indoor spa -- how to deal w/ moisture

[Dougitect]

Hi folks,
I just found this forum and this is my first post. I'm an architect.

I'm designing a two-story addition, 2x4 walls w/ stucco finish. There is an indoor spa room on the first floor, on a slab. My concern is how to prevent the high humidity caused by the spa from rotting the wall and ceiling/second floor framing eventually. I'm putting in P.T. joists above the spa room, an exhaust fan, and green gyp. board.

Do you think a vapor barrier on the inside of the stud walls would be a good approach? Any other ideas? Anyone dealt with this before?

Thanks for any help on this.

[Stacey]

When we've had to deal with excess moisture on such a large scale we have an engineering design and spec the equipment. We use a firm that does mechanical and electrical work in construction. Mostly they help us with the air handling equipment in commercial applications, but we use them occasionally in residential applications. Fresh make up air that is triggered by a humidistat and thermometer is important.

I know that doesn't help you with the interior framing and finishes, but if you can get the air exchange handled better, the finishes will last longer.

I'm in Alaska where we have only indoor pools and spas. There's nothing more depressing than to walk into a house and watch the water run down the walls due to the condensation from the pool. I'd definitely suggest a mechanical method of covering the spa when not in use. Make sure it's easy to use so that HO will keep the spa covered. This will slow down the moisture entering the room.

In situations where the humidity is regulated properly, we've seen drywall and normal framing hold up just fine. Although we've found that fiberglass windows do better than wood.

Good luck.

[Dougitect]

Stacey,
Thanks for the quick reply.

When you say mechanical cover, is that just a typical cover with buckles all around or something different?

I'll definitely look into a humidistat... frankly I've never heard of one before. As for make up air, I'll have to look into that, too. How is that accomplished? As you can see, this is different from my usual projects.

Thanks again.

[Brad S]

Any time I have built a room to house an indoor pool which is only 3, I used what is locally called a 'Dryotron" which is basically a dehumidifier although it also recycles heat from the pool. Not cheap to do though, but keeps the humidy at proper level. Also, as Stacey suggested, a cover contains the moisture from the pool water, best is an automatic cover which makes it easy for the homeowner to not forget to cover the pool after use. Also, I have always used a poly membrane over the insulation and behind the wall finish, although lately it seems not a great idea for my climate (CT). These ideas might be overkill for just a spa room, but the idea is to keep the humidity at normal levels so that the finishes and structure are not destroyed. Some good sources of information can be from a mechanical engineer, a mechanical contractor who has done pool rooms, and the pool contractor who has done indoor pools. Then put it all together.

[Dougitect]

Thanks Brad. More good tips. Appreciate it.

[epsdryair@aol.com]

The best way to treat any indoor pool or spa room, is think in terms of your home. You heat it, you may want to cool, and in a pool/spa room YOU MUST DEHUMIDIFY it. How do you do this:
This is done with mechanical/refrigeration dehumidification systems with a forced air system of ductwork for this room. The ducting is to ensure good air flow (minimum 4-6 air turnovers per hour, sometimes more depending upon the project). MAKE UP AIR OR OUTSIDE AIR & WASTE VENTILATION (EXHAUST FAN SYSTEMS) will not control the humidity and maintain the recommended levels. That can only be done with mechanical refrieration dehumidification. These rooms are generally maintained separately from the rest of the living space, separate mechanical systems also as you don't want moisture and chlorine in your home. NEGATIVE PRESSURE is required in a pool (a home is under positive).

ASHRAE recommends maintain 50-60% RH in all pool rooms, and temperatures will of course vary if you are using a "in home therapy" pool which is warmer than a residential swimming pool.

To protect the room, there is a wealth of information on our website at www.dry-air.com. Just click on Design Guidelines. That will give you everything you need to know about handling the pool room.

A VAPOR BARRIER is required on the warm side of the pool room
before you put on your finished surface. This can be Alumi-Seal, 10-12 mil. polyethelene sheeting or you can use a good waterproof vapor barrier paint (this is not latex paint!).

We have 3 projects currently in Anchorage and Juno, one is a hotel and 2 are residential projects. We designed the system for these projects, and our experience dates back to the early 80's.

Feel free to use our website for any information -- that's why we put it out there.

Good luck, and let us know if you need help, WHETHER YOU BUY FROM US OR NOT is not an issue -- we are here to help!

Christine Leonetti
EPS Inc.
epsdryair@aol.com

[Martin Holladay]

Christine,
It is simply untrue that "a home is under positive pressure." The pressure dynamics in a typical home are much more complicated and varied. In most homes with forced-air heating systems, some rooms are under positive pressure, and some rooms are under negative pressure. Relatively small duct leaks in the supply or return duct systems, as well as the fact the most bedrooms lack return air grilles, affect room-to-room pressure imbalances. In a two-story house with hydronic heat in winter, the stack effect often results in first-floor rooms being under negative pressure and second-floor rooms being under positive pressure. Ventilation systems also vary; in some regions of the country, whole-house exhaust ventilation systems are common, tending to place at least some of the rooms under negative pressure.

