ERV Requirements for New Construction in Massachusetts (2026)

What the Code Requires (225 CMR 22)

Section	Requirement
R403.6	Each dwelling unit gets a continuously operating, balanced mechanical ventilation system, site-verified to meet a minimum airflow (HERS/RESNET 301, ASHRAE 62.2, or the Massachusetts formula)
R403.6.1	Heat or energy recovery is required: an HRV or ERV
R403.6.1.2	Systems of 300 cfm or less: SRE of at least 65% at 32°F (0°C), shown by the HVI Certified Product Directory
R403.6.1.1	Systems over 300 cfm: enthalpy recovery ratio of at least 50% (cooling) and 60% (heating), AHRI 1060
R403.6.3	Airflow tested and verified by a HERS Rater, HERS Rating Field Inspector or BPI Certified Professional (RESNET 380 or ACCA 5)
R403.6.4	Equipment HVI 920 certified and labeled
R403.6.5	Whole-house ventilation fans 1.0 sone or quieter
R403.6.6	Owner gets the ventilation design and operating instructions
R403.6.7	Outdoor inlets at least 10 ft from plumbing vents and similar sources, rodent screen of 1/2 in. or smaller, no air drawn from an unconditioned basement

Why Proper Ventilation Matters

Today’s code-built homes are sealed tight and tested with a blower door. That saves energy, but the old leaks that used to air a house out are gone. Without working mechanical ventilation, everything made inside stays inside.

Moisture: showers, cooking, breathing and drying new framing and drywall add water vapor every day. The EPA recommends keeping indoor humidity below 60%, ideally 30–50%. Above that, windows sweat and mold can start.
Indoor air quality: CO2, cooking smoke, and chemicals off-gassing from new finishes, cabinets and flooring build up in a sealed house.
Comfort and health: steady fresh air in bedrooms and living areas, without opening windows in January.
The building itself: controlled humidity protects framing, insulation and finishes from hidden condensation.

That is why Massachusetts requires continuous, balanced ventilation with heat or energy recovery in new homes, and why it has to be tested before final.

How an ERV Works

Diagram of how an energy recovery ventilator (ERV) works: fresh outdoor air and stale indoor air pass through the core without mixing

Two fans run continuously: one brings fresh outdoor air in, the other pulls stale air out of kitchens, baths and laundry.
Both airstreams pass through the core side by side but never mix.
In winter the warm outgoing air pre-warms the cold incoming air, so you get fresh air without a big heating penalty (code requires 65%+ sensible recovery).
In summer an ERV also moves some humidity from the incoming air to the outgoing stream. An HRV recovers heat only.

Choosing between them? See ERV vs. HRV.

Why Proper Balancing Is So Important

Diagram showing balanced, negative-pressure and positive-pressure ERV settings and their effect on a tight house

In a tight house, even a small mismatch between supply and exhaust changes the pressure of the whole home:

Too much exhaust (negative pressure): the house pulls replacement air through walls, the garage and the basement, which can bring in dust, fumes and soil gases, and can backdraft fuel-burning appliances.
Too much supply (positive pressure): warm, moist indoor air is pushed into wall and attic cavities in winter, where it can condense and grow mold.
Wrong total airflow: too little leaves stale, humid air; too much wastes energy and dries the house out in winter.

We measure supply and exhaust with a calibrated flow hood or flow grid, adjust with your HVAC contractor until they match the design rate, and document it for the inspector. See ventilation testing and balancing.

Stretch and Specialized vs. Base Code Towns

Town type	Ventilation rule
Stretch Code	Balanced ERV/HRV required (R403.6.1)
Specialized Code	Same as Stretch: balanced ERV/HRV required
Base code (780 CMR 10th edition)	Continuous exhaust, supply or balanced ventilation; no ERV/HRV requirement; airflow still tested (R403.6.3)

Most towns around Boston are Stretch or Specialized. Check your town in our stretch code report guide.

How Much Airflow Your Home Needs

The required rate depends on floor area, bedrooms and how tight the house tests. Massachusetts uses Q = 0.03 × floor area + 7.5 × (bedrooms + 1) − 0.052 × Q50 × S × WSF, where Q50 is the blower door result. Tighter houses get less infiltration credit, so they need more mechanical ventilation.

Full walk-through: mechanical ventilation CFM requirements.

Worked example of the Massachusetts R403.6 mechanical ventilation CFM calculation

What We Do

Size the ventilation rate from your plans and blower door results.
Check the ERV/HRV model against the 65% SRE, HVI and sone requirements before you buy it.
Test and balance the installed system at final, and document it for the inspector and your HERS rating.
See ventilation testing and balancing and ERV vs. HRV.

FAQ

Is an ERV required in Massachusetts?

In Stretch and Specialized Code communities, yes: new homes need balanced ventilation with heat or energy recovery (an ERV or HRV) under 225 CMR 22 R403.6.1. Base code towns allow exhaust, supply or balanced ventilation.

When did ERVs become required in Massachusetts?

The updated residential Stretch Code that added heat or energy recovery ventilation took effect January 1, 2023.

What efficiency does the ERV or HRV need?

For units of 300 cfm or less, a sensible recovery efficiency of at least 65% at 32°F, as listed in the HVI Certified Product Directory.

Who tests the ventilation system?

A HERS Rater, HERS Rating Field Inspector or BPI Certified Professional, using RESNET Standard 380 or ACCA Standard 5 (R403.6.3).

Can I use bath fans as whole-house ventilation in a Stretch Code town?

Not on their own. Stretch and Specialized require a balanced system with heat or energy recovery. Bath and kitchen exhaust are still needed for local exhaust.

Is there a Mass Save rebate for an ERV?

Mass Save offers a $500 instant discount on qualified ERVs and HRVs for existing homes (retrofit only, not new construction), applied at participating distributors. New all-electric homes can instead get the <a href="https://homeenergyefficiencyconsultants.com/services/mass-save-new-construction-incentives-massachusetts/">Mass Save new construction incentive</a> through a HERS rater.