Posts Tagged ‘Water vapor’

Efficiency & Bathroom Humidity

January 27, 2010

Reader Frank recently commented:

“Another strategy that I’ve found useful is the proper use of the bathroom vent fan. I know the cfm rating of it and after figuring the size of the room determined that the fan is capable of completely exhanging ALL the air in the room in under two minutes! Excess humidity is no good either; the windows throughout the house frost up noticeably more when the fan doesn’t get used and interior humidity is too high. Anyway~ fan stays off during shower operations and gets flipped on for 1-2 minutes right after, and that’s it. Most of the humidity goes out, most of the heat stays in.”

This reminded me that I’ve been meaning to to discuss bathroom vents.  To start with my conclusion: unless you use them as Frank does (i.e., most judiciously) I think they are a horrible idea in winter.  They are the equivalent of cutting a hole in the wall and blowing cold air in through it at somewhere between 50 and 200 cubic feet per minute.  Oh, I know– they don’t blow air in, they blow air out.   But that air is replaced with air from some other part of your house… which is replaced with air straight from outdoors.  There’s no way around this fact.  You don’t really notice it, probably, because it’s sneaking in through a thousand cracks, and you’re likely in the shower while it’s happening.  But it’s a travesty.

In fact, it’s a double travesty, because besides replacing warm air with cold air, you are losing the (much larger) amount of heat contained in the water vapor.  One of my Cold House mottos is that water should leave the house in the same phase of matter (more…)

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Clothes Drying: Big Improvement

December 7, 2009

Longtime readers will recall my ongoing struggles (intellectual, physical, moral) over the issue of drying wet laundry (first, second, third.) To summarize:

1) I have found no simple, dependable way of reclaiming heat from the dryer (i.e., re-condensing the moisture from its exhaust air);
2) Air-drying indoors in the winter is not much more energy-efficient (it uses almost as much heat as it saves) and not practical in the Cold House (things take eons to dry at our temperature, and we already have more than enough moisture in our air); and
3) Air-drying outdoors is fine in summer, but just not functional here in winter (clothes freeze before they dry, no one wants to wade through snow drifts to get to the laundry, etc.)

Now as the days get colder, I’m particularly displeased with running the dryer: I’ve done some math, and determined that in 45 minutes of running, the dryer sucks all the air from our cellar (which is replaced, of course, with cold air from outside.)

Frustrated with efforts to get back heat from the dryer, I turned my attention to the idea of using it less. One option was to not do laundry till spring: this was quickly squelched by J. The next option was extracting water mechanically rather than thermally. The idea there is that moving water uses much less energy than evaporating it.

I first tried giving laundry an extra run through the “spin” cycle of the washer, but that had no measurable effect. So, I made in investment in a commercial product, the hyper-drive spin-dryer from Laundry Alternative ($135). Success! Running a recent medium load of just-washed mixed clothing through the spinner, I extracted an extra 1.5 liters of water that would otherwise have been boiled off in the dryer. Based on some previous measurements, that represents about half the water content of the laundry load– which should, at least theoretically, reducing the dryer time by 50% (we do have a dryer that senses humidity and shuts itself off at a certain “dryness”, so there’s no guessing with a timer.)

Putting some real numbers to all this: the spin dryer uses 300 watts, and I ran it for about six minutes for this load of laundry– so that’s 0.03 KWh of electricity used. Compare this to the energy needed turn the same volume of water to steam: 0.95 KWh (and that’s assuming absolute efficiency– in reality of running the dryer, it would be more.) In other words, getting this 1.5L of water out with the spinner saves at least 97% of the electricity that the dryer would use to do the same job. Oh, and as an added (trivial) bonus: the 0.03 KWh it does consume winds up as heat inside the house, rather than sent outdoors!

The downsides to the spinner: (1) it isn’t dirt-cheap– at current electricity rates, it will take several years to actually pay for itself. Then again, our big dryer may last twice as long and need half as many repairs if we run it half as much, so you have to figure that in… (2) It’s a bit of a hassle– the spinner basket only hold a third what the washing machine does, so you need to spin a load in two or three stages. (3) The instructions have an inaccurate diagram which resulted in damage to the first unit I bought, having to return it, etc– if you actually buy one, email me and I’ll tell you how to avoid making the same mistake!

Silly "Green" Products, Part I

October 22, 2009

Here’s a silly “green” product, sold by a major “green” retailer whose catalog arrived in the mail yesterday:


This is basically a 25¢ plastic tray, sold for $16, which holds water. It alleges to “sustainably” “save your home” from “parched winter air.”

My critique: Firstly, my home does not need to be saved from being “parched”. What part of the house is damaged by dry air? Perhaps they mean save the home’s inhabitants from being parched– in that case, I refer the reader to last year’s posts discussing why it is not winter that causes air to feel dry– it is over-heating the house (here, here, and here.) Yes, if you insist on a hot house in winter, you will parch yourself. So you should turn down the thermostat, rather than buy gadgets to add artificial humidity to artificially hot air.

