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I know I want to future proof my new construction by installing conduit instead of trying to guess what wires I'll want in 50 years.
But I want to understand the cost of conduit vs. non-conduit, at time of construction (before the drywall goes up).
EDIT An important bit of context here: I plan a concrete slab under the floor, and unconventional exterior walls that are nearly impossible to fish through later. So getting conduit right is particularly important.
Running conduit now is definitely cheaper than fishing behind drywall later. It requires a lot of holes in drywall to fish wires, and then each hole needs to be patched, painted, etc. It's also a difficult and potentially time-consuming job, as existing wiring, plumbing, etc gets in the way.
It also depends on how much conduit you're installing of course - you can go overkill and that obviously costs more. Typically in a retrofit, the hardest places to get cables are outside walls (due to insulation/vapour barriers), and walls where there is no unfinished access above/below. It's pretty easy to get wires into first floor walls when you have an unfinished basement or drop ceiling.
Running cables now is not totally future proof, because you can spend a ton of money and run every cable imaginable, and still end up not having the one you need 10 years from now (because it doesn't exist today).
Here are some general tips:
Here's what I would recommend as a balance:
I personally can not advocate running (mostly empty) conduit all over your unfinished house. The costs will add up to hundreds and hundreds of dollars, and could add several man days of labor. Then, when you need a new outlet, what are the odds that there will be conduit in the spot that you need it? What do you do if there isn't? Then you're back at the original problem.
Realistically, the odds that you will need additional cables run in the house someday are pretty darn good - however, the odds that you will need additional cables run in any one spot in your house are pretty darn low. Why waste the time and money when it's really not that much trouble to run cable through finished walls anyhow?
I'd say the exception might be for some low voltage services, say, if you've got a drop in each room for cat5/coax/component in a keystone plate or something. That is, a situation where any new runs you would want going to the same plate. In that case, you know where your hookups are going to be, and you'll never want any anywhere else, so putting in a hundred or so feet of conduit in the whole house would (potentially) wind up saving you a pile of hours when you do upgrade.
I agree with a lot of what gregmac is saying. My real question to you is what kind of wiring are you really thinking about for the future? Keep in mind that the trends are moving quickly to wireless technology and simple modulated (multiplexed) digital signals over existing conventional wiring systems. Today cat5 is used a lot, but I can see it giving way to fiber optics as the price falls and multiplexers are being coupled to computer automation for everything from remote lighting controls to energy monitoring systems. My son was telling me about a new virtual technology that they are testing at Microsoft where actual wall coverings are interactive monitors and control panels. They actually have working displays there in Redmond. He is a computer engineer there and says to hang on to your hats, some of the new stuff is gonna blow you away. The current trend is moving towards low voltage for many applications as well. So I guess it is really hard to anticipate needs for 10 years from now, let alone 20 years.
If you decide that conduit is really a good investment, (I seriously doubt it however) be sure to check the most recent electrical codes if you are going to run any 120/240VAC in them, or if you intend to mix AC with any low voltage or data. RF interference is a valid concern. Also, improperly installed conduits can be a serious fire danger if not terminated properly in boxes etc. open ended pipes that run between floors, basement to attic for example, can be a direct path for fire to travel through a structure quickly. The other disadvantage of hard tubing is placements. Modifying locations of outlets or boxes of any kind after your walls are covered is much more expensive and difficult than with regular NM wire or cat 5 cabling.
I know this probably doesn't really answer your original question, or what you may be hoping to hear, but I figured some of this might be food for thought. Good luck.
Yeah, I know, it's not an answer, but it's really too long for a comment ...
Basically, conduit makes it faster to run cables later, but depending on what exactly you're doing, it might not be that fast -- if you don't know where you're going to need the cables to go to, and you don't have the necessary junction boxes to be able to re-route everything, it's not really going to solve anything.
Most of the problems with running cables are when you have to run them through, rather than parellel to wall studs, or trying to run cables in walls packed with insulation.
Because of the insulation issues, I'd be inclined to run conduit in those walls if the walls are open already, to the existing wall boxes, with the assumption that I could always either add a few more items to a given plate. (I tend to use quad leviton blanks, but could swap 'em out for the 6-hole ones, to give me a couple more items to fit in there).
But I wouldn't run them horizontally -- I'd run them vertically to either the attic or basement (if you're lucky enough to be in an area with basements), and bring them to where I could then run them through a larger chase. For interior walls, I'd just be concerned with knowing where the walls are in the attic, basement, crawl space, etc., so I could get into the wall cavity to add more cables down the road. (see my comment re: running wiring through a crawl space)
The only time you really have problems are on houses on slab that are 3+ story houses (can only really handle the top and bottom floors easily), or 2 story houses on a slab (can't run the lower floor to the basement when there's no basement). In those cases, it might be worth running conduit to a central location (eg, the attic), so you can then connect any two points in the house, even if it's a more circuitous route. But, as @shirlock homes pointed out -- these sorts of runs require capping or similar due to fire codes.
The only other times I can think that I might run conduit is if I were to have a wall that I couldn't patch easily down the road (maybe real wood paneling, or tile walls?), or if I had to run an outlet to somewhere in the ceiling, as it's harder to snake cables through the ceiling than it is the wall.
