ERV vs. HRV and Humidity in Cold Climate
Hi I’m in Ottawa Canada and I’m deciding between a HRV and an ERV.
I live in a row house, the square footage is 20 x 40 feet, two stories. 1 bathroom. 2 occupants.
A while ago we got high-efficiency windows and furnace so now the house is air tight.
Ottawa has hot humid summers and cold dry winters. However, complicating things, in recent years we’ve had longer bumper periods in the fall and spring where it is cold and wet for several weeks. Very muggy.
I was thinking of this PANASONIC FV-10VEC2 ERV Assuming it’s true this unit is less likely to freeze up and stop working once it goes lower than -20.
However I’ve heard ERV’s can build up too much humidity in smaller houses.
Considering the weather I might have at times, and the size of the home, would it be compatible if I paired the Panasonic ERV with a whole house dehumidifier? To offset build up of humidity during muggy periods?
Or would the humidity build up beyond times it’s actually high humidity out?
And they would just be constantly working against each other?
Or would the dehumidifier not be able to compensate in a small house?
Thanks for any feedback.
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Replies
Until I see a blower door test under 1 ACH50 I very much doubt your home is tight.
Do you run a humidifier in the winter? Hint if you own a humidifier, you don’t own a tight house.
What is your indoor humidity on the coldest day of winter? Hint if it is over 60% you have a very tight house and need HRV.
Walta
It is interesting to me as I am in a newer construction house 2009 and have done some limited air sealing. The attic plane is fully sealed and I did all the electrical junction boxes.
This fall so far I am sitting much higher on CO2 and VOCs than I was previously (CO2 hitting daily peaks of 1300-1700ppm with averages above 850ppm).
I'm not sure a blower door would tell me that I shouldn't have an HRV/ERV similar to the OP.
I think it would help determine that a very tight house needs an HRV maybe, but I can't imagine an ERV wouldn't work either. My understanding is the ERV would still reduce moisture due to the efficiency not being 100%.
FWIW, I am looking at doing the same ERV.
2009 was a lot better than 1989, which was better than 1959. But in terms of building science it was a long time ago.
Totally agree - my point was really that I was interpreting Walta's comment to read that without a blower door a house couldn't be tight enough to need ERV/HRV. I'm not sure that is what he meant - just how I read it.
I was just commenting that I think (anecdotally) newer construction houses can be tight enough to need supplemental ventilation more than people might expect.
The way to know if a house needs supplemental ventilation is by measuring the air tightness with a blower door test. Until you do that, you only think the house is airtight but it may actually turn out to not be that tight. Mechanical ventilation is not necessary in a leaky house and will just run up your electric bill.
Walta is right.
What device are you using to measure the air? Thanks in advance!
I have an Awair Element from before the pandemic when they were more cost effective ($120 IIRC https://www.getawair.com/products/element). After having that for a year or so and seeing how much small occupant behavior tweaks could change air quality in my own living space - I got ones for the family. I switched to recommending the Airthings View Plus as it includes radon as well (https://www.airthings.com/en/view-plus) and at one point they were the same price.
While they aren't necessarily precise, they seem to do a great job at trends and patterns. It helped identify which cleaners spiked VOC and how small adjustments to the tightness of window (in an apartment) could provide just enough fresh air. It also showed how ineffective recirculating range hoods are, but also how effective Corsi-Rosenthal Cube was as a supplement.
I respectfully disagree - the way to know if a house needs mechanical ventilation is to measure the air. If a blower door says a house is somewhat leaky, but air quality is still bad (ruling out external sources)... what does it matter? The air exchanges aren't happening if the indoor air quality is bad.
In that situation, I guess you could run exhaust only ventilation, but wouldn't an ERV/HRV be better? It could be the house is situated in such a way or the leaks are located in such a manner that the artificial pressures of a blower door don't happen to create the anticipated air exchanges.