Secondly, the purveyor’s assertion that their “ingenious” plastic pan moisturizes the house “without… a single watt of power” is misleading. True, you don’t have to plug it in. But turning liquid water to vapor requires large quantities of heat, no matter how you do it. The fact that the unit does not have its own source of heat does not change the amount of heat it needs to do its job. In this case, that heat is supplied by the baseboard heater over which the device is located. Whatever fuel is being used to heat the house– electric, gas, oil– some of that will now be used to evaporate the water, at the expense of warming the room. Specifically, for every gallon of water poured into the device, you’ll need to burn close to an extra pint of fuel oil (or equivalent) just to make water into steam. And you don’t get that back as warmth– before long all that water vapor finds its way outdoors, and the heat poured into making it is lost.

In the final analysis, this device is no greener, or more sustainable, or even more useful, than gently simmering water in the tea kettle you already have on the cooking stove you already have. But again, I don’t recommend that, either.

You’re Not Dry Until You’re Hot And Dry

January 15, 2009

Well, here we are: in the (statistically, on average) coldest week of the year here. And reality is keeping up pretty well with statistics. The high temp today was about 10F/-12C, and the low tonight is predicted to be around
-8F/-22C. Housemate has been ridiculously supportive of the minimal-heat concept. Since January 1 we’ve pretty much had the furnace switched on only from 5pm to 10pm, and set at 60-64F/16-18C.

It wasn’t quite as cold last night as it will be tonight, but it was cold enough for me to wake up about 4am and go looking for a hat (foolishly, I’d left them all downstairs.) We may leave the heat on a bit longer tonight.

Housemate, and many others, have expressed a concern that keeping the house cool will increase risk of respiratory infections during winter. I theorize that it’s just the opposite (barring extreme life-sapping cold): that keeping the house hot causes the humidity to go way down, drying out your mucus membranes and making you susceptible to infection.

Here’s a Q&A article from a Minneapolis newspaper. The writer first complains that his house gets unhealthfully dry in winter, so he bought a humidifier. But then he got ice on his windows and, presumably, a lot of moisture condensing on other cool surfaces (not to mention and increased electric bill). Woefully, he states he cannot afford new, better-insulated windows, which the newspaper had previously suggested for preventing condensation, and asks if there is any other solution.

The newspaper’s expert responds, “You have discovered one of the conundrums of living in climates as cold as ours. Research indicates that for health and comfort, a relative indoor humidity of 40 to 60 percent is desirable. But keeping the air that moist over the course of a winter is more than most Minnesota homes can handle.” He goes on to advise that the dryness problem can be ameliorated by “slow the infiltration of cold, dry air by caulking and sealing windows, doors and other leaking areas.”

“More than most Minnesota homes can handle”?? This is peculiar. You can easily keep your home this humidified, if you really want to. What you won’t be able to handle, though, is the mess it makes of your house if you simultaneously insist on keeping the indoors at tropical temperatures.

In fact, this whole answer is just phony. The winter air in Minnesota is cold, but in terms of relative humidity, it is not dry. In fact relative humidity is about 70% all winter long in Minneapolis. It’s 59% right at this moment. Going outside in this air will not dry you out, and letting it into your house will not do so either. What does dry you out is excessively heating this air, which causes it to be capable of containing much more moisture, which causes it to suck moisture from you. Air that is 50% humidity at 32F/0C will become just 16% humid at 68F/20C, and 12% at 76F/24C.

So, I argue the writer’s problem is probably not that he had too little moisture without the humidifier and too much with it, but that that his house was too hot at both times. Chasing a severely unnatural goal of a hot house in a frigid climate has left the writer with more problems (the “solutions” to which will create only yet more problems.) Nowhere in the expert’s “solution” does he suggest the logical first step of turning the thermostat down a bit. Because, I gather, that is a step backward into historical wisdom, rather forward into the glorious technological future.

Simple Experiments In Heat Reclamation: Part II – The Shower

December 19, 2008

Increasingly, I’m becoming convinced that one of the keys to keeping the house warm(er) is paying attention to water.

I mentioned before about the huge energy it takes to evaporate a gallon of water– 2.5 killowatt hours. That got me thinking about the fate of water around the house.

The conclusion I’ve come to: one of the worst things you can do, when trying to keep a house warm(ish) without heat, is to turn liquid water into water vapor, then let it get out of the house in that form. Ideally, any water that enters the house as liquid, should leave as liquid. (Similarly, any frozen water that comes in should leave frozen– or, at worst, liquid.)

