# Humidity Control in Basement



## MSU Fan (Apr 30, 2010)

Before everyone starts in, I cannot simply remove the source of the humidity - I have 4 fishtanks and 2 turtle tanks in my basement.  The evaporation keeps my dehumidifier running constantly.  I would like to install a dehumidistat and some kind of exhaust fan to vent the humidity outside.  

My question is this - what is the best way to bring fresh air in as a replacement to the air I am removing?


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## CraigFL (Apr 30, 2010)

This could be a very complicated answer... First, is this a summer and winter problem? We would also need to know things the average relative humidity in Appleton as well as the average temperature and humidity in your basement.


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## mclauga1 (Apr 30, 2010)

There is something at home depot called Damp Rid they are to take the moisture and smell out the air without over drying. A big one is like $12 and small ones $3 the last for 3-4 months this could be a cheap solution to your problem


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## Cork-Guy (Apr 30, 2010)

I have 6 fish tanks in my basement; the trick is to keep them as air tight as possible to prevent evaporation. A dehumidifier is really your best best; damp rid won't work because you'd need a ton of 5 gallon buckets of it to make it have any effect. Also, trying adding in a good amount of live plants; they help suck a lot of the moisture out of the air as well.


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## Perry525 (May 3, 2010)

Interesting question, simple answer.
Water vapour/humidity always moves from hot to cold or to an area of low pressure like down wind of a building.
Make a hole in the wall, about 4 to 6 inches square, the water vapour will just disappear.... the air outside will nearly always be colder and drier, not always, and your problem will disappear on the wind.


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## inspectorD (May 3, 2010)

I have to disagree...not a simple answer. 
In Wisconsin?
There are many variables to look at, exaust fans, boiler vents, Ductwork if you have any, insulation in your house, dryers, and fireplaces.Does your heating system or hot watwer heater alreday have a backdrafting issue?/ who knows??
 Not to mention all the other air leaks at doors, windows, and other points of entry. Lightswitches, electrical outlets, sill plate insulation and radon gas mitigation systems. 
ALL these things come into play on your home,,,yes even the architecture is a factor, ranch, 3 story or split level?
Air is always moving through your home with use also, doors and windows open and close, even the tempurature outside compared to inside matters.
Is your house ballon framed?? Is the air traveling up through the walls and carrying the moisture with it? Adding a vent hole will only add to the problem.

Get a reputable company , HVAC that does blower door testing, or even a building performance person over there to give you the advice you need....heck...we don't even know if you already have water leaks in your basement you don't know about.

Good luck, hope this helps.


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## Perry525 (May 4, 2010)

MSU Fan asked:

"My question is this - what is the best way to bring fresh air in as a replacement to the air I am removing?"

I recommend that MSU tries the no cost option, that answers his question perfectly. Not only that but, the hole will allow the humid air out and keep the space in balance.

If the result is not satisfactory, he can throw money at it.


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## inspectorD (May 4, 2010)

Again...it may not let the humid air out. 
And I am aware of the question,and agree you gave a simple, no cost answer. The poster asked for the best way.....this is the cheapest, not the best.
However the question needs further evaluation as the poster does not understand the consequenses of the question.
I just disagreed, and recommended further evaluation to a not so simple problem.....which you stated was a simple solution.

Your idea may well work perfectly, I recommend someone actually in the home with experience evaluate it, this is not a DIY evaluation.:2cents:


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## Perry525 (May 4, 2010)

It is interesting that so many people find it  hard to get their mind round relative humidity.
Perhaps MSU Fan........... could advise if he has a combined hygrometer temperature gauge and what the current readings are in his cellar and immediately outside.
That will confirm if there is relatively high humidity in the cellar and advise what is happening outside.
The logic being, that after he makes the hole, the water vapour in the cellar will migrate outside and drier air will move in.


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## frozenstar (May 4, 2010)

Well I think choosing the best dehumidifier is a good solution to the problem. It's quite hard to choose the best out there but with reading some of the specs of a dehumidifier can be helpful. Consider how big your basement is as well so you can pick the size of your dehumidifier. I also suggest to pick energy star dehumidifier to save more energy than the standard models.


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## Perry525 (May 5, 2010)

frozenstar, MSU Fan has a dehumidifier that is costing him a lot to run.
Buying yet another will cost a lot and will not improve the situation.(unless its a lot larger) I suspect that he is currently trying to dry out the whole of Appleton. Dehumidifiers attract water vapour by creating a cold (freezing) coil and as a bye product push warm air into the room making it even hotter.
If he wants to throw money at it, then an extractor fan complete with outside shutter, to keep out the cold wind, and a built in heat exchanger and humidistat will undoubtedly solve the problem and it will only run when water vapour energizes the humidistat. And it will help to lower the overall running costs by warming the incoming air. It should save upwards of 90% of his heat, lowering the running costs of his hobby.


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## frozenstar (May 6, 2010)

Agree on that. But the question is if he's willing to throw some bucks on it. If yes, it won't a big problem at all.


