Sizing an HRV/ERV System
Hello, I am choosing an hrv/erv for my 950 square foot house that is in the design stage, zone 6, coastal Maine. Using the formula, I have determined that the cfm rating for my house is 17, or perhaps 25 when my gf is around. I researched one unit and have attached the screen shot below. I can’t make sense of the table enough to know if this unit is properly sized for my house. I would appreciate help on this.
Also, since my ventilation needs seem to be small compared to most, can someone recommend a good mini unit? Naturally, I would like high SRE, Efficacy and ASE but would also like it to be affordable and quiet. I am leaning towards an erv in order to help with dry air in the winter, but would also consider a hrv. Come June, I will shut it off completely and open the windows until October. I am going for super tight, r-40 in the walls, r-60 in the roof.
Thanks!
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For value and performance you can't beat a Panasonic intelibalance 100. A bit larger than what you need which is a good thing as you can run it at very low speed to get better efficiency and still have plenty of flow when on boost.
If you want more budget friendly, I've used their Whispercomfort ERV for smaller spaces. The unit is not very efficiency but it is also not much more than a quality bathroom fan and gets you some energy recovery. If you are careful there is enough space to drill into the side of the unit and connect a 3" duct to the fresh air supply (see attached). This way you can mount the unit in the bathroom, exhaust from there, but still have it supply the fresh air to your living space. The blower is low powered so stepping up to 4" duct right at the unit is recommended even for short runs.
Thanks Akos,
I checked them both out online. Also, the Renewaire EV90. Am I correct that the Intellibalance and the EV90 would be a more traditional set up where I could vent from the kitchen, bathroom and down stairs utility room say(with ducts and intakes) and the units would be in a conditioned attic? Whereas the Whispercomfort would be a single exposed unit in one room (the bathroom as you suggest) but could still adequately vent the whole house, but might use more energy doing it? Also, is there generally only one penetration to the outside with these units?
" Am I correct that the Intellibalance and the EV90 would be a more traditional"
Correct. Just to make sure, for the kitchen vent, you are not venting directly from the fume hood but kitty corner from the range at least 8' away. A kitchen still needs a proper hoot vented to outside. Utility rooms don't need venting, but a basement/crawlspace does, a stale air pickup there is important sized to meet the required ventilation (usually 50cfm/1000sqft).
The Whispercomfort units I have are plumbed into the return of the heat pumps which circulates the air through the house. I find this works quite well for smaller spaces. The control units on these is not best sealed, so don't mount it above a shower/tub, anywhere else in a bathroom is fine.
Most manufacturers offer a tandem vent so only a single larger hole is needed, this is my preferred install. The Panasonic one is small, so it is good for the Whispercomfort. This would be too small for the IB100 but Lifebreath has a larger dual vent you can use.
Make sure to read the manual as the wiring is not standard on the Panasonic units, you have to provide constant power with a separate 14-3 control wire for on/off/boost.
"Most manufacturers offer a tandem vent so only a single larger hole is needed, this is my preferred install. The Panasonic one is small, so it is good for the Whispercomfort."
Akos, I think Panasonic recommends setting CFM to no more than 50 in/out on the Intelliballance 100 when using the tandem vent. Do you have any experience using the full 100 cfm in/out on an Intelliballance 100 when using the tandem vent? Is it possible? Does it work well?
I'm thinking about installing an Intelliballance 100 and like the tandem vent but I do need to be able to use the full 100 cfm that the unit is capable of.
You can use the Lifbreath one (99-190). It can take 5" or 6" ducting so you can connect it to the IB100 with 6" flex.
Thanks. Found that online and it does indeed appear to support 100 cfm intake and 100 cfm exhaust.
"Most manufacturers offer a tandem vent so only a single larger hole is needed, this is my preferred install. The Panasonic one is small, so it is good for the Whispercomfort. This would be too small for the IB100 but Lifebreath has a larger dual vent you can use."
Thanks again. The above quotation seems to suggest that I would be using a Panasonic and a Whispercomfort at the same time (as well as a heat pump). Just to be clear... I could simply mount a Whispercomfort in the bathroom, not over the shower, and plumb it into the return of the heat pump. This would be sufficient to vent my entire house, without a more traditional unit like the panasonic having to also be used.. In addition, I would just need a standard range hood that would be vented to the outside (and not run through the ERV). And, I would not need an additional bathroom vent other than the Whispercomfort. Is this right?
" I could simply mount a Whispercomfort in the bathroom, not over the shower, and plumb it into the return of the heat pump" "I would not need an additional bathroom vent other than the Whispercomfort"
Yup. It won't win any efficiency awards but it is simple, cheap and works for smaller spaces. Keep in mind the unit does only 40CFM, so that is about 2 beds.
If you do want better, you can also plumb an IB100 in similar way. Mount it into a cabinet outside the bathroom, run the stale air pickup to the bath and the fresh air supply to your HVAC return.
P.S. Even with a regular ERV you never connect the range hood to the stale air pickup, the fine grease from cooking will clog the core in no time. With a regular ERV you still want to pick up air from the kitchen area but this should be located at least 8' away from the stove.
Akos, did you do the external duct mod based on that youtube vid out there on the topic? How well does that work for you?
I have a spare in hand now so might consider it for our upstairs bath...
For some reason I was under the impression the unit came with a knockout for the fresh air supply, which would make a lot of sense, when it didn't, I just drilled it where there was room and foamed in a 3" coupler. The factory fresh air feed port was blocked off with a piece of metal.
The unit doesn't have any balancing ports and it is hard to measure such low flow rates with the pitot tube setup I have, so I have no idea how well it is balanced. The air coming out is warmish, so there is some recovery. We will have to see how it holds up in the long run.
This fellow at 4:20 https://www.youtube.com/watch?v=eq4zMNcHOXw
Does the same mod, 3" vent, apparently under the advice from a Panasonic contact. I have measured the same unit in place at pretty much 30 CFM, fresh, 40 CFM stale, in line with the specs.
At cold temps it is pretty much exhaust all the time, but that drops to 20 CFM so I wonder if this will suffice for the bathroom.
Efficiency on the small ERV is not good at at all though, from 42 to 62 % at best in my tests. The image attached is a snapshot of data at 39 F ambient, with air entering the home at 52 F. That works out to 44% efficiency :-(
The installation manual advises specifically against installing this unit in a bathroom:
https://www.berriman-usa.com/pdf_brochures/op_manuals/panasonic_erv_fv-04ve1_op_manual.pdf
Page, 6, point J.