Ventilation from a Licensed Silicon Valley HVAC Contractor
The math first. ASHRAE 62.2-2022 sets the residential whole-house ventilation rate at 7.5 CFM per occupant + 0.03 CFM per square foot of conditioned floor area, with occupancy defaulted to bedrooms + 1. A typical 2,200 sq ft Palo Alto home with 4 bedrooms calculates to 5 occupants × 7.5 + 2,200 × 0.03 = 37.5 + 66 = 103.5 CFM continuous. That number must be delivered, not nameplate-rated. Cheap ceiling fans rated "110 CFM" routinely measure 38-55 CFM at the grille after duct losses. We size to deliver the calculated rate at the grille with a Retrotec DG-700 or TEC DucTester verifying flow under operating conditions.
For balanced ventilation we install Energy Recovery Ventilators (ERVs) almost exclusively in the Bay Area. ERVs transfer both heat and moisture between incoming and outgoing airstreams; HRVs only transfer heat. In our coastal Climate Zone 3 with 70-90% summer marine layer humidity in cities like Pacifica and Daly City, an HRV would dump cool dry conditioned air outside and pull in damp 65°F outside air — comfort wins go to the ERV. Common units we install: Panasonic Intelli-Balance 100 (100 CFM, ECM, $1,800-$2,400 installed), Broan AI Series 130 ERV (130 CFM, $2,200-$2,800), and Zehnder ComfoAir Q450 (premium, $5,800-$8,500) for high-performance homes in Atherton and Los Altos Hills.
Spot ventilation matters as much as whole-house. We install Panasonic WhisperGreen Select FV-0511VKL2 bath fans almost exclusively — they ship at 50/80/110 CFM selectable, 0.3-0.6 sones at the lower setting, and qualify for both ASHRAE 62.2 spot and continuous credit. The unit pulls 7.3W at 50 CFM continuous, which means a single fan running 24/7 costs about $7.50/year on PG&E E-TOU-D rates. For kitchens, range hoods over 400 CFM trigger Title 24 makeup air requirements: passive damper for hoods 400-1,200 CFM, active interlocked makeup air for hoods over 1,200 CFM. We size and install Broan EcoVent or Fantech RVF makeup air dampers tied to the hood circuit so they open simultaneously.
Attic ventilation is its own calculation, governed by California Residential Code R806. With a Class I or II vapor retarder on the warm side of the ceiling (the typical assembly in Bay Area homes built post-1995), required net free area is 1:300 of attic floor area. Without a vapor barrier, 1:150. A 1,800 sq ft attic at 1:300 needs 6 sq ft NFA, split 50/40-50/50 between intake (eave/soffit vents) and exhaust (ridge, gable, or static roof vents). We measure existing NFA on every retrofit — most 1970s Bay Area homes have 30-50% of code minimum and run summer attic temperatures of 130-145°F that drive cooling loads up substantially. During wildfire smoke events we recommend MERV-13+ intake filtration at the air handler combined with closing operable attic vents (where present) to limit smoke ingress through soffit pathways.
