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n W H A T I S H U M I D I T Y ?

Humidity is defined as the amount ofwater vapor in air. Absolute humidityis a measurement of the actual watervapor in a given volume of air, usuallyexpressed in grains of water per cubic

foot or pound of air. Relative humidityis the amount of water vapor in a givenvolume of air compared to the amountof water vapor the same volume of airwill hold at saturation (100% RH) at agiven temperature.

When a volume of air at a known % RHis heated, the % RH decreases as thevolume of air increases. The absolutehumidity or total moisture available in

the air remains the same. In order toincrease the % RH of the air once it hasbeen heated, it will be necessary to addmoisture.

Example: One cubic foot of air at 0Fholds 0.48 grains of water at saturation.

One cubic foot of air at 70F holds 8.10grains of water at saturation. When the0F air is heated to 70F, the absolutehumidity remains at 0.48 grains percubic foot. The relative humidity of the70F air will be 6% RH, (0.48 grainsdivided by 8.10 grains) the amount ofwater in the 70F air relative to theamount it can hold at saturation. SeeFigure #1.

Air-conditioning and heatinginstallations are designed for comfort

conditions. However, in many casesthese systems reduce the humiditybelow the level recommended forpeople to operate at maximumefficiency in a working environment.

Only rarely is an HVAC systemdesigned to maintain the controlledrelative humidity needed in modernoffices and industry. Therefore, it isstrongly recommended to add to the

HVAC installation, a carefully designedhumidification system to keep the areaat the proper RH levels.

n V A P O R B A R R I E R S A N D

I N S U L A T I O N

Water vapor can easily move within aspace as well as infiltrate from outdoorsor exfiltrate through the buildingenvelope due to vapor pressuredifferentials caused by differentabsolute humidity. Under certaintemperature and humidity conditions,condensation problems and possiblestructural damage can occur. Toprevent these problems, NORTECrecommends that proper design criteriabe followed regarding the installation of

vapor barriers and insulation inbuildings.

Design data on vapor barriers andinsulation can be found in the 1997ASHRAE Fundamentals Handbook,Chapters 22, 23, 24 and 39.

n

T H E N E E D F O R

H U M I D I F I C A T I O N

The problems caused by dry air willvary from one building to another and

from one area to another, but basicallythere are three major problems. Theseare:

Static Electricity

Poor Moisture Stability

Health and Comfort

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W H E N Y O U N E E D

H U M I D I T Y

O g d e n s b u r g , N e w Y o r k , U . S . A .

( 3 1 5 ) 4 2 5 - 1 2 5 5

O t t a w a , O n t a r i o , C a n a d a

( 6 1 3 ) 8 2 2 - 0 3 3 5

In recent decades, manufacturers have begun to realize that many processes and

machines operate best at optimum humidity conditions. This thinking is now

being extended to an even more valuable asset: People.

Investigations into Indoor Air Quality (IAQ) show a direct relationship between

the psychological well being of employees and the environment in which they

work. When the indoor relative humidity drops below 40%, the incidence of

absenteeism and respiratory illness increases.

Control Humidity to Increase Productivity

Contracting Business

F i g u r e # 1

A b s o l u t e H u m i d i t y

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S t a t i c E l e c t r i c i t y

Static electricity is a condition causedby stationary charges of electricity andis a major problem in mostunhumidified areas. Since staticelectricity is caused by friction,particularly when the elements infriction are dry, the problem increasesproportionately with the speed ofproduction machinery.

Without sufficient humidification,todays high-speed machinery mightwell defeat its own purpose. Reduce

efficiency is frequently the result ofstatic electricity.

For example, when static electricityoccurs in fibrous items, the properoperation of production machinery canbe disrupted. This applies particularlyto the printing industry where pressesmust self-feed paper evenly, one sheetat a time at very high speeds. When thestatic electricity causes sheets of paperto stick together, the paper bunches, thefeeding becomes uneven, and

eventually the paper jams the presses.

The textile industry is another exampleof a manufacturing process that requirescontrolled humidity to ensure qualityproducts. For example, if staticelectricity causes the yarns to adhere toeach other, the shuttles miss threads andimproper weaving patterns result.

In the modern business offices, staticelectricity can disrupt operations andincrease operating costs. In manyphotocopiers, sheets of paper sticktogether and jam the machine, wastingtime and paper. Severely jammedequipment may even require servicecalls.

Static electricity can also be dangerous.Sparks caused by static are extremelyhazardous where volatile fumes arepresent. Many flash fires - evenexplosions - are caused by staticelectricity.

NORTEC humidifiers are designed to

eliminate these problems.

n W H Y R E L A T I V E

H U M I D I T Y C O N T R O L S

S T A T I C

Dry air may well be the cause of the

static electricity in your plant. If it is,

a properly installed NORTEC

humidification system is sure to help

solve the problems.

