Do dehumidifiers help in hot weather?

Dehumidifiers are appliances that remove excess moisture from the air. They work by drawing humid air into the unit, removing moisture, and expelling drier air back into the room. Dehumidifiers can be helpful for reducing humidity levels and discomfort during hot summer weather.

In hot conditions, high humidity exacerbates the effects of heat by limiting evaporation of perspiration from the skin. This can make hot days feel even more oppressive. Dehumidifiers work to lower indoor humidity, which can provide a cooling sensation and greater comfort.

Using a dehumidifier during summer can provide several potential benefits:

• Makes indoor air feel cooler by removing moisture.
• Alleviates muggy feeling associated with high humidity.
• Prevents musty odors and growth of mold, mildew and dust mites.
• Reduces condensation on windows, walls and other surfaces.
• Helps maintain indoor air quality by controlling humidity.

However, dehumidifiers also have limitations. While they reduce humidity, they do not lower air temperature. Dehumidifiers also consume electricity and can increase energy costs when running frequently. Determining if a dehumidifier will be helpful depends on several factors.

How does a dehumidifier work?

Dehumidifiers reduce humidity by drawing moist air over cold refrigerated coils. The water vapor condenses and drips into a collection reservoir while the dried air is re-heated and circulated back into the room.

Most units have an in-built humidistat that allows desired humidity levels to be set. The dehumidifier automatically cycles on and off to maintain these levels.

There are two main types of dehumidifiers:

• Refrigerant dehumidifiers – These are the most common and use a refrigeration cycle with cold coils to condense moisture from the air.
• Desiccant dehumidifiers – These use a material called a desiccant, like silica gel, to absorb moisture. They can continue to operate down to low temperatures but are less energy efficient.

Dehumidifier capacity is measured in pints (or liters) of moisture removed per 24 hours. Larger capacity units are able to dehumidify large spaces more quickly.

What humidity level is recommended?

Ideal humidity levels generally range from 30-50% relative humidity for comfort and health. At higher humidity:

• Air feels muggy and oppressive.
• Evaporation of sweat is hindered, increasing perceived temperature.
• Condensation and dampness facilitate growth of mold, mildew and dust mites.
• Viruses and bacteria survival rates increase.
• Allergens like pollen and dander thrive.

Below 30% humidity:

• Eyes, throat, sinuses and skin may become dry and irritated.
• Wood floors, furniture and musical instruments may warp or crack.
• Static electricity increases.

Ideally indoor humidity should be kept year-round between 30-50% relative humidity for the best comfort and air quality. During hot summer weather, this generally requires active dehumidification.

When does humidity become excessive?

Humidity outdoors is considered high when relative humidity exceeds 65-70%. At these levels, dehumidification can help offset the effects of humidity indoors.

However, relative humidity alone does not determine whether dehumidification is needed. Humidity should be assessed based on the dew point temperature.

The dew point is the temperature at which condensation begins to form. When indoor air temperature drops to the dew point, moisture will condense on surfaces.

As a guideline:

• Below 50°F dew point – Air feels dry
• 50°F-59°F dew point – Humid air
• 60°F-65°F dew point – Very humid, dehumidification needed
• Over 65°F dew point – Extremely humid, dehumidification required

During summer, dew points exceeding 65°F indicate excessive moisture that warrants dehumidification. This is typical of hot, humid climates.

Factors that influence humidity

Indoor relative humidity is influenced by several factors:

Outdoor humidity – Outdoor moisture can enter the home through ventilation, open windows and doors. High outdoor humidity directly raises levels indoors.

Indoor moisture sources – Showers, cooking, laundry and human occupancy all add moisture to the indoor air. Leaks can also allow entry of ground moisture.

Indoor temperature – Warmer indoor temperatures allow air to hold more moisture. Cooler temperatures reduce moisture capacity, resulting in condensation.

Home construction – Tight, well-insulated homes with reduced ventilation hold moisture indoors. Older homes with leaks allow indoor humidity to escape.

Geographic location – Humid climates experience high outdoor humidity. Coastal areas also have abundant moisture from marine influence.

Weather conditions – Seasonal changes and weather patterns dramatically influence outdoor humidity levels.