What's Included in Every Ventilation Job
- ASHRAE 62.2-2022 ventilation rate calculation specific to your home (square footage, bedroom count, climate zone)
- Title 24 makeup air damper installation for kitchen exhaust over 400 CFM
- Panasonic WhisperGreen Select FV-0511VKL2 or equivalent low-sone continuous bath fans
- ERV or HRV equipment selection and ducted installation with dedicated supply/return runs
- Flow-hood verification at every grille (Retrotec DG-700 or TEC DucTester)
- Attic ventilation NFA calculation and intake/exhaust balancing per CRC R806
- Dryer booster fan installation for vent runs exceeding 35 equivalent feet
- Wildfire smoke MERV-13+ intake filtration integration
- Written commissioning report with measured CFM at every grille, fan watt draw, and code citations
Common Ventilation Issues We Resolve
Bath fan runs but bathroom still steams up
Cause: Rated 110 CFM nameplate but delivering 35-55 CFM due to long flex duct runs, 90-degree elbows, or undersized 3-inch duct (should be 4-inch minimum)
Fix: Replace with Panasonic WhisperGreen FV-0511VKL2 sized for actual duct path; verify 50+ CFM at grille — typical $450-$850 installed
Range hood causes backdrafting at gas furnace or water heater
Cause: Hood over 400 CFM creates negative pressure that reverses atmospheric flue draft; common in tight homes without makeup air
Fix: Title 24-compliant makeup air damper interlocked with hood switch — typical $850-$1,800 installed
New build or major remodel feels stuffy and humid
Cause: Home tested under 3 ACH50 (typical for post-2016 construction) — ASHRAE 62.2 mandatory mechanical ventilation not installed or not running
Fix: Whole-house ventilation solution (continuous exhaust, ERV, or supply ventilation) sized to occupant + sq ft formula
Attic is 140°F in summer, drives upstairs hot
Cause: Insufficient NFA — many 1970s-1990s Bay Area homes have soffit vents painted shut or screened with insect mesh that drops effective NFA by 50-60%
Fix: Calculate existing NFA, add ridge vent or static roof vents to reach 1:300 ratio with vapor barrier
Wildfire smoke entering home despite closed windows
Cause: Continuous ventilation pulling unfiltered outside air; or attic ventilation drawing smoke into ceiling assembly
Fix: MERV-13+ filtration on supply ventilation intake, smoke-mode shutoff control, sealed return-side ductwork
ERV core freezing in cold snaps
Cause: Without defrost cycling, condensate freezes in core when outside temps drop below 23°F; some Bay Area mountain homes hit this overnight in January
Fix: Verify defrost cycle programming, recirculation damper function, or upgrade to ERV with active preheat
Dryer takes 2+ cycles to dry a load
Cause: Vent run exceeds 35 equivalent feet (each elbow = 5 ft equivalent); lint accumulates and airflow drops
Fix: Booster fan installation (Fantech DBF series) or vent re-routing — typical $450-$900
Our Ventilation Process
Ventilation Assessment
Measure home airtightness with a blower door if not already documented, calculate ASHRAE 62.2-2022 required rate, inspect existing exhaust paths and attic ventilation NFA.
Design Proposal
Written design with equipment specifications, calculated CFM at each grille, makeup air requirements, and code citations. Itemized so you can choose scope.
Permitting
Mechanical permit pulled from your jurisdiction (Palo Alto, Mountain View, San Mateo County, etc.) — required for ducted ERV/HRV installs and most makeup air dampers.
Installation
Equipment set, duct runs installed (rigid metal preferred, smooth-bore flex where space requires), electrical and controls wired, MERV-13+ filtration at intake.
Commissioning
Flow-hood readings at every grille, fan watt draw measured, controls programmed, written commissioning report delivered. HERS verification scheduled if required by Title 24 scope.
Ventilation Pricing in the Bay Area
Typical ventilation pricing in our Silicon Valley service area runs $450 – $8 500 installed. Most jobs complete in Bath fan retrofit 2-4 hours; whole-house exhaust 4-6 hours; ERV/HRV install 1-2 days; full ventilation overhaul 2-4 days.
Every quote is flat-rate and provided in writing before work begins. Diagnostic fees are waived when repair is approved. We never use time-and-materials billing surprise pricing.
Local Context: Ventilation in Silicon Valley
Bay Area construction has tightened dramatically. California Title 24 Part 6 (2022 update) raised envelope requirements to the point where new homes routinely test at 1.5-2.5 ACH50 — well below the 3 ACH50 threshold that triggers mandatory ASHRAE 62.2 ventilation. Cities like Palo Alto, Menlo Park, and Mountain View have adopted reach codes that require ERV/HRV in certain new-construction tiers. Older neighborhoods carry the opposite challenge: 1920s Craftsman homes in Professorville, 1960s ranches in Crescent Park, and Eichler tracts in Greenmeadow that have been re-weatherized over the past decade often have spot ventilation (bath fans, range hoods) sized to obsolete code. Coastal cities with marine layer humidity (Pacifica, Daly City, Half Moon Bay, Pacifica) need ERV-based balanced ventilation; inland valley homes (San Jose, Sunnyvale, Cupertino) can sometimes get away with simpler exhaust-only strategies but benefit from MERV-13+ filtration during wildfire seasons.
