Constant-temperature dehumidification

[nicksanspam]

Joe Fischer errs again:

You might enjoy figuring that out :-)

Not on a mild day.

Not at all, with an exhaust fan.

Only your hairdresser knows for sure.

Nick

[Robert Gammon]

Now it was Nick who pointed out that IDEA 2000homes in Canada leak at

2.5CFM vs 200CFM for good US houses, and now he won't even read the pages from whence these figures were quoted!!!!!!

Aha should back at you, as if my house can be adequately conditioned (Heated and cooled) by burying 500 feet of 6 inch diameter pipe 6 feet below the surface and blow 300 CFM thru the pipe. In SOME parts of the US that will work in combination with solar heat management, great insulation.... Temperature to cool climates yes, however I do not live in a temperate climate. AC runs a few hours EVERY SINGLE MONTH OF THE YEAR.

It just won't work. One size does not fit all!!!

[amde]

Leaving the door open is more frugal. It's not that cold here unless you're in Eastern Washington.

[daestrom]

What do the numbers look like with an average outside dewpoint of 0F ?? While the daily 'highs' here can sometimes reach 30F, the overnight low and dewpoint of outside air is usually much lower for Jan/Feb. My psychrometric charts don't go down that far so I can't do the calc.

Seems like 'always' is a pretty risky statement considering some parts of the country. Pellston MI is often one of the coldest places in CONUS, or International Falls MN.

How much air exchange happens when the door is opened eight times a day (four people leaving for work/school and returning). Just wondered if you have some data on that?

daestrom

[daestrom]

You really are 'reading' Nick the wrong way.

Yes, warming outside air as it enters a house lowers its RH (doesn't change its dewpoint or specific humidity though). Yes, most people are more comfortable with RH around 50%, and many household items such as wood furniture are less likely to shrink/crack if the humidity is maintained.

Nick is *only* saying that you don't need to add a lot of moisture to the air *if* you don't have a lot of air exchange. If air exchange is kept down to a minimum, then the amount of moisture you have to add is also a minimum. Experts/standards tell us that you *don't* need a whole-house air change every 2 or 3 hours. *That* level of air exchange does require you to add a lot of moisture. And that takes a lot of energy.

Reducing the air exchange rate to something a lot closer to the 'standards' level will greatly reduce the amount of moisture that needs to be constantly added to a house. Nick *has* said that with the minimum air exchange, the moisture given off by people and activities will accumulate enough to raise the humidity into the 'comfort zone'. But I think that would only be true in mild winter climates such as his (Philidelphia).

Nick also maintains that the old wive's tail that humidifying your house saves energy is bunk. It may feel more comfortable, but it takes more energy to maintain that humidity level than it does to just maintain the air temperature. Lowering the exchange rate will save energy in two ways, a) it lowers the amount of heat lost with the outgoing air, and b) it lowers the amount of energy needed to maintain comfortable humidity levels.

daestrom

[daestrom]

No, I don't think so. I was pointing out that dewpoint is a much better measure of the amount of moisture in the air than RH. After all, in the winter time around here when it's 20F, the weather report often says humidity is above 75%. Of course that's the RH at the prevailing temperature (20F) and not very meaningful. You have to do a lot of calculations or use a chart to figure out what that would be if heated up to

70F. But compare the dewpoint (about 15F) with a desired dewpoint of 45F and it's easy to tell that the air is really 'dry'.

My son has that problem. If I don't humidify the house, he'll wake up with blood stains on his pillow each morning.

Airplane trips are another nasty one. The air at 35,000 feet has a very low dewpoint.

I'm sure there is. Museums often put precious relics in climate controlled cases. Gettysburg has a lot of Civil War memorabilia that is preserved this way. Uniforms and leather items are subject to this issue as well.

Well, I agree with Nick that humidification costs you energy, it doesn't save energy. But that's not to say that you shouldn't do something to control the humidity levels. Nick likes to play with numbers and posit some 'we could' or 'it might'. Gets people thinking. If we reduce the air-exchange rate, we don't have to work as hard to maintain a nice humidity level. Nick is fond of quoting ASHRAE (the manuals cost a lot, may as well get his money's worth). I'm not so sure that as little as 15 cfm is enough to maintain "indoor pollution" levels, but I have to agree that most US homes are much too 'leaky'. An air-exchange every couple of hours seems like way too much.

But then, I lived on a submarine for years, so I may be a little more sensitive to air contamination issues than some folks. Ventilation is one way to reduce indoor air pollution levels, but removing the source of the contaminants is another. No contaminants, don't need much ventilation. Little ventilation, less moisture needs to be constantly added to maintain 'comfort' levels.

daestrom

[daestrom]

Well of course colds are caused by virsuses (virii??). But if someone's natural defenses are weakened, doesn't that make them more susceptable to infection? If your sinuses are cracked and bleeding, isn't it more likely you will 'catch' one of those viruses floating around in a closed space?

