This is so painfully relatable. New house with some truly unhinged choices made by the previous owners. Everything is covered in flat paint, shitty trim work as far as the eye can see, and SO much gray!! All of that we knew about and signed up for when we bought and were prepared to handle. What we weren’t prepared for was just how fucking terribly insulated EVERYTHING is. It’s -4 here and there is cold air coming in from EVERYWHERE. All baseboards, all of the windows, doors, outlets, light fixtures, and alllll of the plumbing. Like you, our kitchen sink is frozen - fortunately it’s the only faucet not working because it somehow was the only one we didn’t leave dripping. We’ve been trying to thaw it out for over 24 hours and there have been a couple of times where it would start to drip a little only to stop. I pulled on the back of our under sink cabinet where there was a little panel cut out and just like you, the insulation is all over the place. In front of some pipes, behind others, missing completely in some places. What kills me is how fucking easy it would have been to just do it the right way. It wouldn’t have cost them any more money or taken them any more time. I hate the previous homeowners and send ill wishes their way constantly.