There are two kinds of air intake: one is for the furnace and one is for air circulation for your house. For the high efficiency furnace, it should be a white PVC pipe. And it should never get frost. For the air circulation, The pipe is 8 inch and it might get frost if the insulation is damaged. " `8 D$ q& ~! W# n8 y# A
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You should have someone look into this right away.
It's not right. You need get it fixed by the builder. The insulation should keep the cold air inside the pipe without any leaking. The builder just try to get away from this.