Not trying to argue that blower doors are somehow bad, but I think I'd rather just keep measuring the air quality and solve that in existing buildings. If an occupant is seeing bad air quality and the choice is to spend money on a blower door or a ventilation solution... I'd pick the ventilation.
As far as the humidity question, the ERV should help in the summer keep the humidty out (assuming outdoor air is more humid than indoor). ERV will dry the air out less so in the winter as compared to an HRV (assuming outdoor air is drier than indoor).
I don't see why you couldn't also have a dehumidifier as well if you need it in the wetter shoulder seasons - it wouldn't need to be a ventilating type or likely even whole house depending on the amount of moisture needing to be removed.
I can't tell if the -20 is Celsius or Fahrenheit, but the install instructions have a nice chart of operation down to -22F/-30C and specifications on net moisture transfer at different temperatures. (81% at 32F/0C and only 64% as -13F/-25C).
While recommendations from high-performance home pros will always advocate for ensuring the envelope is tight (which they would also say can’t be determined until proven with blower-door testing) before even talking mechanicals (because it’s not an energy-efficiency-minded approach), when it comes to choosing between an HRV and ERV, here are two articles to read: You Probably Need an ERV, Not an HRV and Balanced Ventilation With HRVs and ERVs.
If your home is in the great frozen north and you have high indoor humidity in the winter then you need more ventilation and energy recovery.
If your home is in the great frozen north and you have low indoor humidity in the winter, then your home has enough ventilation and you own a humidifier.
If where you live someplace 10 months of the year the outdoor temp is within 40°of the indoor temp like most of us do the amount of energy such a device could recover is so small it will never recover its cost, crack open your window if the room feels stuffy.
I am sure they recover lots of energy when it is -40° outside and 75° inside but when it is 100° outside and 78° inside, I think they do nothing but move air around.
Walta
IMHO if your CO2 is sitting over 1000ppm then I think ventilation is justified. Measuring tightness can help identify problems and predict the necessity, but if you have poor air quality you have to ventilate. Regardless of the tightness.
My house is a 1950's bungalow (not tight but I'm working on it), with newish (15year old windows and doors). My CO 2 often 1100-1500 if I'm not ventilating.
Agree a ERV is probably best, it basically allows for less humidity transfer between inside and outside which is often beneficial in summer and winter. Note that you're still losing humidity in the winter with an ERV, but at a slower rate. So ventilating results in humidity control regardless.
Hi thanks for the feedback from everyone , I had some reading to do.
The question of whether I need an ERV kind of took over here.
I live in a row house built in 1984, the windows were replaced with more efficient ones and the furnace replaced with a high efficiency furnace. The old furnace vented out the chimney and the new doesn't which made a big difference, I've been told. My breathing became very constricted after that. I've had windows cracked open on all floors, for several years...but it's bad for the house. So I need a system.
BUT!...going back to my OP....I was really wondering if an ERV is certain to build up too much humidity in a house of my size during the winter?
Or not necessarily?
So, with the dehumidifier for muggy periods, I could benefit from a system less likely to freeze up in the winter. If that's not all wishful thinking.
My house is 20 x 40 feet (basement measurements), 3 stories, (a narrow row house). I guess that counts as small. With 2 occupants.
Pardon the long post, and thanks again.
The answer around here is go for an ERV.
That is not a small place for two people, unless you have major moisture moving up through the basement slab, you want an ERV to maintain indoor humidity. I'm a bit further south of you but when it gets bellow -10C, even with an ERV the indoor air gets dry.
If you do start to see higher humidity in the winter, you can always run the unit at higher flow rate to dry the place. ERV efficiency drops as flow rate increases, so at higher flow rate it will dry the air more in the winter.
During shoulder season, neither HRV/ERV will matter. The only way I've found to get basement humidity under control is a dehumidifier.
thanks for the feedback.
About the basement, it does get super muggy in the basement in the summer.
Like I said I leave the dryer door open to let some air in there. I also crack the garage door open and somehow that let's some extra air wafting into the basement.
