Hello, I have built a full icf two story house in central Wi. The dilemma I’m having with my HVAC guys is HRV vs ERV. The house is approx. 7500sf with basement. There will be Infloor heat in the basement and 1st floor. The reading that I’ve done says to go with ERV. My builder is contacting his sales reps but he is currently thinking a HRV and then has mentioned humidifier for RH in winter. Any help with this would be greatly appreciated. Thank You

I have a 3700sf ranch with a walkout and had to turn off the heated floors in the basement the first winter and haven't had them on since(Ann Arbor Michigan). That is with half our basement exposed out of the ground. The first floor heated floors heat both upward and down ward and is more then enough to heat both levels. We have 2 inched XPS under the basement floor.

I have a HRV that we have piped to suck air out of the bathrooms so we only run it when the bathrooms are occupied. I have never used a ERV and they seem to complex for what they do. IMHO.

What are you doing for air-conditioning?

http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/85967/afv/topic/Default.aspx

Thank you for the info. I think our HVAC guy has a bit of over kill on the hvac. Air-conditioning is 5 ton I believe.

I had gone though that post earlier. Just a lot of info to decipher. To much humidity and condensation in the winter is probably my biggest concern as well as comfort level. We do have a wood fire place as well, so that will be some dry heat.

Yes, grossly over sizing HVAC is a common HVAC company problem. HRVs remove humidity. ERVs do not...but are a little more efficient as a result of this.

If you have very cold and dry winters, many days with very low relative humidity, especially when the incoming air is heated to 55-65 degrees F from the exchanger, some say you should forego the ERV and just get and HRV instead. But the moisture exchange will send a lot of the moisture out into the dryer incoming air in an ERV. An HRV has no such humidity exchange. So based on your location and the feedback you received, I would suggest that you get an ERV, possibly with an additional humidifier as an addon. After the exchange has occurred, the humidifier should only be activated at humidity levels below your thermostat set point and turn off immediately when the high level set point is reached. The Conservation Energy Recovery Ventilation System at Equinoxbuild has such an add on feature. Plus it uses auxiliary heating or cooling using small heat pump plus heat strip (when below freezing). I went to their site and bookmarked it as I am planning on using their system on all the projects that I get involved in. CERV2 is the newest and best system they have at this time. www.buildequinox.com. Be advised it is designed for projects that meet or surpass the Passive house standard (90-95% reduction in heating costs per month during the winter months from standard stick built homes). The problem I have with just ERV systems is the separate ventilation ducting with colder air entering the rooms than the thermostat is set for, requiring a separate Conditioner/Heating Air handler air being vented into the same rooms. The following article states that it is best to separate the ventilation from the Air handler system with separate ducting. https://www.zehnderamerica.com/why-ventilation-should-be-separate-from-heating-and-cooling-systems/ This does make sense. What I like about the Equinox build CERV system is that it combines both augmented cooling after fresh air goes through the ERV and all recirculated air only cooling when CO2 and VOC sensors show below threshold for both. That with MERV 13 filtration for both incoming and exhaust air is great. Protects the ERV/handler and the inhabitants of the house. Filters all bacteria at that level, much less, pollen, dust, dust mites, etc. The caveat is after talking to the Equinox build people, they told me that if the house is not extremely tight, energy efficient insulation windows surpassing the passive house standards with a separate CERV system for each conditioned floor, an additional Air conditioning system may be needed. Hope this info helps you.

Air at 73 degrees 50% Humidity has the same amount of moisture in it as air at 60 degrees with 100% humidity.

Posted By sailawayrb on 07 Apr 2021 01:51 AM
Yes, grossly over sizing HVAC is a common HVAC company problem. HRVs remove humidity. ERVs do not...but are a little more efficient as a result of this.

I disagree. While HRVs remove humidity in pretty efficient manner, ERVs can do it as well.

ERVs transfer both heat and humidity...total energy...which is what the "E" stands for. HRVs only transfer heat...which is what the "H" stands for...and humidity is condensed and removed. So if you want to retain humidity in a building, you should use an ERV. I would not recommend using an even more complicated device...an ERV that can also remove humidity...when a much simpler HRV can accomplish the same purpose.