified pros; they test to published procedures (e.g., ANSI/RESNET/ICC 380 for volumetrics). Building Performance Association

Interpreting test results → Technical targets

• Envelope airtightness: New homes under the 2021 IECC prescriptive path typically need ≤3 ACH50 (zones 3–8). Existing homes rarely start that tight, so prioritize sealing. oneclimatefuture.org
• Duct leakage: Aim for ≤4 CFM25/100 ft² (or better) if ducts are outside the thermal envelope. Leaky ducts can waste 25–40% of system energy. Building America Solution Center
• Ventilation after tightening: If you drive leakage down, provide mechanical ventilation to ASHRAE 62.2 rates. A common sizing method: Qₜₒₜ = 0.03 × floor area (ft²) + 7.5 × (bedrooms + 1) CFM (current editions; check local adoption). Energy Code Ace

Priority 1: Air‑sealing & duct‑sealing (fast payback)

Where & how to seal

• Attic plane: Seal top plates, can lights, chases, and penetrations before adding insulation. DOE/Building America guides provide details and sequencing. The Department of Energy’s
• Materials: Polyurethane foam, acoustic/air sealant, weatherstripping; for ducts use mastic and UL‑181 tapes (or aerosolized sealing if accessible). NREL/BASC have measure guidelines. National Renewable Energy Laboratory
• Performance & savings: Air infiltration can represent 25–40% of heating/cooling costs; air sealing often pays back in ~1 year or less. NREL

Typical installed prices

• Attic air‑sealing + insulation (context dependent): Reported project data show roughly $2–$3/ft² for confined attics in multifamily; single‑family varies by access and scope. Use the audit for a site‑specific bid. Energy Efficiency and Renewable Energy
• Duct sealing: $500–$4,000 (avg. ~$2,250); aerosolized methods frequently price at the higher end. Angi

Priority 2: Foundations done right (moisture first, then insulation)

Foundations fail thermally when they first fail hygrothermally. Control bulk water, capillarity, vapor, and air before adding R‑value. (Building Science Corporation’s Joseph Lstiburek has hammered this for decades.) buildingscience.com

A. Site & water management (all foundation types)

• Slope and move water: Positive grade, gutters/downspouts to daylight.
• Perimeter drain tile: Pipe below slab level, surrounded by ≥6 in. washed gravel and fabric; drain to daylight or sump with gasketed lid. ENERGY STAR
• Capillary breaks: Crushed stone under slab plus polyethylene vapor barrier sealed to walls and penetrations. buildingscience.com
• Composite drainage mats are acceptable alternatives where specified (ICC‑ES AC243). RESNET

Pricing benchmarks: Interior drain/perimeter systems commonly $40–$100/lf (many basements 100–150 lf), or $2,458–$8,182 (avg. ~$5,223) for full waterproofing (method‑dependent). Home Advisor

B. Basements (conditioned)

• Insulation location & type: Rigid foam on the interior of concrete walls to let assemblies dry to the interior; foam‑based insulations are preferred (avoid interior Class I vapor barriers against concrete). buildingscience.com
• Spec: R‑10 to R‑15 continuous (typ. 2–3 in. EPS/XPS). IECC 2021 prescriptive for many CZs includes basement wall R‑10 ci or R‑13 cavity. harfordcountymd.gov
• Below slab: Vapor barrier (≥6 mil), sealed; consider R‑10 insulation at slab edge per code path and climate. buildingscience.com
• Radon: Rough‑in sub‑slab depressurization; mitigation install $800–$2,500; fans $200–$350 to replace. US EPA

C. Crawlspaces

• Make them mini‑basements: Prefer unvented/conditioned crawlspaces with sealed ground vapor retarder and insulated crawl walls, not the floor above. buildingscience.com
• Spec: ≥6 mil poly ground cover, lapped and sealed up walls; R‑10 continuous foam on walls (thickness by climate/code); provide mechanical air (supply or dedicated fan) per 62.2 and local code. ENERGY STAR

D. Slab‑on‑grade (new or retrofit opportunities at perimeter)

• Code trend: 2021 IECC increased slab insulation in several zones—e.g., CZ 4–5 require R‑10 to 4 ft; CZ 3 now R‑10 to 2 ft. Details vary by climate and whether heated slabs are present. Energy Codes
• Spec: Use Type II EPS (15 psi) or Type IV XPS (25 psi) for durability; protect exposed edges. Typical R‑values per inch: EPS ~4–4.8, XPS ~5.0; EPS is more vapor‑open, aiding drying potential. Universal Foam Products

E. Frost‑Protected Shallow Foundations (FPSF) for new builds/additions

• When & why: FPSF lets you keep footings shallower than local frost depth by adding horizontal/vertical insulation sized to the site’s air‑freezing index (AFI)—a code‑recognized path in IRC R403.3. ICC Digital Codes
• How to size: Follow the NAHB Research Center / HUD guide tables; use derated effective R‑values for foam below grade (vertical vs. horizontal). Protect horizontal “wing” insulation from damage. Home Innovation Research Labs

Priority 3: High‑ROI equipment & controls (post‑envelope)

Heat Pump Water Heaters (HPWH)

• Performance: ENERGY STAR listings show UEF ≈3–4.5 and first‑hour ratings ~75–90 gal for 70–80‑gal units—far above resistance heaters. ENERGY STAR
• Installed price: ~$2,800–$8,000 (avg. ~$4,200) before incentives; check federal/utility rebates. Angi

