No, you don’t. Although dehumidifiers, just like heaters, air conditioners, and other HVAC appliances, work best in the room they’re located, a single dehumidifier can serve multiple rooms or even the entire house.
Of course, it also depends on the size of the home and whether it’s a single-floor or multi-story building. You’ll certainly need a bigger dehumidifier or multiple smaller units to dehumidify a large area. The same applies to a multi-story house.
Below, we discuss various considerations to help you make the right decision, highlighting instances when you may only need one dehumidifier and when you might need multiple dehumidifiers.
Why Do We Need Dehumidifiers?
Let’s begin by explaining why you need a dehumidifier. Why do people buy dehumidifiers, and do you even need one in the first place?
People invest in dehumidifiers to remove excess moisture from the home to improve indoor air quality. A dehumidifier is an electrical appliance designed to extract moisture from indoor air. It does so in two ways;
- Condenser dehumidifiers: Condenser dehumidifiers eliminate moisture from home by condensing moisture in indoor air. They comprise a refrigeration mechanism that draws indoor air and condenses the moisture in the air before returning dry air into your home.
- Desiccant dehumidifiers: Desiccant dehumidifiers use a desiccant (hygroscopic) material to “suck” moisture out of indoor air. Desiccants are a category of materials that have a very high affinity for moisture. They readily absorb moisture from the surrounding environment.
Removing excess moisture from home allows us to lower humidity levels (also known as relative humidity) to a healthier level, typically between 30% and 50% RH.
Otherwise, we’d be exposed to excess moisture. Excess indoor moisture is terrible for human health, pets, plants, and even the building itself.
- Health issues: Excessive humidity levels create the perfect breeding ground for fungi, viruses, and bacteria that can cause all kinds of illnesses. Respiratory illnesses are prevalent in damp conditions.
- Plant and pet issues: Overly humid conditions can promote mold and fungi that cause plant diseases. Your pets may also have respiratory issues. For instance, hot, humid conditions easily cause heatstroke in dogs.
- Structural issues: Damp conditions are usually associated with wet rotting, which causes wood to become soft and rot. This can weaken your home, especially if it happens in the attic or crawl space. Remember that damp conditions can also damage wall paint.
Finding the Right Humidity Level Across the Home
From the discussion above, you can tell that you must achieve a certain optimal humidity level across the home to enjoy quality indoor air and protect your pets, plants, and the home. According to the World Health Organization, this optimal range is 30% to 50% relative humidity.
To achieve 30% to 50% relative humidity throughout the home (not just one room), you need to consider several factors, including;
Size of the Dehumidifier
Dehumidifiers are primarily sized by how much moisture they can remove per unit time. The industry standard is pints per day though many manufacturers also use gallons per day. Some may also give their dehumidifier sizes in pints or gallons per hour. All you need to remember is that one gallon = 8 US liquid pints.
Regardless, the most important thing here is how much moisture the dehumidifier can remove per day. Most portable dehumidifiers are rated at 30 to 40 pints/day, while medium-s0zed units are rated at around 70 pints/day. However, larger units are available that can remove up to 130 pints/day. That’s roughly 16 gallons!
Typically, you need a 20-pints/day dehumidifier for a slightly damp 300 square-foot room with relative humidity between 50% and 60%. The same room, but damper, at 80% to 100% relative humidity requires a 30 pint/hour dehumidifier.
It tells you that you may need only one dehumidifier for the same room if you pick the right dehumidifier size. However, you’d need multiple units for the same room if using smaller, portable dehumidifiers.
Size of the Home
The size of the room also matters. Why? Because moisture covers every inch of the home. Moisture doesn’t just sit in the kitchen or the bedroom. You can’t lock it up in the living room or bathroom. Indeed, moisture spreads so fast that you may have similar relative humidity levels in all your rooms.
So, if you’re trying to find a dehumidification solution for the entire apartment, you must consider every room in the house, including the corridors. The easiest way to go about this step is to retrieve your floor plan and determine your floor size. Now, you can begin the calculations.
Assuming mildly humid conditions with relative humidity between 50% and 60% RH, you need a 20-pint dehumidifier for a 300 square foot area, a 30-pint dehumidifier for a 500 square-foot area, a 40-pint unit for an 800 square-foot area, and at least a 50-pint dehumidifier for a 1,200 square-foot room. That’s if we use the latest (2020) dehumidifier sizing regulations.
Given that the standard American home is about 2,500 square feet, you can see that all portable dehumidifiers may fall short. You’d need at least two 50-pint units or three 40-pint units to cover 2,400 square feet. If you only want one dehumidifier, your only option here is a whole-home dehumidifier that connects to your duct system.
Many such units are rated 130 pints/day and can serve 3,000 square feet in mildly damp conditions. However, for a larger home humidification, say 4,000 square feet, even a standard whole-home dehumidifier wouldn’t be enough. You’d need at least two.
Finally, whether you need a dehumidifier in every room will also depend on the level of humidity in your home. In mildly damp conditions, a single whole-home dehumidifier may suffice. However, you typically need more power or more dehumidifiers in damper conditions.
For example, in a standard 500 square-foot room, you only need a 25-pint dehumidifier if the conditions are mildly humid, between 50% and 60% relative humidity.
However, if the conditions become damper or you live in a more humid location, between 60%and 80% relative humidity, a 25-pint dehumidifier is insufficient. So instead, you need a 30-pint dehumidifier. Otherwise, you may not achieve ideal indoor comfort.
The dehumidification needs are even higher in more humid conditions or locations. For example, in California, where humidity levels can rise to 100% RH, you need a 40-pint dehumidifier. Otherwise, you’ll be doing zero work.
It means that whereas one 130-pint whole-home dehumidifier is sufficient for the entire home in mildly damp conditions, between 50% and 60%, you may need two or more of the same in damper conditions or locations.
In other words, someone in New York that doesn’t experience extreme humidity may be able to survive on a 130-pint dehumidifier in a standard-size home. However, people in more humid states would need two or more such dehumidifiers to achieve similar comfort levels, assuming the same home size.
So, Do You Need a Dehumidifier in Every Room?
The short answer is no. You don’t necessarily need a dehumidifier in every room. You can even have one dehumidifier, or maybe two, for the whole home. However, it depends on three critical factors, i.e., the size of the home, the size of your dehumidifier(s), and the relative humidity in your home.