It is more cost-effective to add insulation during construction than to retrofit it after the house is finished. To properly insulate a new home, you'll need to know where to insulate and the recommended R-values for each of those areas.
Before you insulate a new home, you also need to properly air seal it and consider moisture control.
In most climates, you will save money and energy when you build a new home or addition if you install a combination of cavity insulation and insulated sheathing. Reduce exterior wall leaks by taping the joints of exterior sheathing and caulking and sealing exterior walls. Cavity fibrous or cellulose insulation can be installed at levels up to R-15 in a 2 inch x 4 inch wall and up to R-21 in a 2 inch x 6 inch wall. R-values can be higher for foam insulation and other advanced insulation systems.
Rim Joist - Foundation Wall insulation - Basement/Crawlspace Ceiling Insulation - Basement Chase Hole Air Sealing - Bulk Head Doors/Hatche.
Old Insulation Removal & Disposal - Ventilation Management (gable, eave, ridge) - Insulate Around Skylights - Build/Install Raised Storage Platforms - Insulate Flats, Slopes & Vaulted Ceiling Sections.
Drill & Fill (interior/exterior) dense pack cellulose only, Swath Access (interior/exterior to remove existing insulation - i.e. fiberglass) dense pack cellulose only, Open Stud Wall Cavity (New Construction/Renovation): dense pack cellulose, rock wool batting, closed cell spray foam, Insulweb netting, Intello Plus smart barrier.