I dont understand why go thru the expense of a facadectomy and not go bigger in this location? I think the neighborhood wouldnt even push back much
Look at Figure 1-12 on page 26 (that's the page # as pagination of the pdf is counted). It's got some massing illustrations that show only about 20% of the footprint of the old building being torn down, the rest of it remains. And the new building is then up above parts of it. That doesn't look like a pure facadectomy to me.
Having said that, I'm sure they have to seriously gut the old building to provide structural support for that portion of the new building rising up above it. So much of the old building that "remains" will indeed be gutted to the point that it does sort of approach a facadectomy.
Anyhow, this looks like something of a grey zone between extreme facadectomy at one end of the extreme, versus an adaptive reuse with an expansion tacked on.
And setting aside whether this is or isn't a facadectomy (I don't care so much), I like the overall proposed design. The design elements of the new building plays off the old facade's design elements pretty well, while still having their own modern flair. And while they're doing some of the now-popular thing of having arbitrarily differing patterns of materials / fenestration, they haven't gone completely bonkers with it like some architects do. It doesn't look so crazily over-designed and cluttered like some recent designs. I like it.
As for your point on going bigger? I'm one of the ones who sometimes complains about the height fetishists around aB, but ...... OK, I admit it: this is in a location where I agree it could have gone taller and I'd even argue should have, for the sake of getting more units in play within walking distance of downtown / Back Bay / multi-line T access.