AMAZON multi-meters discounts AMAZON oscilloscope discounts We once owned a large colonial home that had a fireplace in the living room. A fan-forced stove insert was installed in the fireplace. In order to keep the herd of household cats—six of them—from running rampant over some valuable antique furniture, we started closing the doors to the room at night. There was no humidifier in the room, and soon it became apparent that the hot, dry air was going to be more deadly than the six sets of back claws (the front ones already having been removed). Being rather lax about the very drying situation, we were not motivated to go buy a humidifier until Carl closed one of the doors one night. It split almost off the hinges! The next day we added some moisture to the room and the rest of the house. Humidity must be rather precise for people and property. If the level is not right, then the toll will be devastating to things and highly uncomfortable to people and animals. Outside, when the humidity is excessive, perspiration informs you that it is definitely too humid. Take a glass of water at room temperature and put it on a table. Take another glass of room-temperature water, drop some ice cubes in it, and you will cause that glass to “leak.” Indeed, a lot of water will soon be on the table around the glass. When people forget to use a coaster for drinks on good furniture, damage occurs! See Fig. 1. Fig. 1. Millions of glasses will ‘leak’ today due to poor ventilation. The crawl space under a house is often a humidity factory even when there is good drainage. Efficient ventilation must prevent what happens too often! When there is groundwater within 18 feet of a crawl space under just a 1,000-square-foot house, as much as 19 gallons—that’s 162 pounds— of water can be released into the air during one day! This is the reason why vapor barriers, ventilators, and other efficiency measures must insure that a house is not resting on a geyser. Foundation vents will literally keep the floor from falling through. VAPOR BARRIERS When outside walls are not insulated and there is no vapor barrier, warm, moist air passes through the walls. No condensation occurs except on the windows, the space inside the walls is warm due to the rapid heat loss from inside. When the outside wall is insulated but has no vapor barrier, or if the vapor barrier is installed on the cold side of the insulation, vapor penetrates the insulation and condenses inside the wall cavity—causing rotting and decay. The condensation also wets the insulation, making it ineffective. Using vapor barriers installed on the warm (the room) side of the insulation makes it possible to build tightly constructed insulated houses without having condensation on the walls, providing there is effective ventilation. Vapor barriers should always be placed on the room side of the insulation. They should be properly installed with joints lapped and securely fastened to studs, joists, or bracing. All tears should be sealed with tape, and openings around light fixtures and plumbing pipes should be sealed. The wrong humidity levels can even cause your carpets to suffer much more wear and damage. Too little humidity can make the nap on rugs become brittle, and that will cause them to wear faster than normal. Not enough moisture in the air will dry out the glue in furniture and loosen the joints as the wood shrinks. Not having enough vapor in the air also does injury to people. Dryness of lips, eyelids, and membranes in the nose throat can occur, and the skin can get dry and flaky. Research Products Corporation of Madison, Wisconsin, manufactures many high-quality energy products. It has an excellent line of Aprilaire humidifiers. The firm also has one of the most informative pieces of literature on water vapor. The following pages are quoted from The Story of Humidity. STORY OF HUMIDITY Humidification is, unfortunately, one of the least understood, most important aspects of comfort conditioning. It is understandable that it is misunderstood. Humidity is an intangible; you can’t see it, you can’t touch it, it has no odor, no color, no sound. The Story of Humidity covers, in detail, theory and definitions relating to humidity; the benefits of humidity; psychrometrics and the psychometric chart; sizing, what to look for in humidifiers, and how to select a good humidifier. To make sure we are all starting out on common ground, let’s define some of the words that we are going to run across in the discussion of humidity and humidification, WHAT IS HUMIDITY? Humidity is the water vapor within a given space. Absolute humidity is the weight of vapor per unit volume. Percentage humid4y is the ratio of the weight of water vapor per pound of dry air to the weight of water vapor per pound of dry