We just found out that our builder does not use a Tyvek wrap. We hadn't really thought about this (to be honest), but are now wondering how big of a deal this is. Neither my husband nor I are well versed in construction... but they said something about using foam caulking to seal the places where air might penetrate (window sills, joints, etc.). Is this adequate? I can't seem to find a lot of information on advantgaes/disadvantages. Not that it matters at this point - it's too late. But I just wanted to be informed. If it matters, our house is brick on the front and vinyl siding elsewhere. Thanks!