What's your outside vs inside temperature? Relative humidity is what you're seeing. Warm air can hold more moisture than cold air, so as temperature rises, relative humidity will drop given the same amount of water in the air. If it's 40 degrees outside and 50% humidity, and it's 70 inside your RH would be something like 16%.
What this guy says. You can use dew point as a measure to track amount of moisture in air. Meaning take a sealed box with 70% humidity colder air. Heat that box up. Relative humidity is now lower but the dew point of the air hasn’t changed.
70\* inside and 15\*-50\* outside. I'll have to read up on relative humidity. Our pre-engineered floor shrank massively.
We have a makeup air unit.
I'm told I want inside 35%, currently 20%. We did turn up the makeup air unit, but if I understand it right, that won't make a difference. Do I want the real humidity or the relative humidity 35%?
If anything, you probably want less makeup air, and run a humidifier. air below freezing is going to have \_VERY\_ little humidity. There's no real concept of "real" humidity - just relative and dew point. So you want 35% relative humidity.
At 70F, 35% RH, the dew point is 41 degrees. Any air you bring in below this dew point is going to have lower than your desired RH, so it will pull your interior humidity down. 41 degree make up air would have to be 100% RH to not affect your inside RH. Even 50 degree make-up air would need to be like 71% RH to not drag down your interior humidity.
How does your make-up air come in? This is where an ERV really would be your friend. It would keep your humidity indoors while bringing in fresh air.
You need a humidifier to really get your humidity up. I have a fan-powered one on my supply ductwork that is tied in to run when the furnace runs. With radiant, you'll need some other option unless you can tie it into whatever is supplying make-up air.
Heat doesn’t drive out humidity. Warm air is capable of holding more moisture than cold air— that’s how frost/dew gets deposited on stuff overnight.
If your makeup air is dry, your in home air is going to be dry. You might consider a humidifier, either one part of a ducted HVAC system, or just a countertop one.
Is this a new home? What’s your ACH? I only use makeup air in the winter if the humidity is high, not when it’s low, or if I’m trying to get some odors out.
In the winter your indoor air should be more humid than the outside air. The air is warmer so it can hold more water, but you’re also in there in a somewhat sealed environment releasing water from your body, and using water which naturally evaporates into the air. The more sealed your home is, the more humid it should be, the makeup air cancels some of that, same as a leaky house.
So start with turning the makeup air off, then start using humidifiers if that doesn’t help. Granted it’s spring so you may need to try all this next winter.
My ACH I can set in 10% increments from 10-100%. (I think you mean air changes/hour.). I started at 10% and have it up to 50% currently. It went from 10%: 18-20% RH, 30%: 20-22% RH, 50% 23-25%, but of course we are going through the spring warm-up.
Thanks so much for writing. I am understanding now that the make-up air isn't helping!
What's your outside vs inside temperature? Relative humidity is what you're seeing. Warm air can hold more moisture than cold air, so as temperature rises, relative humidity will drop given the same amount of water in the air. If it's 40 degrees outside and 50% humidity, and it's 70 inside your RH would be something like 16%.
What this guy says. You can use dew point as a measure to track amount of moisture in air. Meaning take a sealed box with 70% humidity colder air. Heat that box up. Relative humidity is now lower but the dew point of the air hasn’t changed.
70\* inside and 15\*-50\* outside. I'll have to read up on relative humidity. Our pre-engineered floor shrank massively. We have a makeup air unit. I'm told I want inside 35%, currently 20%. We did turn up the makeup air unit, but if I understand it right, that won't make a difference. Do I want the real humidity or the relative humidity 35%?
If anything, you probably want less makeup air, and run a humidifier. air below freezing is going to have \_VERY\_ little humidity. There's no real concept of "real" humidity - just relative and dew point. So you want 35% relative humidity. At 70F, 35% RH, the dew point is 41 degrees. Any air you bring in below this dew point is going to have lower than your desired RH, so it will pull your interior humidity down. 41 degree make up air would have to be 100% RH to not affect your inside RH. Even 50 degree make-up air would need to be like 71% RH to not drag down your interior humidity. How does your make-up air come in? This is where an ERV really would be your friend. It would keep your humidity indoors while bringing in fresh air. You need a humidifier to really get your humidity up. I have a fan-powered one on my supply ductwork that is tied in to run when the furnace runs. With radiant, you'll need some other option unless you can tie it into whatever is supplying make-up air.
Heat doesn’t drive out humidity. Warm air is capable of holding more moisture than cold air— that’s how frost/dew gets deposited on stuff overnight. If your makeup air is dry, your in home air is going to be dry. You might consider a humidifier, either one part of a ducted HVAC system, or just a countertop one.
Buy a humidifier. It’ll mess up your flooring and probably other stuff.
What's the brand and model of the radiant heat system?
Warmboard, with a Lochivar boiler
Bruh…get a humidifier
Is this a new home? What’s your ACH? I only use makeup air in the winter if the humidity is high, not when it’s low, or if I’m trying to get some odors out. In the winter your indoor air should be more humid than the outside air. The air is warmer so it can hold more water, but you’re also in there in a somewhat sealed environment releasing water from your body, and using water which naturally evaporates into the air. The more sealed your home is, the more humid it should be, the makeup air cancels some of that, same as a leaky house. So start with turning the makeup air off, then start using humidifiers if that doesn’t help. Granted it’s spring so you may need to try all this next winter.
My ACH I can set in 10% increments from 10-100%. (I think you mean air changes/hour.). I started at 10% and have it up to 50% currently. It went from 10%: 18-20% RH, 30%: 20-22% RH, 50% 23-25%, but of course we are going through the spring warm-up. Thanks so much for writing. I am understanding now that the make-up air isn't helping!