If somebody has handed you two brochures and asked you to choose, this page is for you. A recovery-ventilator spec sheet carries roughly eight lines that matter, most of which are true of both technologies and therefore cannot help you pick one. Exactly two of them describe the real difference. The table below translates each line, says whether it separates the cores, and then matches the common housing patterns on the St. Croix side of the county to a recommendation.
Furnace Direct installs licensed recovery ventilators in Oak Park Heights and the river-bluff neighbourhoods near it. We publish no prices and sell no equipment through this page; what follows is how we read a sheet before scoping a job.
| Line on the sheet | What it is actually telling you | Does it separate the two cores? |
|---|---|---|
| Sensible recovery efficiency | The share of heat in the outgoing air that gets handed to the incoming air. Every recovery ventilator publishes it, and it is the number salespeople quote because it is the flattering one. | No. Both core types recover heat, and good examples of each land in similar territory. |
| Total or latent recovery efficiency | A combined figure that accounts for moisture moving with the heat. It only means anything on a core built to transfer vapor, which is why a heat-recovery sheet often does not carry the line at all. | Yes. This is the line that genuinely distinguishes the two technologies. |
| Net moisture transfer, or a humidity-transfer rating | How much water vapor the core hands back to the incoming stream instead of sending it outdoors. Published as a rate or a percentage depending on the manufacturer. | Yes, and it is the line to read second. It is the physical mechanism behind the whole argument. |
| Frost control or defrost strategy | What the unit does when the outdoor air is cold enough to freeze condensate inside the core: recirculate, preheat, or pause on a schedule. The method matters more than the trigger temperature. | No, but it decides how the unit behaves in a deep cold snap and how much you notice it. |
| Airflow at a stated external static pressure | The honest airflow number: what the unit actually moves once real duct is attached, rather than what the fan could do with nothing connected. Always read the pressure the figure was taken at. | No, but it decides whether a given unit suits your duct system at all. |
| Sound rating | How loud the unit is at its operating speeds, usually measured at a stated distance. Mechanical rooms under a bedroom or beside a finished office are where this line earns its place. | No. It decides whether you leave the thing switched on, which is not a small matter. |
| Filtration listed for the intake stream | What the unit filters incoming outdoor air with, and whether a better filter can be fitted without choking the airflow the sheet promised. | No, though it matters more on a lot facing a busy commercial corridor than on a quiet bluff street. |
| Commissioning and balancing instructions | The pages at the back telling the installer to measure supply and exhaust and adjust until they agree. The least-read section of any manual and the one that determines whether the rest of the sheet is true in your house. | No. It decides whether you get the performance the rest of the sheet described. |
| Two of the eight lines distinguish the technologies. The other six distinguish a good unit from a mediocre one, which is a different question and still worth asking. | ||
Everything else on the sheet is a quality measure. Moisture transfer is a category measure: a core either hands a share of the outgoing water vapor back to the incoming stream or it does not, and that single behaviour is the entire choice you are being asked to make. Read it alongside the total or latent figure, and then ask one question about your own house. Does this building need to shed vapor or hold on to it through January? A full household inside a tightened shell needs to shed, and wants a core that sends moisture outdoors. A quiet household inside the same shell is already shedding faster than it produces, and wants a core that returns some of it. No published number can answer that question for you, which is why the sheet goes second and the house goes first.
Sensible recovery efficiency is quoted constantly and settles nothing here, because both core types recover heat and competent examples of each publish similar figures. Treat it as a floor rather than a differentiator. Filtration is the other one: worth reading, occasionally worth upgrading, and never a reason to pick one technology over the other. A better filter restricts airflow, so any upgrade has to be checked against the airflow line rather than chosen from a catalogue. The honest hierarchy is that moisture transfer picks the category, airflow at real static pressure picks the model, sound and service access decide whether you are still happy in three years, and efficiency is a tiebreaker between two units you were already willing to own.
| Housing pattern | What we would recommend | Reasoning |
|---|---|---|
| Bluff-side home with a finished walkout, full household | Heat recovery | High indoor vapor production against a tight shell. The summer behaviour of a lower level on a river bluff is a grade, drainage, and dehumidification question rather than a core-selection one. |
| Re-glazed and re-insulated mid-century, one or two occupants | Energy recovery | The envelope work removed the accidental air change, and a small household cannot produce enough moisture to keep pace with what a heat-only core would send outdoors. |
| Newer sealed build near the commercial fringe | Check what is already there | These frequently have a cabinet or at least a roughed-in connection. Service, measure, and balance before buying anything; an uncommissioned unit mimics the wrong technology convincingly. |
| Townhome or association building, shared walls | Either core, routing decides | Short exterior runs and limited wall space constrain where two terminations can legally and quietly go. The core still follows indoor winter humidity, not the building type. |
| Older house with a bare outdoor-air duct on the return | Replace the arrangement | A motorised lid on a cold-air duct recovers nothing and is usually the cause of the complaint. Core selection then follows the symptom rather than the existing hardware. |
| Any house with glass that films every hard freeze | Heat recovery, with confidence | Visible condensation is the only evidence on this page that cannot be produced without a genuine vapor surplus. It outranks every other input, including anything on the spec sheet. |
Found your pattern? One window reading turns it into a scoped quote.
Match my patternPublished airflow depends on the pressure it was measured against. Your duct, your run length, your hood screens, and your plenum connection decide what the same unit does in your mechanical room. This is the gap between a brochure and a commissioning report, and it is why the balance step is not optional.
Bluff-side houses frequently put the mechanical room at the lowest level with the only convenient exterior wall two floors above it. Lots nearer the commercial fringe have more wall and more noise to think about. Neither situation appears anywhere on a spec sheet and both appear in the price.
Three questions get you through any brochure. Does it publish a latent or total recovery figure, or only a sensible one? At what external static pressure was the airflow measured, and is that pressure realistic for a house your size? And does the installation section include a commissioning procedure with measured airflows rather than a sentence telling you to set it and leave it? If the answer to the third question is no, the rest of the sheet is a hope. Send us the model numbers you were given and we will tell you plainly which lines are doing the work and which are decoration — and if the unit you were quoted is the wrong category for your house, we will say that too.
It settles nothing between the two cores, because both publish sensible recovery efficiency and good examples of each are competitive on it. Ask instead for the latent or total figure and the moisture-transfer line. Those are the two that describe the actual difference, and one of them is often absent on a heat-recovery sheet.
Because efficiency is a property of the unit and airflow is a property of the installation. A unit that cannot reach its rated airflow through your duct at your static pressure will underperform every number on the sheet. That is also why we will not promise performance before seeing the plenum and the run.
Enough to ask which one it uses. Recirculating defrost pauses fresh air briefly; a preheater uses energy to avoid that. Both are legitimate. Where it matters is a house where somebody notices every change in sound, or a mechanical room sitting directly under a bedroom.
It changes the filtration conversation and where we would rather put the intake, and it changes nothing about the core. Between November and March the outdoor air at your intake is cold and dry whichever direction it arrived from; indoor moisture is produced indoors.
Usually yes. Send what your coldest window does on a hard freeze morning, how many people live there, and whether the envelope has been tightened. That is enough for a confident core recommendation. The price is what needs the visit, because it follows routing and penetrations.
Model numbers if you have them, plus your housing pattern and what the coldest window does on a hard freeze.
The rest of the batch gets there through a fill-in worksheet, the objects in your own house, and a part-by-part audit of an existing installation.