Humidity at Home: What You Need to Know this Winter

Understanding Relative Humidity in the Home

Relative humidity comfort ranges on a scale of 0 to 100.

Humidity simply refers to the amount of moisture in the air. Breaking down the math, relative humidity is the percentage of water vapor that’s in the air at a certain temperature. When the relative humidity is at 30 percent, for example, the air is holding 30 percent of the moisture it’s capable of containing.

During colder months, the air’s ability to hold water decreases, and during warmer months, it increases. The ideal relative humidity level for the inside of your home is between 30 and 50 percent. This is important because the level of humidity in your home can impact your overall health and comfort and potentially affect the cost of heating or cooling your home.

Infographic showing the risks of humidity levels that are too high and risks of humidity levels that are too low.

If humidity levels are too high you run the risk of:

  • Growing mold and bacteria
  • Stuffy conditions
  • Overall discomfort

If humidity levels are too low you run the risk of:

  • Catching a cold or infection
  • Dry and itchy skin
  • Damaging the wood, paint or siding of your house

Oh, the weather outside is frightful…

Let’s say it’s a cold day in December. The temperature outside is 10° F with 70 percent humidity. Meanwhile, indoors, your thermostat is set to 72° F. When the cold air creeps into your home, your furnace heats it to 72° F, and the air expands. While the moisture in the air remains the same, the relative humidity is significantly reduced. This means that the cold air from outside with 70 percent humidity has an indoor relative humidity of only 6 percent.

The dry air inside your home will steal moisture from wherever it can find it, including your body. As moisture evaporates off your skin, you feel cooler. When you feel cooler, you tend to turn up your thermostat, which can become an expensive habit given the high cost of heating.

Protecting yourself and your wallet

To combat the negative effects of dry air, it’s important to keep your home’s indoor relative humidity level somewhere between 30 and 50 percent. This minimizes the air’s need to replenish moisture and little or no evaporation from your body takes place. As a result, you can actually turn down your thermostat about three degrees and maintain comfort and warmth while saving on energy costs.

There are many different ways to humidify the air in your home. You can use a single room humidifier or install a home humidifier connected directly to your HVAC system. These humidifiers work automatically to ensure the air in your home is at an ideal relative humidity level. It is also recommended to use a more accurate digital thermostat with humidity control to automate the process and keep your system at peak efficiency.

Ask your contractor about humidity in your region and the best way to protect your health and comfort while saving money.

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21 thoughts on “Humidity at Home: What You Need to Know this Winter

  1. My biggest problem i found having installed a new high efficiency furnace this winter is the humidifier runs when furnace is on. It is not a closed loop system. Fresh hot water runs through it and unused water runs to drain. Measured the wasted water to achieve 35% humidity and it was 1, 5 gallon Homer Bucket in 2 hours. 60 gals a day / 1,800 gals a month 5,400 gals a quarter
    Savings on gas gone on water bill.

    • Many manufacturers make a water-saving humidifier that turns the solenoid on and off during a humidifying cycle to help conserve water. Another option is to use a steam type humidifier to greatly reduce the amount of water being used.

    • Replaced my old furnace with a new high efficient one and I’m noticing my humidifier is not providing as much moisture to the house as it was before. Is that related to how the new furnace works or should I look for better options?

      • We recommend consulting your furnace installing contractor ensure it is working properly. There may be a damper in the bypass pipe that may be closed or the humidifier may not be getting proper water flow due to debris in the saddle valve or the solenoid valve.

    • first wrong math 1.5 gallon in 2 hours, would not equal 60 gallon a day.. rather 18 gallons a day, still huge number, I doubt it, there must be error

  2. There seems to be a basic error here. An assumption that high humidity means the temperature will be warm. This is just not true for many regions in the world. Where I live, southern Europe, we have hot dry summers and cold wet winters. The winter temperatures aren’t cold enough to dry the air and we get almost three months of mostly rain. The winds in from the north or east, the east being the coldest. A humidifier in the house would be the last thing one would need. I know these conditions exist in the US as well – I’ve been in Cape Cod in the winter, a very wet winter and it was just as cold. When it’s winter and very humid outside I want a thermostat that recognises the change and increases the inside temperature accordingly. Nothing sucks the energy from your body more effectively than a cold humid wind. When there is frost or snow the moisture is no longer in the air and warm clothes are all you need to cope. In fact it’s all about insulation – cold dry air, easy to insulate against, cold damp air, difficult to insulate against. Obviously there’s no wind in the house but air enters as it must and we immediately notice the change yet the temperature has not changed, just our perception of it.

