What do engineers change in their houses that other people would not think of?

My home currently has

• Large, operable skylights. A whole-house fan would be an alternative, but I prefer these because, once open (along with a selection of windows), they cool the house rapidly with no additional input of energy. They are also silent. As I live in an area with cooler nights and fairly dry air in summers, they are sufficient to do without air conditioning.
• Double-pane windows (we do not live in an area with temperature extremes, so this is sufficient). I believe they have a coating to reduce solar gain.
  
• Front and back yard timed, programmable irrigation.
• Cordless blinds. No dangling string, just pull up or down on the middle so that it stops where I want it.
• A programmable convection oven with a 100F dough proof cycle.
• LED bulbs in most of the most-frequently used fixtures, including the shop lights in the garage.
  

As I build and remodel, I would like to add:

• More durable roofing, suitable for rainwater collection and, eventually, for solar panel installation.
  
• Rainwater storage with timed watering. (One engineer whose open house I visited was going on about his rainwater collection system, and his 2000-gallon tank. I asked where he put the tank. I was standing in front of it. It was a plastic tank, covered with ivy.)
  
• Systems to reuse graywater. At the very least, water from hand- and clothes-washing could be used to flush toilets.
• Instant hot water heater.
  
• Built-in CAT5 wiring from a central closet.
  
• Open tubing or conduit in the walls, so that additional wiring/fiber, etc. could be "fished" through easily
• Smart windows and/or blinds that could selectively reduce solar gain, so that south-facing windows could let in warm sun in winter but all windows could close out direct sunlight in summer. (Currently, this is a manual process of opening and closing blinds.)
• Passive solar heating, as a primary source of heat.

From Dilbert's Ultimate House, the one idea I would certainly incorporate would be the Christmas tree closet. No decorating and un-decorating each year, just wheel it in or out, and close the door.

• I have a DSL connection (specifically ADSL2+), and installed a DSL splitter & dedicated "homerun" from the demarcation point (aka MPOE) to the DSL jack where the DSL modem is, as opposed to in-line splitters installed at each phone jack that a typical self-install DSL involves. My download speeds increased > 2x (from ~6Mbps to ~15 Mbps) when the splitter/homerun was installed vs. using the in-line splitters, so something with my inside wiring was attenuating the DSL tones
  
  
  
  
• I wired the house with CAT-6 throughout (hooked up to GigE switches). Two 802.11n WiFi access points provide whole house coverage for wireless/portable devices (same SSID for both APs, set to the least congested non-overlapping WiFi channel at each location for maximum throughput). Stationary devices are all hardwired into the GigE network.
• Like Ethan Kaplan, I installed Insteon light switches, appliance modules, motion sensors, etc, but they are controlled/scheduled instead by a Universal Devices ISY994i Series dedicated controller. I can remotely control the Insteon switches using the Java-based desktop app or the MobiLinc iOS app. 
• Installed LED lights for the lights that are the most commonly used, connected to Insteon switches which are programmed with adjustable ON/ramp levels depending on the time of day (eg. late at night the lights initially turn on to 30% instead of 100% -- this is via the ISY994i controller)
• Since we love natural light, had skylight tubes installed in the bathrooms and in the main hallway (we've got a single story home)
  
  
• Installed additional attic insulation (from R-19 to R-38) to better insulate the home, thus reducing the need to run the A/C in the summer or the furnace in winter as often + sealed potential points of air leakage between the living space and the attic. Every single utility bill since has been lower than the same month from the year previous
  
• Installed radiant barrier in the attic, primarily to reduce summer heat gain in the attic, which in turn transfers into the living space (plus our AC unit and AC ductwork are mounted in the attic so anything to help lower the attic temps helps the AC & ductwork).
• Installed a Nest thermostat
  
• Configured ControlByWeb temperature module with 1-Wire sensors to monitor temps around the house, graphed using rrdtool (with daily/weekly/monthly/etc graphs). This was mainly used to plot the effectiveness of radiant barrier installed in the attic. I plan on adding the Nest thermostat data to the graphs (most likely via nest-api) since I don't currently plot the living space temperature or when the AC or furnace is running. The outdoor ambient temp is also uploaded to Weather Underground (though my weather station doesn't have humidity, pressure or wind speed that a dedicated weather station would have...some to put on my TODO list)
  
  
• Installed a Xceltronix AC100130 Garage Door Autocloser, for those times that I get distracted and forget to close the garage door. It's only happened twice, but one was during a trip to Tahoe from the Bay Area...thankfully my neighbor called and closed it for me. Auto closer installed soon after that incident.
  