[epsdryair@aol.com]

Martin, do you have an email address that we can forward some data to you on this?
ours is epsdryair@aol.com
Regards,
Chris

[Chad Fabry]

Hi Chris,

I'll have a hard time learning anything if you and Martin go private on this.

Show the data... c'mon

[epsdryair@aol.com]

Not a problem. Your negative pressure/positive pressure observations are on the money. There are times when a home or areas within a home experience slight negative pressure. I should have provided a better explanation rather than a shortcut on wording.

However, the home negative pressure does not relate to maintaining negative pressure in the pool room. ASHRAE recommends all pool rooms be maintained under a negative press for the following reasons:

1. To prevent moisture migration from doorways,doorwalls into the home.
2. To prevent moisture migration into ceilings,cracks & crevices, top hat recessed cans (which are not recommended for a pool room anyway

This will be simple to understand if I use this example: ever walk into a hotel and check in at the lobby desk, AND SMELL THE POOL? You haven't seen the pool yet however you can smell it.

This means two things: (1) that the pool room is not being maintained under negative pressure, so when the doors to the poolroom open for patrons, that moisture and chlorine migrates into the hotel structure where it should not go, and (2) they are not maintaining proper pool chemistry or you wouldn't smell CHLORAMINES.

Moisture in a pool room is a "vapor pressure" and this moisture tends to migrate into areas that it does not belong. Up into top hat recessed can lighting, out thru doorwalls, doorways when they are opened to other areas of home or commercial building, cracks & crevices in ceilings, above ceilings and into attic spaces. Where cold air meets warm air, you will get condensation.

We have seen homes and commercial properties ruined because moisture migrated into drywall, up into ceiling/attic areas where it deteriorated the structure. YMCA ceilings have come down & some with the mechanical equipment installed above the ceiling came with it, a sports complex in Michigan ceiling caved in.

ASHRAE's 1999 HVAC MANUAL STATES:

"Pool and Spa areas should be maintained at a negative pressure of 0.05 to -.15 in. of water relative to adjacent areas of the building to prevent moisture and chloramines odor migration. Active methods of pressure control may provide more effective than static balancing and may be necessary where outdoor air is used as part of an active humidity control strategy. Openings from the pool to other areas should be minimized and controlled. Passageways should be equipped with doors with automatic closers to inhibit migration of moisture and air".

Negative Pressure can be established two ways:
1. Using the outdoor air method, or
2. Exhaust fan (very small exhaust fan, do not think in terms of a large waste ventilation exhaust fan), installed on any wall of the pool room -continuous run, exhaust outside.

I hope I have provided a better explantion this time!

[epsdryair@aol.com]

Chad, I see by your website that it appears you are a home inspector. Correct? If so -- we receive a lot of phone calls to help inspectors when it comes to looking over existing pool rooms. I have an INSPECTOR'S CHECKLIST if you ever want it! Just let us know and I'll be happy to email it to you.

[Hausdok]

Hi,

I would think that isolating the pool room from the rest of the house through good gasketing at doorways; using good vapor barrier type finishes and installing an air-to-air air exchanger in that room coupled to a couple of intake ducts and contolled by a humidistat would be all that you'd need.

ONE TEAM - ONE FIGHT!!!

Mike

[epsdryair@aol.com]

Mike, air to air exchange is great if the temperature outdoors and humidity outdoors stays consistent all of the time. In the real world, that doesn't happen, and waste ventilation systems cannot maintain humidity levels within ASHRAE reocommended guidelines on a consistent basis. Tight fitting doors etc. are always recommended, but it is recommended to maintain negative pressure within ASHRAE guidelines.

Your "design" if you will, can only provide effective humidity control if the outdoor air is the same temperature, but drier than the indoor air; these conditions rarely exist, and it will also not perform well in humid weather. (i.e. it is 75 degrees outside and raining. You bring in this 75 degrees and the 100% humidity with it, making it impossible to control the humidity to ASHRAE guidelines of 50-60% RH.

You didn't mention how you want to heat this room (if the air outside is 20 degrees that you are bringing in, and you want to main the "AHSRAE 2 degrees wamer than the pool temperature" to prevent a chill effect on bathers, and from pulling the water out of the pool and increasing evaporation? How do you prevent glass surfaces (windows, doors, skylights, etc.) from reaching DewPoint Temperature and condensing?

No fight here, it just a good idea to share!

[Hausdok]

Hi,

I gave a simple answer. I'm sure it's much more complicated than that, but since I've never even contemplated the issue before I could be all wet.

However, I don't think one needs to over-think it. Perhaps a direct vent forced warm air system could be used to heat the room in cold weather and that could be coupled to the air exchanger to warm incoming air in any system used to reduce humidity.

I think maybe one could do it with some type of dual controller and humidity and temperature sensors inside the pool room and outside. Given the state of the art and the amount of time indoor pools have been with us, I'm guessing that it's probably already been done by half a dozen manufacturer's.

OT - OF!!!

M.