Ventilation – Active ventilation dilutes indoor humidity by exchanging indoor air with drier outdoor air. Stagnant air allows humidity buildup.

These factors help determine whether high humidity is an issue and if dehumidification is warranted. Homes in damp climates are much more prone to humidity problems.

Does a dehumidifier cool the air?

Dehumidifiers reduce humidity but do not lower air temperature. However, lowering humidity can create a cooling effect for the human body in warm conditions.

The natural process of perspiration and evaporation helps cool the body. When humidity is high, evaporation of sweat off the skin slows, hampering this cooling mechanism.

By removing moisture from the air, dehumidifiers improve the evaporation of sweat. This creates a cooling sensation as more body heat dissipates, even though air temperature remains unchanged.

While they do not replace air conditioners, dehumidifiers can provide perceived cooling relief and greater comfort through this mechanism. Reduce humidity by 10-15% and the indoor environment feels 2-3°F cooler.

However, some dehumidifier models have a secondary ventilation fan that can assist with air circulation and add an air movement cooling effect. Overall though, dehumidifiers themselves do not lower air temperature.

Do dehumidifiers heat the air?

The process of dehumidification itself does not heat the air. However, some heat is generated as a byproduct of the moisture removal process:

• Heat is absorbed to evaporate moisture off refrigerated coils.
• The compressor in the refrigeration system produces heat.
• Fan motors generate a small amount of warmth.

This heat is dissipated into the room by the exhaust air stream. While minimal, this heating effect can add a degree or two if the dehumidifier runs continuously in a small space.

Larger capacity dehumidifiers are more energy efficient and product less heat per volume of water removed. Mini-dehumidifiers generate more heat but are suited for confined spaces.

Overall, dehumidifiers only minimally warm the air in the process of removing moisture. This is generally not problematic except in small, enclosed rooms with inadequate ventilation.

Are dehumidifiers effective for indoor allergies?

Dehumidifiers can help improve some common indoor allergy and asthma triggers like mold, dust mites and cockroaches by maintaining lower humidity levels.

Several studies have demonstrated that dehumidifiers can significantly reduce airborne allergens in the home:

• Dust mite populations declined by over 80% at humidity below 50%. Mold growth is also inhibited.
• Cockroach presence was reduced by 95% when relative humidity was maintained below 50%.
• Cat allergen levels dropped by over 50% with home dehumidification used.

For allergy sufferers, keeping humidity around or below 50% can minimize exposure to these common allergens. This is a helpful add-on treatment along with regular cleaning, HEPA filtration and avoidance of triggers.

However, dehumidifiers do not remove allergens that are already present like dander, pollen or dust. Portable air cleaners with HEPA filters are much more effective for actively filtering allergens from room air.

But for controlling humidity-loving allergens at the source, dehumidifiers can be an effective preventative measure when used properly.

Disadvantages of dehumidifiers

While offering benefits in hot, humid climates, dehumidifiers also have some drawbacks:

• Added energy costs for operation which increases with runtime.
• Noise production, especially by less expensive units.
• Need to frequently empty the water collection tank.
• Contain refrigerants that must be disposed of properly.
• Possibility of over drying the air if set too low.
• Do not lower air temperature or replace AC need.

Dehumidifiers also provide no ventilation benefits compared to running a central air system fan. And in very damp spaces, multiple dehumidifiers may be needed.

Portable units require relocating from room to room and proper placement for effectiveness. Built-in HVAC dehumidifiers avoid these issues but have a higher upfront cost.

Are dehumidifiers worth it in the summer?

For homeowners dealing with humid indoor conditions during hot weather, dehumidifiers can provide:

• Lower humidity for improved comfort.
• Elimination of condensation and musty odors.
• Reduced allergen levels from mold, dust mites.
• Less opportunity for bacterial and viral growth.
• Prevention of wood cracking and warping.

If high humidity is an ongoing issue in your climate during summer, dehumidifiers can be an effective solution.

Look for ENERGY STAR rated models with higher moisture removal capacities and energy efficiency. Size the capacity appropriately for the room size you need to dehumidify.

