Jerome & Sandy:
First off, thank you for trying to do everything right when you had work done on your home. Getting permits and trying to use qualified contractors is critical. As a homeowner it is nearly impossible to know when your contractor is doing the work correctly. Permits are important, but unfortunately they do not guarantee that the work was done properly. That is why selecting reputable contractors is so important. (FYI see section on “Construction Consultant”)
This is also the reason why an inspection by a qualified property inspector is critical when selling a property. In some areas of California the sellers arrange for the inspection and provide the property inspector’s report to qualified buyers. This way the seller has a “heads up” on any current defects that may be turned up by the buyer’s property inspector. This in turn give the sellers the choice to have the discovered defects corrected before the home is officially on the market of just disclose them thus removing the bargaining chips from a buyer after they get their own inspection. Of course the buyer is encouraged to obtain their own inspector or to retain the seller’s inspector for an update.
With regards to the insulation; Faced insulation includes a vapor retarder and has a "right" and a "wrong" side. The vapor retarder performs an important function. The air inside the living space carries a significant amount of moisture from cooking, bathing, people breathing, etc. Heat moves from warmest to coldest. The warm/moist air inside living space naturally wants to rise into the attic.
Insulation is like a sponge. It tends to hold moisture. In California, due to the climate we have the vapor retarder is generally installed facing the home’s “conditioned space” meaning the interior that is heated in the winter months. i.e. the living areas. The vapor retarder keeps the moisture in the air infiltrating into the attic space from the living areas from condensing inside the insulation. Otherwise, it would be similar to holding a damp sponge against the ceiling.
The batt insulation you selected is a wrapped material. This material performs no better or worse than insulation with plastic or paper on one side only. The wrap on all sides simply limits fiberglass dust and make it more comfortable for the installers. Wrapped insulation is manufactured by a number of companies. Certainteed and John-Manville are two of the larger companies. This material generally has a white plastic face with printing and grey plastic on the other faces. It we look at the manufacturers installation instructions on the bag that the batts come in, you will see that the white/printed face is identified as vapor retarder. The instructions will indicate that the vapor retarder should be installed in accordance with local requirements. This is because in certain climate zones - not California - the vapor retarder is installed away from the living space.
You can actually see which side is the vapor retarder as well. Look closely at the surface of the white faced side - it is a smooth piece of plastic sheeting. This is the vapor retarder side. Now, look closely at the grey plastic facing. You will see it has many small holes in it. The holes allow moisture vapor to pass making the grey material vapor permeable. See the attached photos.
If your insulation is installed with the vapor retarder side away from the living areas, it is in fact improperly installed. The moisture from improperly installed insulation can create a host of issues over time. The buyer’s property inspector may have saved you significant grief latter on. A thanks to the inspector may be in order.