  3. Our house in Maryland (on the Delmarva peninsula) had low winter humidity which made it feel cold. Additionally we had all those electrical (static?) shocks when we touched something with our fingers and our wood furniture was a bit dried out. Our house is a 1 story with about 1650 square feet of living space.
    We bought a name brand, stand alone humidifier on casters from the big online company about 4 years ago for well under $100. It is a cool air, evaporative, recirculating model and holds 4 1/2 gallons of water. It works great for our house and has fan speed and humidity controls. I replace the filter every year and clean the interior with a weak bleach/water solution every 2 months of use. The fan is a bit noisy, but then most, if not all fans are. It works for us!

  4. I don’t know – doesn’t chime with my experience. Winter warm sun in the morning and 20C is fine then it clouds over and the late afternoon and early evening it feels much colder yet the inside temperature remains the same. I know on damp days outside it always feels much colder – there’s no expansion of air then – your explanation doesn’t seem to hold water.

  5. You do not need a professional contractor.. Go to Menards , Get a Honeywell whole home humidifier for around 160 bucks . Install is super easy and takes just a couple hours and some simple home tools.. I did this and it works amazingly well . dont waste money on an over priced ” pro ” if ya have a small amount of diy ability

    • Hello! We have a whole house humidifier finally but it’s super cold out and have only managed to get humidity to 28-30%, which is just too dry for me. How can I get humidity up so it then maintains as the heat kicks on and off?

      • We recommend following the manufactures recommendations on the humidistat or in their owners manual on the recommended humidity percentage for various outdoor temperatures. If the humidity level gets too high when it’s super cold out, then you could develop condensation on your windows, in your walls, or in your attic space.

    • It sure is .. I have been researching this hard since installing my humidifier and yes 40 to 50 % at 68 is ideal

  6. When installing a whole-home humidifier, we recommend an integrated outdoor temp sensor also be a part of the installation. This offers the ‘automatic’ adjustments to lock-out the humidifier, or reduce the moisture to be introduced into the home, when colder temperatures take hold (inc. Gaylyn’s question). Advanced thermostats may provision it, but in many cases it’s an accessory that needs to be added by the contractor/installer. Also, more careful planning for a humidifier choice and installation should be taken into account when heat pumps are in use.

    • The charter for our site does not allow us to comment on particular brands, service providers or prices. However, we would suggest that you contact a qualified contractor nearest to your area for a quotation and usually, we encourage people to get at least 2-3 quotes from a few different contractors not only to get competitive prices but to also get different opinions on the installation project, equipment sizing, types and efficiency levels. The ACCA – which is a national contractor organization have a contractor locator tool which may also help you find a qualified contractor in your area. Here’s the link: http://www.acca.org/locator

  7. I️ was looking for a grid that showed the outside temperature and suggested inside humidity. Our windows have moisture and ice at the corners.

    • The answer comes down to do you want to know or do you want to control the humidity level in your home as part of your Indoor Air Quality? For a comfortable home you want to control three things; 1) the humidity, 2) the temperature, and 3) the air quality (filtration). As far as the humidity, Indoor Air Experts suggest maintaining 35% rH to 55% rH in your home at the temperature you find comfortable.
      Options:
      Digital Humidity Readouts: These devices are low cost, battery operated and sit on a table in the home. They just give you an indication of the humidity level in your home. These can be purchased from your local hardware store.

      Stand Alone Humidity Control: These are stand alone units comprised of a humidifier or dehumidifier that are controlled by a Humidistat to maintain a selected humidity. They do not control temperature-just humidity levels in some areas of the home.

      Whole House HVAC System Humidity Control: You should consult a professional HVAC company when considering a whole house Indoor Air Quality solution. They are trained to do a thorough evaluation and make appropriate recommendations. The system will likely be comprised of a humidifier installed on the air handler for adding humidity in the heating mode. In the cooling mode a dehumidifier to remove humidity by varying the speed of the air handler blower motor in your home. These can be controlled by a digital thermostat with humidification control. If you add a high efficiency filter, you now address the three components of Indoor Air Quality. While it is the most expensive option it is also very effective to giving you the best comfort level in the home.

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