Ideal Relative Humidity


Controlling the environment can be crucial for a lot of different reasons from your own comfort to maintaining health and preventing the destruction of artifacts. What is Ideal Relative Humidity?

Ideal Relative Humidity is a ratio of Absolute Humidity dependent on Temperature in a range of 45-55% which is a key factor to Control Chemical & Organic Decay in Indoor & Outdoor areas. According to EPA, indoor humidity levels should be kept below 60% relative humidity & ideally between 30 & 50%.

Too Much or too little Relative Humidity has a bearing on many things but can be adjusted and maintained in a controlled setting for a variety of different reasons.

 

What is Relative Humidity and How is it Measured

Absolute humidity simply measures the level of water vapor in the air, while Relative humidity measures the ratio of the absolute humidity level to the highest possible absolute humidity level for the current temperature. Warmer air is able to hold more water vapor than cooler air.

When you’re talking about humidity, you have to distinguish between Relative Humidity or (RH) and absolute humidity. Air can absorb different amounts of humidity at different temperature values. In general, the higher the temperature, the more humidity the air can absorb.

In addition, there is a certain point at each temperature at which it is no longer possible for air to absorb any more humidity. This point is known as the Saturation point or Dew Point. Condensation begins to form at this point. In contrast to relative humidity, absolute humidity describes the precise amount of humidity contained in the air, specified in grams of water per kilogram of air.

If the air is at 100 % Relative Humidity then the sweat will not evaporate into the air which is what happens when we sweat in order to cool ourselves off. This will make it feel hotter than it actually is. This is why hot humid weather is dangerous to people involved with any kind of activity or sport.

If the Relative Humidity is low then it will feel much more comfortable and cooler no matter what the temperature is. Relative Humidity can be measured with a Hygrometer like this instrument. They can be very useful for detecting for the protection of humidity.

Hygrometer you can purchase through MyWaterEarth& Sky and Amazon

Inside a building when the Relative Humidity is high or on the wet side, it can have an adverse effect on the lumber, sheetrock, and other materials in the room being attacked by molds.

If Relative Humidity is too low or on the dry side, there are other adverse effects that can happen to your health and the health of physical things like wooden floors, Art pieces, or your Guitars.

If you shop for Acoustic Guitars you’ll notice that expensive Guitars, especially wooden Acoustics are kept in Climate/Humidity controlled rooms. Humidity is a key element in keeping wood from drying and cracking or warping from excess water vapor in the air. 

Relative humidity tells us how much water vapor is in the air, compared to how much it could hold at a given temperature. It is given as a percent. For example, the relative humidity of 50 percent means the air is holding one half of the water vapor it can hold.

 

What is Dew Point In Simple Terms

The Dew Point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%.

At this point, the air cannot hold any more water in the gas form. If the air were to be cooled, even more, water vapor would have to come out of the atmosphere in a liquid form, usually as fog or precipitation.

The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how “comfortable” it will feel outside.

Many times, relative humidity can be misleading. For example, a temperature of 30 and a dew point of 30 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 produces a relative humidity of 50%.

It would feel much more “humid” on the 80-degree day with 50% relative humidity than on the 30-degree day with 100% relative humidity. This is because of the higher dew point.

So if you want a real judge of just how “dry” or “humid” it will feel outside, look at the dew point instead of the RH. The higher the dew point, the muggier it will feel.

If The Temperature(T) is 70 & the Relative Humidity(RH) is 70 then the Dew Point(DP) would be 60

If The temperature is(T) 60 & the Relative Humidity is 70 then the Dew Point is lowered to 50.

Use this calculator to explore the  At a constant dew point, when the temperature goes up, the RH goes down and when the temperature goes down, the RH goes up. Controlling the dew point is key to managing the risk of material decay. What’s your dew point? If you know the Temperature & Relative Humidity in your space you can use the DP Calculator to get the DP.

If your building does not have humidification or dehumidification, the Indoor Dew Point works the same as the Outdoor Dew Point.

 

Decay Rate Equation

 

If your building has no Humidifier or Dehumidifier in it then the Dew Point is the same inside and outside. 

  • High temperatures (generally above 75°F/24°C) increase the rate of chemical reactions, which determines how fast or slow organic materials will decay or “naturally age”.
  • Cool temperatures slow the rate of chemical decay. Lowering the Temperature can improve preservation IF you also maintain an appropriate Relative Humidity (determined by the dew point).
  • At higher temperatures biological activity (insects, mold growth) increases.
  • High Relative Humidity (generally over 65%) can result in mold, metal corrosion, and mechanical damage.
  • Low Relative Humidity (generally below 35%) can result in mechanical damage.
  • Wide and frequent Relative Humidity fluctuations influence the rate of mechanical decay.
  • The Dew Point determines which Temperature will give you which Relative Humidity.

Cigar Humidor with Hygrometer                Guitar Humidor with Hygrometer                    Weather Hygrometer

Understanding the interaction of Temperature, Relative Humidity, and Dew Point can help you plan, evaluate, and manage storage environments with respect to preservation benefits, decay risks, or the realities and capabilities of your mechanical system.