air saturated at the same temperature. Relative Humidity by definition is the ratio of the mol fraction of water vapor present in the air, to the mol fraction of water vapor present in saturated air at the same temperature and barometric pressure. Approximately, it equals the ratio of the partial pressure or density of the water vapor in the air, to the saturation pressure or density, respectively, of water vapor at the same temperature. Although there is a difference between percentage humidity and relative humidity, it is only very slight and is practically negligible at normal room temperatures. So, for our purposes, we can say that relative humidity indicates the amount of water vapor, in percent, actually in the air compared to the maximum amount that the air could hold under the same conditions. The warmer the air, the more moisture it can hold. Air in a home heated to 700 can hold about 8 grains of moisture per cubic foot. That’s 100% relative humidity. If there are only 2 grains per cubic foot in the home, this is 1/4 of the air’s capacity to hold moisture. Therefore, the relative humidity is also 1/4 or 25%. The air could hold 4 times as much water. But, the important thing is what happens to air when it’s heated. The outdoor-indoor relative humidity conversion chart illustrates this. See Table 1. And this phenomenon -- this capability of warm air to hold more water than cold air -- this substantial reduction of relative humidity is taking place in every unhumidified or under-humidified home where winter heating is prevalent. To solve it, we add moisture, artificially -- so there’s more water available for that thirsty air -- so it can exercise its ability to hold more water. WE HUMIDIFY. We humidify because there are benefits that are as important as heating to over-all indoor comfort and well-being during the heating season. and these benefits are actually what you have to sell. These benefits can be grouped into three general classifications: 1. Comfort 2. Preservation 3. Well being Table 1. Outdoor-Indoor Relative Humidity Conversion Chart. OUTDOOR TEMPERATURE vs. RELATIVE HUMIDITY EXAMPLE: (See circled figures). Outdoor relative humidity, 70%; outdoor temperature Locate outdoor relative humidity at left of chart and outdoor temperature at bottom, and the indoor relative humidity is where the vertical and horizontal columns meet, this calculation assuming that outdoor air is brought into the home and heated to 70 degrees. BENEFIT NO. 1... COMFORT Did you ever step Out of your shower in the morning, start shaving, and notice how warm it is in the bathroom? It’s actually muggy. It’s probably about 75° in there, and the relative humidity is probably about 70-80% -- because of the water vapor being added to the air while showering. Now, if the phone rings and you have to step out into the hall to answer it what happens? You freeze. Yet the temperature there is probably about 70°. Just 5° cooler than in the bathroom … and you’re shivering. Why? Because you just became an evaporative cooler. The air out in the hall is dry the relative humidity is possibly about 10-15%. You’re wet … and this thirsty air goes to work on your skin. It evaporates the water, and as it does, your skin is cooled. and this same type of thing goes on day after day, every winter, in millions of homes. People are turning their thermostats up to 75° and more in order to feel warm and even then, it feels drafty and chilly -- because the evaporate cooling process is going on. Proper relative humidity levels make you feel more comfortable at lower thermostat settings. But -- this cold effect is not the only discomfort caused by too-dry air. Static electricity is usually an indication of low relative humidity levels and a condition that’s consistently annoying. PROPER relative humidity will reduce this discomfort. BENEFIT NO. 2… PRESERVATION The addition or reduction of moisture drastically affects the qualities -- the dimensions -- the weight of hygroscopic materials. Wood, leather, paper, cloth, although they feel dry to the touch, contain water. Not a fixed amount of water, but an amount that will vary greatly with the relative humidity level of the surrounding air. Take for example a cubic foot of wood with a bone-dry weight of 30 lbs. At 60% relative humidity, the wood will hold over 3 pints of water. Now -- if the relative humidity is lowered to 10%, the water held by the wood will not fill even one pint bottle. So we have, in effect, withdrawn 2 1/2 pints of water from the wood by lowering the relative humidity from 60% to 10% (1 pint = approx. 1 lb.). And, this type of action goes on, not only with wood, but with every single material in the home that has the capability of absorbing and releasing moisture. Paper, plaster, fibers, leather, glue, hair, skin -- practically everything in the home. These materials all shrink as they lose water -- all swell as they take on water. If the water loss is rapid -- warping and cracking take place. and as the relative humidity changes, the condition and dimensions of the materials change -- as constantly as the weather. This is why humidity must be added. This is why relative humidity must be controlled. This is why PROPER relative humidity is important. Now -- what are the effects of this constantly changing or constantly low moisture content of the air?
