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Fighting high levels of humidity inside the house

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[OP]
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Jul 18, 2012
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Toronto

Fighting high levels of humidity inside the house

Hi all - I’ve been noticing extremely high levels of humidity ranging from 60% to hitting the 70% mark this summer. The house is 2 years old, and I didn’t notice these levels last summer. During the day I can feel a damp air around the main floor (we are a 2 level house + basement). Upstairs the humidity levels are between 45-55%.

I am worried about mold forming, and will be looking to purchase a dehumidifier ASAP. But I am trying to understand the big increase in humidity levels from last summer to this one.

1) we started work in our basement last month - for which the door to the cold room (located in the basement) was removed to allow for framing. This is still removed. Though I’ve asked the contractor if this would be the cause for the high humidity, and he doesn’t think so.
2) We have a VaNEE LT HRV unit which was set to intermittent (yellow) - should we be turning these off outright?
3) The windows have not been fogging up due to condensation

I’ve read anything over 50-60% is not good for the home, and really concerned about mold forming as a result. Do I need to have an HVAC contractor come and review what might be happening, and perhaps check for any early sign of mold?
40 replies
Deal Addict
Apr 18, 2005
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Mississauga
Is your A.C. working ... ? Is it sized correctly for your house? Rough rule 1T/1000sqft
[OP]
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Jul 18, 2012
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TLSRULZ wrote: Is your A.C. working ... ? Is it sized correctly for your house? Rough rule 1T/1000sqft
Thanks for your reply - AC has been working non-stop; and was provided by builder at time of close. I am not sure how many tons the ac is - I’ll check tomorrow, but I believe it was 14 seer.
Sr. Member
Jan 7, 2013
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Oshawa, Ontario
If it is indeed a "cold cellar" connected to the outside by a vent, then removing the door will allow humid air into your home.

I also only run my HRV in the summer on the rare cool, non-humid nights.
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May 10, 2005
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Shaidin wrote: If it is indeed a "cold cellar" connected to the outside by a vent, then removing the door will allow humid air into your home.

I also only run my HRV in the summer on the rare cool, non-humid nights.
The HRV (ERV pretty close to the same) should be on all the time, especially when it is humid as it exchanges the humid indoor air for fresh outside air.
https://www.aldes.ca/summer-hrv/

If you do not have a HRV, I suggest you have the furnace fan running 24/7. It will take a few days to realize a difference but it does help by circulating all the air in the house.
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Dec 17, 2007
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Pete_Coach wrote: The HRV (ERV pretty close to the same) should be on all the time, especially when it is humid as it exchanges the humid indoor air for fresh outside air.
https://www.aldes.ca/summer-hrv/
That is wrong.
And an HRV and ERV are not the same, the provide 2 different functions.
The HRV does NOT exchange the incoming high humid air with the outgoing lower humid air. An HRV will attempt to cool the hot incoming air with the cooler outgoing air. So running it all the time in the summer will raise the humidity levels in the house and fight the a/c that's trying to do the opposite.
You even linked to an article that explains that.
Deal Addict
Dec 6, 2017
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60-70%? Those are rookie numbers...you gotta bump those numbers up! Smiling Face With Open Mouth And Smiling Eyes

If I remember correctly 70% is still acceptable but should not go beyond that for extended amounts of time. I usually run dehumidifier in the basement every off peak (10pm-5am) to keep humidity in check.
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Aug 22, 2011
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schade wrote: That is wrong.
And an HRV and ERV are not the same, the provide 2 different functions.
The HRV does NOT exchange the incoming high humid air with the outgoing lower humid air. An HRV will attempt to cool the hot incoming air with the cooler outgoing air. So running it all the time in the summer will raise the humidity levels in the house and fight the a/c that's trying to do the opposite.
You even linked to an article that explains that.
I run my HRV all year round set at 20min on and 40min off and my RH rarely goes above 50%
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May 10, 2005
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schade wrote: That is wrong.
And an HRV and ERV are not the same, the provide 2 different functions.
The HRV does NOT exchange the incoming high humid air with the outgoing lower humid air. An HRV will attempt to cool the hot incoming air with the cooler outgoing air. So running it all the time in the summer will raise the humidity levels in the house and fight the a/c that's trying to do the opposite.
You even linked to an article that explains that.
Bottom line is to recirculate the air in the house and bring in outside air with a HRV or ERV.
A 2 year old house is sealed very well (if up to code) and getting the stale humid inside air out is the key.
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Feb 11, 2007
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OP, what temp is your AC set to and can it maintain that temp?
Are your windows closed?
Do you use your exhaust vents when you shower and cook?
What size is house and his many people in it?

