Don't be afraid to mix it up. In fact, the more obvious the stylistic distinction, the more successful the solution is likely to be. But I might suggest making a nod to the existing building by taking an element or two and deploying them on the addition in a simplified way. For example, in this project we broke free of the existing building's traditional design constraints of form, window pattern and ornament, but used the existing stone and pitched roof language (clad now in metal instead of shakes) to unify the building. The result is quite stunning.

That's nice work! Thanks for sharing.

I do not care for modern additions on a older house. I prefer additions that blend so that they might have been there originally.

This looks very nice but I'd sure like to see some pictures that better illustrate the old blending in with the new. Sounds like you had the right ideas. Great job!

You can look through these examples on Houzz. It sounds as if you're not happy with the original exterior and I'm wondering if adding a modern porch will make the existing home any more desirable.
http://www.houzz.com/photos/exterior/traditional-house-modern-addition-/p/40

@bgfuqua that's valid, though in our case, there is nothing particularly redeeming about the 'original' house. It's not particularly old (80's) nor architecturally compelling. @bluenan I'm certainly wondering the same. A front porch is going to be a plus regardless of style, though, so we have that going for the project.

I was wondering if there were modifications to the original exterior that might be made to make it blend better with the porch and make you happier. I'm sure there are budgetary constraints, but you're right, a porch will add wonderful outdoor living space.

This is an old thread, but if you are searching for modern additions on more traditional homes, we've done quite a few in the DC metro area because all the homes are older. I call these updates "contempolonial" -- a combination of contemporary and colonial style. You can see samples on my Houzz profile and on our website.

This is on the back of a Cape Cod home.This addition runs across the back of a brick rambler.