There are also these cracks along the basement floor. They run straight across. I never thought anything of them. That may be part of it.
Could humidity be coming up through those cracks?
But that's all mainly in the summer, if that's any indication of if that would be a problem with the ERV.
Maybe I need to double check the humidity in the basement during the winter. But that means I have to wait longer until it gets colder, close everything and test. When the time to get someone to come is around now.
I am getting a whole house dehumidifier, if that would be enough to take care of any basement issues.
In older homes particularly, temps in the basement will be lower than the upper floors in summer, so you will nearly always have a humidity issue there in summer. If your basement humidity is above 55-60% in summer, you'll likely just want to run a dehumidifier there. An ERV won't fix that problem, but a whole house dehumidifier should :-) AC alone addresses most humidity issues here in Zone 7A, so you don't see whole house dehumidifiers installed here.
With regard to open cracks in the foundation, your issue there is more likely radon, and you may want to either pick up a sensor (like AirThings) or get a kit.
In watching one of Corbett Lunsford's Home Performance Youtube videos on ventilation he says he always recommends an ERV over an HRV in all climates but that in some jurisdictions in Canada it is mandated that only HRV's be installed.
Maybe Malcolm Taylor in BC Canada knows more about this?
On the OP
I think an ERV is indicated here unless there exotic contraindications that haven't been mentioned (e.g. indoor natatorium?!)
The enthalpic advantage is attractive where it's cold (because cold always equals dry, except in some cases when cold always equals wet)
However, an HRV is a safe option too, albeit less efficient. If it's too humid inside in the winter, just buy a dehumidifier
Blower door is good insight, but my experience is that regardless of tightness, mechanical ventilation is indicated on almost all homes that I've seen. I lived in a 10 ACH50 home (kitchen and bath ventilation was big holes in the ceiling) and i measured 3500ppm of co2 in the bedroom.
Yep, ERV for sure in Ottawa as in winter you will always be looking for moisture inside when ventilating. I honestly don't see the use case anymore for HRV.
With respect to tight/leaky houses here are a few observations that apply to both tight and old construction having done longer term logged Co2 studies in both situations. On a windy day (particularly in winter with added stack effect), even a tight structure will see Co2 levels drop, in some cases to the point where ventilation is not required. On a low wind/warmer day, a "leaky" structure will likely still have high Co2 levels and require ventilation to keep levels down.
Older structures without ventilation may also have high VOC and Radon levels that will benefit from constant ventilation. In your position the Panasonic FV-10VEC2 would work just fine. Keep in mind that it will not start defrost cycles until temps fall below -10 C, and below that will go into recirc mode to periodically warm the core. The temp ranges and cycle times are in the manual...it won't freeze up.
I would also take a look at the RenewAire EV Premium L ERV which has a larger core and EC motors. The larger core gets it to 88% efficiency at 59 CFM vs the Panasonic which is at 80%@53 CFM.
HRVs are dead to me.
Forget hair splitting sensible efficiencies and humidity management. You'll probably need a dehu anyway. HRVs make liquid water a become a science experiment inside without a bunch of annoying maintenance most people will not get to regularly (I'm one of them). If it worth going to balanced recovery ventilation an ERV is the only way to go.
Good Luck
Ok one last thing about finding a company to install this Panasonic ERV.
Regarding HVAC companies attached to certain brands:
There is a company I wanted to call, family owned, good reviews, but it says they 'carry' Vanee.
So they would probably push that on me.
Do HVAC companies do special order of other brands if you request or do they not react well to that?
I might waste money if I call someone in for a consult and they just don't do this PANASONIC FV-10VEC2 ERV.
And I've heard mixed things about Vanee, I'm not sure they have the same 'cold climate' resilience I've heard about on the Panasonic.
I'd ask - I would be surprised if an installer would flat out say no. There may be a bit more overhead to pay as they may be less familiar with installing that specific product. They may not get as good of a price for that product as they might get for something they normally install in volume.