The nasal passages are our first line of defense against such airborne infection. If some folks sinuses are particularly sensitive to drying, it seems quite logical that airborne infections have a better chance of taking hold in the body and causing illness.

From your article by the Mayo Clinic, on 'risk factors' : "Some researchers theorize that cold constricts blood vessels in the nose, slowing the white cells that fight infection and disrupting the first-line defense against germs. "

This supports the belief that your nose is the 'first-line defense against germs'. So doing something to keep from degrading its ability seems only natural.

daestrom

[nicksanspam]

Table 2 in the ASHRAE HOF says the humidity ratio wo = 0.0007875 at 0 F, which would make wi = 0.00593 with a 38% RH above, or more, with some outgoing condensation.

Since many house materials (cloth, wood, paper, concrete) can store moisture, it seems like a good idea to ventilate houses during the day in wintertime, when outdoor temps are warmer. An exhaust fan might have a timer, as well as a humidistat.

International Falls has wo = 0.0009 with an average 1.0 F outdoor temp in January. Brrr.

I have no data, but if the door's open for 3 seconds each time, that's 24 seconds total, ie 0.4 minutes per day. With 16.6x16ft^2sqrt(70F-0F)4') = 4444 cfm when the door is open, we might move 0.4x4444 = 1778 ft^3/day of fresh air into the house, ie 1778/24/60 = 1.2 cfm, averaged over 24h.

Airlock entrances just for the purpose of saving heat energy (vs mudrooms that keep a house cleaner, etc.), don't seem worth the cost except for department stores or very large busy families.

Nick

[Joe Fischer]

Aren't they related?

I think the weather man here shows dew points when there is storm danger.

I haven't had it for a long time, because I hate the colds so much. I have had jobs where I was in close contact with a lot of people, and worked outside in all kinds of weather, but only got a cold when the humidity wasn't kept high while sleeping.

I think even food needs to be kept in a controlled environment to stay fresh and edible longer.

Most homes have plaster or drywall walls and ceilings, so there isn't much that can be done other than doors and windows. The modern furnace has eliminated the loss to vented flame, so it gets down pretty much to windows.

Is Nick a window salesman? :-) :-)

I had the impression that I was reducing ventilation when I began using baseboard electric in place of vented gas stoves. Five years ago I turned off the supply valve to my 1960 Magic Chef range so I would not have to run two pilot lights for the top burners and one for the oven.

Two years ago I replaced the gas water heater with an electric, and assumed the new one would be insulated well enough to not use much electric, I have my laundry done out, and only use hot water for bathing (not often enough).

I have done a lot of sealing on the house, not all to reduce ventilation. I sealed one room on the inside with clear silicone so I would not have to repaint at the time, but I sealed that to reduce pollution caused by my Aunt having casual labor blow insulation in the attic, and this house (any house) should have an expert seal the attic and prepare it properly before installing. This house was especially bad because it wasn't plastered, it had one inch oak run vertically for the interior walls, and that leaves cracks.

I also sealed the two back rooms that were replaced in 1937 after the flood took off the two original added-on rooms, but not to save energy, I did it to keep out the rotten Box Elder bugs that are totally harmless and don't get into food, and only want a warm place to winter (but they look too much like young cockroaches). 5000 in the kitchen was too much for me when they tried to find their way outside in the spring, and the neighbor won't let me cut down the Manitoba Maple (Box Elder).

I have pretty much abandoned the outside and back yard, the environment has become hostile with snakes, stray cats by the dozen, raccoons, opossum, groundhogs, moles, squirrels, huge spiders, carpenter bees, wasps, hornets, mosquitos, sand fleas, and fleas and ticks spread by the cats and the rotten Box Elders.

So a little ventilation is not so bad, as long as it is through the screen door. I don't have a powered ventilator with humidistat, but I have a through-the-wall fan, and being every doorway in the house has a door (no arches), I can either circulate air around four rooms to achieve even cooling or heat and to avoid stale air in a room, or I can open the back door and front door and close the kitchen door, and the fan will draw air in the front door screen and out the back porch screen.

A small fan uses a lot less power than an A/C, and if the house is hot on cool nights, the fan is the thing to use, less noise and fresh air.

Note that Nick inserts smileys :-), he does that because he knows the decimal places are meaningless after the calculation is over. :-)

I have no idea how to proceed if I were to try to approach the dry air at night in winter problem by trying to control ventilation. I can't totally seal the outside doors, that is the only place air can enter if I am forced to run the Cozy stoves. I see unvented stoves and heaters for sale, but I don't want one. All I can do is use as little electric resistance as possible, and have full use of the whole house on milder days. And continue to run the steam humidifier/ vaporizer while I am sleeping only, when the outside temp is below 40.

Joe Fischer

[nicksanspam]

Sure. Tdp (R) = T(R)/(1+T(R)ln(RH%/100)/9621.)

Pilots suspect fog if the dew point is within a few degrees of the air temp.

