We are in a situation where we have a choice between a HRV and ERV with no cost consideration whatsoever.  The HVAC contract calls for an ERV (Broan Guardian GSEH3K) but they installed the HRV (GSHH3K).  So we can either keep the HRV, or honor the contract and get the ERV (which they will do upon request).  Like I said, no cost consideration at all.

Pertinent details:

• Location: Madison, Wisconsin area (heating dominated climate)
• Heating/cooling system: Carrier-badged Climate Master Tranquility 27 geothermal, 5 ton
• Projected heating load via manual J: 4.5-5.0 ton; cooling load: 2.5-3.0 ton
  
• Dehumidifier: Whole-house dehumidifer, integral to geothermal system
• Humidifier: None

The main concern we have about the HRV is that winter air is dry and we do not have a humidifier.  The ERV would presumably moderate this, but it reduces flow below 16 degrees fahrenheit (which is probably about 40% of our days and 75% of our nights in the winter).  We're figuring that our dehumidifer makes this much less of a debate, which is why it's a tough call.

Anyone care to comment or recommended one versus the other, or even just say it's a tie?  Thanks in advance!

If you have a tight house in a cold climate, I would suggest leaving the HRV in place. I have seen houses with both types of systems here in MA and the ones with the ERV tend to have higher humidity levels all year round. With an ERV you have no control over your humidiy level other than running the dehumidifier which shouldn't be needed during the winter months when heating. Dehumidifiers consume large amounts of energy. Does the dehumidifier work automatically when the geothermal heating system is on? Most likely only when cooling and not when heating. Most engineers would suggest the ERV because it is more efficient at transfering energy, but in my experience in cold climates with tight houses this creates a problem when you have no other method of drying the house other than running a dehumidifer, especially in an ICF or SIP's envelope. Although HRV's are not designed to control humidity they do when used correctly. I have yet to see a tight house that is to dry, even during the cold winter and the HRV running. One of my customers insisted on a ERV because it is more efficient, and it is, but had to add a dehumidifier to bring down the humidiy levels that were hovering aroung 70%. The ERV maintained the humidity level were as an HRV would allowed them to bring dryer air in during the winter. Another house I installed an HRV and the humidity levels are around 40% during the winter with the HRV running. A Whole house dehumidifier is used during the summer months to maintain comfort, but our cooling season is very short here in MA and it is only running during peak cooling season from early July to mid August. Speaking from experience I would recommend leaving the HRV.

Tom Pittsley
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www.eebt.org