An igloo is cold on the outside but warm on the inside, so an igloo in a dream can symbolize a person who appears to be insensitive and uncaring, but is capable of warmth and affection.
You should consider why this person, whether it is yourself or someone else in your life, feels as though they must hide any degree of emotional warmth they may possess. Perhaps a difficult past experience has caused them to become emotionally numb.
An igloo in a dream can represent a desire to protect yourself from emotional pain by putting up a wall of emotional iciness.
Building an igloo can symbolize taking the resources that are available to you when you are in a difficult situation and using them to create something useful and effective.
The igloo can symbolize the womb, and therefore a desire for safety and security.