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#1 White cobra

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Posted 02 January 2009 - 10:36 AM

I just got a used hot tub. I want to set it up in my basement, but have been told that it will make mold grow on the walls and ceiling. I have a outside patio I could set it up on, but would prefer to have it in my basement for convenience.

#2 JKM

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Posted 02 January 2009 - 11:54 AM

QUOTE (White cobra @ Jan 2 2009, 12:36 PM) <{POST_SNAPBACK}>
I just got a used hot tub. I want to set it up in my basement, but have been told that it will make mold grow on the walls and ceiling. I have a outside patio I could set it up on, but would prefer to have it in my basement for convenience.


Other than the problem of getting the tub down there in the first place, I wouldn't see a problem with mold or mildew. You will need to keep a cover installed on it though.



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#3 fdegree

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Posted 02 January 2009 - 01:11 PM


Every situation will be different. A few factors involved might be the quality and seal of the cover, how often it gets used, the temp. of the water, the temp. and humidity in the basement, ventilation/conditioning of the basement, etc., etc., etc.

Basements are sometimes mold/mildew prone to begin with, so adding a hot tub may make matters worse.

Here is something I wrote previously about ventilation issues regarding a hot tub indoors, it may or may not be relevant:
_______________

Interesting question. It is logical to think that an exhaust fan (EF) will remove humidity, and to some degree, it will. But, unfortunately, EF’s are not usually intended for humidity control. They are typically used to contain and remove odor, smoke, air born particulates, air born bacteria, etc., as well as achieving specific room pressurization criteria.

If you were to use an EF for humidity control, you will need some means of replacing the air that you are exhausting. This will most likely come from outside the building. So, if it is warm and humid outside, you will be bringing in warm humid air to replace the humid air that you are trying to get rid of. Not very practical and somewhat counter-productive. Also, if it is cold outside, you will be bringing in that cold air while exhausting the humid air. Again, not very practical. Plus, this introduction of outside air is unfiltered and unconditioned, causing your heating/air conditioning system to work harder. The only time this would be feasible would be during ideal outside air conditions, which does not happen often enough to make it worthwhile. Another option would be to bring the outside air in through your heating/air conditioning system first. This way the outside air would be filtered and conditioned before it gets to your room. But, this can be costly to install and will certainly cause your heating/air conditioning system to work harder. Perhaps even requiring a completely different heating/air conditioning system to handle the added load requirement.

Controlling humidity within a building is usually accomplished by a heating/air conditioning system alone…no exhaust fans. But, a system designed for this type of control is more elaborate than the average home system. It is also much more costly to install and operate. In most cases, not very practical.

I would suggest you go to your local hardware store and purchase a couple of dehumidifiers. Start off with 1 or 2 and see how it does, and add more if necessary.
_______________

Other things to consider may be...what if there is a leak...what about draining the tub every few months...if it is a living space, what will this do to the comfort/condition of the space?

Having the tub in the basement is a wonderful convenience, but there are risks that my or may not arise.

Hope this helped.



#4 White cobra

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Posted 02 January 2009 - 03:14 PM

QUOTE (degree @ Jan 2 2009, 04:11 PM) <{POST_SNAPBACK}>
Every situation will be different. A few factors involved might be the quality and seal of the cover, how often it gets used, the temp. of the water, the temp. and humidity in the basement, ventilation/conditioning of the basement, etc., etc., etc.

Basements are sometimes mold/mildew prone to begin with, so adding a hot tub may make matters worse.

Here is something I wrote previously about ventilation issues regarding a hot tub indoors, it may or may not be relevant:
_______________

Interesting question. It is logical to think that an exhaust fan (EF) will remove humidity, and to some degree, it will. But, unfortunately, EF’s are not usually intended for humidity control. They are typically used to contain and remove odor, smoke, air born particulates, air born bacteria, etc., as well as achieving specific room pressurization criteria.

If you were to use an EF for humidity control, you will need some means of replacing the air that you are exhausting. This will most likely come from outside the building. So, if it is warm and humid outside, you will be bringing in warm humid air to replace the humid air that you are trying to get rid of. Not very practical and somewhat counter-productive. Also, if it is cold outside, you will be bringing in that cold air while exhausting the humid air. Again, not very practical. Plus, this introduction of outside air is unfiltered and unconditioned, causing your heating/air conditioning system to work harder. The only time this would be feasible would be during ideal outside air conditions, which does not happen often enough to make it worthwhile. Another option would be to bring the outside air in through your heating/air conditioning system first. This way the outside air would be filtered and conditioned before it gets to your room. But, this can be costly to install and will certainly cause your heating/air conditioning system to work harder. Perhaps even requiring a completely different heating/air conditioning system to handle the added load requirement.

