Doors and Windows - window mildew

Our home is only 5 years old. We have double glass windows, metal on outside, wood inside. They have foam around the interior, between glass and wood.
My problem is that the windows on the north side of our home condensate and mildew at the bottom. We do not have storm windows, would this help the problem? Our builder said they weren't necessary.

An additional storm window will keep the interior pane of glass warmer & reduce condensation, but probably not worth the expense. The condensation occurs due to warm moisture laden air contacting the cooler surface of the window. The North being the coolest will experience more than the South or West. Unless your house is virtually bone dry you will have condensation forming on the colder nights. Mildew can be removed with a 10 part water, 1 part bleach solution.

Hi janicehuey, yes the first answer is correct, the problem is moisture laden air with in the house, if you leave a window open as much as possible to rotate the air and let the moisture out and replaced with fresh air this will help with the meldew, also there are balls and trays you can buy that ctually soak up the moisture place one or two of these on your window cills and it will also help keep the problem at bay, but there is nothing better than good alround ventilation, you can buy and fit trickle vents these are fitted the the window and allow you to open and close them with out the chance of people breaking in....