High Humidity in Sunroom

[hudson]

I'm located in the mid south...US.
I have a new 500 sq. ft. sunroom with a hot tub. It has a Daikin mini split heat pump.
In the winter the heat pump get's the moisture down below 50% overnight after a hot tub session.
I would suspect that the heat pump would take care of it in the summer also.

During the spring, when the heat pump doesn't run much, the humidity goes up over 50%...sometimes over 60%.
The heat pump installer said to try the "dry" setting. I did; it makes it cooler, but it doesn't help with the humidity that much. It helps more to put the heat pump on "heat" and turn it up about 5 degrees higher than usual. That's not good because the room is too hot. I'm guessing that the "dry" mode would work during the heat of the summer.

The heat pump installer also recommended a floor dehumidifier. I'm guessing that I would need to run this during the spring and fall. I don't want to empty it...and there's not a drain in the room. I'd have to make a hole in the floor or wall and drain it through there. I would have a power cord and a piece of tubing laying across the floor. The dehumidifier directions say to keep it 18 inches from the wall.

I have 3 ceiling fans in the room. Would running those make a difference?

Any recommendations?

[RickBoglehead]

You're not going to dehumidify a space by running ceiling fans.

Any dehumidifier has to have somewhere for water to drain, or be collected, if you have no drain hose hooked up to it. You pull moist air in over coils and it condenses and produces water. Gotta have somewhere for the water to go.

You will also notice a dehumidifier's electricity usage on your bill.

In the summer, either you run an AC unit pretty constantly or a dehumidifier. In short, this is why putting any type of a pool indoors is problematic. A simple Google search shows that you could also run an exhaust fan to try and remove the humidity.

[greg24]

Best option to reduce humidity is to remove the hot tub.

[mancich]

I would consider an exhaust fan, like those used in bathrooms to clear out the humidity from a shower. Panasonic makes some very energy-efficient and quiet fans. You could hook it up to a wall timer switch so that you don't have to run it continuously. You may be looking at some drywall work in the ceiling, depending on what your setup looks like currently, both to cut it in, get power to it, and run a vent to the outside wall.

[jebmke]

Best option to reduce humidity is to remove the hot tub.

this

hot tub and a de humidifier is a utility companies dream

[lthenderson]

The heat pump installer also recommended a floor dehumidifier. I'm guessing that I would need to run this during the spring and fall. I don't want to empty it...and there's not a drain in the room. I'd have to make a hole in the floor or wall and drain it through there. I would have a power cord and a piece of tubing laying across the floor. The dehumidifier directions say to keep it 18 inches from the wall.

They do make dehumidifiers that mount in the wall that never need to be emptied.

[barnaclebob]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

[fizxman]

You can try Damprid. I'm not sure they'll be enough in a room with a hot tub though. I have the hanging version and it does collect water but not as fast as a dehumidifier.

https://www.amazon.com/dp/B0029EGUNG/ref=emc_b_5_t

[wolf359]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

+1

Or during the summer, relabel the room as a Sauna.

Or just drain the tub when not in use.

[stonerolled]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

Yes, when its warm, embrace the humidity and simply keep the room well ventilated, isn't humidity one of the benefits of a hot tub?
That's why vaporizers are used for children in winter time because respiratory viruses supposedly do not like warm humid air.
Just make sure that the building materials used in that room can handle the summer humidity in your area when well ventilated.

[Ping Pong]

Install an ultra-aire dehumidifier in the crawl space or attic with vents coming into the room. If the house has a crawlspace but the sunroom is slabbed, then the vents could be low on the wall between the room and the house, with the dehu under the house.

[Summit111]

I use a portable dehumidifier in my music studio...just empty it when full...no problems at all...

Summit

[adamthesmythe]

I'm located in the mid south...US.
I have a new 500 sq. ft. sunroom with a hot tub. It has a Daikin mini split heat pump.
In the winter the heat pump get's the moisture down below 50% overnight after a hot tub session.

I have 3 ceiling fans in the room. Would running those make a difference?

Any recommendations?

You have a worst case situation as the hot tub will continually dump moisture into the room. The fans will only help if they exhaust to the outdoors- and not through a piddling little bathroom exhaust, think about something much bigger.

A big-enough dehumidifier will also work. Then you pay to put water into the air and pay again to take it out.

[JoinToday]

Cover the hot tub so the water can't evaporate & fill the room. The better the seal, the lower the humidity.

[hudson]

You're not going to dehumidify a space by running ceiling fans.

Any dehumidifier has to have somewhere for water to drain, or be collected, if you have no drain hose hooked up to it. You pull moist air in over coils and it condenses and produces water. Gotta have somewhere for the water to go.

You will also notice a dehumidifier's electricity usage on your bill.

