When I consult with clients about window film there are two things I consider the most important factors: do you have furnishings, art, etc. that you want to protect? Do you have a bad exposure that will pose a heat and glare control issue?

North exposures typically do not have direct sunlight so fading does not occur as quickly. UV is still entering through these windows and windows that are partially shaded with awnings, trees, etc. If light is entering, so is UV. Your local window film professional should have the ability to measure the UV entering into your home.

The investment will be well worth it if you have furnishings you want to protect. New hardwood floors, furniture, draperies, artwork, etc. are all susceptible to fading without protection. It is a small insurance policy to protect these items.

The windows we've chosen are also triple glazed, is there some prevention in the additional glass?

There should be but you will have to check the specs from the window manufacturer to know the actual UV rejection and energy performance numbers. There are a wide range based on the manufacturer of the film and the type of coatings used on the glass.

I cannot say whether additional protection is needed without knowing the specs on the window or testing it. It also depends on what you are trying to protect and whether there is any direct exposure. 50% UV rejection is not enough to protect from fading, even on a northern exposure.

The UV Coating was standard on these windowss

Lowees, it sounds like your new triple pane windows will probably be good enough. I have never encountered anything resembling a standard when it comes to UV protection. The manufacturer of the windows should have detailed performance numbers for the particular windows you are purchasing. Never assume unless it is in writing. I have seen far too many clients get burned because someone told them they had UV protection, and they did have some, just not enough to make a difference.

Most dual pane windows will block about 30-40% of the UV. Low E windows have a bigger range in the 35-99% with most of them I see in the 40-50% range. Triple pane should be 50-99% but again that is a wide range depending upon the types of coatings the manufacturer is using. 60-70% sounds good but imagine if you went to the beach and only put sunscreen on 70% of your face...

Educate yourself and get the actual performance specs for your windows. Only then can you make an informed decision.