ERV vs. HRV for HERS Ratings in Massachusetts: Why ERVs Make More Sense
In Massachusetts’ cold climate, proper ventilation is critical — especially in today's airtight, energy-efficient homes. But many still question the value of Energy Recovery Ventilators (ERVs). Aren’t they just energy-wasting fans?
Not at all. In fact, an ERV is one of the best tools you can install to maintain indoor air quality (IAQ) without wasting energy. In this article, we’ll break down:
Why ERVs outperform HRVs for most Massachusetts homes
How ERVs improve your HERS score
How CFM requirements are calculated (including infiltration credits)
Best practices for ducting and setup
And why we love the Broan BLP150E75NS-HWF ERV
What’s the Real Difference Between an ERV and HRV?
Both ERVs and HRVs bring in fresh outdoor air and exhaust stale indoor air. The key difference?
HRVs (Heat Recovery Ventilators) transfer only heat between the outgoing and incoming air.
ERVs (Energy Recovery Ventilators) transfer both heat and moisture, which is especially helpful in humid summers and dry winters.
In Massachusetts, where both humidity control and energy conservation matter, ERVs give you more balanced performance year-round.
Myth: “ERVs Waste Energy”
Truth: Leaky Homes Waste Energy — Not ERVs
Some still believe that running a ventilation system wastes energy. But consider this:
A leaky home exchanges air uncontrollably, forcing your HVAC system to work harder
A tight home with an ERV controls that airflow, recovers energy, and preserves comfort
In other words, ERVs don’t waste energy — they recover it, helping your HVAC system run less often and more efficiently.
What Does It Cost to Run an ERV in MA?
Let’s break it down using a real-world example. The Broan BLP150E75NS-HWF ERV provides 64 CFM of balanced ventilation while consuming just 31 watts. It also has an Adjusted Sensible Recovery Efficiency (ASRE) of 81% — one of the best in its class.
Annual operating cost:
31 watts × 24 hours/day = 0.744 kWh/day
0.744 kWh/day × 365 = 271.56 kWh/year
271.56 kWh × $0.34/kWh (Massachusetts average) = $92.33/year
✅ For less than $100/year, you get high-performance, energy-efficient, code-compliant ventilation.
How Do You Determine the Right CFM?
There are three widely accepted ways to calculate ventilation rates in Massachusetts:
RESNET HERS Index (ANSI/RESNET/ICC Standard 301)
ASHRAE Standard 62.2-2019 or 62.2-2022
Massachusetts amendment formula for low-rise residential buildings:
Q=0.03×CFA+7.5×(Bedrooms+1)−0.052×Q50×S×WSFQ=0.03×CFA+7.5×(Bedrooms+1)−0.052×Q50×S×WSF
Where:
CFA = Conditioned Floor Area (sq. ft.)
Q₅₀ = Final blower door test result in CFM @ 50 Pa
S = Infiltration credit constant (typically 1.0–1.3 based on volume)
WSF = Wind sheltering factor
Example: 2,500 sq. ft. home with 4 bedrooms
Let’s say your final blower door result is 900 CFM@50, with:
S = 1.32 (based on volume)
WSF = 0.58 (moderate shelter)
Plug into the formula:
Q=0.03(2500)+7.5(4+1)−0.052(900)(1.32)(0.58)Q=0.03(2500)+7.5(4+1)−0.052(900)(1.32)(0.58)Q=75+37.5−35.8=76.7CFM
Thanks to the infiltration credit, your required ventilation drops significantly. Without this credit, you'd need 112.5 CFM.
Why We Recommend the Broan BLP150E75NS-HWF
We’ve tested and installed many ERVs, but the Broan BLP150E75NS-HWF consistently stands out for:
Adjustable CFM range (up to 147 CFM) — easily scales to meet code
High energy efficiency — just 31 watts for 64 CFM
Boost mode — perfect for timed exhaust from bathrooms
Durability and reliability in cold New England climates
Easy damper tuning and flexible duct layout options
This model checks all the boxes for homes needing balanced ventilation at a low operating cost.
Best Practices for Ducting and Installation
Proper installation is crucial. Here’s what we recommend for optimal performance and HERS scoring:
Insulate supply and exhaust ducts — prevents condensation at roof or wall penetrations, especially in cold attics
Minimize bends — reduces resistance, maintains airflow efficiency
Use dampers — fine-tune each port’s CFM during commissioning
Exhaust from: bathrooms, laundry rooms, kitchens
Supply to: bedrooms, living rooms, office/family rooms
Also, follow manufacturer instructions for wall/roof terminations and filter access. A poorly installed ERV won’t perform as modeled in a HERS rating.
How ERVs Help Lower a HERS Score
Ventilation systems directly impact your HERS Index. Here’s how an ERV improves your rating:
✅ Low wattage per CFM (W/CFM) = higher efficiency score
✅ High ASRE = better energy recovery performance
✅ Tight home + balanced ventilation = reduced heating/cooling loads
✅ Air quality assurance = helps meet newer code requirements for mechanical ventilation
As of 2025, many MA code officials and HERS raters expect continuous ventilation with boost control in bathrooms— ERVs like Broan’s make this easy.
Final Thoughts
Massachusetts homes need smart ventilation — and ERVs are the clear winner. They recover energy, regulate humidity, improve comfort, and help meet code and HERS compliance.
Combined with a tight building envelope and efficient mechanical systems, an ERV is not just a best practice — it’s a code-compliant, cost-effective, and high-performance solution for indoor air quality.
Need help choosing or modeling an ERV for your next project? Contact us for HERS support, product selection, or design help.