So, we’ve discussed the problems of too little humidity; let’s also talk about the problem of too much humidity and the effect of vapor pressure. You have all seen windows fog during the winter. Maybe a little fog on the lower corners. Or maybe a whole window fogging or completely frosting over. This latter condition is an indication of too high indoor relative humidity. This condensation formation is due to the effect of vapor pressure. Dalton’s law explains vapor pressure. It states, “In a gaseous mixture, the molecules of each gas are evenly dispersed throughout the entire volume of the mixture.” Taking the house as the volume involved, water vapor molecules move throughout the entire home. Because of the tendency of these molecules to disperse evenly -- or to mix -- the moisture in the humidified area moves toward drier air. In other words, in a house the moist indoor air attempts to reach the drier outside air. It moves toward the windows -- where there is a lower temperature and therefore, an increase in Relative Humidity -- to a point at which the water vapor will condense out on the cold surface of the window. This is the Dew Point and it occurs at various temperatures, depending upon the types of windows in the home. The following chart (Table 2) illustrates it. An indoor temperature of 70° F is given. At 20° outdoor temperature, for example, condensation begins on a single glass pane at about 24%R.H. At 38% for a single pane with a loose storm. At 50% for a Thermopane with 1/2” space. At 58% for a single pane with a tight storm. Table 2 Usually condensation on inside windows is a type of measurement of the allowable relative humidity inside a home. and we can further assume that if this condensation activity is taking place on windows, it may also be taking place within the walls if there is no vapor barrier. A vapor barrier, as the name implies, is a material that restricts the movement of water vapor molecules. Examples of a typical vapor barrier are aluminum foil, polyethylene film, plastic wall coverings, plastic tiles, and some types of paint and varnish. Actually, practically every home has a vapor barrier of some type of which at least retards the movement of the water molecules from a high vapor pressure area (inside) to a low vapor pressure area (outside). Fig. 2 shows a cutaway of a typical outside frame wall construction. The typical outside wall has drywall, or plaster -- a vapor barrier (on the warm side of the insulation) -- the insulation air space -- sheathing -- building paper -- siding. Now given an indoor temperature of 70° and Relative Humidity of 35% -- and given an outside temperature of 0° -- what happens to the temperature of the air passing through the wall? It drops to about 63° at the vapor barrier, down to 170 at the sheathing and on to 0° outside. and , if we checked a psychometric chart, we’d discover that 70° indoor air at 35% R.H. has a dew point of 41°. and where does that temperature occur in our wall? Right in the middle of the insulation. This is where we have condensation, and this is where we have trouble -- or would have trouble without a vapor barrier -- and without a humidifier that we can control. The important aspect is then -- properly controlled relative humidity -- to avoid the damaging effects of too dry air -- and equally as important -- to avoid the damaging effects of too high relative humidity. Fig. 2. Vapor barriers are very important. BENEFIT NO. 3. WELL BEING What do doctors say about humidity? Dr. John Adams, eye, nose and throat specialist, says in the Annals of Otology, Rhinology and Larynogology: “In the struggle between the nose and the machinery in the basement, sometimes the heater wins and sometimes the cooler, but seldom the nose. The nasal mucus contains some 96% water. To begin with, it is more viscous than mucus elsewhere in the body and even slight drying increases the viscosity enough to interfere with the work of the cilia. Demands on the nasal glands are great under usual conditions and they can't cope with extreme dryness indoors in winter. “Experience has shown that with approaching winter, the first wave of dry-nose patients appears in the office when the relative