Where abouts are you located in zone 6? Does your area experience ice storms? I'd suggest white pine for fast growth but they're prone to breakage from ice in my area.

Same here cecily, one down the road from my house broke during a snowstorm. Whole leader snapped off, now the top of the tree is like a J-hook.

Logan/cecily, thanks for the advice. I am in NYC metro. We do get storms. I have a white pine on the property already and it faired well so far. A different tree may type bring some variety in the yard.

Would you consider the green giants after all? What if I plant them 2 feet from the fence and keep trimming them regularly? Is 2 feet too close?

2 feet is too close. I would go about 8ft from the fence. Green Giants (as the name implies) get gigantic. I would plant a row of these paired together:

English Oak 'fastigiata'

European Beech 'dawyck purple'

I know many people don't like fastigiates, but I think this would be a good situation to use them in.

Not green giants. Maybe a couple of white pines for fast screening with the intent to remove them in ten years. Also plant a holly for the long term. The pines will provide privacy while the holly grows.

Hmmm...if green giants get too large, use white pine, that get even larger, just trim them to a trunk? You could do that with the green giants.

There are other arbs that have the height and faster growth, and while they are wider than emeralds, they aren't as wide as the green giants. Brandon, pyramidal, rushmore, and some newer ones, north pole and similar names. There's several.

The fastigiate tree suggestion is not a bad one...if you are seeking to screen high and want to use limited space, they are exactly what you want. Frans Fontaine hornbeam, slender silhouette sweetgum, red obelisk beech...these are just a few.

The holly isn't a bad choice. Not sure i'd worry about the staggered planting.

no on GG .. and norway spruce.. nor white pine ... you simply dont have the space ...

now this took me a long time to figure out.. exactly how much time.. in winter.. are you going to be seeing that house ... i figured out.. i dont really sit on my porch/patio/deck .. so i really dont spend a lot of time looking out there ... so by that point.. i realized i did not need an evergreen ....

your fastest.. solution ... is a deciduous tree ... which will block the site line.. for all the months you might be outback there ...

if you have a kitchen window or something.. consider a window film...

ken

https://www.google.com/search?q=window+film&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiFrrPXjbfPAhUHxoMKHWoMAW8Q_AUICSgC&biw=1037&bih=745&dpr=0.9

Existing arborvitaes are actually pointing at the house: "Hey! Look at this!". That's the problem with columnar plant shapes, they are exclamatory. Better to plant an assortment of rounded plant shapes there, that eventually screens the house. And in the meantime provides its own center of interest.

An assortment because (in addition to it being more interesting) when you plant things in rows of one kind that actually draws attention to their vicinity, even when they are not slender and pointed in shape. An exception would be a formal garden where the entire design is a comparatively small selection of plants in rows and squares etc., so that any given single row of shrubs is not going to stand out on its own.

Conifer hedges with the bottom branches pruned off are not attractive. In fact no conifers not old enough and situated such that they now have most of their branches concentrated in the upper part look good with the bottom branches cut off - whether they are part of a hedge or not.

Thank you all for the suggestions. These are all interesting ideas...and they give me more answers than I'd want :)

ken_adrian made me think to prioritize the features I am looking for and here is how I stack rank them in importance:

1. space saving - I cannot plant beyond 5' from the fence , however it is possible to have the trunk close to the fence and have larger high raised crown
2. quick privacy - I hope to get some privacy above 8-10 feet in 2-3 years. Full privacy is not required since I have the fence, blocking the view will be sufficient.
3. blocking the view year round - day and night. the house has very annoying flood lights visible from my kitchen window which sits at 10'.
4. aesthetics - no plant can be uglier than the view now
5. preserve the existing evergreens (cost effective)
6. less maintenance

It seems that the ideal answer to these will be
(1) several columnars or single larger raised crown (provided that the crown can be formed in 2-3 years)
(2) fast growing
(3) evergreen
(4) some color (deciduous??) or interesting shape will be nice
(5) I'd prefer single specimen to combine with the current evergreens rather than planting a new row
(6) natural shape better than sheared/trimmed

What do you think is the best match for these requirements? Or are they even compatible?

Pine or spruce seemed a good choice but Embothrium has a point - how long before the crown can be raised and how much space a growing pine will need?

Fastigiate trees look like a good choice but not for year round screening. Except that some trees preserve the leaves during the winter. Crimson Spire Oak is a fast growing one and an interesting option.

What about juniper Skyrocket? These seem to be of very interesting color and shape. Not sure if they are suitable for my zone 6. It gets hot and humid during the summer.

And here is why I need screening all year round

Did you look into the fastigiates that I mentioned above? Another option would be american holly, or monrovia's variegated english holly.

Logan, yes I did. Thanks to you I settled on Crimson Spire oak. A hybrid of the English oak and white oak. It retains leaves during winter.

What you think?

I think it is a good choice! Hope to see pictures after they are planted!

Those arbs in ten years will fill that gap very nicely, as Ken said a well placed decidous or two would help for the crucial warm season screening. I'd go for a honey locust or two so as not to block the sun too much to the arbs.

Another suggestion to consider. Plant the screening tree close to YOUR house so that you look out that window into an interesting close-up view of branches, hopefully with birds' nests and flowers. One of the many dogwoods might be tall enough. Leave the arbs to fill out the fence, beefed up with some other shrubs and maybe a fastigate tree, or birches? I wouldn't consider any of the non-fastigate trees five feet from the fence, because the crown could extend very deep into the neighbor's yard. That's not neighborly and she may well lop off the overhanging branches leaving you with a less than attractive specimen. I would also have no hesitation about talking to them about the floodlight. I'm sure they have no idea, and would be happy to tilt or move it so it's not shining in your window. You can make the point that it is creating a security problem for you as it is -- you can't see out because you're blinded. What would be most attractive for both of you is some uplighting on a tree you both agree on..

I would just use the crimson spire oak, with shrubs under them. You can underplant with things like nandina 'firepower', abelia grandiflora 'rose creek', berberis thunbergii, hibiscus syriacus, etc.

When you plant so close to a property line you should also consider the other property, what's planted or going to be planted on the other side. The roots from your choice of tree are going to go on the other side of the fence. Just saying.