Depending on what you are storing or what kind of equipment needs to be in a controlled environment depends on the amount of moisture is needed for the best possible environment.

You Storage Facility Business–  are using Mechanical dehumidifiers, also known as refrigerative dehumidifiers, to keep your stored items protected temperature and humidity. They are using a Relative Humidity of 55% as a standard around the country as a general rule of thumb. 

Because of this, tenants can store valuables that were not being stored before. Art, Delicate Fabrics and Upholstered Furniture. Magazines and Photographs can turn yellow.

They favor a 55% Relative Humidity. Computers, Cameras, and Electronics a little higher at 55-60% RH. Optical Disc like CDs and DVDs prefer 45-60%.

There are Climate Controlled Storage Facilities that advertise High-Quality HVAC systems, heating ventilation & air conditioning systems with humidifiers and dehumidifiers, customizable thermostats and heavy-duty insulation to manage temperature and humidity.

Air conditioner systems can change humidity levels fast by dropping the temperature. This is not such a good thing because of the temperatures fluctuating. Dehumidifiers are better at controlling temperatures at stable longer intervals without the drops at peaks that big airconditioners can 

Military Industry- Humidity is a crucial element in the long term storage of Military equipment of thousands of dehumidifiers protect expensive military equipment in all parts of the world, cutting maintenance costs drastically, and increasing the combat readiness of aircraft, tanks, ships, and supplies.

Modern light equipment like computers, telecommunications gear, lightweight composite materials, and high-energy batteries. While these are less subject to gross rusting, they are very sensitive to microscopic-level corrosion.

These circuits simply do not have much material, to begin with, so small amounts of corrosion create disproportionately large problems. Desiccant systems save owners literally hundreds of millions of dollars each year by preventing both gross and microscopic corrosion.

Water and Power Plant Industry Technical equipment that are intricate and exact devices and controls that are needed to be house and operated in a controlled atmosphere that is dependent on the relative humidity of the area.

Chemical and Pharmaceutical Industry –Many chemicals and chemical processes are sensitive to moisture. For example, production of plastics generally requires a low relative humidity for the plastic to maintain its proper quality. The humidity level is very important in pharmaceutical industries.

Wrong humidity in the production of pharmaceutical products can lead to degradation of active ingredients or that the end product does not fulfill the required quality. Drying of temperature sensitive products is also something that greatly benefits from dehumidification. As a general rule of thumb The Relative Humidity is 45-55%

Art & Museum Industry RH measures the amount of water vapor in the air according to temperature. When a volume of warm air is cooled the Relative Humidity goes up. When the volume of cool water is warmed the RH goes down. In the Art world for collections the recommended RH of 50% +/- .5 % and a temperature of 20 degrees C +/- 2 degrees. Artifacts like books, paper documents, and wooden sculptures are all vulnerable to Relative Humidity.

 

Musical Instrument Industry Taylor Guitars are manufactured in controlled Relative Humidity at their production localities. Taylor factory is a 46% Relative Humidity 24 hrs. a day 7 days a week. They feel this kind of control of each part of the process makes for a better guitar.

Absolute hydration for the lifetime duration is part of the upkeep for their wooden guitars. They recommend a Digital Hygrometer and say Hygrometers with needles aren’t as exact as Digital ones. Where ever you store your guitar,  Taylor recommends 45-55 % RH but 40-60% RH will do. They recommend the hygrometer stays in your Guitar case for a better more exact reading.

Martin also uses the 45-55% Relative Humidity range. In fact, any good guitar will offer that range. I have been playing for years and use a Taylor with an Oasis OH1 Guitar Humidifier with OH-2 Digital Hygrometer. It’s a great Humidifier system

Humidistats

A humidistat is an electronic device analogous to a thermostat but which response to relative humidity, not temperature. Humidistats are used in a number of devices including dehumidifiers, humidifiers, and microwave ovens. In humidifiers and dehumidifiers, the humidistat is used where constant relative humidity conditions need to be maintained such as a refrigerator, greenhouse, or climate-controlled warehouse.

Hygrometer

A hygrometer is an instrument that’s used to measure the level of moisture that’s in a room. Its sole function is to give the user either a digital or manual read-out.
You can either buy a hygrometer as a small unit that operates off of batteries, or a unit that can be placed on a shelf in order to get a quick readout. Hygrometers are sometimes put in the same group as other air measurement devices, like thermometers.
Sometimes hygrometers are built directly into humidifiers, dehumidifiers or air scrubbers.
One thing to take note of, in this case, is that unless the hygrometer is combined with a humidistat, it won’t control the level of humidity in the room.

What is Considered Comfortable Humidity

Relative Humidity is considered most comfortable at 45-55%. Humidity levels measure the amount of water vapor in the air around us. The amount is different from the location you are around the globe. While most people feel that temperature has more to do about feeling comfortable, high, and low levels of Relative Humidity can significantly change how comfortable we feel.

