Causes of Low Humidity in a House & How to Increase It

Low humidity levels in a house can lead to discomfort and potential health issues. Several factors can cause low humidity, and there are various methods to increase it. Here’s a summary of the causes of low humidity and how to raise it:

Causes of Low Humidity

  • Seasonal Variations: Low humidity is common during winter when cold outdoor air has lower moisture content and indoor heating systems further dry the air.
  • Climate: Regions with naturally low humidity levels, such as arid deserts, may experience chronically low indoor humidity.
  • Poor Sealing: Poorly sealed windows and doors can allow dry outdoor air to enter and displace indoor moisture.
  • Heating Systems: Forced-air heating systems can dry the air as they circulate warm air throughout the house.
  • Ventilation: Frequent use of exhaust fans, especially in bathrooms and kitchens, can remove moisture from the indoor air.
  • Humidifier Issues: A malfunctioning or improperly maintained humidifier can fail to add moisture to the air effectively.

How to Increase Humidity

  • Use a Humidifier: The most direct way to increase humidity is to use a humidifier. These devices add moisture to the indoor air, improving comfort.
  • Houseplants: Indoor plants release moisture through a process called transpiration, increasing humidity levels naturally.
  • Boil Water: Boiling water on the stove or using a kettle releases moisture into the air, especially in the kitchen.
  • Open Containers of Water: Placing containers of water near heat sources or on radiators allows the water to evaporate, adding humidity.
  • Seal Leaks: Ensure windows and doors are properly sealed to prevent dry outdoor air from entering your home.
  • Limit Exhaust Fans: Use exhaust fans in bathrooms and kitchens judiciously to avoid excessive moisture removal.
  • Use a Hygrometer: A hygrometer can help you monitor indoor humidity levels, ensuring they stay within a comfortable range.
  • Adjust Heating: Lowering your thermostat slightly can reduce the drying effect of heating systems. Using a humidifier in conjunction with heating can help maintain humidity.
  • Ventilation Control: Consider using a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV) that can exchange stale indoor air for fresh outdoor air while retaining some of the moisture.
  • Damp Towels: Hang damp towels to dry indoors, which releases moisture into the air as they evaporate.

Let us look at the causes of low humidity in more detail.

Causes of Low Humidity in the House

In a nutshell, low humidity in a house is usually causes by the following:

  • Low temperature
  • Dehumidifiers
  • Excessive Air conditioning
  • Poor insulation
  • Excessive Heating

1. Low Temperature

As I have mentioned, relative humidity changes with changes in temperature. The higher the temperature the higher the humidity. Hot/warm air therefore holds or has the potential to hold more moisture than cold air.

When warm air (containing moisture) is subjected to low temperature, condensation occurs. That is why you will notice condensation on windows because glass windows are usually cold, as opposed to walls which tend to retain heat.

Humidity is especially low during the cold months of winter. That is because the air is so cold and can hardly hold enough moisture for your comfort.

Location also greatly determines the relative humidity of your house. The temperature could be high but relative humidity would still be low.

For instance, the average relative humidity in Arizona is 38.5% despite being one of the hottest places in the United States. On the other hand, the average relative humidity of Florida is 74.5% and will rise to as high as 90% during the summer.

Usually, the closer an area is to a water body the higher the relative humidity. High temperatures do not therefore always mean high humidity.

When winter kicks in, the relative humidity in arid areas like Arizona, Utah, Nevada and New Mexico will be way lower than in other areas. The effects of low humidity will therefore be felt there more than in other areas.

2. Over Heating

Needless to say, you need to keep your indoors warm during the cold months of winter. That can also have negative effects on your indoor relative humidity levels.

Most homes are heated using a furnace. When the furnace blower pulls cold air from the house, it heats it and in the process causes the little moisture in the air to evaporate.

As a result, the warm air being circulated in the house will be dry (low humidity). And that is where the problem starts.

During the summer when the relative humidity is high, the air feels hotter than it actually is. That is because the excess moisture in the air prevents our bodies from cooling themselves down through sweating.

The opposite of that is what happens in winter. The dry indoor air pulls moisture from our skin leaving our bodies exposed to the elements. As a result, our bodies feel colder and what most folks do is increase the heat on the thermostat.

Increasing the heat will remove even more moisture from the air, reducing the relative humidity even more.

3. Poor Insulation

insulating a window

During winter, you want to retain the heat produced by the furnace indoors to increase its efficiency. You also want to keep the cold and dry outside air at bay.

That can only be done if your house is properly insulated. If dry outdoor air is penetrating inside your house, it could drastically reduce your relative humidity and also render your HVAC system ineffective.

If there are cracks on your walls, gaps on your windows and doors and basically any other way that outdoor air is entering your house, you will always struggle with low humidity unless you can find another way to compensate for it.

