ENERGY STAR Dehumidifiers - tips for cutting humidity issues without breaking the bank
It seems almost everyone has basement humidity problems. Where does all that water come from?
Dampness can sneak into your house naturally in the air, in spring or summer through open windows and doors, and through air leakage when the heat or air conditioning is on, such as poorly sealed windows and doors, cracks in outdoor wall plaster in older houses, cracks in upstairs ceilings, or attic openings that lack proper weatherstripping. Anything that sucks air out of your house, such as a fireplace insert, kitchen fan, or a low- or mid-efficiency furnace, will also pull outdoor air in.
So one way you can reduce moisture is to limit the flow of fresh air, especially during humid weather.
Water can seep through your basement masonry from outside. You need to keep surface water away, seal the outside of the foundation, improve drainage underneath the foundation, and you may even need to seal the inside of the basement wall as well.
Human activities such as sweating, showering and cooking, can also add moisture when the house is closed. The daily presence of people indoors can add as much as 20 gallons of water to your indoor air each day.
Rain collecting in your driveway, or pouring out of an eaves trough, finds its way downhill. If the soil is porous around your foundation, or if there is a gap between the pavement and the house, the water will percolate through the soil or the gap until it meets the water table or is otherwise halted. Once it can't flow down, it flows sideways, which is when it starts seeping through your foundation.
So keep surface water from collecting around the walls of your house. Keep eaves troughs cleared of leaves and properly angled, and downspouts in working order with their outflow running away from the foundation. Your driveway should slope away from your house, or you can run a line of mortar along the wall between the driveway and the house to keep water that puddles in the driveway from working its way down your foundation.
Gardens, lawns, and other outdoor areas should also draw water away from your home, and if you have a sump pump it should drain far from the house also.
Keeping groundwater out is rather more problematic and can be expensive. A basement contractor can dig a trench to your foundation from outside, and apply a waterproofing compound to the exterior below-grade walls. They should also fill in the trench with gravel and sand to improve drainage, and they should put in drainage tile at the bottom to draw groundwater down below the floor of your basement.
A cheaper choice, if your basement masonry is exposed, is to scrub down the masonry to a hard, clean surface free of loose grit or mineral sweat, and use a thin mortar slurry to improve the waterproofing on the inside of foundation walls. This works for minor humidity problems but is not a solution if you have serious basement humidity problems.
Any moisture you can avoid producing indoors will help minimize moisture problems. You can't stop breathing, but you can cook with lids on, and run the range hood when boiling water; you can have shorter showers or run the bathroom fan when showering; and be mindful of aquariums, decorative fountains, and other possible humidity sources.
If winter humidity is a problem and your home is of recent vintage and well insulated, it is possible that your home is sealed too well. A well sealed home cuts your heating costs, but if it's too well sealed moisture will build up, as will off-gassing from synthetics, softwood, carpeting, and other materials that may harm your health. You might consider buying a heat exchanger rather than a dehumidifier if this is your problem. Heat exchangers allow air to flow in and out of your house, while keeping the heat in as the exhaust air is blown out.
Before go out and buy a dehumidifier to solve moisture problems that can't be addressed by the points made above, you should understand how humidifiers function, their capacity rankings, how ENERGY STAR dehumidifiers are rated, and how to choose the best model for your home.
Dehumidifiers remove water out of the air using a compressor, condenser, and fan. They work the same way a refrigerator works, except that the cold is used to condense water out of the air. They have a humidistat that keeps the compressor on until the humidity reaches a predetermined lower level, or until the tank is full, whichever comes first.
Dehumidifiers are grouped based on extraction capacity - how much water they extract from the air in a day - and tank capacity - how much they can hold in their tank. In the United States, extraction capacity is rated in pints per day and capacity is rated in quarts. In most other countries, extraction capacity is measured in liters per day and capacity in liters.
Once your tank reaches its capacity, the dehumidifier stops extracting any moisture until you empty the tank. If you place your dehumidifier near a basement floor drain, you can run a hose from the tank to the drain, so that you never have to empty the tank. (Most dehumidifiers come with an opening for a hose.) If you can't do this in the room where you're putting the dehumidifier, make sure you buy a unit with adequate tank capacity.
The energy factor for dehumidifiers is the number of liters or pints of moisture removed from the air per kilowatt hour (kWh) of electricity. The higher the energy factor value, the more efficient the dehumidifier is. This means bigger is better - unlike the efficiency rankings for most other types of appliances.
ENERGY STAR dehumidifiers are rated from 3.56 (excellent) to 1.2 (marginally efficient) with a median rating of 1.62. Only two companies, Therma-Stor Products and Munters Corporation, make dehumidifiers with an energy factor better than 2.2.
But bear in mind that an ENERGY STAR sticker does not mean the dehumidifier is really energy efficient - just more efficient than some others in its category. For example, ENERGY STAR dehumidifiers can have an energy factor of as little as 1.2, while the best score is 2.02 and the worst for a non ENERGY STAR rated dehumidifier is 1.0.
Always buy a dehumidifier that can handle the amount of dampness in your house. You will typically not need a pints-per-day rating greater than 25 unless your basement is sopping wet and at least 1,200 square feet in area, wet and at least 1,500 square feet, or usually damp and mildewy (but not wet) with at least 1,800 square feet.
On the other hand, higher capacity ENERGY STAR units are typically more energy efficient because of the different capacity thresholds used to rate dehumidifierS. So don't skimp and buy too low a capacity unit - overestimate rather than underestimate.
If you have a very cool basement, buy a dehumidifier model that can handle lower temperatures. Otherwise, the cold basement will cause frost to build up on the coils, which will make them less efficient and may cause the motor to short cycle. If you are running a dehumidifier in a cold space and you notice this behavior, turn the dehumidifier off until the ice has melted and fallen away. If the behavior persists you may need to replace the unit with a unit designed for cooler temperatures.
Assuming you do own or buy a new dehumidifier, you'll want to cut your energy costs with whatever dehumidifier you own.
If your basement is damp, and the dehumidifier is on, keep the doors to the basement closed so moist air doesn't creep in from upstairs.
Keep your dehumidifier coils and fan clean and free of dust. Some dehumidifiers include a washable air filter you can rinse out to get rid of dust build-up; if you have such a filter, keep it clean.
If you replace an old dehumidifier with a new, properly sized energy efficient dehumidifier, and you handle your humidity sources as best you can, you could cut your energy use by half or even two thirds over what you were paying before for the same level of comfort. But more likely, you'll use a little less energy with a replacement dehumidifier, while getting much better humidity control, or you'll use more energy than before (if you didn't have a dehumidifier) but you'll be far more comfortable and won't be spending your life savings on electricity.
With all the news turning up about the ill health impacts of indoor humidity and the resulting mold and mildew, you'll surely benefit from tackling your humidity problems and buying an energy efficient dehumidifier. You'll save money and be healthier.
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