Controlling humidity within a building is usually accomplished by a heating/air conditioning system alone…no exhaust fans. But, a system designed for this type of control is more elaborate than the average home system. It is also much more costly to install and operate. In most cases, not very practical.

I would suggest you go to your local hardware store and purchase a couple of dehumidifiers. Start off with 1 or 2 and see how it does, and add more if necessary.
_______________

Other things to consider may be...what if there is a leak...what about draining the tub every few months...if it is a living space, what will this do to the comfort/condition of the space?

Having the tub in the basement is a wonderful convenience, but there are risks that my or may not arise.

Hope this helped.

Draining the tub would be no problem. I like the idea of not using a EF to control the humidity and using the heating & air system. The room I will be putting it into doesn't have yet, but does have a heat & air duct running along the ceiling. So I will be cutting a small hole in it and put 1 of those louvered plates on it, which should have been done along time ago since it is a downstairs den with a brick fireplace. Thanks for the tips and idea!

#5 Jake the dog man

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Posted 02 January 2009 - 03:40 PM

I don’t think mold/etc would be too much of an issue. You have you own reasons for wanting it in the basement, but you will likely be better off putting it outside anyway. Give it a try in the basement though. You may want to look into heavy duty bathroom exhaust fans, which are made specifically to exhaust steam from showers. I have a huge fan in my small bathroom and it wasn’t the biggest. It not only sucks out steam & smell, but almost sucks out light! LOL! The increased humidity & temperature of the rest of your house would be my concern, the room containing it should be expected. An exhaust fan is going to almost be a must because house ac/heat systems are not made to deal with the large amounts of humidity & smell of chemicals that a hottub will introduce.

I’d be tempted to under do the preparation, rather then over do it at this point. You may come to realize why an outside tub is going to be much less problems.

Good Luck & please let us know.


#6 Matt87109

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Posted 02 January 2009 - 04:52 PM

QUOTE (White cobra @ Jan 2 2009, 11:36 AM) <{POST_SNAPBACK}>
I just got a used hot tub. I want to set it up in my basement, but have been told that it will make mold grow on the walls and ceiling. I have a outside patio I could set it up on, but would prefer to have it in my basement for convenience.


I have recently been working on a couple of ventilation projects in my house and may have a unique idea for you. There are devices called HRV (Heat Recovery Ventilators) and ERV (Energy Recover Ventilators). They have two air streams: One brings in air from the outside to the inside and the other exhausts air from the inside to the outside. The whole idea is that they constantly bring fresh air into your house even during relatively cold and hot times of the year while scavenging energy. In the HRV/ERV unit itself is a heat exchanger. In the winter the outgoing waste air stream heats the incoming fresh air stream and "recovers" some of your energy while expelling elevated levels of Radon and any other contaminates that may be in your house. In the summer the cooler waste air leaving the house cools down the hot fresh air entering your home.

The difference between a HRV and ERV is simple. In an HRV the heat exchanger core only allows sensible heat to transfer, that is to say no humidity crosses the heat exchanger boundary from the exhaust air and is reintroduced into the house. An ERV allows both sensible and latent energy to transfer, that means both sensible heat as well as humidity will transfer back into the house. In the deep south ERV's are required in the summer because they actually allow the very humid air coming into the home to transfer some of its humidity to the outgoing air stream that the home A/C has worked very hard to remove the humidity or latent energy from.

For your application I would suggest an HRV because you don't want humidity in the exiting air stream to cross the heat exchanger as it would in an ERV and reenter your basement in the fresh air stream. It is generally recommended that a ventilated space has .33 air changes per hour. In other words 33% of the entire volume of air in your basement should be replaced with fresh air from outside each hour. You use this number to calculate what size of HRV you need. If you basement is 20ft x 30ft x 8ft high you have 20x30x8=4800ft cubed. 33% of that volume is .33x4800 =1584 cubic feet per hour or divide by 60min/hour and you get about 26cfm. That's the size HRV you would need. From my experience if you don't install it perfectly (very clean and low restriction duct work) you lose 30% of the cfm rating rather quickly. Fan Tech and many others for that matter have small and large models. http://www.fantech.net/hrv_erv.htm