In the summer, either you run an AC unit pretty constantly or a dehumidifier. In short, this is why putting any type of a pool indoors is problematic. A simple Google search shows that you could also run an exhaust fan to try and remove the humidity.

Thanks RickBoglehead!
The hot tub only causes high humidity when it's being used. The top seals it pretty good...well fairly good. As long as the mini split heat pump is heating, the humidity is fine. It's springtime, the unit doesn't run much. I imagine that fall will bring the same problem.

[hudson]

Best option to reduce humidity is to remove the hot tub.

Ha! It just got installed....now you tell me

[hudson]

I would consider an exhaust fan, like those used in bathrooms to clear out the humidity from a shower. Panasonic makes some very energy-efficient and quiet fans. You could hook it up to a wall timer switch so that you don't have to run it continuously. You may be looking at some drywall work in the ceiling, depending on what your setup looks like currently, both to cut it in, get power to it, and run a vent to the outside wall.

Thanks mancich! The heat pump clears out the fog from the hot tub pretty quickly...in the heating season....we haven't had a cooling season yet.
I thought about that in the beginning. Wouldn't an exhaust fan pull in outside air...although the room is pretty tight. The outside air is humid most of the time. It's 79% humidity outside right now.

[hudson]

Best option to reduce humidity is to remove the hot tub.

this

hot tub and a de humidifier is a utility companies dream

$50 per month before the dehumidifier.

[hudson]

The heat pump installer also recommended a floor dehumidifier. I'm guessing that I would need to run this during the spring and fall. I don't want to empty it...and there's not a drain in the room. I'd have to make a hole in the floor or wall and drain it through there. I would have a power cord and a piece of tubing laying across the floor. The dehumidifier directions say to keep it 18 inches from the wall.

They do make dehumidifiers that mount in the wall that never need to be emptied.

I have a commercial unit like that in the crawl space...it's ugly but it works well.
I'm likely going to get quotes on something like that.

[hudson]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

The humidity outside is worse.

[hudson]

You can try Damprid. I'm not sure they'll be enough in a room with a hot tub though. I have the hanging version and it does collect water but not as fast as a dehumidifier.

https://www.amazon.com/dp/B0029EGUNG/ref=emc_b_5_t

I now have Damprid on my Amazon wish list. That wouldn't be my first choice, but it's worth a look.
Thanks!

[hudson]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

+1

Or during the summer, relabel the room as a Sauna.

Or just drain the tub when not in use.

HA! if only a sign would work.
The tub holds 500 gallons....
All I wanted out back was a screened in porch...it morphed into an extra large climate controlled room with tub....ha!

[hudson]

Why not just vent the space to outside in the shoulder seasons? Crack a window or install an exhaust fan of some kind.

Yes, when its warm, embrace the humidity and simply keep the room well ventilated, isn't humidity one of the benefits of a hot tub?
That's why vaporizers are used for children in winter time because respiratory viruses supposedly do not like warm humid air.
Just make sure that the building materials used in that room can handle the summer humidity in your area when well ventilated.

Good idea...the humidity and pollen is a killer. I really like this room climate controlled.
We built the room to handle the hot tub. We figured the mini split heat pump would take care of the humidity....all of the time....but it can't dehumidify when it's not running.

[hudson]

Install an ultra-aire dehumidifier in the crawl space or attic with vents coming into the room. If the house has a crawlspace but the sunroom is slabbed, then the vents could be low on the wall between the room and the house, with the dehu under the house.

The mini-split heat pump doesn't have ducts. It will dehumidify ok when it runs.
There's no crawlspace...it's insulated underneath...I'm not finished that part....but it's open under the insulation.
I think that the dehumidifier will have to be in the room....maybe on the ceiling or on a wall. I don't want a floor unit with a cord and a piece of tubing running across the floor....and out through the wall or out through the floor.

[hudson]

I use a portable dehumidifier in my music studio...just empty it when full...no problems at all...

Summit

That's where I'm going, except I'm too lazy to empty anything.

[hudson]

Cover the hot tub so the water can't evaporate & fill the room. The better the seal, the lower the humidity.

It's got a great cover that seals well. The hot tub only fogs the place up when it's in use; The mini-split heat pump can dehumidify it pretty good when running.
I think that it's the rainy weather with high outside humidity that's the problem.

[hudson]

I'm located in the mid south...US.
I have a new 500 sq. ft. sunroom with a hot tub. It has a Daikin mini split heat pump.
In the winter the heat pump get's the moisture down below 50% overnight after a hot tub session.

I have 3 ceiling fans in the room. Would running those make a difference?

Any recommendations?

You have a worst case situation as the hot tub will continually dump moisture into the room. The fans will only help if they exhaust to the outdoors- and not through a piddling little bathroom exhaust, think about something much bigger.