humidity indoors falls to 25%. It would seem, therefore, that 35% would be regarded as a passing grade but 40% something to shoot at. It boils down to this, a pint of water is a lot of water for a small nose to turn out. In disease or old age, it simply doesn’t deliver and drainage stops and the germs take over.” This is Dr. Joseph Luther, an expert on the common cold talking. He says, in the New York State Journal of Medicine: “Prevention of the common cold at present is our nearest approach to a cure. The most important prevention measure would appear to be proper regulation of the humidity especially during the heating season with its distressing drying of the indoor air and the creation of an environment favorable to the cold bug.” The right-hand column on the following chart (Table 3) is the number of cases of respiratory disease per 1000 population, taken from the U.S. Public Health statistics. The left-hand column is a typical indoor relative humidity in Madison, Wisconsin during these same months. Proper relative humidity is helpful for relieving problems aggravated by too dry air. Those are the three major benefits of proper relative humidity: Comfort, Preservation, Well Being. Table 3. Relative humidity and Health. WHAT INDOOR RELATIVE HUMIDITY IS CORRECT? While some humidity conditions may be ideal for comfort, they are, in many cases, less ideal for other reasons. An indoor relative humidity of 60% may fulfill all the requirements for comfort, but it can result in damage to walls, to furnishings, etc. The fogging of windows is usually an indication of too high relative humidity, and it must be remembered that this same condensation is taking place inside walls and other places vulnerable to damage by excessive moisture. It is therefore, necessary to set safe limits of indoor relative humidity levels to receive the maximum benefits from correct humidity, without making the structure itself susceptible to damage. It is recommended that the temperature-humidity be followed to insure these benefits. See Table 4 and Table 5. Table 4. Temperature-Humidity. Table 5. Temperature-Humidity. EFFECT OF WATER CHARACTERISTICS Fundamentally, only distilled water, or rainwater caught before it reaches the ground, is free from minerals. Water from wells, lakes, and rivers all contain varying amounts of minerals in solution. These minerals are picked up as water moves through or across water- soluble portions of the earth’s surface. In many cases, the level of these minerals is sufficiently high to make water-conditioning equipment necessary to remove the objectionable minerals for normal domestic use. It is common knowledge that water evaporated from a tea kettle leaves a residue known as lime. Since evaporation of water is the only way to create and distribute water vapor into the air present in homes, it is apparent that mineral residue resulting from evaporation presents a problem. Water hardness varies in different localities. Drinking water contains some hardness—consisting primarily of calcium carbonate and /or magnesium carbonate. This hardness is expressed in grains per gallon: See Table 6. Tal 6. Grains per Gallon. If a gallon of water of average hardness is evaporated, a residue of 25 grains remains. If 100 gallons of water are evaporated to provide humidity, 2500 grains or 5.7 ounces of solids will build up on the evaporating surface. HUMIDIFICATION and HUMIDIFIERS In the “good old days,” most of the home was closed off for the winter. The family congregated and lived in the sitting room; and the kitchen. These were the most comfortable rooms in the home. The old wood stove generated plenty of heat. and the way grandmother used to cook added a great deal of moisture to the air. Pots or kettles usually steamed or bubbled on the stove. Clothes dried nearby. Well-watered house plants decked the window sills. The stews and the soups and the tea kettle acted as humidifiers. The air was moist. Some of the time. In one or two rooms. The only control was how much cooking you did. How much washing you did. How many house plants you had. You couldn’t call it high-capacity humidification; you couldn’t call it controlled humidification; you couldn’t call it humidifications. We progressed to the gravity furnace. It was hand-fired. A register was cut into the floor in the parlor, maybe in the living room. We lived in three or four rooms during winter now. The furnace had a small reservoir for water. The furnace heat evaporated it. You filled it every week, if you remembered. and it took 2 quarts of water. Two quarts of water evaporated a week. The only benefit of this type of humidification was the self-satisfaction in thinking that we were doing something about too dry air. Then, the forced air furnace -- an improvement