Crackpot idea, I know. But think of all the sources of water turning to vapor around the house every day: The dog’s water bowl. Steam from the tea kettle you leave on an extra minute. The simmering tomato sauce. Houseplant soil drying out. Bath towels drying. Dishes drying. Toilet bowls. Mopping the kitchen floor. Wet boots in the entry way. Steam from the shower. Not to mention the humidifier/vaporizer/kettle-on-woodstove that you might have.

And then there’s you, and your housemates. Everyone is constantly churning out water vapor, half through your skin and half through your breath. About a liter a day per person, if you don’t exercise in the house– more if you do, or if your house is hot. In fact, about 25% of your body heat is devoted to vaporizing water– doesn’t that sort of suck? (And don’t forget the dog is breathing, too.)

I think it’s safe to say that by myself here, completely unintentionally, I am probably turning minimum of a half-gallon of water into vapor every day. If my house were completely vapor-tight, after a few days every surface would be dripping and slimy. Luckily (I think), the house is not vapor-tight– so all this vapor eventually escapes outside. It might not do it in one swoop: probably, it first condenses on a cold window, or the toilet tank, or a beer bottle. Then it drips somewhere. But eventually, unless it gets to a drain as liquid, it goes out through a crack as vapor– taking with it that 2.5 kwh per gallon.

It used to be, if I spilled some water on the floor in the winter, I’d half-heartedly sop up the worst of it and leave the rest to evaporate. I look at it a bit differently now… I see the puddle of water and I ask myself, do I want to put that down the sink, or do I want to run the space heater to make it go away? Because that’s what it comes down to.

I’m not being nutso about it, but I am trying to eliminate unnecessary sources of standing/evaporating water around the house. Putting lids on soup pots, for example. Not leaving dishes with water in them lying around.

But the big potential source of improvement here, I think, is from the shower. I admit to liking a nice hot shower, no less now that the house is Cold. But it does produce a lot of water vapor. Step one: trying to keep the vapor in the shower. A fully enclosed shower stall would be great for this; my old clawfoot tub,not so good. But, throwing some bubble-wrap over the top, with a little temporary duct tape for effect, made some difference– shower is warmer, with less hot water, and less steam in the house after. But still quite a bit.

How to catch the steam, and turn it back into water, to make it give back its heat? Various ideas. Simplest: mop it up from where it condenses, before it can dry. I took a sponge to the bathroom window post-shower this morning, and with 10 seconds of effort I squeezed out 50ml of water. That represents the heat of a 35W bulb for an hour. Plus, Cat could see out the window for the rest of the day. The mirror netted some, too. If I had two or three more windows, I expect most of the steam would’ve wound up there.

But you don’t want to go installing extra windows to try and keep more heat in– that’s backwards. You need something that’s already in the house, is coldish but not connected to outside, has a smooth surface, a high heat capacity, a high thermal conductivity, and can be kept up towards the ceiling where the vapor rises. Granite and marble aren’t conductive enough. Something like a slab of copper or aluminum would be good. Silver would be perfect, but pricey. My fantasy image is a border around the top of the walls made of plate copper, with a little gutter under it to catch condensed water and deliver it to drop into the sink. If the room is cold when you start the shower, I think this could be designed to catch, condense, and dispose of most of the steam.

There is a simpler but less elegant solution at hand: a dehumidifier. I tried running it during a shower. First attempt was no use: it was on the floor, and the humid air was not.

It’s Not Winter’s Fault

December 14, 2008

I mentioned before that the complaints of “it’s too dry in the winter” may have more to do with excessive indoor heating than with actual climatic conditions. Here’s a graph of the Smallish City’s annual humidity pattern, which seems to confirm:

This shows that there is almost no seasonal change in afternoon humidities. There is a slight seasonal change in morning humidity (ranging from about 75% to 85%), but even this is not a clear winter/summer effect– it’s as humid in December as it is in June, and the least-humid month is actually April.

Right now, in spite of being 16F / -9C outside, we do have 73% humidity. Unfortunately by warming things up to 48F / 9F indoors here, I’ve lowered the humidity to about 20%, which is a bit dry. Still, I’ve had much less in the way of chapped lips, etc., this winter than usual. If I heated the house up to 68F / 20C, the humidity would be only 10%… parching.

Psychology Of Water Vapor

December 12, 2008

SUNDAY, NOVEMBER 30, 2008

Now here’s another fascinating tidbit I came across in my cold-adaptation research: Did you know that the “relative” in “relative humidity” is “relative to how much water the air could hold, at the current temperature”? Hot air can hold more moisture than cold air. So if you keep the actual amount (mass) of water in the air the same, higher temperatures give lower relative humidities. And since the relative humidity determines how fast damp objects (such as our bodies) dry out, this is what we perceive. From a human perspective, the absolute amount of water vapor in the air is fairly meaningless, unless you know the temperature.

From the limited data I can find out there, humans seem to feel physically and psychologically best at relative humidities between 40% and 60%. More than that starts to feels “muggy” in hot weather and “dank” in cool weather.

