A basement finishing project can be a great way to increase your home’s living space without having to do major renovations. Many basements are cold and unappetizing, even after they’re finished. This discourages guests and family members from using basement spaces. Why are basements so cold? There are many factors that contribute to the cold air in basements.
Ground Temperature
Temperatures below the surface of the Earth don’t fluctuate nearly as much as those above. It is not subject to daily sun changes and has a high thermal mass. This means it can store heat. The temperature changes by just a few degrees Fahrenheit per hour, only two feet below ground level. The temperature in many caverns and caves is always in the mid-50s. This stable, relatively low temperature is transmitted to the basement by the ground, which makes it feel colder.
Slow Heat Adjustment
Basement temperatures adjust slowly due to the slow response of the thermal mass to surface changes. Sometimes, the lag can be almost a whole season behind outside weather. Basements can seem colder than average in the spring and early Summer, but they aren’t quite as unpleasant during the fall season.
Solar Heat Gain
The solar heat gain from the upper floors can also indirectly affect the basement temperature. This problem could occur if your heating system has both basement and upstairs areas supplied by one furnace. The furnace will shut off when the basement is warm enough to take advantage of the sun’s heat. Walk-out basements have more windows and heat gain, so this problem is lessened.
Heat Rises
The heat that your furnace produces can quickly rise through your home, especially if your basement is not ventilated. Even if you have electric heaters or supplemental heat sources, your basement might feel cold. This problem can be mitigated by using fans to circulate the air downstairs.
High Humidity
Basements can be humid because of the moisture that rises up from the ground and through the slab. Older homes lack a vapor barrier beneath the slab, so humidity can reach 60 percent. This is where mold starts to grow. Basement humidity can make your downstairs feel cold and clammy, even if it is lower. The extra water in your basement allows your body heat to be shed more quickly. This is similar to sweating on hot days. To dry the basement air and increase the temperature, add a dehumidifier.
Heat Register Imbalance
This is most common in single-zone heating systems, where the homeowner does not open and close all registers equally. This technique allows warm air to be pushed into rooms that have different heating requirements. If you have a lot of windows and south-facing rooms, consider closing the registers. Registers that have good seals will keep heat in colder rooms of your house rather than making sunny rooms feel stuffy. For maximum efficiency, motorized registers can be set up to perform this task on a specific schedule.