Wattage for Deck/Stair lighting?

[Dublin]

Hiya Folks,
I'm in the process of building a deck. I have the framing done and am about to install my posts. I've drilled my posts for wire and have found some fixtures that I think will work ok but am unsure if they carry enough wattage. One of them is a 120V 7w light, essentially a nightlight. The other is 12v/11w. I plan to install 4 of these on a small stairway (4 steps) and on the posts that surround the deck (approx. 12" above the deck). I don't want to flood the deck with hugely bright lights but also want to ensure I light the area properly. I will have additional lighting from above so aside from the stairs, the rest is essentially 'mood lighting'. So I guess my question is two-fold. 1) would you recommend the 120V solution (on GFCI of course) at 7w or the 2) 12v solution at 11w? I'm mostly concerned with the lighting output at the stairs for obvious reasons. I don't want to put 100w bulbs there but don't want to place something that won't give me adequate illumination. Some additional information: This is for a deck on a cabin in the woods so it's very dark at night (ie. no additional light sources nearby). I suspect either will work but thought I'd ask the collective wisdom of the group for their opinions. Thanks very much for any advice.
Cheers,
jlc

[Richard A Hetzel]

What you need to compare is not wattage but LUMENS for each option. Lumens is the gross output of light. Wattage tells us nothing about the quantity of light, and that's what you're concerned with here.

[Dublin]

Good point Richard. I'll request that info from the mfg. Is there generally a range of acceptable lumens for stair lighting? I looked at the various codes (limited to searching the internet as I don't own the books) but didn't see any specifics around min. lumen levels. Thanks for the help.
jlc

[Richard A Hetzel]

All you really need for stairs is a soft glow...almost anything will be sufficient. In fact, too much light might be worse, because people may be coming out of the dark, and excess light will demand that their eyes adjust to the intensity. Dim lighting will not cause this problem.

If there is anything in building codes, I think it would apply mainly to interior stairs, where people will be mostly coming from lighted spaces to the stairs, and there, the light levels should be much higher.

It isn't just the light, it's often also the difference in the lighting levels that's important. If you can conceal the light sources from the view of people approaching the deck stairs, that would be a big step in the right direction. That is often done in stair lighting with louvered fixtures that conceal the light source and direct light downward on to the stairs.

[Dublin]

Thanks Richard. I took a nightlight outside last night and concluded pretty much what you said regarding intensity. Given the darkness around here, it doesn't take much light to see where you are going. The fixtures I'm looking at do have a "hood" that directs the light down so you wouldn't see the light directly. Now my only decision is 120V or 12V. 120 is cheaper up front (fixtures wise) as the 12v needs a transformer and the fixtures are more expensive as well. But there are obvious advantages to the 12v system. Anyway, thanks much for the help!
jlc

[Mike44]

When deciding on 12V or 120V, I suppose it just comes down the distance that you will be running your lights. To prevent excess voltage drop and 'dim' lights at the end of the run, 12V is technically limited to about 200' before you start noticing dimmer lights (max 250' I would say). A 120V system will maintain less voltage drop to further outlets in excess of 250', so it might be more advantagous to you if you plan on having a run over 200'.

Although 200' sounds like a lot, you might get pretty close to it after you consider the wire run to try and conceal a transformer or something. I used an extra 40' to hide the transformer, but its worth it as long as you don't go over about 200'. You can reduce voltage drop as well buy using 12 gauge low voltage wire - try not to use 16 though except for when your tapping off to a light or something.

Personally, for a deck lighting system where you are only putting in step lighting, I would suggest the 12V system. Yeah, I suppose it would be a higher cost with the transformer and stuff, but I guess I'm just more familiar with it for accent lighting. Plus, you don't have to stick with the 11W bulbs if you find they are too bright. There are 7W available that can be used in place of the 11W (the ones I'm thinking of are the Single Contact Bayonet Base bulbs). I'm also thinking that 11W bulbs may be too bright for steps. I would use that wattage more for path lighting, but I would use a 7W bulb for step lighting if I was able to.

Anyways, those are just my thoughts but whatever you end up doing I'm sure will look nice!! Best of luck on your project!

Mike