that initiated a varied assortment of humidifiers -- with varied degrees of success. There are many, many humidifiers available -- and they vary in price; they vary in capacity; they vary in principle of operation. For classification purposes, it is simpler, and more logical, to consider humidifiers in three general types: 1. Pan-Type Units 2. Atomizing-Type Units 3. Wetted Element-Type Units The pan-type unit is the simplest type of humidifier. Capacity is low. On a hot radiator, it might evaporate .0083 gallons of water per hour. In the warm air plenum of a furnace, it would evaporate approximately 0.18 gallons of water per hour. To increase capacity, the air-to-water surfaces can be increased by placing water wicking plates in the pan. Capacity goes up as the air temperature in the furnace plenum increases. Greater capacity is also possible through the use of a steam, hot water or electric heating element immersed in the water. A 1200-watt heating element, for example, in a container with water supplied by a float valve could produce .48 gallons of moisture. The second type of humidifier is the atomizer. This device atomizes the water by throwing it from the surface of a rapidly revolving disc. It is generally a portable or console unit -- although it can be installed so the water particles will be directed into a ducted central system. The third type of humidifier is the wetted element type. In its simplest form, it operates in the manner of an evaporative cooler. Here air is either pushed or pulled through a wetted pad material or filter and evaporative cooling takes place. By increasing the air flow or by supplying additional heat, the evaporation rate of the humidifier can be increased. The heat source for evaporation can be from an increase in water temperature or an increase in air temperature. The air for evaporation can be taken from the heated air of the furnace plenum and directed through the humidifier by the humidifier fan -- or it can be drawn through the wetted element by the air pressure differential of the furnace blower system. Furnace-mounted humidifiers, usually of the wetted element type, can be constructed so they produce 0.5 or more gallons of moisture per hour. Because of their high capacity, this type usually has a humidistat or control which will actuate a relay or water valve and start a fan that operates until the control is satisfied. Normally more water is supplied to the unit than is evaporated, and this flushing action washes a large portion of the hardness salts from the evaporative element to a floor drain to eliminate them from the humidifying system. See Figs. 3, 4, and 5. Fig. 3. An atomizing humidifier. SIZING Sizing for humidification is similar to sizing for heating and cooling. The humidifier capacity required will be determined by various factors such as (1) the volume of the air being humidified, (2) the air change rate (infiltration or ventilation), (3) the inside and outside design conditions, and (4) other sources of humidity. 1. The Volume of the Home Being Humidified: The volume can be determined from a floor plan or from measurements taken within the home. If the basement is heated and ventilated, its volume should be included. 2. Air Change Rate: The amount of infiltration was probably calculated when computing the heating and cooling load. The following method also may be used. An average house will normally have about 1 air change per hour. A tight house may have as low as 1/2 air change per hour and a loose house may have as high as 2 air changes per hour. For purposes of definition an average house is assumed to have insulation in the walls and ceilings, vapor barriers, loose storm doors and windows, and may or may not have a fireplace. If it has a fireplace, however, it will be dampered. The tight house will be well insulated, have vapor barriers, tight storm doors and windows with weatherstripping, and its fireplace will be dampered. The loose house will probably be one constructed before 1930, have little or no insulation, no storm doors or windows, no weatherstripping, no vapor barriers, and quite often will have a fireplace without an effective damper. 