PART TWO: Lackluster Efficiency?
Part of what we do at BPE, Inc. involves busting myths that prevent folks from ruling out the very thing that can improve Indoor Air Quality (IAQ) and comfort, heating and cooling bills, and health. Last week, we tackled the issue of cross contamination in ERVs. This week, let’s dive into efficiency:
Myth Two: “What good is an ERV if the word on the street says they are, on average, only 55% efficient?”
There are many ERVs on the market with average efficiencies of 45 to 70%, and quite frankly, such units give today’s high-efficiency models bad press. It was only a few weeks ago, when we crossed the border into Canada on a business trip and encountered that stigma. The border guard asked what we had in the van. We told him we had an ERV back there and he said, “Oh I have one in my house.” We were impressed; the Canadians are so well informed! But he went on to say how when it gets really cold out, he turns it off because it’s really not that efficient. We gave him a business card and told him we can do better if he’s so inclined. Nice guy, but there are others like him with inefficient ERVs and we can do better for them.
So, those folks searching for superior ventilation that significantly reduces energy costs need not concern themselves with inferior-efficiency units. Ventilation technology has come a long way, and high-performance ERVs can perform 10 times more efficiently than standard HVAC equipment when properly installed and utilized. We’re talking about recovering 80 to 98% of the energy that would otherwise be sent out of the building as exhaust. On top of that, superior ERVs working with high-efficiency inline fans can boast Energy Efficiency Ratings (EERs) of 36 to 160 where typical HVAC systems average 10 EER. How can an ERV hit such a high EER? EER is derived by dividing BTUs by the electrical watts used to generate airflow. When a model can run on a mere 38 watts of fan power, you have a superior system in place.
Example of a high-efficiency ERV model. (Image: BPE, Inc.)
What qualities make for a high-performance ERV? Let’s begin with airflow. Cross-flow ERVs are not much more efficient than an air conditioner thanks to the different temperatures from two corners of the unit meeting as they encounter each other. ERVs utilizing an enthalpy wheel are given to a higher level of leakage between airstreams, and you could never operate it efficiently without an HVAC system in place. A fixed-plate, direct counter-flow heat exchanger design, however, is essential for serious high efficiency and, given the right conditions, such an ERV could be your HVAC system.
Pressure drops are another part of the equation and high drops can interfere with efficiency. Today’s direct counter-flow, high-efficiency technologies boast low pressure drops–as low as a quarter of an inch. How? Superior ERV tech design includes larger cores than older tech as well as the ability to run on lower fan pressure.
BPE-MIR-XE-1000 (Image: BPE, Inc.)
You might be wondering how energy savings compares to the price tag on a highly-efficient ERV. Indeed, units are rarely considered cheap, but you need to compare the cost with potential energy savings. It’s a good idea to ask the manufacturer how long it will take for you to recoup your investment thanks to recovering all that energy. At BPE, Inc., we routinely note payback periods of two years. Nice, right?
Want to explore what high-efficiency ERV models look like? Feel free to check out BPE, Inc.’s product performance specs!
For more information, please give us a call to discuss your commercial or residential ventilation needs. Getting involved with BPE, Inc. professionals and our products can be–quite literally–a breath of fresh air!