4. Running Dehumidifiers

A dehumidifier is used to reduce the relative humidity in the house. Dehumidifiers should however only be used when relative humidity in the house is high, especially in summer.

Running a dehumidifier in winter means that the unit will suck up the little moisture in the air, leaving it dry. If anything, you need to run a humidifier instead of a dehumidifier.

It is common for most folks to run a dehumidifier especially after doing laundry. While that is recommended in summer to prevent growth of mold, you don’t need it when relative humidity is low.

As a matter of fact, the extra moisture from your laundry can be used to increase the indoor humidity when the air is dry.

5. Excessive Air Conditioning

Apart from cooling the indoor air, air conditioners are also used to dehumidify the air. Whole-house air conditioners can remove anywhere between 5 and 20 gallons of water from the indoor air in a day.

As the warm air comes into contact with the cold evaporator coil, condensation occurs and the condensate is drained outside. Dehumidification by air conditioners is very helpful if you are struggling with high humidity.

Excessive air conditioning can however remove more moisture in the air than you may wish to. That is usually not a problem in humid areas like Florida but in arid areas it can considerably reduce the indoor humidity.

Signs of Low Humidity in the House

How do you know that the relative humidity in your house is low? What are the signs/effects of low indoor humidity?

The following are the telltale signs of low humidity in a house:

1. Dry/Itchy Skin and Eyes

As I have mentioned, low humidity causes the dry air to pull moisture from the surrounding including our bodies. That leaves our skin and eyes dry. The skin becomes itchy while the eyes become easily irritated.

2. Respiratory Infections

There are lots of viruses which thrive in low humidity. Dry air is less dense than humid air which causes virus particles to move about with ease and that is how they find their ways inside our respiratory organs causing infections.

An irritated sinus membrane as a result of a low humidity can also cause nasal congestion.

3. Dehydration and Nose Bleeds

Because your body loses so much moisture to the dry air, it is natural to feel dehydrated as the body tries to make up for the lost water. If you are therefore constantly feeling dehydrated then it is a sign that the humidity levels in your house are slow.

Dry air also causes the sensitive nasal membrane lining to crack resulting in nose bleeding. Low humidity can also cause headaches.

4. You Feel Cold

Are you feeling cold despite having the thermostat set at a comfortable temperature? You have dry air in the house pulling moisture from your skin and leaving you exposed to the elements.

5. Static Electricity

Dry air is usually responsible for static electricity. The moisture in the humid air is a natural conductor which will naturally earth the electricity charge. If you are experiencing shocks when you touch things in your house you definitely have low humidity.

6. Cracked Wood/Furniture

Low indoor humidity causes the dry air to pull moisture from wood causing it to shrink and therefore crack. You really don’t have to wait for it to get to this level to notice that you have a low humidity in the house.

7. Low Relative Humidity Reading

Modern thermostats will not only show you the temperature but also the relative humidity. You can also buy a humidistat which is specifically made to indicate the relative humidity in a room.

The ideal indoor humidity is between 30% and 50%. During summer, the recommended indoor humidity is 40-50% while in winter the best humidity is 30-40%.

Therefore, if the relative humidity in your house is less than 30% then you need to look for ways to increase it.

How to Increase Your Indoor Humidity

The following are the different ways to increase indoor humidity:

  • Humidifiers – Humidifiers evaporate water and inject it to the indoor air. They can either be whole-house humidifiers or portable humidifiers for just a single room.
  • Boil a pot of water – Boiling water in the kitchen is one of the fastest way to increase indoor relative humidity.
  • Leave bathroom door open when you shower. The excess moisture from your shower will spread across the house and increase the humidity.
  • Don’t drain bathtub immediately – after you are done soaking in the tub, let the warm water sit for a while. Dry air in the room will pick up moisture from the bathwater and increase the humidity.
  • Have water pots/bowls in the house – Again, dry air will readily pull the water from the bowls and increase humidity.
  • Cook on stove top – Regularly cook on your stove top and avoid the oven which can dry out the moisture in your house.
  • Have house plants – Plants will always release moisture inside the house which will definitely make your indoors more comfortable to live in.
  • Dry you laundry indoors – Drying your laundry indoors or venting your dryer indoors adds moisture to the air which increases relative humidity.
  • Weather-stripping or replacing windows and doors – Weather-stripping you doors and windows can help you seal the cracks and therefore retain the moisture and heat indoors. If possible, replacing the old windows and doors with modern and more efficient ones will help to retain the arm indoor air and keep at bay the cold and dry outside air.

And basically those are the causes of low humidity and the solutions. I hope that this post was as detailed and helpful as possible. For more information on how to increase your indoor humidity check out this post.