3. Design Conditions: The principal factors involved are (1) the desired indoor temperature and relative humidity and (2) the prevailing outdoor temperature and relative humidity. Comfort is usually the prime requirement in residential humidification. The human body is comfortable within a broad range of relative humidity. Humidities of 35 % or more are desirable from a health standpoint. However, in the winter these high humidities can present a condensation problem. Table 7 is a compromise between the humidities preferable from a health standpoint and the humidities desirable from a construction standpoint. Because of the condensation problem, the humidity maintained with a home should be lowered as the outdoor temperature drops. However, if the house is designed to withstand higher humidities or if for medical reasons a higher humidity must be maintained, then higher values can be used. Fig. 4. Wetted element humidifiers are combined with heat source. Fig. 5. Pan-type humidifiers constitute the third way of putting moisture in the air. Table 7. Temperature-Humidity. CALCULATIONS When calculating the amount of humidity required, the following formula can be used: H = V R (Wi – Wo) / 13.5 x 8.3 V = Volume to be humidified, cubic feet. R = number of changes of air per hour. W = pounds of moisture per pound of dry air at desired indoor conditions (from psychrometric chart). W = pounds of moisture per pound of dry air at outdoor conditions (from psychrometric chart). The value of 13.5 cubic feet of air per pound of air is an average that is suitable for calculations where extreme accuracy is not required. The value of 8.3 is the number of pounds of moisture in a gallon. SELECTING A GOOD HUMIDIFIER There are many types of humidifiers -- and many models of each type. There are probably about 100 different brands available. How, then do you select the best humidifier? You look at them from 5 angles -- and you compare them from these same 5 angles. 1. Capacity 2. Control 3. Operational Efficiency 4. Ease of Maintenance 5. Ease of Installation CAPACITY. The average size home requires about 9 gallons of water per day. If the humidifier can’t evaporate this much water -- forget it. It’s undersized for most installations. CONTROL. This really goes hand in hand with capacity because, if the capacity isn’t there, you just can’t reach the relative humidity levels required. But, control is as important in keeping relative humidity levels low enough as it is in keeping them high enough. So, you must have both -- the capacity to reach the proper relative humidity level -- and the control to maintain it. OPERATION EFFICIENCY. A good humidifier operates so that working parts are not affected by the build-up of mineral deposits. A good humidifier adds humidity in vapor form -- so no “white dust” -- no water droplets are distributed. A good humidifier maintains the relative humidity at the recommended levels -- every hour of every day. A good humidifier is so designed from an operational standpoint and from a structural standpoint that unnecessary, expensive, time-consuming callback and complaints are virtually eliminated. EASE OF MAINTENANCE. A good humidifier is so designed that preventive and periodic maintenance is easily and readily accomplished. EASE OF INSTALLATION. The installation of a good humidifier is uncomplicated, accomplished in a time period that makes it profitable. TEMPERATURE and HUMIDITY MEASUREMENTS Arguments over how hot, cold, or humid it is at home or work can be accurately settled with the Dickson Temperature/Humidity Recorder. It’s almost $400 price restricts it primarily to businesses, and virtually every type of business needs one! The Dickson Company instrument measures and permanently records temperature and humidity variations from 0 degrees to 100 degrees Fahrenheit and from 0 percent to 100 percent relative humidity over a seven-day or 24-hour period. A pen inside the device records the readings on a 4-inch circular chart. The quartz movement is accurate to plus or minus 3 percent of full scale. It operates on a small alkaline battery. This temperature and humidity recorder is a necessity to determine the proper temperature and humidity for employees. The more comfortable the workers the more efficient and productive they are. This unit is essential to the mental and physical well being of the workers. Executive offices also need to be at precise temperature and humidity levels at all times. Management must be as comfortable as its employees. The instrument will pay for itself maybe on the first day it is used. In order to obtain the most accurate energy readings, the unit is a necessity. Even the furniture in a building needs protection against too much or too little humidity. Humidity does indeed affect humans as well as things. and a great number of businesses have one or more antiques around that demand the right environmental conditions. A Dickson recorder is essential for those highly sensitive areas of a business. Data processing and word processing equipment need proper temperature and humidity settings. A $400 recorder to ensure the protection of computers and related equipment is a most modest investment. Cartridge pens and 100 charts come with the unit. This device documents the energy readings for maximum efficiency. Prev.: Ventilation
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