HVAC Brands We Service for Ventilation
Ventilation FAQ
How do I know if my home needs mechanical ventilation?
Two ways. First, blower-door test result: if your home is tighter than 3 ACH50, ASHRAE 62.2 mandates mechanical ventilation. Most Bay Area homes built post-2010, and any older home that has been re-weatherized (new windows, air sealing, spray foam), test that tight. Second, symptoms: condensation on windows in winter, lingering cooking odors, stuffy air, persistent humidity in bathrooms, occupants with allergies or asthma. Either signal warrants assessment.
ERV or HRV — which is right for the Bay Area?
ERV almost always. Our coastal climate has high summer humidity (70-90% RH marine layer in Pacifica, Daly City, Half Moon Bay) and dry winter heating air. An ERV transfers both heat and moisture, so summer-incoming air gets dehumidified by drier outgoing air, and winter-incoming air picks up moisture from the home. An HRV only transfers heat — fine for Minneapolis, wrong for Palo Alto. The exception: certain inland mountain homes (Los Gatos, Saratoga foothills) where summer humidity is genuinely low.
How much does a whole-house ERV cost installed?
Panasonic Intelli-Balance 100: $1,800-$2,400 installed for a typical 2,000 sq ft home. Broan AI Series 130 ERV: $2,200-$2,800. Zehnder ComfoAir Q450 (premium, dedicated ducting): $5,800-$8,500. Costs vary based on whether the ERV ties into existing HVAC ductwork or runs dedicated ducts (the latter performs better but costs more). Includes equipment, dedicated supply and exhaust runs, intake/exhaust hoods at exterior wall, controls, and commissioning.
What is the Title 24 makeup air requirement for my range hood?
Hoods 400-1,199 CFM: passive makeup air damper sized to hood (typically 6-8 inch). Hoods 1,200+ CFM: active makeup air interlocked with hood switch, with damper opening before hood reaches full speed. Most pro-style ranges (Wolf, Viking, Thermador) ship with 600-1,200 CFM hoods that need passive at minimum. We install Broan EcoVent or Fantech RVF dampers — typical $850-$1,800 depending on hood size and exterior wall accessibility.
Can I just run my bath fan instead of installing a whole-house system?
Yes — ASHRAE 62.2-2022 explicitly allows continuous bath fan operation as the whole-house ventilation strategy if the fan delivers the calculated rate at the grille and runs continuously (or programmed for total daily runtime equivalent). The Panasonic WhisperGreen FV-0511VKL2 was designed for this — 50 CFM at 0.3 sones at 7.3W. For most 1,500-2,500 sq ft homes a single WhisperGreen running continuous covers code. Larger homes need two fans or a dedicated whole-house exhaust.
How does ventilation interact with wildfire smoke events?
Carefully. Continuous ventilation pulls outside air inside — exactly what you do not want during AQI 200+ events. We design systems with smoke-mode capability: a manual or AQI-sensor switch that closes makeup air dampers, shuts off ERV/HRV, and runs only the air handler with MERV-13+ filtration in recirculation mode. After the smoke event, ventilation resumes. Some newer ERVs (Panasonic Intelli-Balance) have built-in MERV-13 intake filters that meaningfully reduce smoke ingress even during operation.
My attic is brutally hot in summer — will more vents help?
Likely yes, but verify NFA first. California Residential Code R806 requires 1:300 NFA-to-attic-floor ratio with a vapor barrier on the ceiling, or 1:150 without. Most pre-1990 Bay Area homes are at 30-60% of code minimum because soffit vents got painted, screened with insect mesh that clogs, or buried under insulation. We measure free area on a site visit. Adding a continuous ridge vent and clearing soffit baffles typically drops attic peak temperatures from 140°F+ to 105-115°F.
Is mechanical ventilation eligible for any rebates?
Limited. ASHRAE 62.2 mechanical ventilation is mostly a code requirement, not a rebated upgrade. However: ERVs installed as part of a heat pump retrofit can be included in IRA 25C credit calculations (up to $1,200/year). BayREN Home+ and PG&E Energy Savings Assistance offer some envelope/ventilation incentives for income-qualified households. Newer construction projects pursuing TECH Clean California pathway certifications include ventilation as part of the eligible scope.