Estimated reading time: 7 minutes
During a recent home inspection, I walked into a well-kept house where a proud homeowner was eager to show off his latest DIY projects. One was a 6-inch flex duct running from the roof to his HVAC return plenum.
“Fresh air on a budget?” Hardly.
Here’s the reality: that wasn’t fresh air—it was an express lane for dust, pollen, and smoke to travel straight into his home.
Unfortunately, duct tape, foam globs, and gaps are wide enough to allow unfiltered air from the attic and outdoor air to enter the air conditioning system. This wasn’t a smart ventilation upgrade but a $50 shortcut that could cost much more in terms of air quality issues and system wear.
I commend the effort; however, with this crude and poorly designed system, the indoor air filters clog faster, the HVAC wheezes harder, the A/C coil is subjected to tons of unfiltered air, and you’ll breathe junk you’d rather sweep off your porch. Ventilation is supposed to clean things up, not turn your furnace into a dirt cannon.
The contaminants should stay outside where they belong, and there is a proper way to achieve excellent indoor air quality.
The Right Way to Bring in Fresh Air
Indoor air quality professionals rely on two key systems for controlled ventilation, and they are primarily tied to climate zones: HRVs (Heat Recovery Ventilators) and ERVs (Energy Recovery Ventilators).
These systems exchange stale indoor air with fresh outdoor air while maintaining energy efficiency.
- HRVs (Heat Recovery Ventilators): Ideal for colder climates, HRVs bring in fresh air while retaining heat from the outgoing air, helping to maintain indoor comfort without excessive energy loss.
- ERVs (Energy Recovery Ventilators): Perfect for humid areas, ERVs exchange heat and help manage moisture, reducing the risk of excess indoor humidity. Dr Allison Bailes gives us southerners some good advice here.
Choosing between an HRV and an ERV isn’t a guessing game—it’s a data-driven decision based on climate, humidity levels, and home construction.
Here’s what professionals consider:
- Climate: In colder regions like Minneapolis (IECC Zone 5), an HRV keeps warmth inside while ventilating. In humid areas like Mobile, AL (Zone 2), an ERV helps control moisture.
- Humidity Levels: If summer humidity exceeds 70% (like in the Southeast), an ERV helps maintain comfort. In drier locations like Denver (30% humidity), an HRV does the job.
- Indoor Air Quality Needs: Homes with tight insulation benefit from ERVs to manage moisture, while older, draftier homes often do well with HRVs.
- Heating vs. Cooling Demand: If heating days outnumber cooling days, an HRV is usually the best option. For homes with a high cooling demand, an ERV makes more sense.
- Local Air Quality: Areas prone to wildfire smoke or high pollen counts need proper filtration, making a professionally designed system essential.
- IMPORTANT: Reducing the amount of moisture coming into your home is not the same as dehumidifying the air “in the home”. An ERV is not a dehumidifier.
Question and Answer for ERV and HRV Air Ventilation Systems
What’s wrong with simply connecting a duct to the outside to bring in “fresh air?”
Connecting a duct directly to the outside, like from the roof to an HVAC return plenum, is a common DIY mistake that can negatively impact indoor air quality. Instead of bringing in fresh, clean air, it often introduces unfiltered outdoor pollutants such as dust, pollen, smoke, and attic contaminants directly into the home. This can clog air filters faster, strain the HVAC system, and degrade the quality of the air you breathe.
What are HRVs and ERVs, and how do they improve indoor air quality?
HRVs (Heat Recovery Ventilators) and ERVs (Energy Recovery Ventilators) are two key systems designed to provide controlled ventilation in homes. They work by exchanging stale indoor air with fresh outdoor air while minimizing energy loss. HRVs primarily recover heat, making them suitable for colder climates, while ERVs recover both heat and moisture, making them ideal for humid climates. These systems ensure a continuous supply of fresh air without significantly increasing heating or cooling costs.
How do I choose between an HRV and an ERV for my home?
The choice between an HRV and an ERV depends on several factors, primarily climate, humidity levels, and home construction. In colder climates with low humidity, an HRV is generally preferred as it focuses on retaining heat. In humid climates, an ERV is better suited as it helps control moisture levels, preventing excess humidity indoors. Consider whether your region has more heating or cooling days, with HRVs being better for areas with more heating days and ERVs for areas with more cooling days. Also consider indoor air quality needs – tightly insulated homes benefit more from ERVs.
Why is professional installation important for ventilation systems like HRVs and ERVs?
Professional installation ensures that the ventilation system is properly sized, installed, and configured for your specific home and climate. Professionals can assess your home’s needs, including climate zone, humidity load, and local air quality, to recommend the most suitable system and filtration options. Proper installation also prevents issues like duct leaks, which can compromise the system’s efficiency and introduce unfiltered air into the home.
What are the hidden costs associated with DIY ventilation solutions?
While DIY ventilation solutions may seem cost-effective upfront, they can lead to hidden costs in the long run. These costs include frequent air filter changes due to increased dust and pollutant exposure, increased wear and tear on the HVAC system as it works harder to compensate for unfiltered air, and potential health issues resulting from poor indoor air quality. Additionally, DIY solutions may not be energy-efficient, leading to higher utility bills.
What are the key factors to consider before upgrading my home’s ventilation system?
Before upgrading your home’s ventilation system, consider your climate zone and your home’s humidity load. Knowing your climate zone helps determine whether an HRV or ERV is more appropriate. Assessing your home’s humidity load, especially during the summer, will indicate whether moisture control is a primary concern. Additionally, consider local air quality issues like pollen counts or wildfire smoke, as these may require enhanced filtration options.
What is the typical cost of a professionally installed HRV or ERV system?
A professionally installed HRV or ERV system typically costs around $3,000 to $4,000. While this is a more significant investment compared to DIY solutions, it ensures proper installation, energy efficiency, and improved indoor air quality. The long-term benefits of a professionally installed system, such as reduced energy costs, fewer maintenance issues, and improved health, often outweigh the initial investment.
Why is good indoor air quality considered a necessity rather than a luxury?
Good indoor air quality is essential for overall health and well-being. Poor indoor air quality can lead to various health issues, including allergies, asthma, respiratory infections, and other illnesses. Investing in a proper ventilation system, such as an HRV or ERV, ensures that you and your family are breathing clean, fresh air, creating a healthier and more comfortable living environment.
The Bottom Line
That DIY rooftop duct may have only cost this homeowner $50 upfront, but it came with hidden costs—frequent filter changes, a struggling HVAC system, and poor indoor air quality. A professionally installed HRV or ERV is a more considerable investment (typically around $3K to $4K), but it ensures fresh, clean air without compromising efficiency or comfort.
Before making a ventilation upgrade, start with these two questions: “What’s my climate zone? What’s my home’s humidity load?”
Investing in the right system ensures you’re breathing clean air without the unintended consequences of a quick fix. After all, good air quality isn’t a luxury—it’s a necessity.