Most of the better quality brands do NOT have a "4-season" option package because their standard construction already has those features. It's basically just decent insulation in walls, roof and floors, plus dual pane glass in the windows. You want the same benefits whether the weather is hot or cold outside, so the better brands provide them. You generally find an option package only in brands/models that have a low-priced "stripped" model, i.e. one that can be advertised at a low price. Then you have to add on one or more option packages to make it fully usable.