At the other end of the spectrum, people around here often complain that the “air is too dry in the winter”, causing dry eyes, chapped lips, etc. But it seems that to at least some degree, this perceived “too dry”ness is primarily indoors, manmade, and a result of (guess what?) artificial heating.

Take this morning, for example. In the Smallish City right now it’s cool and cloudy outside. A small sleet-storm is edging its way towards us for later in the day. The temperature is 28F (-2C) and the relative humidity is 78%. Walking around outdoors, you certainly don’t feel the air is “too dry”. The cold air can’t hold much absolute moisture, but it’s holding about as much as it can– so your body isn’t drying out quickly. If anything, it borders on feeling “dank” out there. And when the sleet starts, it will surely feel downright wet.

Here in my kitchen, however, I have a space heater running to keep the temperature at a toasty 51F (10.5C). The actual amount of water in the air is about the same as outside. But at this indoor temperature, the air could hold a lot more water vapor. The relative humidity drops to 32%– feeling just a bit on the dry side, but still fine for me.

I look out at Accordion Neighbor’s house, though, and notice that he’s got his woodstoves cranking. He probably has it up to 68F (20C) in his house, like “normal” people. At that scorching temperature, the relative humidity in his place right now is a parching 17%. The water is being sucked out of his family’s bodies into the hot air. He probably has chapped lips, his kids might have bloody noses and dry throats (indeed, I haven’t heard them scream in several days), and they are all probably going through hand-moisturizer at a rapid clip.

A.N. is probably trying to counter this problem with an old trick: keeping a kettles of steaming water on top of the woodstoves to get some extra humidity into the air. (A similar old trick is used around here by those with radiator heat: narrow buckets of water that hang from the radiator, getting warm & evaporating moisture into the air.) This trick isn’t necessarily a bad idea, for human comfort– but from a standpoint of energy-efficiency it’s very much a losing battle. In an old house, it won’t be long before that water vapor makes its way back outdoors. And, as we learned in a previous thought-experiment, evaporating water costs you temperature, and energy. Every gallon of water you purposefully evaporate costs you a couple pounds of nice firewood, or cup of fuel oil.

So, call me a crackpot, but: one way to keep yourself feeling dried out in winter is to keep your house cooler.
POSTED BY TURBOGLACIER AT 10:17 AM
7 COMMENTS:

Johanna said…
Me, I am not swayed by all the arguments for sitting around feeling cold, and I am still trying to wrap my head around this concept of not turning on the furnace to save energy while managing to convince oneself that using an inefficient electric clothes dryer makes economic, environmental or common sense.

I am waiting for the day you actually turn on the heat and focus your thoughts on preventing heat loss, because that’s information I could apply.

11/30/08 12:56 PM
Turboglacier said…
Oh, I’m focused on preventing heat loss, too, inasmuch as that is reasonably feasible. I’ve gone around and caulked all the window cracks. I am putting additional plastic insulation on some of them. I injected foam in many baseboard cracks. I put foam behind drafty electrical outlets. I’m sealing up holes in the basement through which cold air came in (such as the big hole formerly used by the dryer vent.) But, short of a multi-thousand dollar jobs such as re-insulating the walls or replacing all the windows, this is all I can do for the moment.

As for the electric dryer: I have to disagree with the common sense. The dryer is basically just a big electric heater. It’s electricity (in fact, ANY electricity used in the house) is ultimately turned, with 100% efficiency, into heat (with the exception of a miniscule amount that may escape as light.) So, as long as you manage to keep that heat in the house, you’re maintaining perfect efficiency.

(Making the electricity in the first place, of course, is not a 100% efficient process– but neither by a long shot is running the furnace. Depending on the source of the electricity, it’s arguably “greener” than burning oil here at home.)

11/30/08 1:33 PM
C Neal said…
Remember that warm, dry air is actually perceived by humans to be less warm than warm, moist air. A room with a thermostat set at 60 and with 80% relative humidity feels just as warm as a room where the thermostat is set at 65, with only 10% RH. See this chart from NOAA:

http://www.infoplease.com/ipa/A0001434.html

As I understand it, dry air feels colder because it increases the rate of evaporative cooling on your skin (conversely, in the summer, hot, humid air decreases the rate of evaporative cooling and makes it feel hotter than it actually is). So the kettle on the stove or the bucket on the radiator may decrease performance in terms of actual temperature, but in terms of perceived temps, it may well be an improvement.

I’ll leave it to you to figure out the details of the trade-off.

11/30/08 2:22 PM
Turboglacier said…
C.Neal: That is most interesting. But I think it still doesn’t come out in Accordion Neighbor’s favor. With this morning’s conditions, if AN set his thermostat at 70F, his humidity would be 16%, and chart says he would “feel like” it was about 64.5F (interpolating between the data points.)

