Attics, Televisions and Missouri Summers

April 23, 2009 2:46 PM

New place has a lovely attic, finished but no AC up there. We're planning on having the windows open with fans in them to keep the air moving and bearable. Would it be a bad idea to have a TV (plasma) up there in the humid southeastern Missouri summer?

I know most plasmas have operating humidity of up to 80 or 90%, and it can easily reach that on the worst of summer days here. Would the inside humidity be equal to that of outside with the windows open? Could some dehumidifying solution near the TV (in the middle of the room, far from the windows) prevent an untimely death of a big shiny toy?

I checked out some suggestions from this question, but I somehow doubt a few packs of silica gel would be enough to convince my partner his TV is safe.

posted by luftmensch to technology (14 comments total)

Speaking as an hdtv-owning male, I wouldn't do it unless I could put a window air conditioner up there, the condensation risk is too high.
posted by Oktober at 2:49 PM on April 23

I elected, after one really hot summer, to move my TV and video games down to the living room. I live in Maryland and the attic was already hot enough there.

Ditto on the air conditioner. That was my other option.
posted by kalessin at 2:55 PM on April 23

It's going to be insanely awful up there in the heat of the summer. Get an a/c, for shure, and have a backup plan to move the plasma back downstairs.

My attic in St. Louis got hot enough a few years ago to make the plastic, on a couple old computer devices I left up there, sag.
posted by notsnot at 2:58 PM on April 23

Check the manual for the safe temperature range that your TV can operate within. Even with fans, it's going to be a total oven up there. If you put an a/c unit in you'll have to have it on constantly, which will considerably increase your electricity bill. Seems like it's a nice idea to have a TV room in the attic but not very practical.
posted by Burhanistan at 3:10 PM on April 23

This page references a study of attic temperatures in Florida. On days when the outside high was 88-95 degrees, which is pretty typical of SE Missouri, the attic temperatures averaged 103 degrees just above ceiling insulation and 127 degrees near roof peak. With a turbine ventilator running the attic temperatures cooled by six degrees at most.
posted by plastic_animals at 3:31 PM on April 23

That's a nice study, p_a, and definitely going to impact our usage plans. Even if the TV won't die, we might if we hang around there too long! The space will probably still be used as an evening-night hang-out room, when hopefully the ventilation and lower outside temp in combination with refreshing beverages will make things tolerable.
posted by luftmensch at 3:38 PM on April 23

Well, wait. That seems to be in reference to small, unfinished, uninsulated attic spaces, whereas mine may be better described as an insulated, oddly-shaped room on the third floor.
posted by luftmensch at 3:40 PM on April 23

My bedroom is a finished, insulated attic with an a/c. During the summer, the attic regularly heats up to mid-to-high 80s by the afternoon, even though western NY summer temperatures are usually quite mild. If that's what my attic does, I shudder to think what an equivalent space would do in Missouri...
posted by thomas j wise at 4:06 PM on April 23

Attics, even furnished ones, get freakin' HOT during Missouri summers. My bedroom growing up was basically a finished attic space and sometimes the air conditioning could not keep up.
posted by zsazsa at 5:11 PM on April 23

Um, yeah... growing up in MO, I've been in lots of non-climate-controlled, finished attics that were dangerously hot during the summers. I don't mean uncomfortably hot, I mean literally dangerous to your health (heat stroke, exhaustion, prickly heat, heat rash, etc.) from about 10am to midnight.

Even some of the airconditioned ones were very uncomfortable--like, strip down to your boxers and wifebeater uncomfortable.
posted by Netzapper at 5:21 PM on April 23

Are you really going to want to hang out in this room and watch TV when it's sweltering?
posted by pluckysparrow at 8:41 PM on April 23

My main question was just whether the humidity (or heat i suppose) would be damaging to a television. I'm willing to wait and see on how comfortable it might be, but not to risk ruining the electronics.
posted by luftmensch at 11:01 PM on April 23

Okay. There's not a lot of Googleable material in this realm (at least for a casual Googling). I'm assuming this has partly to do with trade secrets, etc.

But. This study talks about the deterioration of art collections with respect to temperature and humidity and especially gives numbers and effects for wood and humidity. Interesting.

This discussion about enterprise class data centers and humidity talks about how RH should be 2% or under in high availability data centers. No sources, just "experts" saying so. They also talk about how the primary goal in controlling humidity around electronics is to reduce the likelihood of condensation of humidity on the surfaces of electronics and circuit boards.

So assuming these guys know what they're talking about, what we are going for here is a situation where the humidity in your attic stays at a point that is less than or equal to whatever humidity is required so that the dew point in your attic is lower than the actual temperature in your attic.

The way we figure this is, well, by looking at articles about humidity, temperature and relative humidity. Or maybe using a calculator. What you'd be looking for would be some way to plug in some numbers and make a graph so you'd know when you get to the critical humidity, so you can figure out how often you put your electronics at risk.

Of the calculators linked, I would recommend the Relative Humidity Calculator. You're going to need to know your average atmospheric pressure (assume, if you like, 760 millimeters of mercury from 1 standard atmosphere). Other than that, plug in some numbers. 90 F with 90% humidity gives you a dew point of 86.67 F and a wet-bulb of 89.67 F. I don't know what the difference between dew point and wet-bulb are when talking about electronics, but I'd probably tend to go with the conservative figure given that the TV is expensive to replace. Plug in some other typical numbers as well for your attic, then make an informed decision.
posted by kalessin at 9:18 AM on April 24

I'm sorry, I should clarify the "what we are going for here" paragraph. It's all muddy.

The ideal situation for your TV in the attic is for the dew point to never be higher than or equal to the actual temperature. That would be bad because it would mean that condensation was happening inside your electronics.

So for example, if you had a relatively low humidity (10%) you might have a dew point of 26.19 F at an ambient temperature of 90 F. That would be good. If, on the other hand, you had a higher relative humidity (95%), your dew point would turn out to be 88.37 F. Normally, RH doesn't go above 100% at which point the dew point is equal to the current temperature.

However, it turns out that statistically, the closer your actual temperature and dew point are, the more likely you'll sort of randomly get some condensation. The closer your dew point is to actual temperature, the more moisture your electronics will randomly have on it. So for any given temperature, the higher the humidity, the worse off your electronics are likely to be.

If instead you prefer the thermodynamics/kinetics approach, you want to look at psychrometrics.

Also, I should say that wet-bulb is apparently primarily affected by atmospheric pressure, gives an idea of heat index - by gauging how well evaporation is working to cool things in the current pressure and humidity, and goes up as pressure goes up (the lower your altitude is, the higher the higher pressure system you're in is) so I reverse my earlier assertion that you should use the wet-bulb value. Instead use the dew point value to determine how much you are tempting fate.
posted by kalessin at 9:30 AM on April 24