Space‑heating/cooling heat pumps

• Specs to demand in 2025: SEER2 ≥16 / HSPF2 ≥8 (≥8.5 for “cold‑climate Most Efficient”); COP at 5°F ≥1.75 for cold‑climate models per NEEP. ENERGY STAR
• Proof point: Manufacturer submittals for cold‑climate minisplits document COP values at 47°F/17°F/5°F and rated outputs—use them to size correctly. mitsubishitechinfo.ca
• Installed price: Broad range depending on tonnage/ducting; national averages cluster in the mid‑$5k to low‑$12k range for whole‑home systems. Angi

Smart thermostats

• Savings: ~8% off heating/cooling bills on average with certified models; ensure HVAC compatibility and (often) a C‑wire. ENERGY STAR

Materials & specs cheat‑sheet (foundations & below‑grade)

All prices are national medians/ranges; your bids will vary by region, access, and scope.

Costs, performance & what “good” looks like (audits & upgrades)

• Audit + tests: Energy audit $212–$698; blower‑door $200–$450; IR scan $200–$500. Ask for a written scope with diagnostics and code/standard references. Angi
• Airtightness goal (existing homes): 3–5 ACH50 is a realistic interim target depending on vintage; add mechanical ventilation if you approach code‑tight. oneclimatefuture.org
• Duct leakage goal: ≤4 CFM25/100 ft² (or better) when ducts are outside the envelope; sealing pays off because leakage wastes 25–40% of HVAC energy. Building America Solution Center
• Duct‑sealing cost: $500–$4,000 (avg. ~$2,250), depending on method and access. Angi
• HPWH performance & cost: UEF 3–4.5; $2,800–$8,000 installed (avg. ~$4,200) before incentives. ENERGY STAR
• Space heat pump performance: Target ENERGY STAR Most Efficient or NEEP ccASHP listings; verify COP at 5°F in manufacturer submittals if you’re in a cold climate. ENERGY STAR Northeast Energy Efficiency Partnership
• Smart thermostat savings: ~8% of heating/cooling bills on average. ENERGY STAR

Product & material selection notes (below grade)

• EPS vs. XPS: Typical per‑inch R‑values: EPS ~4–4.8; XPS ~5.0. EPS is more vapor‑permeable (~1.2 perm for R‑12 EPS vs ~0.3 perm for R‑12 XPS), which can help assemblies dry toward the interior. Choose ASTM C578 types for required compressive strength: EPS Type II = 15 psi, XPS Type IV = 25 psi. Universal Foam Products
• Environmental note: XPS blowing agents have been transitioning under the U.S. AIM Act/SNAP program to lower‑GWP alternatives; check current product declarations in your market. US EPA

Example, step‑by‑step plan (suitable for most existing homes)

1. Commission a pro audit with blower‑door, IR, and (if applicable) duct testing. Budget: ~$437 + tests. Angi
2. Air‑seal the attic and big leaks first; then add insulation as needed. Target: drop ACH50 significantly and meet ventilation with ASHRAE 62.2. Budget: varies; attic air‑sealing often $2–$3/ft² in tight spaces. Energy Efficiency and Renewable Energy
3. Seal ducts to ≤4 CFM25/100 ft² (or bring ducts within the envelope). Budget: $500–$4,000. Building America Solution Center
4. Fix water management at the foundation (drain tile/sump/gasket, capillary break). Budget: $40–$100/lf interior drains; broader waterproofing $2.5k–$8k. Home Advisor
5. Insulate foundation walls/slab edge to meet local IECC 2021 tables (e.g., R‑10 ci or better). harfordcountymd.gov
6. Electrify hot water with a HPWH (if site conditions permit), then upgrade space heating to a heat pump sized off the new, lower loads. Budget: HPWH $2.8k–$8k, heat pump variable. Angi
7. Add a certified smart thermostat for operational savings and comfort. Savings: ~8% of HVAC energy. ENERGY STAR

Expert sources you can cite in your SOW

• U.S. DOE / Energy Saver: Professional energy assessments; air sealing best practices. The Department of Energy’s
• RESNET: HERS/ANSI 301 standard and 2025 update notice. RESNET
• DOE Home Energy Score: What the 1–10 score means and methodology. Better Buildings Solution Center
• PNNL Building America Solution Center: Duct leakage criteria and code briefs. Building America Solution Center
• ICC / IECC 2021: Envelope leakage testing and slab/basement R‑value tables. oneclimatefuture.org
• Building Science Corporation (J. Lstiburek): Basements, crawlspaces, vapor control, FPSF protection details. buildingscience.com
• ENERGY STAR: HPWH criteria, smart thermostat savings, water management checklists. ENERGY STAR+2ENERGY STAR+2
• NEEP: Cold‑climate heat pump spec (COP at 5°F). Northeast Energy Efficiency Partnership
• LBNL / NREL: Duct leakage impacts and retrofit measure guidelines. Intellectual Property Office
• EPA: Radon mitigation costs and maintenance. US EPA

Final word

If you’re aiming for the biggest bill cuts with the least regret: measure first (audit + tests), fix water and air (foundation & envelope), then right‑size and electrify (HPWH + heat pump), and finally tune operations (smart thermostat + ventilation to 62.2). This sequence is backed by national standards, building‑science experts, and 2021 IECC code paths—so it’s easy to spec, bid, and verify. The Department of Energy’s

Note: All costs are U.S. national medians/ranges from 2024–2025 sources and vary by region, access, and project scope. Always verify local code amendments and utility incentives before contracting.