Meanwhile, even if I (uncharacteristically) let my house go up to 60F, I would have a humidity of 23%, and would “feel like” 56.5F. So, AN’s house feels 5.5˚ cooler than it is, but mine feels only 3.5˚ cooler than it is. To make up the two degrees in “feel”, he can make the house warmer, or more humid, but either way he’s using even more fuel. Chasing the tail, I call it.

[Also: I was annoyed with that chart, because it only goes down to 60˚F, whereas my house is considerably cooler. But then I noticed a trend which leads me to question its validity altogether: as the temperatures go down, the chart says you need more humidity to “feel” like you’re at that actual temperature. By 60F, you need 80-90% humidity just to “feel” like it’s 60F. If you extrapolate this pattern just a few degrees, at about 57F you’ll need 100% humidity to “feel like” 57F. At temperatures below that, “feeling like” the actual temperature would take humidity >100%, which isn’t possible. So… I surmise that this chart is good only for a very narrow range of temps– probably not even down to 60F, and certainly not below that.]

11/30/08 3:34 PM
girltuesday said…
ok, i’ll bite: crackpot.

11/30/08 10:51 PM
Victor said…
Oh, I grew up in Very Smallish town with cold (-20°C) winters and, the chart cannot be – as you suggest – valid for colder temperatures. The amount of water in the air also affects the convection and conduction of heat. In “cold” (< 4°C as a qualified guess) temperatures an increasing relative humidity will be percieved as the air getting colder. This is why +3 and rain feels in october feels like -8°C and -20°C with a clear sky in january feels like -8°C.

This are just opinions. And this was a very nice blog!

12/10/08 9:57 AM
Anonymous said…
More than you ever wanted to know about apparent temperature (with equations!): http://www.srh.noaa.gov/ffc/html/studies/ta_htindx.PDF

12/10/08 6:50 PM

Factual Data

December 12, 2008

FRIDAY, NOVEMBER 21, 2008

My estimate of 1.5 gallons of residual water in a load of wet laundry was slightly high. I did an average-size load of darks yesterday (including two towels) and took measurements:

Weight before washing: 13.5 lbs
Weight after washing: 22.0 lbs
Weight of residual water: 8.5 lbs
Volume of residual water: 1.06 gallons
POSTED BY TURBOGLACIER AT 11:05 AM
4 COMMENTS:

Valerie said…
Only 1 gallon? Great! If you’re tempted to run a humidifier during the winter, now all you have to do is hang your laundry all over your radiators (or over your woodstove, if you want to live on the edge). If you’re worried about aesthetics, well, I guess it just means you need nicer clothes.

11/21/08 3:26 PM
Anonymous said…
Just remember that anything that slows the velocity of air exiting your dryer will decrease it’s efficiency (using more energy) and potentially create a fire hazard if lint collects nearer the hot center of the dryer.

11/22/08 11:38 PM
jcat said…
Are you sure you were meant to become a psychiatrist? Somehow actuary or ….accountant…. seems more fitting

11/23/08 1:57 PM
Anonymous said…
Fascinating. So this is what you do when you can’t play outside. It’s going to be a loooooong winter.

11/25/08 10:19 AM

No Free Thermodynamic Lunch

December 12, 2008

WEDNESDAY, NOVEMBER 19, 2008

Just an addendum to the last post, with regard to comments suggesting air-drying clothes as an eco-friendly alternative to using the electric dryer:

Air-drying is great for outdoors. And maybe even indoors in the summer. But is it really “free”/super-eco-friendly to dry things indoors in winter? My data says, no. It says that drying clothes in your house cools your house down, and not insubstantially.

Consider: turning liquid water to water vapo(u)r takes energy, and a lot of it, no matter how it’s done. If you’ve ever tended the fire in a maple-syrup evaporator you know how much firewood it takes to boil 10 gallons of sap down to a one gallon of syrup. Similarly, if you’ve ever stood outside on a cold day getting hypothermic in wet cotton clothing you have a sense much energy water evaporation sucks out of you. And, just as in melting ice to water, the vast majority of that energy is not to make the water warmer, but to change its phase from liquid to gas.

So– maybe you want numbers. Well, the first question is: how much residual water is left in a big load of wet laundry, when it comes out of the washer? I am going to determine this when next I do laundry, using a bathroom scale– but for now let’s guess maybe 1.5gal = 6litres? Which doesn’t seem like that much… until you do the thermodynamic math*, and find that it takes 3.76 kWh = 3,234 kcal to dry up that much water.

Perhaps you don’t have a sense of how much heat 3.76kWh is. It’s about 3.4lbs / 1.5 kg of nice, dry maple firewood, if you have an efficient woodstove. It’s about 1/2 a liter of gasoline, burned efficiently. It’s 125 sixty-watt lightbulbs, left on for half an hour. It’s the energy my particular electric dryer uses if you run it for 40 minutes.

