Indoor Pool - Dehumidification System

[esn13_jrr14]

Just received my first estimate, $50k. Apparently my mechanical room is too small for the Desert Aire system they said I needed so they'd need to build an outbuilding for the equipment and run duct work to my pool room. They're working on a proposal for installing multiple in-wall dehumidification units, kinda like a hotel room AC unit.

1. Is there another piece of equipment or vendor that I can use to control humidity? What would the approximate cost be?
2. Is there another method to control humidity, like keeping the right temperature in the pool room?

Just looking for options, other than spending $50k or having multiple ugly units on my wall. Thanks!!!

 

[Arizonarob]

I’m just thinking out loud, but maybe a pool cover would help keep the humidity down?

 

[JoyfulNoise]

Water evaporates when the water temperature is above the air temperature in the room. The larger this differential, the greater the evaporation rate. Controlling humidity is obviously important for the general integrity of your home (eg, mold) but any method to actively control it (dehumidification) is going to be costly and expensive both to install a unit as well as running it (it’s line running another A/C in your home). To compound the problem, there are few indoor pools around and even fewer HVAC contractors that deal specifically with indoor pools. Those that do are used to working with commercial customers that can handle bigger budget projects.

Perhaps in your case it’s best to start off simple -

• Add in sky lights that open and/or an exhaust fan to pull humid air out
• Keep the pool covered when not in use
• Only heat the pool as-needed and don’t allow the temperature difference to be too great
• Only uncover as much of the pool as you plan to use leaving the rest covered to avoid excessive evaporation.
• Add mid-level windows or floor/wall vents to allow fresh air in
• Buy a few portable dehumidifiers and run them on days when you need extra dehumidification

Unfortunately TFP has not see any threads, as far as I know, of dehumidification system installs on indoor pools. Plenty of people with indoor pools have issues with humidity but most can not afford the costly installs to manage it.

 

[tstex]

well stated by matt

I have ranch house that I do not run the HVAC system when I am gone, but before I leave almost everytime, I run a dehumidifier. It pulls out 3 gallons of water each time I return to empty it. It doesn't even seem possible, but it does.

Not sure of the humidity levels in your area, but in SE TX, we see 80-90% humidity often, or higher. I learned that covering my 2 toilet seats helped a lot at the ranch bc they are humidity portals. In comparison, your pools surface area is exponentially larger in surface area than 2 toilets. therefore, as stated, you have to really step-up the investment to keep pace w your evaporation rates. Keeping your poo; covered all the time, at least to me, is a PITA and self-defeating. You could run 4-5 small dehumidifiers but it's really a waste bc one system is only feeding the other and all at your expense. And think of this, the greater you "remove the water from the air", the greater the delta is btw the pool surface and air, thus creating a greater rate of evaporation to create a stable state of equilibrium [when temps are optimal to do so].

The best and most economical option is to open your windows when the RH is less outside than the humidity levels in your pool room. A large fan used to pull air out of your pool room would speed up the removal, but make sure all your windows are shut...

 

[Jon123]

I'm in a similar situation. These are some good ideas. I am tempted to try a remote controlled skylight, and possibly a fan of some kind... I was thinking about using a greenhouse fan (these things move a lot of air). On a different forum I was dissuaded from doing this with the fear being that it would pull cooled air from the house. I'm wondering if the combination of the two would work out (or just leaving some of the sliding doors open during the pool/humid season) - or if that would just make things works...

I'd need to get a better/easier to move cover to make that suggestion feasible.

 

[JoyfulNoise]

Any time you move air in a confined space (home) you have to consider both the exhausted air flow and the make-up air flow. The make-up air has to come from somewhere and it’s either going to get sucked in through an open window OR pulled in from some other part of the house. If you did an exhaust fan, then you may need to install a jumper vent near the entrance of the pool room to avoid causing a negative pressure and making it hard to open/close doors.

 

[Jon123]

Never heard of a jumper vent before, thanks for that!
I'm wondering if mid-summer the fan would do any good with the humidity. Average RH values for MA (from a quick google search) looks to be in the 70s during normal pool season early morning, and 60s by afternoon. Not sure yet what we'd want those to be inside the room, or whether it's just a matter of trying to equalize inside the room match outside the room (in which case, the fan may work well).

 

[Rollercoastr]

As you can almost see in my avatar, my pool is in the center of the house and open to the living spaces.

I manage humidity with the 3 methods mentioned above:

- water temps lower than ambient air
- pool cover when the water is warm
- an exhaust fan while the pool is in-use

When I say manage, I guess I can really say avoid/eliminate. I don't have humidity problems.

That's not to say there aren't challenges. The exhaust fan is a cheap to install, cheap to operate method that's highly effective. The replacement air is another discussion. My pool equipment is on the lower level. The pool pump, filter and heater share a room with dual gas water heaters. That room has a large vent from the outside, presumably to provide replacement air for combustion. When the house is closed-up, the pool room exhaust fan will draw some air from that vent. That's not always the case though. It can also backdraw from sources such as the fireplace flue, from the oven vent, and a bathroom exhaust fan that either lacks or has a broken damper.

I don't have to worry much about it when outside temps are above the teens. The pool exhaust will cool the house down by a few degrees, but nothing unmanageable. However, single-digit temps change the game, and sub-zero temps cancel it!