Use humidistat controls to monitor humidity levels. This allows the unit to run only as needed to maintain lower humidity for comfort and efficiency.

Dehumidifiers are generally most useful in hot, humid climates where indoor relative humidity exceeds 60% for extended periods. This is where occupants will experience the most benefits in perceived cooling and air quality.

However, dehumidifiers should be used as a supplemental tool along with proper home ventilation. Make sure bathroom and kitchen exhaust fans are used consistently to remove additional moisture at the source during summer.

Tips for using a dehumidifier effectively

Follow these tips to use a dehumidifier most effectively during hot weather:

Size capacity correctly – Choose a unit that can remove 70-100 pints of moisture per day for every 1000 square feet of space. Large capacities dehumidify more effectively.

Isolate usage – Close doors and windows in rooms being dehumidified to concentrate the effects. Limit operation to problem areas.

Allow continuous drainage – Use a drain hose to avoid constantly emptying the tank and maximize run time.

Set humidity goal – Use built-in humidistats to set desired humidity, typically 45-50%.

Supplement with ventilation – Run bath and kitchen exhaust fans to remove additional moisture at the source.

Use fan-forced units – Dehumidifier fans help circulate air which improves efficiency.

Clean filters – Dirty air filters reduce airflow over the cold coils and lower performance.

Watch humidity levels – Use a hygrometer to monitor humidity and adjust unit operation accordingly.

Manage air leaks – Seal any air leaks which allow humid outdoor air to enter and ventilation losses.

Proper dehumidifier setup and use will provide the best results in lowering humidity during hot, muggy weather.

Adding air conditioning

For very humid climates, using air conditioning may be a better solution than relying solely on dehumidification. Air conditioners cool and dehumidify since cold coil temperatures below the room’s dew point remove moisture from the air.

The big advantage of air conditioning over just using a dehumidifier is the removal of heat along with lowering humidity. This provides a more complete solution to summer discomfort.

Homes that already have central AC systems can run the fan on a regular basis to circulate air over the cold evaporator coil. This provides supplemental dehumidification.

Window AC units also provide localized cooling and dehumidification for single rooms. In damp climates, mini-split heat pumps offer both heating and cooling along with humidity control.

Some key benefits of adding air conditioning:

• Cools air temperature for greater comfort.
• Lower humidity enhances the cooling effect further.
• Prevents moisture damage and mold growth on cool, condensing surfaces.
• Less drying of wood furnishings than dehumidifiers alone.
• Provides air filtration to reduce allergens, smoke and odors.

The combination of air conditioning and supplemental dehumidification can help maintain indoor humidity in the 30-50% range for optimal comfort and air quality.

Conclusion

Dehumidifiers can provide noticeable humidity relief and perceived cooling during hot, humid weather. They extract moisture from the air without reducing temperature. Lower humidity improves evaporation for comfort and inhibits the growth of allergens like mold and dust mites. However, dehumidifiers increase energy costs and only treat the symptoms of humidity, not the underlying cause.

For long-term humidity control, dehumidifiers work best alongside proper home ventilation, adequate insulation, sealed air leaks and appropriate HVAC equipment. They serve as an additional tool for managing humidity. Air conditioners are often the best permanent solution for both cooling and dehumidification in damp climates. When used properly, dehumidifiers can be an inexpensive way to temporarily alleviate the discomfort of humidity during hot weather.

Pros of Using a Dehumidifier	Cons of Using a Dehumidifier
Lowers humidity for comfort Removes musty smells Lessens dust mites and mold Prevents condensation Perceived cooling effect	Added energy costs Noise production Requires draining tank Doesn’t lower temperature Can over-dry air if set too low

Ideal Humidity Levels
30-50% – Recommended comfort zone Below 30% – Air feels dry and irritation possible Above 50% – Air feels muggy, health issues Above 60% dew point – High humidity, dehumidification needed

Tips for Effective Dehumidifier Use
Size capacity to room size (70-100 pints/1000 sq ft) Isolate usage to problem rooms Use continuous drainage Set humidistat (45-50% RH) Supplement with ventilation Select fan-forced model Clean air filter regularly Monitor humidity Manage air leaks