The advantage of using an HRV/ERV over simple ventilation is energy saved as well as potentially reducing the radon and other contaminate entering your house through the ground or basement if you run it 100% of the time. I don't know if your house would start to smell like hot tub chemicals if the hot tub is in the basement, but an HRV would certainly mitigate some of that. Depending on how large you size the HRV it won't pull the humidity out as fast as a honking ventilation fan, so maybe you would want to oversize the HRV and then just run it for six hours each time after you use your hot tub. A hygrometer would be a useful way to know how long you need to ventilate after you use your tub. Heck you can even buy a humidistat that would turn on a simple ventilation fan or HRV at a certain humidity level. If you were going to the expense of installing an HRV you would want to run it all the time and get the benefit of fresher air in your house due to Radon and chemical removal. Radon is a gas that is created when small amounts of Uranium (in all dirt everywhere) breaks down. We are all constantly exposed to Radon at a certain background level, but in some buildings radon can actually build up in concentration. Ventilation does not eliminate Radon, but it does bring it down to near the background level that is outside the home.

In my home I run an ERV 24/7 so every few hours the air in my house is turned over. There are energy losses no doubt. I think my ERV is rated at 77% energy recover when the outside ambient air is 32deg f and 50% relative humidity. An HRV is less efficient because it does not scavenge the energy tied up as humidity in air, it just sends it to the outside, as you would want in the case of you hot-tub-humidified basement.

I recently bought a fan tech ERV that does 60cfm for about 500 dollars. I bet the HRV variant is similar in price. You can spend several hundred more in installation materials too.

#7 ChicagoMike

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Posted 03 January 2009 - 06:00 AM

I really only want to use the tub when it is cool or cold outside. I think using it in the house would be more like a bath.

#8 White cobra

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Posted 03 January 2009 - 08:01 AM

Privacy is the main reason I want it in the basement!

#9 SmilinBare

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Posted 03 January 2009 - 01:28 PM

QUOTE (White cobra @ Jan 3 2009, 11:01 AM) <{POST_SNAPBACK}>
Privacy is the main reason I want it in the basement!


You'll be far better off investing in a fence or barricade for privacy for an outdoors-install than what it will ultimately cost you to control the excessive humidity if you put your tub INSIDE your home. With the cover off of a tub (and even with it on) there will be a helluva lot of water vapor in your house and, like it or not, without a carefully designed and installed ERV (see Matt87109's post) that humidity will wreak havoc. For a mini-demonstration of what you can expect, try boiling a large stockpot full of water on your kitchen stove for an hour. If your home is as "tight" as it should be, in these days of high energy costs, you'll see the water leaving your stockpot in a vapor state condense back to liquid and run down the inside surfaces of your kitchen windows. Put a hot tub in your basement without controlling the humidity and the water vapor leaving your hot tub will condense on your foundation walls and, worse, probably inside the wall cavities on the exterior of the upper house level, too.

Putting a hot tub inside a house, in a cold climate, is just a bad idea period. BTW, if you go the two-dehumidifiers-route, don't blame the huge increase in your electric bill on the hot tub!

#10 Matt87109

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Posted 04 January 2009 - 07:32 PM

I just read that bathrooms (more similar to your spa situation) require 8 air changes an hour. The HRV idea is only .33 so maybe that was not such a good idea.

#11 fdegree

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Posted 04 January 2009 - 08:48 PM

QUOTE (Matt87109 @ Jan 4 2009, 10:32 PM) <{POST_SNAPBACK}>
I just read that bathrooms (more similar to your spa situation) require 8 air changes an hour. The HRV idea is only .33 so maybe that was not such a good idea.


Even with 8 air changes per hour all of the humidity is not always removed. After a few months of not cleaning the walls and ceiling, look up into the corners of the bathroom, near the ceiling, and most people will have a little mold growing. This just shows how exhaust fans are not the ideal means of controlling humidity. Another example of this is a public indoor pool...look around and you will likely notice there are no exhaust fans. If you happen to see an exhaust fan, its purpose is to remove chemical odors. The heating/air conditioning system handles the humidity, and sometimes odors with charcoal filters.

The best way to control humidity is with a dedicated (serving the basement only) heating/air conditioning system. Without getting too deep into the engineering, basically the air handler will pull the room air across a cooling coil to drop the air temperature below the dew point, causing the moisture in the air to condense on the cooling coil so it can then drain outside. If the room doesn't need cooling, just dehumidification, then a heat source will reheat this cooled air back up before it gets pushed back into the room. Quite costly to operate and install for the average residence.

