The dead air space needs to be of sufficient size to work, and the extra distance will help to prevent potential problems with mildew, insect pests, and humidity, which might lead to fungal diseases. Visually, you will want to select different types of dense evergreens for your planting scheme, with varied heights, shapes, leaf textures and colors. Planting a simple row of junipers, for example, all growing at the same height, is both boring and impractical. Shrubs with different heights provide a more effective wind barrier, while a mixture of foliar colors and forms is more appealing to the eye. Of equal significance, using the same species repeatedly increases the likelihood that a plant disease could spread from one shrub to another, even to the extent of wiping out the entire planting.
Windbreaks are certainly the most effective components in cutting winter heat loss.
A mature windbreak, normally comprised of several rows of tall evergreens, can reduce wind velocity by up to 50 percent, and otherwise deflect or channel wind movement away from the house. Unfortunately, in many urban areas, there may not be sufficient space for a fully developed windbreak, although new housing developments, especially with larger lots, are prime candidates. That can mean a sizeable number of trees. However, few of us strive for textbook perfection, anyway. Even an incomplete or immature windbreak can start to deflect some wind movement.