One of the easiest and most common

methods of minimizing static electricityis to increase the relative humiditylevel. Electrostatic charges do notdissipate through moist air, but througha moisture film that is absorbed on thecharged surfaces. This moisture filmdecreases the surface resistivity andcauses static charges to be drained.This effect is most pronounced at RHabove 30-35% and it also correspondswith a decrease in ozone production (aby-product of electrostatic discharge).

In computer rooms and data processingareas, the lack of humidity results instatic electricity that causes problemssuch as circuit board failure, dustbuildup on heads, and storage tapebreakage.

Static electricity is a problem thatshould be of primary concern to anymanufacturing plant interested inrunning efficiently and accurately.

For more information:

1996 ASHRAE HVAC Systems andEquipment Handbook

Atlanta: ASHRAE

M o i s t u r e S t a b i l i t y

Moisture stability is the ability of amaterial to maintain a level of moisturecontent despite fluctuations thehumidity of the environment. Many

materials give off, or take on moisturerapidly which can result in serious

damage to the material or the process inwhich it may be involved. The dryingout of a material can result in productdeterioration, while conversely, a drymaterial can also suffer damaging sideeffects of moisture regain.

In many cases, product deterioration isdirectly related to the lack of moisturestability. Products such as vegetable,cut flowers, fruit and many groceryitems cannot be brought back to originalquality once they have lost their

moisture.

By installing an efficient humidificationsystem this costly loss of products canbe avoided. Today many foodprocessors humidify their plant andstorage areas and are able to store fruitsand vegetables for months without anyloss of product quality or weigh.

But deterioration caused by loss ofmoisture is also a problem for treasuressuch as antiques, rare books and the

worlds greatest works of art, all ofwhich are susceptible to damage causedby moisture loss. It causes antiques,paintings, paper and bookbindings tocrack, warp and deteriorate.

Fortunately, most libraries andmuseums are well aware of the need forcontrolled humidity to protect theirpriceless treasures. They know thatproper humidity control is a veryinexpensive, preventive measure thatwill avoid costly and often impossible

restorations.

For any product that requires a certainpercentage of moisture to maintain itsquality, loss of that moisture reduces itsvalve. Some products can be broughtback to their original condition byreturning the moisture to them.However, among those that cannotreabsorb moisture to regain their lostquality are fruit and vegetable products,

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paintings and art objects, what aboutyour product?

A specific moisture content in materialsis essential to the quality of productsproduced by a wide range ofmanufacturers of hygroscopic or fibrousmaterials. Wood, paper and textiles areexamples of materials particularlyaffected by changes in content.

If these materials have a correctmoisture content when they arrive at aplant, and if they are used immediately,they will respond properly to the

manufacturing process. But problemscan be anticipated if the materials arestored in a dry atmosphere.

All hygroscopic or fibrous materialseither lose of gain moisture in directrelation to the relative humidity of thesurrounding air. It is evident that anyproduct that is purchased and sold byweight must have a carefully controlledenvironment.

Paper provides a good example of the

effects of dry air and the lack ofmoisture stability. When it is storedunder dry atmospheric conditions,moisture from the outer layers andedges of the stacks escapes into the air.The moisture loss is obviously muchmore rapid from the outer edges thanfrom the center of the stacks. The resultis not only curled stock, but also unevenmoisture content which creates printingand processing problems.

If moisture stability in the surrounding

atmosphere is the answer to amanufacturing operation, then completehumidification of the plant and storageareas is an absolute necessity.Humidification is the best and leastexpensive way of maintaining moisturestability. If the air surrounding thematerial is maintained at a proper andconstant relative humidity level, so thatno moisture is emitted or absorbed bythe materials, then the products will

remain stable in both moisture contentand dimension.

Ideally, humidification equipmentshould be installed in raw materialstorage areas, manufacturing facilities,and finished goods storage rooms, forfull control of the product moisturecontent.

H e a l t h a n d C o m f o r t

During the heating season, inside airdries to the point where the humidity is

substantially lower or comparable tothat of the Sahara Desert. Dry airextracts moisture wherever it finds it,especially from hygroscopic materialssuch as wood, carpets and furniture.This extraction causes floors to warp,carpets to wear out faster due to brittlefibers, and furniture joints to loosen.

The effect on people is to dry out nasaland throat membranes. For employeesthis means more susceptibility to coldsand virus infections. The subsequentincreased absenteeism proves costly forany employers.

Another aspect of comfort is the factthat humidity in the air makes a room

feel warmer , so there will be fewerrequest to have the thermostat turnedup.

Most employers today provide airconditioning for employee comfort andproductivity during the hot days ofsummer. Adding humidification for fulwinter comfort and productivity is justas important as air conditioning in thesummer months. In fact, it is one of themost important functions of thecomplete air conditioning or total

comfort system.

The advantage of conditioning theinterior space of a building to increaseproductivity and reduce the downtimeof machinery has been documentedmany times. Unfortunately it is usuallyequipment, such as computers andcommunications systems, that is placedin separate climate controlled rooms,while the majority of employees havetemperature control only.