By the way, white cobra, placing a register in the exposed duct of your basement will not help any potential humidity issue. Also, by doing this, you will take air from the rest of the house. Possibly starving the rest of the house if your system is not sized to handle the basement and upstairs simultaneously. I don't want to see you create a problem by "solving" a problem.

Now...are you going to have a humidity/mold problem if you place your tub in the basement??? It's hard to say for sure, there are too many unknown factors involved. Typically, it is not something I would suggest, but you can always remove it if it starts giving you trouble. But, as SmilinBare said, mold problems are not always immediately noticeable, it can easily develop inside walls and grow for years before you become aware of it.

Good luck, and whatever you decide to do, I hope it works out great for you.


#12 bizdoc

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Posted 04 January 2009 - 10:10 PM

Many hot tub users (myself among them) find the experience of using them outdoors to add immeasurably to the enjoyment. Sitting in the warm water on a crisp sunny day or a cold starry night is a part of the fun. For me, it kind of takes me back to the experience humans have had for thousands of years--sitting outside and soakin in warm water. Go the basement route if that works for you, but try an outdoor soak if you havent already.

#13 newbuyerin09

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Posted 18 January 2009 - 04:31 PM

QUOTE (bizdoc @ Jan 4 2009, 11:10 PM) <{POST_SNAPBACK}>
Many hot tub users (myself among them) find the experience of using them outdoors to add immeasurably to the enjoyment. Sitting in the warm water on a crisp sunny day or a cold starry night is a part of the fun. For me, it kind of takes me back to the experience humans have had for thousands of years--sitting outside and soakin in warm water. Go the basement route if that works for you, but try an outdoor soak if you havent already.


It would cheaper and less costly in the long run to just add a spa/tub to your bathroom. No chemicals and every bath is a relaxing and gives you the privacy you need to from what I understand "get your groove on"


#14 IACinger

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Posted 22 January 2009 - 03:03 PM

We had friends that put a tub in their three season porch. You would think that the amount of humidity that would actually enter the house would be minimal in that situation, but it wasn't. You would also think that if the porch's glass panes were down, humidity wouldn't cause any problems with the porch ceiling, etc. ...but it did. They regretted doing it, so I opted to put mine outside on a slab next to our porch. If you doubt the amount of humidity that is generated by a tub with the jets on, just sit in one when the temperature is like 10F on a very still night. The fog rising high in to the air is so thick that you can barely see out. Imagine all that moisture entering your house. Is it really worth trying to deal with this?

#15 Soonerdal

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Posted 23 January 2009 - 06:08 PM

The very best part of having a hot tub is sitting outside on a cold night under the stars with a glass of wine. I would just do some sort of privacy fence. I don't think I would even get in mine if it was inside.

#16 Raeven

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Posted 23 January 2009 - 10:30 PM

QUOTE (Soonerdal @ Jan 23 2009, 06:08 PM) <{POST_SNAPBACK}>
The very best part of having a hot tub is sitting outside on a cold night under the stars with a glass of wine. I would just do some sort of privacy fence. I don't think I would even get in mine if it was inside.


I think privacy is a huge consideration, however you have to accomplish that. Personally, I wouldn't chance putting a large spa indoors, concurring with the concerns previously stated here regarding humidity and such. But like you, Soonerdal, I wouldn't use my spa much if privacy was an issue.

Yesterday I wet-tested a used spa at the owner's home, which was remarkably kind of her to permit. While we were chatting, I thanked her for allowing me to test-soak. She shared she hadn't wet tested the spa before she purchased it because she was too embarrassed to soak at the dealer's. She is a tiny, almost anorexic thing and I couldn't imagine why she was worried!

Anyway, my interest in determining if the tub was the right one for me overcame my own natural shyness. So I was happily turning levers and adjusting jets and trying out one seat after another and all the while wondering why the owner was getting rid of such a new, well-maintained spa. Suddenly I glanced up and looked around. I realized that all her neighbors' 2-story homes looked right down into her spa area. And after what she'd told me, I understood exactly why the spa was for sale.

whitecobra, is there any way you can create privacy without putting the spa indoors? Strategic plantings? A gazebo? In the long run, I think it will cost a lot less, and you will enjoy the experience more if you're not worried about the walls slumping from too much humidity in the years to come.

Raeven
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