Modern home construction techniques achieve tight building envelopes. The upside is that highly efficient homes are more comfortable and cheaper to heat and cool. The downside is that there is little to no natural ventilation. A solution is to install a mechanical ventilation system. There are three core types: whole-house fans, heat recovery ventilators (HRVs), and energy recovery ventilators (ERVs). Let’s explore the key differences between them.
Whole-House Fans
Whole-house fans are ventilation systems that draw air from a home’s living spaces into its attic. Fresh air enters through natural ventilation, such as open windows and doors. This helps to cool the attic as an attic fan does. It also provides circulation throughout the home, which you should be augmented with ceiling fans in all rooms where practical.
Installers estimate fan sizes based on many factors. That said, the guideline is that the airflow, in cubic feet per minute (CFM), should be at least half the home’s total volume. In other words, if you have an 8,000-cubic-foot home, you need a 4,000-CFM fan. It’s all right to opt for a higher CFM than needed, but a lower CFM will result in suboptimal performance.
Installing a whole-house fan isn’t a DIY job because proper attic ventilation is crucial. The fan requires dedicated wiring and one or more vents, typically installed in ceilings. A home generally needs one square foot of vent area for every 750 cubic feet of living area. You can have twice as much vent area for even better performance.
Heat Recovery Ventilators
You generally wouldn’t use a whole-house fan in the winter because it would make your home too cold. You also wouldn’t run a whole-house fan when cooling or heating your home. The fan would allow the conditioned air to escape.
An HRV is a more advanced whole-house fan that can transfer heat energy as needed. In cold weather, an HRV extracts heat from the stale air and uses it to preheat the fresh air. In warm weather, an HRV can run this cycle in reverse. It will move heat from the fresh air to the exhausted air. Note that this is an integral function, so you can’t simply run an HRV in whole-house fan mode.
An HRV’s added capabilities open many options for a household. You can operate your ventilation system year-round. Homeowners can even run it with their heating or cooling system on. Typically, the HRV will run as needed in between the heating or cooling cycles.
Energy Recovery Ventilators
ERVs are similar to HRVs. The main difference is that they also move water vapor. Ambient air is naturally drier in cooler weather and more humid in warmer weather. In the fall and winter, an ERV will extract moisture from the stale air and add it to the fresh air. In the spring and summer, it will extract moisture from the fresh air and add it to the stale air. Again, this is an integral function. You can’t set an ERV to operate as an HRV or a whole-house fan.
Climate
The industry provides general recommendations based on climate and even has maps available. It suggests an ERV in northern climates where winters are cold and dry. The industry advises an ERV in the southeast where summers are hot and humid. It recommends an HRV in many areas of the southwest where summers are hot and dry. That said, many homeowners live in moderate climates where you can make an argument for either an ERV or HRV.
Attic Temperature Control
Builders generally design attics to be unfinished spaces that serve as an insulation buffer. In these scenarios, it’s important that the attic air normalizes with the ambient air. If that doesn’t occur, heat and moisture accumulate in the attic and undermine the building envelope. Many homes rely on passive attic ventilation. Attic fans and whole-house fans provide active attic ventilation, but HRVs and ERVs do not because they are closed systems. If you need attic ventilation, you may have to install an attic fan in addition to your HRV or ERV.
Energy Efficiency
Whole-house fans can improve household energy consumption by delaying how early in the year you need air conditioning. HRVs and ERVs do this as well and also delay how soon you need heating. They precondition the air and lower the heating and cooling the main HVAC system must provide. ERVs, in particular, decrease the workload on an AC and lower its energy consumption.
Whole-house fans require electricity but generally use less energy than air conditioners, heat pumps, furnaces, and so forth. Homeowners can also integrate solar power to mitigate the power requirement.
Home Comfort
All whole-house fans make a home more comfortable by introducing fresh air, providing circulation, and promoting more even temperatures. HRVs and ERVs allow you to enjoy your home for more of the year without heating and air conditioning. ERVs provide the added benefit of adjusting moisture content in the air. That can make you comfortable at a higher temperature in summer and a lower temperature in winter.
Air Quality
Without air purification, the air inside a home will have at least as much pollution as the ambient air. It may even have more due to indoor pollution sources. One of the issues with tight building envelopes is that pollutants accumulate and become concentrated. Whole-house fans alleviate this problem and improve indoor air quality through a regular influx of fresh air. They also have filtration systems that prevent the intake of pollen and other allergens. HRVs and ERVs are even better because they allow for this ventilation when running your main HVAC system. Most heating and cooling systems simply circulate the air in the home and don’t provide ventilation.
Relative Humidity
Relative humidity (RH) is an important aspect of indoor air quality and comfort as well. High or low RH can irritate your respiratory system and make you more prone to illnesses. It also makes you less comfortable and requires more cooling or heating, respectively. ERVs help to regulate RH in a home by adding and removing moisture as needed. They can offset the drying-out effect that can be the byproduct of running a furnace. ERVs can also make a notable difference on high-humidity days when your AC would otherwise struggle.
Cost
Whole-house fans are the cheapest option because the equipment and the installation are less complex. Consumers can expect to pay between 50% and 100% more for an HRV. The difference between an HRV and an ERV is an additional 25% on average. You can claim whole-house fans, HRVs, and ERVs through the federal Energy Efficient Home Improvement tax credit. For HRVs and ERVs, there may be rebates available through your local utilities. The U.S. EPA has set HRV and ERV standards but does not certify them through ENERGY STAR as of 2025.
Whole-House Fan, ERV, and HRV Installation in Salem
Woodward Heating Air Plumbing is an top heating and cooling company located in Salem, OR. We have served homeowners in this region since 1989, and we offer a wide array of ventilation options. Those include whole-house fans, HRVs, and ERVs. We’re certified by the EPA, and we employ NATE-certified technicians who install and configure all our ventilation systems.
Our company often has specials available, assists with HVAC incentives, provides free installation estimates, and offers financing on approved credit. Call today with questions or to schedule an in-home installation consultation.
