Many homes built over a crawlspace will seem cold, particularly the floor. You can make your home more comfortable and more energy-efficient – and save on your heating and cooling costs – by insulating your crawlspace. This, unfortunately, is something some builders either don’t do or don’t do adequately. Using a moisture barrier or insulation backed with a moisture barrier is particularly important in a crawlspace. Outside air blows through crawlspaces, even with the vents closed. Ground dampness also seeps up into the sub-flooring. Installing a moisture barrier and proper insulation will protect your family and the structure of your home from mold and mildew, will make your home more energy-efficient, will reduce your cooling and heating costs, and will make your living space far more comfortable. You will need to either install the insulation with a staple gun or use small rods to hold the insulation in place.

{google2493298872}

If you found this tip helpful, you might also want to read these:
Add exterior insulation covered with synthetic stucco
Air seal around plumbing and electrical penetrations, as well as gas lines and dryer and fireplace vents
Use environmentally-friendly products to save money and the environment