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## Perry525 (May 7, 2010)

This is an interesting problem.
If he had his tanks in the middle of a field, there would be no problem loosing heat and humidity, although the heating cost would increase.
Having the tanks indoors creates the problem.
Going to the next step, knocking out a complete wall, would also solve the problem, he could have an open mesh wall.
Then as the hole gets smaller and the natural ventilation gets reduced, the problem grows.
 It would be interesting to know at what size hole the balance between, humidity loss, heat loss and cost of heating the tanks becomes satisfactory.


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## MSU Fan (May 11, 2010)

Sorry, I haven't been for a couple of days, but I appreciate the discussion.  

Let's keep the arguement relatively simple as I don't have a lot of money for this right now.  I just got a Ranco dehumidistat at a local ReStore for a $1.50.  I would throw in a another $50 or so for ducting, an inline fan, a dryer vent, and a register if that would be an acceptable solution.  

Nominally, in my basement, it is about 68 degrees and about 60-65% humidity confirmed via an Aprilaire digital hygrometer and the readout on my digital dehumidifier.  It seems to want to stay there as I haven't heard my dehumidifier running in the last couple of days. I am a little concerned with it being that high.  I would prefer it to be nearer to 50% (heck, even lower if possible, but I am not getting my hopes up at this point).  

I cannot spend the money for a converter and all that other jazz which would no doubt do the job effectively.  And unless a new super awesome dehumidifier would do the job, I definitely don't want to spend the money on that...

My tanks are not very sealed, so that is definitely one of the problems.  It is on my to-do list, which is enormous.    Anyway, I am hoping once the A/C kicks on it will help, but I am not sure that will be the case.


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## Perry525 (May 12, 2010)

In most peoples eyes the figures you quote are perfectly acceptable. I imagine you feel comfortable?
Why do you want to have a lower humidity?
The existing humidity and temperature are perfectly acceptable.

 Humidity dropping to 22-23% on a hot day @ 25-26 degrees C or higher.
Humidity as high as 70%  on cold days @ 22 degrees C.
Both of these are comfortable for most people.
99% @ 30C that is unpleasant.

The fish and turtles are happy.

You could fix sheets of polystyrene to the bottom and sides of the tanks that you do not look through, depending on thickness that will save on your heating cost.

But as you lower your temperature the humidity will go up!
68f @ 60% humidity has a dew point of 53.59F, when you get there you have 100% humidity, however I would not expect you to notice the difference.

The existing humidity/temperature is OK.
Save your money.


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## MSU Fan (May 12, 2010)

Thank you Perry, but I have dealt with mold issues on my window frames from the evaporation/humidity put off by the tanks in the winter.  In the summer I am not too worried.  With the temp higher, obviously the moisture capability of the air is higher as well.  But I figure why wait until it is colder to do the work?  

When the winter comes, and the temp is somewhere between 0 and 20F for a couple of months straight, and the windows don't get opened - that is when the humidity is the most dangerous for mold development.


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## Perry525 (May 13, 2010)

My Koi Carp are in the garden pond, others are on my lap top screen. You are a first as far as keeping fish and turtles in a cellar.
As I wrote earlier 68f @ 60%RH results in condensation at 53.59f.
68f @ 65%RH results in condensation at 55.79f.
When those temperatures and humidities get near a cold window or wall or ceiling, then you have condensation, visible on the window, hidden in the walls etc.
Mould spores are every where, from the North Pole down.
They do not grow unless there is warmth, food and water to keep them alive.
(otherwise the world would be covered in mould)

Condensation forms when the temperature drops.
This usually happens when the heating is turned down or off, or when warm wet air meets a cold surface.

In the home, the problem can be solved by opening a window for a short time and letting the warm wet air out and letting some cold drier air in.
I understand that the prospect of opening a window in winter does not appeal.

You have already tried an alternative, using a dehumidifier, this works, at a price.
And of course the cost goes on every day and night through every autumn, winter and spring.

I suggested using a extractor fan, this has installation costs and running costs.

You can also keep the basement temperature steady 24/7 and blow warm air over the window. This has an on going cost.

Then we have insulation. From what you have already written, the weak link in your basement (at the moment) is the window. This needs to be upgraded to the same level of insulation as the rest of the room. You can do this by adding a sheet of plastic during the winter. This will add another layer of still insulating air (providing it is not more than 16mm from the inside of the glass) and improve things. Or you can buy a sheet of perspex and fit that over the window. Or buy a purpose made piece of secondary glazing.

Using insulation to get rid of the condensation solves one problem. But then it creates another. The condensation will then form on the next nearest cold surface, that is below the dew point of your mix of temperature and humidity.

You need to buy an infrared temperature gauge. You can use one of these to scan the surfaces in the cellar, to identify the cold spots and discover if you have another spot temperature below the dew point where condensation will form.
If you have, this could lead to interstitial condensation, resulting in damp walls, mould and dry then wet wood rot.

Sometimes, the problem you have that is more easily managed, by wiping down with a dry cloth and using some bleach...............?


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