A dehumidifier will help. I set mine to 55% and let it run continuously, though only at low price times when that was in effect.
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Dec 17, 2007
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Pete_Coach wrote: Bottom line is to recirculate the air in the house and bring in outside air with a HRV or ERV.
A 2 year old house is sealed very well (if up to code) and getting the stale humid inside air out is the key.
With an ERV, sure. But while getting that slightly humid air out, you are bringing in air that's very high in humidity. If you want to run your HRV in the summer, do it at times that outside humidity is lower. Newer houses are built fairly air tight, but you still have air exchanged through leaks in windows and doors and other areas.

Some choose to run their HRV on a timer year round, and that's fine if your a/c can compensate for it and run longer to keep your indoor humidity at appropriate levels. But if you're humidity is high, like with the OP, turn the HRV off until fall
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Apr 18, 2005
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robbiemurray wrote: Thanks for your reply - AC has been working non-stop; and was provided by builder at time of close. I am not sure how many tons the ac is - I’ll check tomorrow, but I believe it was 14 seer.
The a.c. should not run continuously ... find out why that is happening.
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Nov 12, 2015
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One important note, if you have the fan running all the time and not set on Auto, then the AC will have trouble dehumidifying.
Stay strong, situation always looks harder and that it will never end when you are in the middle of it, but remember past experiences, everything has an ending.
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PriceHunter wrote: One important note, if you have the fan running all the time and not set on Auto, then the AC will have trouble dehumidifying.
I have my fan running all he time and my A/C works perfectly. It comes on at preset temps and goes off when it reaches tit.
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Pete_Coach wrote: I have my fan running all he time and my A/C works perfectly. It comes on at preset temps and goes off when it reaches tit.
I reference the information provided within this link https://www.cooltoday.com/blog/hate-hum ... -like-this

"But if the fan is set to ON, the moisture on the refrigerant coils does not get the chance to drain away. Because the fan blows constantly, most of the moistures evaporates and gets blown right back into your house!"

Please correct my understanding if you have a different reference.
Stay strong, situation always looks harder and that it will never end when you are in the middle of it, but remember past experiences, everything has an ending.
[OP]
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Jul 18, 2012
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Toronto
engineered wrote: OP, what temp is your AC set to and can it maintain that temp?
Are your windows closed?
Do you use your exhaust vents when you shower and cook?
What size is house and his many people in it?

A dehumidifier will help. I set mine to 55% and let it run continuously, though only at low price times when that was in effect.
AC is set to 22 - and it maintains the temp for most part. The windows are always closed - and we do run the exhaust during a shower or cooking.

The house is about 3000 sqft. The basement is in the process of being finished. And we are a family of 4...

Getting a Frigidaire Dehumidifier from Rona today.
[OP]
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Here is the Humidity reading for the last 24 hours.

At around midnight was when I started to panic lol. So changed the filter, switched off the HRV completely and turned the temp for AC way down for it to run through the night. It’s down to 54 right now.
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PriceHunter wrote: I reference the information provided within this link https://www.cooltoday.com/blog/hate-hum ... -like-this

"But if the fan is set to ON, the moisture on the refrigerant coils does not get the chance to drain away. Because the fan blows constantly, most of the moistures evaporates and gets blown right back into your house!"

Please correct my understanding if you have a different reference.
I have told you what I do and what is working for me.
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PriceHunter wrote: I reference the information provided within this link https://www.cooltoday.com/blog/hate-hum ... -like-this
"But if the fan is set to ON, the moisture on the refrigerant coils does not get the chance to drain away. Because the fan blows constantly, most of the moistures evaporates and gets blown right back into your house!"
Please correct my understanding if you have a different reference.
I very much doubt that MOST of the moisture is blown back in your house. MOST will go down your drain. SOME water left on the coil when the AC turns off will be blown back into your house.
robbiemurray wrote: Here is the Humidity reading for the last 24 hours.
At around midnight was when I started to panic lol. So changed the filter, switched off the HRV completely and turned the temp for AC way down for it to run through the night. It’s down to 54 right now.
Have you verified the humidity with another meter? Be sure that the hole behind your ecobee is sealed, so it doesn't get air from the wall. Easiest is to just tape over the hole to seal it.
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Selling 18x8 Winter Wheels/Tires 225/60R-18 for Audi Q5, A5, Mercedes, PM for info, lots of tread.
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[OP]
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engineered wrote: Have you verified the humidity with another meter? Be sure that the hole behind your ecobee is sealed, so it doesn't get air from the wall. Easiest is to just tape over the hole to seal it.
Thanks for the suggestion!

I’ve just ordered a hygrometer from Amazon to read the moisture. That said I have the Dyson Link fans and they have been indicating around 45-55% upstairs. Also my humidifier (which is off) in the basement was reading the humidity levels similar to my ecobee.

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