And unfortunately, when you rack-dry clothes in a house that you’re trying to keep warm, that energy doesn’t come from the kcal-fairy. It has to come from your furnace, or woodstove, or space-heater, or whatever fuel you’re using to keep your house warm, running longer or hotter. Really. Disbelieve? Close off one room & try covering the radiator there with wet towels… see what happens.

But I have no contest with the argument that line-drying is better for your clothes.

(* Johanna: I will send you the math, if you insist.)
POSTED BY TURBOGLACIER AT 1:44 PM
10 COMMENTS:

Johanna said…
Any farmer can tell you that it’s not just temperature that dries out the soil, it’s also wind and humidity. If you are heating with wood or have central heating, chances are, your home is fairly dry (and hence the humidifier in the furnace kicks in, and why my mother always has a pot of water sitting on the wood stove). Assuming evaporation is entirely based on temperature is a bit too simple – even your energy pig clothes dryer uses the moving air bit + temperature + low humidity. And *then* it sends the by-product out the vent, and even if you were to capture it, you wouldn’t get all of it.

I’ve line-dried clothes in the polar desert and attempted to do so in humid tropics. In the tropics, they would have grown mold if I hadn’t managed to get direct sun on them. In the High Arctic, it took a couple of hours on a windy day colder than inside your house right now.

And even if it *were* *just* temperature, many homes have spaces that are not really used but heated by default. My furnace room is one such place – all the ducts converge on the beast, and it’s the warmest room in my house. Even when three loads of laundry are strung out…

Of course, you are welcome to set up shop down there. It can be your bunker. I promise it’s toasty warm.

11/19/08 9:00 PM
Turboglacier said…
No, for reals, it *is* just heat. Wind and low humidity just help the drying happen faster; they don’t change the total amount of energy transfered into a unit of water to turn it into vapor. The do accelerate the process, though– hence the “wind chill” concept, and the usefulness of evaporative coolers in deserts, but not in tropical jungles…

11/19/08 10:33 PM
Weeble said…
Dig it. Based on your recent posts, I would like to propose a new name for your blog: “May Hypothesize and Compute”

11/19/08 10:57 PM
s said…
Yeah, I have a rack in a room no one ever goes in anyway so it doesn’t really matter if it’s cold in there.

11/20/08 12:29 PM
Johanna said…
This is great!
Now that I have been enlightened on the amazing room-cooling properties of wet laundry, next summer will no longer have me suffering through hot nights because I refuse to turn on the AC. I’ll just fill my house with laundry racks. Should cool it right down, no?

11/20/08 3:50 PM
Turboglacier said…
Yes, it definitely will cool it down!

However, if the ambient humidity is high, the clothes won’t dry very fast, so the cooling may be spread over a long period of time, and completely unnoticeable.

Also, it’s possible that the further increase in humidity FROM the drying laundry will cause your sweat to evaporate more slowly off YOU, resulting in reduced ability to cool yourself, and causing you to FEEL hotter, even if the room is a little cooler.

But, you know, give it a try 🙂

11/20/08 3:55 PM
Johanna said…
Ah, but I know how to get around that, thanks to you – wind will speed up the evaporation. Thus, my bedroom will be filled with laundry racks and an ordinary fan pointing at them to speed up the cooling.

Or, you know, I could ask you to come up with some complex equations which have the ultimate outcome of scientifically proving that turning on the AC is actually the sensible thing. Given that you can justify a 5600W dryer, should be a piece of cake.

11/20/08 4:00 PM
Turboglacier said…
Oh, that will work J.– but it might be more efficient just to point the fan at yourself, to speed up the sweat evaporation! That’s a little trick I use here in the summer!

As for the AC… nope, can’t argue for it. The dryer and AC are both net producers of heat. It’s just that heat is something desirable in the winter, but not in the summer….

11/20/08 4:05 PM
Anonymous said…
I thought that the low humidity *did* matter. something to do with the water going from high concentration to low concentration. When I lived on the steppe the snow would sublimate at minus 20.

11/21/08 8:33 PM
FrozenLaundry said…
My mother used to dry her clothes in winter OUTSIDE, in Buffalo, NY. She’d wait for a sunny, no snow day, then hang the clothes out. The air is very dry in winter. There’s wind. Some got dry and some came in stiff as a board to be hung until completely dry in the basement (which was unheated and separated from the rest of the house by a door.

11/22/08 6:41 PM

Heat Reclamation

December 12, 2008

TUESDAY, NOVEMBER 18, 2008

Heat Reclamation
You may be saying to yourself, “I wonder what kind of whack-o schemes and projects that wing-nut has been up to lately?” Well, I’m glad you asked.

