Proper insulation and ventilation is the first and most important energy saving measure. It can reduce heating needs to one-third (about 50 kWh heat/m2/y) or even one tenth (less than 15 kWh heat/m2/y) of what an average house would need.

Remarkably, a properly insulated house, which only needs a third of the heat to keep you warm, will not be more expensive to build. The extra investments in insulation, ventilation and high-efficiency glazing, can be offset by a smaller and cheaper heating system. 
An efficient house will also be healthier and more comfortable to live in - it avoids 'cold radiation' (as from windows), the differences of temperature between heated and non-heated rooms is less, and it can be more efficiently ventilated.

Checking your home's insulation is one of the fastest and most cost-efficient ways to use a wholehouse approach to reduce energy waste and make the most of your energy dollars.

• Remember that new windows must be installed correctly to avoid air leaks around the frame. Look for a reputable, qualified installer.
• Install white window shades, drapes, or blinds to reflect heat away from the house.
• Use higher density insulation, such as rigid foam boards, in cathedral ceilings and on exterior walls.
• One of the most cost-effective ways to make your home more comfortable year-round is to add insulation to your attic.

Additional Resources

1. EERE Home Insulation Tips
2. DoE Insulation and Air Sealing Tips