|I need a fast growing evergreen tree to place beteen my neighbours house and mine. The tree will be 15-20 feet from his house and should be|
|Based on your zip code you are in zone 6A or the coldest part of zone 6; depending on your microclimate it might be as cold as zone 5. This means you need to look for cold tolerant evergreens that meet your size criteria. Unfortunately, most evergreens are relatively slow growers.
Although Leyland cypress are fast growing, they do not usually make a good long term planting in that they break apart in ice and snow storms and outgrow their spot very quickly unless trimmed often. These will exceed 25 feet in height so will be much too tall for your location.
I would suggest you consider some of the naturally columnar shaped arborvitaes instead. These grow to a predictable size and are often used in just this situation because they do the job well. Thuja occidentalis 'Emerald' (T.o. 'Smaragd') for instance should reach about 15 feet in height and stays narrow at about 4 feet wide. Thuja occidentalis 'Degroot's Spire' reaches about 20 feet tall and five feet wide. They will need at least a half day of full direct sun to stay healthy and dense. The drawback is that they will need protection from deer. This can be done via fencing or, in some cases, by using the repellents sold at garden centers.
Another possible option might be the blue hollies, for example Ilex x meserveae 'Dragon Lady' Plant Patent No. 4996 grows just about 15 to 20 feet tall and stays narrow at about six feet across. And, deer usually leave these alone. These also need at least a half day of sun and will not do will in a windy situation.
Your local county extension and local professionally trained garden center staff should also be able to make suggestions based on a more detailed understanding of your design goals and the growing conditions where you are trying to plant. Good luck with your evergreens!