Fresh air for tight New York homes with ERVs, HRVs, range-hood makeup air, bath exhaust and filtration

Why a tighter home needs planned ventilation

Air sealing, new windows, spray foam and dense-pack insulation reduce the accidental air exchange that once ventilated older houses. That saves energy, but moisture, carbon dioxide, odors, cooking particles and, in homes with gas ranges, nitrogen dioxide now stay indoors longer.

Current energy codes pair tighter construction with whole-house mechanical ventilation. In practice, any gut renovation of a brownstone, a Queens two-family house or a Long Island cape that includes new windows and insulation should include a ventilation plan from the start, before walls and ceilings are closed.

How much fresh air a home needs

The national reference for residential ventilation is ASHRAE Standard 62.2, which the NYC Mechanical Code references for dwelling units. Its whole-house formula is 0.03 cfm per square foot of floor area plus 7.5 cfm per person, with occupancy taken as the number of bedrooms plus one. A 2,000 square foot house with three bedrooms therefore needs about 60 plus 30, or 90 cfm of continuous ventilation.

The standard allows a credit for measured air leakage in single-family homes, based on a blower-door test, but not for apartments in multifamily buildings. Model codes also allow intermittent operation if the fan is sized up to deliver the same daily volume. The applicable code edition differs between New York City and the rest of the state, and we design to the edition that governs your property.

Three ventilation strategies and how each behaves in New York

Supply-only systems and humidifiers combine poorly, because slight pressurization drives humid indoor air into cold wall and attic cavities. Balanced ventilation avoids that problem and is the approach we recommend for most tight homes.

Choosing between an ERV and an HRV in New York

Both units exchange heat between outgoing and incoming air. An ERV also transfers part of the moisture. In a New York winter that keeps some indoor humidity in the house, which helps homes that run dry and can reduce the need for a humidifier. In summer it reduces the moisture carried in by ventilation air. An ERV is not a dehumidifier, however, and air conditioning or a dehumidifier is still needed in humid weather. Green Building Advisor describes the winter moisture benefit as real but modest.

An HRV removes indoor moisture in winter, which suits only houses that have too much winter humidity, such as a small, very tight house with a large family. Our practical default is an ERV for New York City and Long Island, with the choice made case by case for colder upstate homes, where core frost and defrost cycles matter more.

• Dedicated ducts give the best results. Connecting to furnace ducts is possible but requires an interlock with the blower and careful balancing.
• The outdoor intake must be separated from exhaust outlets, vents and other contaminant sources, with distances set by the applicable mechanical code.
• Airflow must be balanced with a flow measurement after installation, so that every room receives its share.
• Filters must be cleaned or replaced on schedule, and the unit placed where it can be serviced.
• Apartments can use compact ceiling ERVs or through-wall single-room units, subject to co-op or condo board approval for façade openings and, for landmarked buildings, Landmarks Preservation Commission review of visible louvers.

Kitchen range hoods and makeup air

High-heat cooking, including wok cooking, calls for a well-designed ducted hood. Yet in a tight house or apartment, a hood cannot move its rated airflow unless the same volume of air can enter. Without makeup air, a large hood creates strong negative pressure, doors whistle, odors are drawn from neighboring units, and natural-draft water heaters or boilers can spill combustion gases into the home.

Outside New York City, the residential code is based on the International Residential Code. The model IRC requires makeup air for kitchen exhaust above 400 cfm, and since its 2018 edition only where the home has natural-draft fuel-burning appliances, with a damper interlocked with the hood. We confirm the current New York State text for each project.

New York City has its own Mechanical Code, which sets its own requirements for range-hood makeup air and for dwelling ventilation. Owners should not assume that the 400 cfm figure often quoted online applies in the five boroughs. We confirm the requirement for your hood, appliances and building during design. The NYC code also permits listed recirculating hoods in many dwellings when they are installed to the manufacturer's instructions and general ventilation is provided.

• Size the hood to the cooking, not to the showroom. Rated cfm is measured at zero static pressure, and a long apartment duct with elbows and a wall cap often delivers about half.
• Capture matters as much as fan size. A deep canopy that extends beyond the cooktop often outperforms a larger fan with a shallow hood.
• Makeup air should enter through a motorized damper interlocked with the hood, be filtered, and be tempered in winter so that cold air does not spill onto the cook.
• Ducted hoods need smooth metal ducts and a backdraft damper. Opening a window is not a code-compliant makeup-air solution.

Bathroom exhaust done properly

Model codes call for at least 50 cfm intermittent or 20 cfm continuous exhaust per bathroom, and 100 cfm intermittent or 25 cfm continuous for kitchens. The NYC Mechanical Code has its own table, which we follow on city projects.

• Duct the fan to the outdoors, never into the attic or a soffit. Bath fans vented into the attic are a common cause of attic mold in Long Island capes.
• Use a short, smooth duct with a backdraft damper and a quiet fan with a low sone rating.
• Control the fan with a humidity sensor or timer so it runs for about 20 minutes after a shower.
• In apartment buildings, windowless bathrooms often share a roof exhaust shaft. Registers clogged with paint or dust are common, and booster fans cannot be added to a shared shaft without building approval.

Combustion safety and radon

Tightening a house that still has natural-draft gas appliances requires care. The standard method for combustion air provides at least 50 cubic feet of room volume per 1,000 Btu/h of appliance input. A 40,000 Btu/h water heater and an 80,000 Btu/h furnace together need about 6,000 cubic feet. Before adding a large hood or exhaust fans to such a home, a worst-case depressurization test of the appliance area should be performed, and sealed-combustion or electric replacements are worth considering.

Radon is a separate concern. On the EPA Map of Radon Zones, all five boroughs, Nassau, Suffolk, Westchester and Rockland are Zone 3, the lowest predicted potential, while Orange, Putnam, Dutchess and much of upstate New York are Zone 1. EPA advises testing every home regardless of zone, fixing at 4 pCi/L or higher and considering a fix between 2 and 4 pCi/L. Exhaust-only ventilation can increase soil-gas entry. Radon testing and mitigation should be performed by a certified radon professional, and we coordinate ventilation design with their findings.

Filtration and the right approach for your home

EPA recommends a filter rated at least MERV 13, or as high as the system fan and filter slot can accommodate. A 1-inch MERV 13 filter in an undersized return restricts airflow, which can cause coil icing, noise and higher energy use. A 4 or 5 inch media cabinet usually solves this. ERV filters protect the core and need upgrading if they are also meant to clean the air. For homes without ducts, portable HEPA purifiers are a practical complement, especially on wildfire smoke days such as those New York experienced in 2023.

Planning a kitchen with a powerful hood, a gut renovation or a tighter home is the right moment to design ventilation. We design ERV or HRV systems, range-hood makeup air and bath exhaust to the code that applies to your property, coordinate board and permit requirements, and install the work with our licensed HVAC partner.