Truly modern offices have hot desks AND are wired for teleconferencing - right in the open areas! That's right, if "open" is good for communication then a 60" screen on the wall with video cameras pointing at you is even better! You can share in the dull roar of collaboration with people on other continents ALL DAY! In the average open space you can fit at least two, maybe three such screens. When you have them installed, get the tradesmen to come during office hours. It costs way more if they come after hours and your employees should get the chance to see drills, saws and nailguns operated by professionals, they may learn something.
We all know there's nothing that stimulates productivity like the sound of productivity, right? So when you plan your next office, leave the kitchen open too - the scrape of chairs on the tiles, the sound of the dishwasher being unloaded, the happy PING of the microwave - not to mention the aromas of hot food - all these things will make employees feel right at home. Using only the most modern materials in the office - lots of glass and steel - will ensure the entire workforce shares the joy. You don't want to be damping the precious sound waves with carpet or plasterboard.
I wish I was joking.