  
  
  
  
  
• Hyloft garage ceiling storage racks for additional storage.
  
  
  
  
  
• Installed garage door insulation to reduce heat transfer into the (west facing) garage in the summer & heat loss in the winter.
  
  
• PoE security cameras, powered via a central PoE switch. They proved their worth when they captured someone stealing a package off my front porch. I should have paid for the option where the camera shoots deadly lasers at the thief :\
  

Two words: digital scale.

Seriously.  One like this*.  Cooking is generally viewed as an art form (at best) or something rather random and chaotic (as worst).  In reality, the execution part of cooking is actually just one thing: Chemistry.  And any good chemist will tell you that lab execution mastery starts with your tools.

I could go into a lot of detail now about all the things that molecular gastronomy (the generally accepted term for the scientific/engineering approach to cooking) would suggest you invest in.  I have built most of them into my new kitchen: a sous vide rig, a steam oven, an atomiser, a whipping siphon, a dehydrator, an immersion blender, a smoke gun, a blow torch and so on...

BUT, above all else, start treating cooking like engineering by first measuring everything you do.  To do that buy a proper, accurate, digital scale and, next, a fast meat thermometer (this one would work*).  These two <$40 investments will massively improve the quality of most things you cook.

* No, I haven't put my affiliate code into these links!

1. The tank is embedded into the wall, saving space and providing for a more elegant, minimalistic look.
2. The bowl is wall mounted, making the floor underneath very easy to clean.
3. The dual flush means that the toilet has two modes: One to flush liquid (that only uses half the water in the tank) and the other to flush solids, saving a significant amount of water.

• Hard wired Cat-6 back to a wiring closet. 3 Wifi access points with the same SSID's on both bands (Airport Extreme's). Most drops have PoE for security cameras, or I power PoE inline
• Fully outfitted Insteon automation hooked to a MacMini running Indigo, software from Perceptive Automation. I have all the lights, the garage door, ceiling fans, the water fountain in the front yard, the thermostat and motion sensors wired in. I can do logic in the software to for instance turn on all ceiling fans when the AC turns on
• A few light switches are KeyPad Link which have four custom LED buttons on them. The one in our master bedroom uses those to indicate the garage door status and control it, as well as turn the reading lamps on in our room
• Indigo has plugins which also let us do "presence" indication for my wife and I. Using the HTTP endpoints for Find My Friends in combination with looking for our phones MAC addresses on the wifi, the house knows if we're home, and when we're approaching home. It configures itself automatically (ie, lights on at night when we get home, shut off all lights when we both are gone).
• We have a babysitter mode to suspend the above
• An iPad with a custom control panel controls all this. It sits in our entryway.
  
  
• Other plugins hook into the Sonos and our Denon receiver so they can be configured along with lighting, and lighting can auto-adjust when things on the receiver change (ie, switching to "Movie Mode")
• On the iPad is a shot of our kid monitor for our son. There is also a dedicated app for that that supports sound. It's a PTZ controlled IP camera
• Our phone system uses OnSip virtual PBX. It has rules set to turn away late night calls, forward to our cells, etc
• All our lights are LED now. We replaced the regular lights as they burned out.
• The MacMini that drives the house also has two DAS systems attached. One of them is a Drobo Elite with about 12TB and the other a regular high speed DAS with 4TB of drives in it. All machines in the house TimeMachine to that box. It also has my DropBox account synced to the 4TB DAS and time machines that to the Drobo. Lots of redundancy. We store raw BluRay rips on that, and down-compress them into iTunes for the two TV's in the house.