Older Pittsburgh homes used to ventilate themselves. Drafty windows, loose doors, gaps around the chimney, and uninsulated walls meant outdoor air constantly traded with indoor air. That was bad for energy costs but good for air quality. The home was always breathing.

Modern homes do not breathe. New construction is built tight to meet energy codes. Older homes that have been weatherized with new windows, new insulation, and air-sealed attics have closed the gaps that used to let stale air out. Add the fact that we keep our windows shut from October through April, and you end up with indoor air that recirculates the same particles, gases, and humidity for months at a time.

ERVs and HRVs solve it. They bring fresh outdoor air into your home automatically, while exhausting an equal amount of stale indoor air, and they capture the heat or coolness from the air leaving so you do not pay to condition fresh air from scratch.

What ERVs and HRVs do

Both products do the same basic job: balanced ventilation. They run two ducts and a small fan unit:

• One duct pulls outdoor fresh air in.
• One duct pushes stale indoor air out.
• The two air streams pass through a heat exchanger inside the unit. They never mix, but they exchange heat (and in the case of an ERV, moisture).

So in winter, the warm air leaving your house preheats the cold air coming in. You bring in fresh air at close to room temperature instead of 20 degrees. Your furnace barely notices. In summer, the cool air leaving precools the hot humid air coming in.

The difference between ERV and HRV

The “E” in ERV stands for Energy Recovery. The “H” in HRV stands for Heat Recovery. The difference is moisture.

HRV (Heat Recovery Ventilator): transfers heat between the two air streams only. Moisture is not transferred.

• Best for: very tight homes in cold dry climates, basements with humidity problems, homes that have a humidity excess.
• Why: HRV ventilation in winter dries the indoor air slightly, which is fine if your home is already too humid.

ERV (Energy Recovery Ventilator): transfers both heat and moisture between the air streams.

• Best for: most Pittsburgh homes. Keeps indoor humidity stable in winter (when you want to retain humidity) and limits incoming humidity in summer (when you do not want to add moisture).
• Why: Pittsburgh winters are dry and Pittsburgh summers are humid. An ERV helps you keep the moisture you want in winter and reject the moisture you do not want in summer.

For 90 percent of Pittsburgh homes, we install an ERV. We install an HRV when the customer has a specific reason: an over-humidified home, a tight new build with high indoor moisture loads, or a contractor or architect specification.

When do you actually need an ERV or HRV?

Not every Pittsburgh home needs one. We typically recommend them in three cases.

New construction or major renovation

New homes are built to current energy codes, which require tight air sealing. Without active ventilation, indoor air gets stale, humidity builds up, and CO2 rises (especially in bedrooms at night). Code now usually requires mechanical ventilation in new homes. An ERV is the standard solution.

Tight retrofit homes

If you have replaced your original windows, sealed your attic, added insulation, and generally tightened up an older Pittsburgh home, you may have inadvertently closed off your natural ventilation. Symptoms: stuffy air, condensation on windows in winter, persistent indoor odors, headaches in the bedroom in the morning. An ERV restores the air exchange you accidentally removed.

Indoor air quality concerns

For homes with chronic indoor air complaints, allergies, or anyone immune-compromised, an ERV plus a media filter plus REME HALO or iWave is the complete picture. You bring fresh air in, you filter it, you purify it.

Installation

This is more involved than most IAQ installs. We are running two new duct lines (one inlet from outside, one exhaust to outside), wiring the unit, and integrating with your existing HVAC.

1. Site evaluation. Pick the location for the ERV unit (usually basement or utility area near the HVAC equipment), identify wall penetration points for inlet and exhaust hoods (typically rear or side wall, away from dryer vents and combustion appliances), and verify clear access.
2. Mount the unit. ERVs are about the size of a large suitcase. They mount on wall brackets or hang from joists.
3. Run the duct. Two insulated ducts to the outside through wall penetrations. Inlet and exhaust hoods on the exterior, weatherproof.
4. Integrate with HVAC. We tie the fresh air supply into your supply ductwork (so it mixes with conditioned air) and the exhaust pickup into your return.
5. Wire and control. ERV needs 120V power and a control. Most installs use a dedicated wall control or integrate with the thermostat.
6. Commissioning. Verify airflow balance (the two air streams need to be roughly equal so you do not pressurize or depressurize the home), check for leaks, set the ventilation rate.

Typical install: one to two days.

Setting the ventilation rate

ASHRAE 62.2, the standard that informs most building codes, recommends a ventilation rate based on home size and occupancy. For a typical 2,500 square foot Pittsburgh home with four occupants, the target is around 60 to 80 cubic feet per minute of continuous ventilation. We set the ERV at install based on your specific home.

Some ERVs include automatic boost mode when bathroom humidity rises or CO2 exceeds a threshold. We can include that if you want.

Maintenance

• Filter change every 3 to 6 months. Both the inlet and exhaust streams have filters.
• Annual core cleaning. The heat exchanger core can be removed and washed once a year. We do this during HVAC tune-up for Wahl Club members.
• Exterior hood inspection. Make sure the inlet and exhaust hoods are clear of debris, snow, or animal nests.
• Service life. 15 to 20 years for a quality residential ERV.

Pricing

Flat-rate install pricing. Member and standard rates side by side. Financing through GoodLeap, Synchrony, Wells Fargo, and EasyPay.