For one thing I (and some hardy friends!) have been trying to see far into the season we can go without turning on the central heat in our homes. This is based on several motivations, including an interest in human physiology, and the fact that the price of heating oil was over $4/gallon when I thought up the idea. But that’s all for a different post. Anyway, I’m aiming now for December 1st, and so far, doing quite well– right now it is 32F (0C) outside, 51F (11C) inside, and I’m typing quite comfortably. We’re allowed to use space heaters, judiciously, but for the most part I haven’t needed to. I have noticed that my house is forming icicles sooner than my neighbors’. Good sign!

So, as part of my overall strategy to reduce oil use, I decided to fashion my kitchen into a winter-bunker. It’s a large kitchen, and already has the sofa, DVD player, etc. in it– not to mention all the food– so I really could just spend the winter in this one room. I made a insulated curtain for one kitchen doorway from a thick quilt, and have bought an old salvage door which I am working on installing in the other doorway. When done, I’ll be able to seal off the bunker from the rest of the house, and, I hope, just stay warm with a space heater. Cool, no?

In the process of all this I got to thinking about the clothes dryer, which is right under the kitchen and vents outdoors right next to the window. In past winters I’ve enjoyed watching the dragon-breath of steam wafting up past the window, and admired the snow-free zone which was kept cleared around the vent all winter. The other day I looked at the dryer to see how much energy, exactly, it uses in doing its thing. Guess what? 5,600 WATTS! Yeah… that’s a lot! Also I got to thinking about the huge VOLUME of air the dryer sucks out of the cellar, which is being replaced by frigid outdoor-temp air rushing in through all the gaps in our cellar windows, etc. Terrible!

I’m considering some type of clothes line for the summer (though my yard is awfully small and shady), but in the winter line-drying isn’t a good option at the Palace. So, for this season, I started to think of ways to reclaim the heat from the dryer, rather than dumping it outside. First idea: just undo the vent hose from the exit hole, and redirect the warm air back into the cellar. E-Z, and stops the air-sucking-out problem, but it seems no good to be humidifying the very air you’re trying to use to dry things. Plus, what good, really, does warm air in the basement do?

So I thought next about instead running the hose up to the kitchen, where the warmth would be useful, and even the humidity might be desirable (in the winter). But as I pictured the amount of humidity involved, and envisioned the dank, dripping windows, etc., as well as the pleasant-only-in-small-quantities aroma of dryer exhaust air, I decided against this as well.

Third incarnation, I thought about sourcing a surplus old iron radiator (Smallish State is littered with such), putting it in the kitchen, running the dryer house in one end of it, another hose out the other, and thence to the outdoors. Thus some of the heat would get transferred from the dryer air to the radiator, warming the kitchen, but the moisture would still get blown outside (some water might condense inside the radiator, but that’s okay.) However, I still pictured half or more of the heat escaping outdoors, which bothered me. And the problem of cold-air-suck remains, because you’re blowing the exhaust outside.

So, for Theoretical Version 4.0, I mentally added a condensing coil of copper tubing to the hose after it leaves the house. Then, another hose at the bottom of the coil returns back inside, downhill all the way, before turning up at the end. A small hole at the low point of the “U” is made, with a bucket below. Water in the humid air leaving the house condenses running through the cold coil, runs down the exit hose, falls into the bucket. The air, now cooler and drier (but still warmer than ambient outside temperature) is returned to the cellar. Voila! Maybe. Suggestions?

POSTED BY TURBOGLACIER AT 5:59 PM
11 COMMENTS:

Johanna said…
Interesting…

Though I challenge your assertion that you need a dryer in the winter. I don’t own one here in this Canadian climate, the vast majority of Europeans have never owned one, and we have no difficulty at all drying everything on racks. It might take a bit longer right now, with the heat off, but once it’s on things dry overnight (better for the clothes, too).

If you are wedded to the idea of having a clothes dryer, I wonder if you could retrofit a heat exchanger like on condensation dryers. I wonder about the insulation loss of running extra pipes outside and in, through either double glazed windows or a window and a storm window. In my climate, the copper coil would ice up fairly quickly.

I’m also confused about your house building icicles sooner, since, given similar sun exposure and the same ambient temperature, icicles will be more common on buildings with greater heat loss. Maybe the cold miser needs an energy audit?

11/19/08 7:09 AM
charlsiekate said…
How is your tropical roommate adjusting to the no heat thing? The low here in Georgia was 24 last night, which I’m sure is laughable to you New England folks, but we definitely enjoyed the heater. And a warm puppy at the foot of the bed.

Of course, I imagine our house is designed more for the summer heat than the winter cold, and I’m sure my house doesn’t have a heater that uses oil.

11/19/08 9:25 AM
Turboglacier said…
J: I may go with “drying racks” at some point. But space is limited here, and with multiple people doing laundry– well, I don’t know. In general these “European ideas” of which you speak are notorious for leading countries into socialism, prolonged life-expectancy, and other evils.

