Planning for a smart home
By Charles Miller August 29, 2008 San Miguel de Allende

Many times I have been called upon to consult with people who want to add a computer network to their homes. It is unfortunate that some of these people wait too late to do this when building a new house.

Too many people naively believe they can rely on cordless phones and Wi-Fi internet connections and not have to install any wires. Unfortunately, these folks who failed to pre-plan for their technology needs end up with computer cables nailed to their new walls, or a lot of additional work and expense retrofitting the wiring after the house is finished.

You cannot use home wiring techniques of the fifties if you plan for your new home to have a computer network, sound system, home theater, multiple phone lines, intercom or security system. You should consult the professionals who will install these modern systems early on in the planning process and especially before any construction starts.

Builders charge significantly more for changes made while building or remodeling is already under way and you have already agreed to a price. This is less of a problem if you plan properly beforehand.

Planning for a modern “smart home” is not overly complicated or expensive. It does add some expense, but if undertaken along with the rest of the construction it is a lot less costly than doing the job over again later.

“Star topology” is important to remember. Wiring should be installed using star topology and not “line” or “bus topology.” If your architect or electrician does not know the definitions of those terms then you had better find one who does.


Star topology means that all cables emanate from one central location, known as the wiring hub. Visualize a wagon wheel with wiring conduits as its spokes. This central point is usually a closet, the garage, etc. Every wire must be a “home run,” meaning it is one continuous piece of cable from the wiring hub to destination with no taps or splices. Be sure to leave some extra slack in the wires and not cut them short.

When designing electrical conduits, consider not only the cables that will be installed now, but the likelihood of having to add new cables, such as fiber optic, at some future date. If your electrician cannot tell you what percentage of “fill factor” is recommended by the NEC, you are likely headed for trouble.

On the subject of the National Electrical Code; if you ever read through the code you would notice that along with almost every rule, there will be an exception to the rule. This recognizes the fact that installations are done in the real world where there are many instances when a rule may not apply or be practical. That being understood, your architect and electrician should know what the NEC recommends and at least aim to comply with it.

Plan the layout of the wiring so as to keep the low-voltage and high-voltage lines separated. High-voltage wires emit stray electromagnetic fields. This radio frequency (RF) interference can play havoc with low-voltage systems such as computer networks, telephones, stereo sound systems and intercoms.

Finally, there is no such thing as too much labeling of all those wires and conduits. It is also advisable to take lots and lots of photographs of the conduits and wiring during construction. After the walls are plastered over, those pictures are worth a thousand words.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 044-415-101-8528 or email FAQ8 (at) SMAguru.com.