Temperature control must be combinedwith humidity control to maintain

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F i g u r e # 2

O p t i m u m r e l a t i v e h u m i d i t y r a n g e s f o r h e a l t h

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proper comfort parameters in an officeenvironment. More than 75% of all

I.A.Q. problems start with a comfortcomplaint. If this is not rectified, theemployees will continue to complainand become less productive.

Temperature control alone does not takeinto account the physiological aspectsof the employees. As demonstrated infigure 2, indoor RH variations aboveand below the 40-60% range have adramatic effect on the comfort and wellbeing of employees. Humidityconditions above this range are usually

controlled easily by the normaldehumidification process of theair-conditioning system. However, asthe cold, dry weather of winterapproaches or in arid climates, theindoor RH can easily drop well belowthe recommended 40% parameter. It isnot uncommon to find relativehumidities in the 10-15% range in mostoffices during this period. This low RHcreates comfort, productivity, andabsenteeism problems costingimmeasurable dollars to employers

worldwide. Studies conducted by Dr.George Green of the University ofSaskatchewan indicates that increasingthe indoor RH from 20 to 30% willreduce absenteeism by 15%. This,along with the productivity maintenanceor increase that can be gained from theadditional comfort economic benefit ofgeneral office humidification.

It is true that energy must be used tomaintain comfort conditions in anoffice. During warm periods, air

conditioning maintains comfortabletemperature and humidity levels andcosts of dehumidification are absorbedwithin the operating costs of theair-conditioning system. Sincehumidification is an additional processto the normal HVAC operating costs, itis easy to define the economic benefitsof humidification versus operatingexpenditures. The following studyshows these cost advantages.

This example used a metropolitan officewith 250 employees where the indoor

design conditions of 72F and 40% RHwere maintained. The recommendedminimum fresh air requirements of 15CFM per person were followed, asindicated by ASHRAE Standard62-1989. When the outdoor designconditions were 0F, a humidificationload of 103 pounds of water per hourwas required. The amount of time thata humidification system is operationalat full output will depend upon thebuilding construction and operation. Inthis example, 2,000 hours have been

used as the seasonal operating hours ofthe humidifiers.

An electric humidifier will requireapproximately 34 kW, a gas firedhumidifier requires approximately133,000 BTUs, to produce therequired output of 103 pounds ofmoisture per hour. Using a rate of$0.10/kWh for electric units the annualsystem will be $6,800.00. Using a rateof $0.45/Therm for gas fired, the annual

system will be approximately$1,200.00.

Using an average salary of $30,000.00per employee (including insurance,benefits, etc.), the offices annual salarypayments will be $7,500,000.00. evenif productivity losses due to lack ofhumidification (comfort, respiratoryproblems, absenteeism, etc.) are only1%, in this office, which really amountsto productivity losses of only a fewminutes a day, the employer will have aloss of $75,000.00. The $68,200.00savings produced by the humidification

system helps assure comfortable, andmore productive employees.

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A v e r a g e o f f i c e - 2 5 0 e m p l o y e e s

F r e s h a i r i n f i l t r a t i o n - 1 5 C F M / p e r s o n

A v e r a g e s a l a r y a n d b e n e f i t s - $ 3 0 , 0 0 0 . 0 0

Electric Gas Fired

F r e s h a i r - 1 5 C F M / p e r s o n = 225,000 CFH/O/A moisture required 103 lbs/hr

A v e r a g e h u m i d i f i e r r e q u i r e s 3 4 k W t o p r o d u c e t h e

m o i s t u r e

1 3 3 , 0 0 0 B T U s t o

p r o d u c e t h e m o i s t u r e

3 4 k W x 2 , 0 0 0 h r s x

$ 0 . 1 0 / K W H

= $ 6 , 8 0 0 . 0 0 o p e r a t i n g

c o s t

1 3 3 , 0 0 0 B T U x 2 0 0 0 x

$ 0 . 4 5 / B T U 1 0 0 , 0 0 0

$ 1 , 2 0 0 . 0 0 o p e r a t i n g

c o s t

2 5 0 e m p l o y e e s x

$ 3 0 , 0 0 0 . 0 0

= $7,500,000.00 annual salaries

1 % l o s s d u e t o r e s p i r a t o r y

i l l n e s s , a b s e n t e e i s m ,

c o m f o r t p r o d u c t i v i t y

= $75,000.00

C o s t o f o p e r a t i o n = $ 6 , 8 0 0 . 0 0 $ 1 , 2 0 0 . 0 0

F i r s t y e a r s a v i n g s = $ 6 8 , 2 0 0 . 0 0 $ 7 3 , 8 0 0

T a b l e 1

E c o n o m i c B e n e f i t s O f H u m i d i f i c a t i o n F o r I . A . Q . A n d C o m f o r t