No...

Airseal your house.

Nick

[wmbjk]

Sure, but he's claiming that he can get a cold by (effectively) weakened defenses alone, as in, without a virus being present to defend against. That's pretty much the same as the old-wives tale about wet hair causing colds.

Wayne

[wmbjk]

No, I don't believe it, and neither would any logical person. Of course if you can deny the well-established cause of the common cold, then I suppose you won't have any trouble denying that you're illogical as well.

Being a widower hardly prevents human contact. All you need to do is put your hands on a grocery buggy for example and you can make contact with a virus.

Wayne

[Derek Broughton]

Building code requires a "balanced ventilation system". What exactly that means is highly dependent on the building inspector you get. _Many_ inspectors take that to mean an HRV.

My friend who builds passive-solar homes has argued this for years. Given that he's a qualified engineer AND architect, he knows what he's talking about, but he still has trouble with some inspectors.

[Joe Fischer]

You have a one-track mind :-)

When you get to be an injun ear, work on the fine points, not the generalities. :-)

If I seal my house ___AIRTIGHT___, leave on vacation when it is 70 F outside with everything turned off, and return after it has been 20 degrees outside for a week, and the indoor temp is 40 degrees F, and RH is 50 percent, how much water would I need to add if I raise the air temp to 70 F and want 50 percent RH.

Joe Fischer

[Joe Fischer]

Maybe you can tell us how many different bacterial and viral diseases go by the name "common cold".

If you premise were correct, if nobody got a cold all summer, then there would be no cold germs around.

I see you claim as requiring that the total reservoir of cold germs are in the nasal passages and airways of humans.

I have to think the germs are more widespread than that, and exist with or without humans.

The link you provided seems to say that colds are the result of the germs overwhelming the immune system, and that it is possible for a person to be exposed and still ward off the bad cold.

Are you claiming that a person gets a cold just because they come in contact with somebody with a cold, and never get a cold otherwise?

Joe Fischer

[nicksanspam]

Good question. And your answer?

And your point?

Nick

[Robert Gammon]

Actually, my local weather posts dew point 24x7

Right now (4:00am ) in Houston TX, using data from a TV station with studios about 3 miles away,

Temp is 81F DewPoint is 75F

Pretty high RH, eh??

[daestrom]

Yes, but you have to 'adjust' the RH from the temperature it is measured at, to the temperature that you want. Dewpoint doesn't need adjusting. A dewpoint above about 55F is 'high humidity' and a dewpoint below 30F is 'low humidity'. Period, all the time, every way you look at it.

No, but I can see how you might think that :-)

Yes, those things do reduce the ventilation. But if you have 'leaky' walls and window casings, a mildly windy day can completely overwhelm those savings. A lot of modern stoves/ovens use electronic ignition to avoid pilots. When you replaced the water heater, did you seal off the flue?

Funny thing about pilot lights though, when the natural gas burns it forms CO2 and H2O. So a small pilot actually puts some moisture into the air. Now, whether that actually raises humidity, or lowers it would depend on the water vapor formed by the burning gas, versus the increase in air-exchange with dryer outside air (and just how dry the outside air is).

Hmmmm.... cracks bad.... nice oak wood walls, good (esthetically pleasing).

As with most things in life, the key is finding the right balance. And what's right for you....

Trade offs. If you could seal the doors better, and maybe a few other obvious air leaks, you might not need the 'Cozy stoves' most days. Depends on how cold it gets, how many sweaters you were, and how much other insulation the house has. But once you have to start them, you need ventilation to avoid CO poisoning.

Good luck.

daestrom

[wmbjk]

Why would I do that? Any web search you do will show that there are hundreds, but that none are called "dry nose" or whatever.

No, that doesn't follow at all. Being exposed to a virus doesn't mean you'll catch a cold. Yet it's both easy to come into contact with a virus, and difficult for the virus to take hold. You can dramatically increase the odds of avoiding affliction by using common sense, such as hand washing before putting your hands near your face after visiting a crowded store full of kiddies for example.

I'm getting that you see the facts however you like.

How would that help rationalize your belief that colds aren't always caused by "germs"?

Of course. And IIRC, if one has already been exposed to a particular virus, then one is unlikely to develop a cold from further exposure to the same virus.

I'm not claiming anything, just telling you the facts. You can't catch a cold without being exposed to a virus.

Wayne

[Rod Speed]

And the evidence for that last is that those who 'live' in isolated environments like lighthouses etc dont ever get colds regardless of what the room humidity is, because there are no viruses around.

Its less clear scientifically whether the room humidity has any effect on the infection rate when there are viruses around. Its unlikely in my opinion and the most likely reason why so many older people dont get colds anymore is likely just because they are immune to the vast bulk of cold seen, just because they have had so much more exposure to them than say kids ever get, just due to the vastly higher number of years of exposure to them and the fact that its been carefully established that there are so many strains extant.