One more ERV vs HRV question – 7A Climate & Winter Humidity
My mechanical contractor is insistent that in my climate (Saskatchewan 7A) an HRV is better than an ERV because it reduces humidity in winter. I will admit that with the very cold winters (-25C to -45C) interior windows can frost up due to excess humidity inside.
I have read extensively on ERV’s being good in cold weather and better at controlling humidity. So on the surface I can see too much humidity being an issue in the winter, but in general all of the modern advice suggests that my climate 7A should us an ERV and the HRV advice is outdated.
For context here are some stats about the weather for my area here: https://regina.weatherstats.ca/metrics/relative_humidity.html
I still think I want to go with Panasonic FV-10VEC2 based on discussion here but now I’m uncertain.
Mechanical ventilation is a code requirement, so I have to do something. It’s a very old house but we may very well cc spray foam and caulk seal the whole house. Brand new triple pane windows. Either that or it will be well air sealed and MemBrain installed throughout. Suffice it to say it will be way more air sealed than previously (7.83 ACH with 238 in² equivalent), but it’s impossible to know the finished product today.
Should I pushforward with an ERV despite pushback from local installers?
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The Panasonic FV-10VEC2 will work just fine. HRVs really have no application any more for cold climates. Your contractor should know this already but in a tight home with correct ventilation, you'll be drying it out in our cold winters (I'm in 7A as well) even with an ERV. An ERV's ability to recover moisture is nowhere close to 100%, and this efficiency goes down as ventilation rates increase. Conversely, on hot days when you want to keep your home as dry as possible, you'll be very glad to have an ERV. What the contractor is also not telling you is that the ERV will not go into defrost mode until it hits -10C outside, where an HRV needs to start doing it at 0C.
I'm in a heavily retrofitted house likely quite similar to yours in 7A and I very much wish my HVAC project included an ERV core, vs an HRV.
This is not necessarly the best unit if you're looking for high end features, but it's quite efficient and not overly costly: https://www.renewaire.com/wp-content/uploads/2020/07/Submittal-EVPremiumL-ECM-May2022.pdf It's the one I would buy right now if looking for a replacment. It has quite a large core which is why it's near the top of the heap right for efficiency if you look it up here: https://www.hvi.org/hvi-certified-products-directory/section-iii-hrv-erv-directory-listing/
What's your approx square footage?
How many occupants?
Will the HRV/ERV be standalone or tied into existing HVAC?
It's approximately 2900 SF of heated space. 850+ 850 + 600 + 600
3
It will unfortunately be tied to HVAC.
CDNReno,
These articles may help. They basically confirm what Dennis said:
https://www.greenbuildingadvisor.com/article/why-you-probably-need-an-erv-not-an-hrv
https://www.greenbuildingadvisor.com/article/hrv-or-erv
Ok, so about 2900 square feet, and an HVAC tie in. You won't need to worry about post heat, as the air mixing in your return and HVAC will take care of that. 60-70 CFM is likely going to be about right if you're monitoring IAQ so that Panasonic FV-10VEC2 will be fine. It also has dampers that will close off cold air flow when the unit is not calling for ventilation so makes for a good choice in your case with an HVAC direct tie in.
If your existing furnace/air handler is not using an ECM motor, the largest cost overall will likely be running that unit to provide fresh air to the home. You'll also want to make sure that the contractor sorts an interconnect to run the furnace fan while the ERV is operating.
Thanks. From my experience with other properties with HRVs the furnace fan always runs when the HRV is turned on so I think the interconnect is standard.
Only if it’s wired correctly :-)
I've read through a bunch of posts about the boost function and I'm still a little confused about boost/wall switch options.
1. I see from here they are claiming you simply need a regular switch, but a regular switch is not a dry contact... https://www.greenbuildingadvisor.com/question/erv-wall-switch. The installation manual says the boost switch should be 120V.
2. I see that Panasonic advertises this swidget 20-40-60. Can you use this with a relay load connection?
3. Are their other options? I would like to use a 20-40-60 timer for the boost function.
4. Can you wire in two separate bathrooms to boost. Can you just junction/three-way the wire to the ERV?
The FV-20VEC1 has a proper wall control, if only it was 2x the price...
1 Regular switch is a dry contact, you can use them without issue on the IB100. The thing that won't work directly is any regular smart controls (timers, motion sensors).
2. The Swidget has a dry contact output, so you can use it no problem. The wiring from the dry contact output to the IB100 needs to be regular house 14-2 wiring, not low voltage wiring.
3. Yes: https://www.greenbuildingadvisor.com/question/wiring-boost-switches-for-panasonic-100-erv
4. Yes. You can put a swidget in each bath wire the dry contact outputs all in parallel to the IB100. This way if any timer calls for boost, the IB100 will turn on. No need for any 3 way wires.
I would suggest you also run a boost circuit to your kitchen an install a paddle switch (or even better a 2h timer) there. This is the boost control I use the most at home. The paddle switch can be wired in parallel with the swidget signals.
Don't forget to install a paddle switch for the on/off signal of the IB100 by the unit. Simply unplugging the unit doesn't turn it off properly as it leaves the outside air dampers open.