The crawlspace under our house seems abnormally cool in the summer and warm in the winter. My first thought is that the ductwork leaks, but a friend said it may be just radiating warm or cold air depending on the time of the year. What are your thoughts? -Scott

Hi Scott,

If your crawlspace is enclosed, it will stay cooler in the summer and warmer in the winter than the outside air due to the more constant ground temperature, but it should not be excessively different as you describe. It’s possible that the ducts are poorly sealed, allowing air to escape, or that they were inadequately insulated.

To check, go under the house when the HVAC system is running and feel along the ducts for air leakage. Also, look for discoloration of the insulation or rusting of the ducts that could indicate a leak. Pay particular attention to the joints in pipes and where runs of ducts meet in case a pipe has become disconnected. Repair any leaks using duct mastic or metallic duct tape rather than standard cloth tape. You can also have a HVAC professional run a pressurized test of the system to check for leaks.

If your ducts are inadequately insulated, you may see condensation forming on the outside of the ductwork during the summer when humidity is high and the air conditioner is running. Poor insulation can not only increase your utility bill in winter and summer by up to 30%, but it may cause excess moisture in the crawlspace which can led to mold. According to the U.S. Dept. of Energy, ducts in unheated spaces should be insulated to an R-value of R-4 to R-8 in warmer parts of the country, and an R-6 to R-11 in colder climates.

Another possibility is that your floor may need insulating. If so, install batts of fiberglass insulation between the joists in the crawlspace with the paper vapor barrier facing up toward the living area and hold it in place with support wires. For more on insulating under a house, see our episode on the Scariest Utility Bill.


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Danny Lipford

Danny Lipford


Danny Lipford is a home improvement expert and television personality who started his remodeling business, Lipford Construction, at the age of 21 in Mobile, Alabama. He gained national recognition as the host of the nationally syndicated television show, Today's Homeowner with Danny Lipford, which started as a small cable show in Mobile. Danny's expertise in home improvement has also led him to be a contributor to popular magazines and websites and the go-to source for advice on everything related to the home. He has made over 200 national television appearances and served as the home improvement expert for CBS's The Early Show and The Weather Channel for over a decade. Danny is also the founder of 3 Echoes Content Studio,, and Checking In With Chelsea, a décor and lifestyle blog.

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