In really cold weather, the impact of the pool exhaust is more than the furnaces can keep up with and it's just not worth losing that much heat in order to swim.

I don't wish for a full-blown dehumidification system. Not only does the installation cost make me choke, but I'd hate to see the utility increase. It's also basically a non-starter for my home anyway. Part of the appeal of the pool is its location. I can close it off with doors so that room alone can be contained and controlled, but I don't want to.

What I wish I had is a heat exchange system. I send lots of very hot air (gas exhaust) out the flues, while bringing in super-cold, dry air. That makes NO sense to me. I've looked at simple air-to-air heat exchange systems. They're not expensive, ($400-$1,000) but they're rated way below the amount of air I need to move. I'd need 3-4 of them, and the installation of that many would be too complicated.

At the end of the day, I can use my pool almost any time I want, the house doesn't suffer from humidity and the simple cover and the fan get credit for that.

 

[Arizonarob]

Hey Roller, could you post up some pics of your setup, it sounds really cool. (I like how it’s in the center of your house)

 

[Rollercoastr]

Sure... Here are a few from the pool room looking into the master bedroom, and looking from the bedroom into the pool. The great room is beyond that. It contains the kitchen, dining and living spaces. I guess I don't have any pics from that space looking into the pool. (I intentionally take pictures at night. It shows less flaws)

This is in the equipment room. The large horizontal flue serves the water heaters that are off the left side of the pic. The angled flue is for the pool heater. The combined flue goes to the roof through the closets that divide the foyer and the pool room. The replacement vent is on the opposite side of the room. It's not very photogenic! The white PVC pipes are returns. The black PVC is the drain for the deck scuppers. The copper pipe in the center has been capped off, but it's connected to the water heaters. I assume that at some point in time it was plumbed into the pool system to add hot water to the pool. There's a spigot in the pool room for filling, so I'm not sure what that thinking was.

I don't have a picture of the exhaust fan at the top center of the pool room ceiling. It too falls under "un-photogenic". I'd like to clean or replace it someday, but that will be quite a project!

 

[JimMarshall]

Thats an awsome setup! Jealous!

 

[Jon123]

@Rollercoastr Very nice set up!

I have a few questions if you have a moment...

Do you know what you're using for a fan/what kind of airflow you get out of it, or better put, how many times you cycle the air in the room with it?
You only run it while swimming, or do you have some kind of controller for running it?

So, you normally keep the room open to the rest of the house without problems? If so, I'm somewhat hopeful that I can make something work in my situation.

Do you know how the room itself was built? I'm curious if there are extra precautions around a water vapor barrier, etc.

My thought is that I should be able to easily set up the room to get make up air from the outside. I think the fan would need to go on the side of the building close to the roof, I'm not sure that putting it in the roof would be feasible in terms of rain/snow, unless I'm not aware of something that would help with this.

I started getting estimates on the full blown dehumidification system, and amazingly the price wasn't blowing me away - but it didn't include installation, so I'm sure it would once that was accounted for (and as you mentioned, the cost to run it).

 

[Rollercoastr]

Heya Jon, thanks.

I have no idea what the specs are for my fan - that's an interesting question. I assume it's original to the house. I'd say the blades have 16-18" diameter? It's on a manual rheostat. That puzzled me at first, as I was thinking it should be tied to a humidistat, but now it makes sense to me. For this strategy, the trick isn't to constantly remove moisture from the air, but to prevent moisture in the first place by water temps or the cover.

Roughly above the margarita in my avatar you can see a big glass french door - it's heavy. I tend to only run the fan at the lowest setting, and even that is enough to pull that door open. On high it's capable of slamming the solid-core wooden door in the bedroom, so it's moving some pretty hefty CFM. On high, I wouldn't be surprised if the cycle time would be measured in minutes. Even on low on a cold winter day, only the sliding glass door in the corner will show any condensation.

I don't see evidence that the pool room ("natatorium" - I learned that word here!) is constructed any differently than the rest of the house, but saying that, the house isn't constructed like any other...

There is almost no drywall in this house. The walls are an oak veneer, or glass or brick. The pine board ceiling (I call it shiplap, but it really isn't) has varnish on it in the pool room, but that's the only difference.

A commercial-sized furnace serves the pool room, foyer and master bedroom. Vents run along the outside wall and exit at the windowsill. It keeps those windows dry and can warm the room comfortably, but it can't heat just the pool room, so 90º air isn't an option for me.

I experimented one time, by blocking all the other vents and closing the doors to heat just the pool room, but since there's no source of replacement air within that space, it just wasn't worth the trouble.

I keep the doors open to the other spaces at all times. When covered or cold, the pool adds just enough humidity to the house that no humidification system is needed, yet it doesn't steam up windows etc.

If I used this pool in spring, summer and fall I'd have no complaints with the strategy as-designed. Winter is when I enjoy the pool most though, so the replacement air challenge is something I wish I could address.

 

[Jon123]

Great, thanks for responding!

I did some fan research and you're probably right about it cylcing the air quickly. I found that the room I have could easily be turned over in about 10 minutes with just an 18" fan, a 24" one was able to do it in about 6 minutes.

I'm thinking that with a combination of the exhaust fan, being diligent about covering when not in use, and the heater in cooler months, I may be able to make something work here.

I'd have to do a lot more work to the room to make it work in the winter though - not nearly enough insulation in there right now for that ?