Since the best place to start is in your own home that is where I"m starting too. There was this cool feature in our home and one I hadn't considered but now want in all the bathrooms:
Its a timer for the exhaust fan. Think of how often you flip this thing on and forget to flip it back off. I know it happens all to often in our house. Exhausts fans are great for getting rid of stinky smells or all the humidity from your shower but they also suck out your air conditioning and heating. Having a time is a great way to make sure you only use it as long as its needed and no worries about forgetting to turn it off!
Our first personal upgrade was going to be the insulation in the attic. It needs to be thicker for maximum benefits but the hubby is still trying to figure out the best way to get it all done. In the mean time the toilet in our bathroom had developed a leak at the bottom and needed replacing anyway (it was rather worn out). So we got this one:
|two stage flush|
As you can see it has two buttons on top. The smaller one is for number 1 and the larger one is for number 2. A great design to help save water and one we will be placing in all our bathrooms when the time comes!