Ideally, you shouldn’t. In residential heating and air conditioning specifically, it’s counterproductive to run a dehumidifier and heater simultaneously.
Instead, you should run a dehumidifier alongside an air conditioner during the cold season and a heater with a humidifier during winter – if you must. You can also run each of the four independently.
For instance, if it’s summer, but it’s not too hot indoors, you can run the dehumidifier alone to bring down the humidity levels. Similarly, you can run the humidifier in autumn before the heating season commences if you feel too dry inside the home.
Let’s find out how the four, i.e., heating, cooling, humidification, and dehumidification, work, when you need each, and how to pair them – whenever necessary – for the best indoor air quality and ultimate comfort.
HVAC Seasons Explained
The US climate is divided into four distinct seasons, i.e., winter, spring, summer, and autumn. However, not all states experience all four seasons distinctly. And, even among those who do, the seasons don’t always start and end simultaneously. For example, summers are much longer in the southern states, whereas northern states experience long winters.
Similarly, the intensity of summer sunshine and winter cold varies from one state to the next. For instance, Florida is the hottest among the southern states, with an average July temperature of 90˚F to 92˚F.
The temperature in the state pass 100˚F regularly. Texas, another scorching-hot state, has an average summer temperature of 65.3˚F, with the hottest days in August typically reaching 93˚F or higher.
The colder regions have similar deviations. For instance, the coldest state in the country, Alaska, has an average temperature of 26.6˚F, sometimes reaching -50˚F in winter. Meanwhile, Minnesota, which is also pretty cold, has an annual average temperature of 41.2˚F, with the coldest winter days usually at around -30˚F.
Naturally, you’d expect people to bring out their heaters during the winter and air conditioner during the summer to mitigate the extreme weather.
Why Dehumidifiers and Heaters Rarely Go Together
Most “experts” don’t tell you that the hottest seasons are humid, whereas the cold seasons are arid.
In many cases, the humidity conditions can be so bad that you need to either remove excess moisture or add a little moisture to your room to achieve optimal indoor comfort.
In Florida, for instance, the hottest month is August, with July and September following in that order. The average high in August is 92°F while in July it’s 89.8°F and in September it’s 87.9°F. You’ll find that these are also the most humid months in the state. August has the highest humidity levels in the state, at an average of 71% RH per year.
The opposite is true for colder seasons. Still in Florida, the coldest months are January, February, December, and March, in that order. The average low for January is 50.3°F, while in February, it is 52.2°F.
Finally, December has an average low of 54.9°F, while the average for March is 56.4°F. As you’d expect, this period has the lowest humidity levels, i.e., driest indoor air conditions. March is the worst at 60.3% average RH.
This tells us that in many cases, you don’t need a dehumidifier when heating (during the colder months) because it’s already very dry in the cold weather. However, you may need a humidifier to boost the humidity levels.
Take a naturally colder state, such as New York, for instance. Januaries in New York can be as cold as 20°F or lower. Indeed, the average low for January in New York is 28.6°F. However, the coldest month in the state is February, with an average low of 27.7°F.
So, how do these months fare humidity-wise? As you’d guess, not so well! In January, the average humidity in New York is 44.2%, while in February, it’s 44.8% RH. Meanwhile, the warmer months tend to post much higher humidity levels, with August and September, the hottest months in the state, recording 60% RH or higher on most days.
It means that while you heat, you’ll also need to humidify the area to ensure healthy indoor moisture levels.
The opposite is true in warmer climates. As we’ve seen with Florida, when the summer temperatures soar to 92°F in August, the relative humidity rises to as much as 71% RH.
At such a high RH, you need a dehumidifier to remove excess moisture from indoor air. Otherwise, the entire home would be damp. So, you’d end up using the air conditioner (to cool) and dehumidifier (to remove excess moisture) side by side.
Other Reasons You Shouldn’t Heat and Dehumidify Simultaneously
We’ve already established the hot summers are generally very humid while biting-cold winters are drier. Thus, in most cases, you’ll end up running the heater alongside a humidifier and air conditioner alongside a dehumidifier.
However, that’s just the first reason. Other reasons why it rarely makes sense to run the heater and dehumidifier side by side are as follows;
Heating Significantly Reduces Humidity
The heater itself will not absorb any moisture. Even the heat doesn’t absorb moisture. However, advanced science shows that heated air can absorb moisture, leaving the area dry within minutes. As air temperature increases, the molecules inside the air gain a higher capacity to hold moisture.
Therefore, running the dehumidifier, which also removes moisture from the atmosphere parallel to the heater, is counterintuitive. It can quickly leave you with a very dry home. If you do this in winter, the damage can be massive when it’s already very dry.
Heating Works Better in a Humid Climate/Environment
Like heated air holds more moisture, scientific studies also show that more humid air tends to hold more heat. So the studies show that by increasing humidity in the home, you can make it feel warmer – without necessarily raising the thermostat.
So, if you want better heating performance, you should raise indoor humidity levels (using a dehumidifier) – not further lower indoor humidity levels (using a dehumidifier). A dehumidifier works better when you’re trying to reduce the amount of heat in the air.
However, since climates vary from one place to another, sometimes you may need to use the dehumidifier when heating.
An excellent example is Nevada. December, January, and February in Nevada can be biting-cold, with temperatures regularly dipping below 20°F. The average low for January in the state, for instance, is 24.4°F.
However, three months are also extremely humid in Nevada – which is the reverse of what you’d expect at such low temperatures. The average relative humidity in Nevada in January is 73% RH! This is exceptionally high even for the most tolerant people. According to the Environmental Protection Agency, EPA, the ideal temperature for healthy living is 40% to 60% RH.
It means that if you live in Nevada, you’ll need to run the humidifier alongside the heater from December through February.
Naturally, you shouldn’t run the dehumidifier and heater together. For one, most winters are already frigid, meaning you need to be adding, not removing, moisture from indoor air. Furthermore, heating absorbs significant amounts of water, which often leaves your home even drier. Bringing in a dehumidifier would worsen the situation.
So, it’s natural to combine the heater with a humidifier (to replace lost moisture) and an AC with a dehumidifier (to eliminate the excess moisture) under normal climatic conditions.
However, the above doesn’t apply to all climatic conditions. For example, in unique climates, such as Nevada, where the humidity levels are extremely high, even in winter, you’re allowed to run a dehumidifier alongside the heater. In any case, isn’t home heating and cooling all about finding a climatic sweet spot?