How much or little we can tolerate the weather that day. Most people know that high temperatures mixed with high Relative Humidity can be dangerous to older folks and young children. That extra humidity prevents your skin from cooling down by the process of sweating. Humans need to sweat to prevent overheating.  You can control the environment of your home by using a Dehumidifiers for Basements & Large Rooms with Fan Wheels and a Continuous Drain Hose Outlet to Remove Odor can help your home become bearable this summer and protect it from the effects of high humidity. The air in your house has a high Relative Humidity level, there is more chance of wood floors, paneling or surfaces shrinking and warping and fungi growing in the house’s structure.

Similar to that not enough humidity can make the temperatures feel cooler than they are. Low Relative Humidity can also have some adverse health effects. Cold Winter air can significantly hold less water vapor than warm summer air. This causes the air in Winter to feel dry. The combination of cold air and colder temperatures can have an effect on respiratory problems, Dehydration, Skin Problems, and a higher likeliness to contract colds and other illnesses.

There are MyWaterEarth&Sky recommended Humidifiers that double as air purification systems also found here through Amazon like the Evaporative air Cooler – 43 Inch with air Humidifying & Fan Function, 3 Speed Levels with Oscillation, 5 Litre Water Tank – White

Your home environment is also susceptible to the effects of low humidity. If during the colder winter months, the interior of your home has a humidity level lower than 45 to 55 percent, If during the winter months the air in your house has low Relative Humidity level there adverse effects that can happen to furniture too.

In order to keep your home at a comfortable humidity level year round, use a humidifier in the winter time, when the humidity level is low. Living house plants can also help raise the humidity of a home, as can placing containers of water near your heat ducts. If the relative humidity level of your home is high in the summer months, consider using a humidifier, an air conditioning system, or exhaust fans to bring the humidity levels back into the 45 to 55 percent range.

 

How Do Home Dehumidifiers Work

 

A Dehumidifier works a lot like an air conditioner. There is a fan that pulls in air from the room. The air blows across the evaporator coils, which are cold. That causes the water in the air to condense on the cold coils. It’s just like water will condense on the sides of a cold glass of iced tea on a hot summer afternoon.
Then the water that has condensed on the coils drips into a collection bucket. Most dehumidifiers have sensors that alert you when the bucket is nearly full. Then you must remove the bucket, empty it and replace it. Most dehumidifiers will shut off automatically if the bucket gets full to prevent it from overflowing.

No matter what type of size all Humidifiers works the same way. Humidifiers function by forcing moisture into your indoor air. An Evaporative Humidifier uses an Internal fan that is used to pull air into the Humidifier and blow the air across a saturated wick. Another type is called a Vaporizer Humidifier that steams the water then releases it. An Ultrasonic Humidifier can either be a humidifier with a cool or warm mist. It is outfitted with a modern high-frequency technology that provides vibration to the water. Now when the water accompanies with the vibration, there will be no such work that can be expected from its weight and mass. This leads to a breakdown of water into small droplets and these droplets will become the vapor that does the humidifying job.

What is a Good Indoor Humidity Level

 

A recent study carried out by the US National Institute for Occupational Safety & Health (NIOSH) has shown that the airborne transmission of the influenza virus is significantly reduced by maintaining an atmosphere of 40% relative humidity (RH) and above.

High humidity in homes can lead to other problems besides physical damage to the room it’s happening in. It can cause health problems like asthma, sore throat and watery eyes that you may think is a cold. It can cause absenteeism from work and school. Humans are very sensitive to humidity because their skin relies on air to get rid of moisture.

High humidity also has other, more serious side effects, from causing sleeping problems to turning on the open sign welcoming various molds, harmful bacteria, and dust mites. Molds are not just an eyesore. Molds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present. There are molds that can grow on wood, paper, carpet, and foods.

Low humidity can absorb moisture from the uppermost layers of our skin causing it to dry out. The results are from mild roughness to flaking or even cracking of the skin. Irritated dry skin can become itchy, which in turn can lead to injury or bleeding through continuous destructive scratching.

Low Humidity drying of the skin typically occurs in winter months, when indoor humidity drops. As cold outside air, with low moisture content, enters buildings and is heated, its relative humidity falls below 40%RH. Desiccated and cracked skin loses its protective, physical barrier function. Microbes, allergens and harmful chemicals can penetrate the cracks, triggering infections, allergic and toxic skin diseases.

Maintaining an indoor humidity level of between 40-60% Relative Humidity has been scientifically proven to combat airborne flu infections. This ideal humidity level shortens the time airborne flu remains infectious.

Low Relative Humidity during the winter months, heating systems dry the air, indoor humidity often drops into the dry danger zone of less than 40% RH. This results in more flu and respiratory infections spreading in the indoor air we all share. Using humidifiers to put moisture into an atmosphere is the only way to ensure the ideal indoor humidity is maintained throughout the winter.

Scientific research has been done on numerous test that proves controlling Relative Humidity can combat and reduce these airborne infections by reducing the number of microbes in the air and inhibiting their infectious capabilities 

The next time someone says to you that “it’s not the heat it’s the humidity” They’re right. The Relative Humidity can make a hot day an unbearable day.

Jim has worked in Water/Wastewater/Industrial Treatment as a Operating-Consultant and in Water Filtration Business for more than 30 years. He has written more than 300 articles on the Worldwide Water Situation

JimGalloway

Author/Editor, MyWaterEarth&Sky

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