Heat exchangers– yes, looked into, but they are expensive to buy (like, $500) and not easy to build. And have to have a second fan, so need electricity, blah blah. I don’t think there would be much insulation loss– I’ve already got a hole through the basement wall for the existing exhaust hose, so I’d just use that (the hoses would really go through a window– that was just artistic license, and so I could draw clouds.)

Icicles: In mid-winter, I’d agree with your assessment– icicles form from buildings melting the snow on their roofs, which water then refreezes dripping off the eves. But we’ve had no snow yet, and the temps have barely been dipping below freezing. The icicle in the photo formed from the dregs of a rainstorm dripping off the window sill as the temp dipped down just to freezing over night. I believe my neighbors’ walls did not form any icicles because their excessively-heated walls kept their exterior temperature above freezing, preventing any ice from forming.

CKate: Luckily for Tropical Housemate, he moved on several weeks ago (he was only temporary). He would NOT enjoy what’s going on here now (this morning, e.g.: 28F outside, 50F inside.) In stroke of fantastic luck, I’ve found a new (more permanent) housemate who grew up in Caribou, Maine– frequently in contention with Bismarck, ND for the coldest spot in the Lower 48. So she will, I hope, feel right at home here. Also, she’s bringing two more cats, so we will have all that extra warmth!

11/19/08 10:21 AM
Turboglacier said…
Excuse: above should say “(the hoses would really NOT go through a window…)”

11/19/08 10:23 AM
The MSILF said…
I also don’t have a dryer as this apartment doesn’t have the hookup, and use the racks, which fold up completely…and it’s cold here in winter, not like your cold, but still…inside it’s cold. Now I’d really never go back. It seems so unnecessary. And I think here, where it’s also dry, a lot of people just redirect the dryer vent right back into the room in winter.

11/19/08 12:26 PM
Claire Colvin said…
I realize the schematic is just an artist’s rendering and not to scale, but I’m wondering about the length of hose/ pipe involved here. Any way to test if the exhaust output of the dryer moves at a sufficient velocity to force the air all the way through the lengthened system?

11/19/08 1:58 PM
Turboglacier said…
“Test” it? Of course there’s a way to “test” it: build it, and see if it works! How else?

11/19/08 3:03 PM
Rossie said…
Forgive me if this is answered farther down in the post – I stopped reading with the first sentence of the second paragraph as I am absolutely dumbfounded. You live in New England and are trying not to use heat? in the WINTER?? and other people have joined you in this effort???

Words fail

11/21/08 10:19 PM
Turboglacier said…
Rossie:

Oh yes– just so.

And some of the others who have joined are actually north of New England. J., are you still in? Sort of?

[Right now: 22F outside, 42 in my bedroom, and 53 here in the kitchen bunker with one space heater on. I’m wearing normal clothes, a hat, and down vest. Have been for comfortable for hours.]

11/21/08 11:52 PM
Anonymous said…
something to consider:

the fine particles in dryer exhaust air(lint) can be potentially explosive if the suspended level of them in the air gets high enough.

you might want to exhaust the air into the top of a bucket filled with water (or get a commercial product similar to http://www.indoorlinttrapfilter.com)

Also heat exchangers can be created simply from easy to get materials.

1)figure out how many sq.in.(cm) you need(= to the cross section of your dryer exhaust)

2)divide the number into a number of 1/8th-1/4 in.(2-5mm)slots.

3)double the number of slots from #2 and figure out how many dividers you need(to separate the slots from each other)

4)accumulate(drink) enough pop/beer (as long as it comes in Al cans) to provide the raw material for your dividers.

5) remove the top and bottom of the cans and cut your material into the correct size (4-6″ squares depends on application and raw material).

6) using cardboard(or something similar) as a spacer create a slot that is open on 2 opposite sides(closed on the other 2). I have found that the Al tape you can get for duct work is perfect.

7) keep adding dividers to your creation alternating which side is open. when your done you want to have made something like (O#O#O#O#O#O) on one pair of sides and (#O#O#O#O#O#) on the other.

you should pre-filter the dryer air to keep the HE from filling w/ lint. you will also need to deal with the condensation. if your exhaust is still too warm add another exchanger or a small fan to pull room air through the other sides.

YMMV- good luck.

12/10/08 12:07 PM
Turboglacier said…
Thanks for the tip on explosive dryer dust, Anon. I found that putting a fine kitchen strainer or a scrap of nylon mesh over the exhaust does a good job of filtering the vast majority of it.

While the http://www.indoorlinttrapfilter.com device is clever, I can’t approve of it for heat-reclamation purposes. Running the dryer exhaust over a pool of water adds even more moisture to the house, causing (ultimately) further cooling. “After a few dryer loads”, the website says, “you simply pull the drawer out and refill back up with water.” But you pay energetically, one way or another, for all that additional water you evaporated…

12/10/08 12:55 PM