A big-enough dehumidifier will also work. Then you pay to put water into the air and pay again to take it out.

I'm going to have to live with this hot tub for a long while. The hot tub only fogs the place up when the tops off. I can turn on the heat pump and it'll move the moisture out. The room will be a little warm, but the humidity will be under 50%.

[hudson]

UPDATE...

An hour ago, I plugged in a Hisense dehumidifier that I bought at Lowes: https://www.lowes.com/pd/Hisense-2-Spee ... 1000731818

The humidity was around 70% last night after the hot tub was used. It was around 60% this morning.
After running about an hour, the humidity is 51%....before I could hit submit, the humidity is 49%.

It has a slide out bucket that I'm using for now. I need to figure out how to put the drain tubing through the wall to a suitable drain area.

I have some digging and plumbing to do. I've got a gutter drain, a crawl space dehumidifier drain, a mini-split heat pump drain, and this new dehumidifier. All are in the same vicinity.

[leeks]

Why can't you just open the windows?

[megabad]

UPDATE...

An hour ago, I plugged in a Hisense dehumidifier that I bought at Lowes: https://www.lowes.com/pd/Hisense-2-Spee ... 1000731818

The humidity was around 70% last night after the hot tub was used. It was around 60% this morning.
After running about an hour, the humidity is 51%....before I could hit submit, the humidity is 49%.

It has a slide out bucket that I'm using for now. I need to figure out how to put the drain tubing through the wall to a suitable drain area.

I have some digging and plumbing to do. I've got a gutter drain, a crawl space dehumidifier drain, a mini-split heat pump drain, and this new dehumidifier. All are in the same vicinity.

Glad this is working for you. If you need a little bit more dehumidification, you might consider overcooling and then reheating via your minisplit. If you have a programmable tstat, this could be accomplished relatively easily by creating an artificial schedule that overcools the room for an hour, then heats the room back up for the rest of the day (or some variation). When you put your mini split in dehum mode, it may in fact be doing something like this, but it depends on the model.

[hudson]

Why can't you just open the windows?

There are plenty of windows...but the humidity outside is usually higher.

[hudson]

UPDATE...

An hour ago, I plugged in a Hisense dehumidifier that I bought at Lowes: https://www.lowes.com/pd/Hisense-2-Spee ... 1000731818

The humidity was around 70% last night after the hot tub was used. It was around 60% this morning.
After running about an hour, the humidity is 51%....before I could hit submit, the humidity is 49%.

It has a slide out bucket that I'm using for now. I need to figure out how to put the drain tubing through the wall to a suitable drain area.

I have some digging and plumbing to do. I've got a gutter drain, a crawl space dehumidifier drain, a mini-split heat pump drain, and this new dehumidifier. All are in the same vicinity.

Glad this is working for you. If you need a little bit more dehumidification, you might consider overcooling and then reheating via your minisplit. If you have a programmable tstat, this could be accomplished relatively easily by creating an artificial schedule that overcools the room for an hour, then heats the room back up for the rest of the day (or some variation). When you put your mini split in dehum mode, it may in fact be doing something like this, but it depends on the model.

I'm not programmable...but there is a dry mode. When I use it, so far in the spring, it cools things down but doesn't drop the humidity. If I turn the heat up 5 degrees, that'll do it.

[megabad]

When I use it, so far in the spring, it cools things down but doesn't drop the humidity. If I turn the heat up 5 degrees, that'll do it.

Interestingly, it is the cooling procedure that removes the moisture from the air. The heating procedure does not actually remove moisture from the air but merely makes this already obtained drop in absolute humidity visible on a hygrometer (since most hygrometers display relative humidity). Ideally, the unit would do both of these things (automatically) to have an end result of a lower relative humidity in the space.

[hudson]

When I use it, so far in the spring, it cools things down but doesn't drop the humidity. If I turn the heat up 5 degrees, that'll do it.

Interestingly, it is the cooling procedure that removes the moisture from the air. The heating procedure does not actually remove moisture from the air but merely makes this already obtained drop in absolute humidity visible on a hygrometer (since most hygrometers display relative humidity). Ideally, the unit would do both of these things (automatically) to have an end result of a lower relative humidity in the space.

The mini split doesn't run much because the temperature is not too hot or too cold. The sunroom (built in 2018) is much tighter and better insulated than the main house.
The heat pump for the main house (built in 1975) is programmable and does have an app to control it. Over the last 7 days, it's been running 4 hours a day....cooling only. I haven't heard the heat pump running in the sunroom for days. I've tried everything...all settings. I've tried open windows...fans, etc. The $300 dehumidifier fixed the problem in 1 hour....we'll see how it works in the long run....When I get tired of manually emptying it, I'll have to make a hole in the wall for the pump/drain.