Re: low voltage home
First I know of no 28 volt DC appliances, lights, etc. available.
Converting 120 VAC to 12 VDC will be expensive to do for more than one appliance. Inverters operate at about 70% efficiency, that means a hough loss.
Very accurate wire length measurements are need for DC circuits because of the losses caused by resistance per foot. Multiple sizes of wire would be needed or extremely large wire through out. A 5 volt drop in 120 VAC circuit is insignificant but a 5 volt drop in a 12 VDC circuit isn't. Wiring would probably be 5 to 10 times more expensive than wiring for 120 VAC.
It is extremely expensive to build a supply to provide enough 12 VDC to power a home or even a significant part of the home.
Be sure you live your life, because you are a long time dead.-Scottish Proverb