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Dry or damp?

My vote is for damp location NEC definitions
Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.
 
Gregg Harris said:
Location, Damp. . . . roofed open porches
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I take that to refer to wiring exposed within the user portion of the roofed open porch, and so possibly directly exposed to moisture from the side. Whereas I understand the OP to be about wiring in the porch's "attic," which would not be so exposed, and hence would be a dry location. Like any other attic.

Cheers, Wayne
 
Is a porch with a ceiling - creating an attic as wwhitney suggests - and "open porch"? Clearly no exposed, just not conditioned.

I did find both damp and wet LED fixtures. Soffit lights being key term. Fewer choices than dry.

Thanks for the discussion. My preliminary search suggested it was clear cut.
 
What about the light fixture? I have not considered a light fixture in a porch ceiling to be in a wet location. The policy has been that unless it can be rained on, it is not a wet location and we just never paid much attention to a damp location. Every bathroom with a shower could be damp.
 
Now it makes me wonder if lights recessed in a soffit and the wiring is dry or damp?

In my case, also substantial porch "attic" and lights and wiring not near any "edge". But a soffit seems closer to that line between dry and damp.
 
bill1952 said:
Now it makes me wonder if lights recessed in a soffit and the wiring is dry or damp?
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Unless the roof above the soffit leaks, the wiring above the soffit would be in a dry location. Whether the luminaire exposed through the soffit needs to be damp location rated depends on your interpretation, but if close to the roof edge, using a damp location luminaire seems like a good idea.

Cheers, Wayne
 
ICE said:
It’s dry or it’s wet. There is no damp.
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If your referring to the location of a recessed luminaire in the soffit of a roof overhang, I certainly don't agree.

Even up against the fascia (the edge of the roof), such a fixture would not be in an "unprotected location exposed to weather." It would instead be "protected from weather" and "subject to moderate degrees of moisture" but not "saturation with water." So a damp location. [Quotes are excerpted from the NEC definitions.]

Move far enough away from the roof edge and it's not even subject to moderate degrees of moisture, but how far you have to go to be a dry location is a judgement call. If your roof overhang is only one to two feet, probably the whole soffit would be a damp location for a recessed fixture.

Cheers, Wayne
 
100% Damp Location. Concerning the fact that it is inside an "attic" space. It is outside the thermal envelope, and often, there is no access to these areas. We all know the implications of hot, humid summers and the dampness of the winter without sunlight. You can still use NM cable, it just has to be NM-C.

Location, Damp. (Damp Location)
Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. (CMP-1)

Informational Note:
Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.
 
jar546 said:
You can still use NM cable, it just has to be NM-C.
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My understanding is that the only product available these days that meets the NM-C standards is UF.

jar546 said:
Location, Damp. (Damp Location)
Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. (CMP-1)
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Indeed. Moisture is liquid water, not humidity or water vapor. How much liquid water will the attic see? Should be none.

Cheers, Wayne
 
wwhitney said:
My understanding is that the only product available these days that meets the NM-C standards is UF.


Indeed. Moisture is liquid water, not humidity or water vapor. How much liquid water will the attic see? Should be none.

Cheers, Wayne
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A moderate degree of moisture would be water vapor, which is water in a gaseous state, and when it reaches its dew point, it will have a change of state and condense into water due to a temperature change. No water should be in the attic to saturate the wiring, but the fixture being outside the envelope and exposed to high humidity will condensate into water, and the wiring in the fixture will become wet. And the cycle will continue
 
jar546 said:
100% Damp Location. Concerning the fact that it is inside an "attic" space. It is outside the thermal envelope, and often, there is no access to these areas. We all know the implications of hot, humid summers and the dampness of the winter without sunlight. You can still use NM cable, it just has to be NM-C.

Location, Damp. (Damp Location)
Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. (CMP-1)

Informational Note:
Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.
Click to expand...
So you don't allow NM-B in an attic, because it's not in the thermal envelope?
 
Gregg Harris said:
A moderate degree of moisture would be water vapor
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While the term "moisture" is sometimes used to refer to water vapor (e.g. "moisture in the air"), in this context it is only referring to liquid water.

A moderate degree of moisture would be e.g. indirect splashing on the ceiling from a shower, which is why 410.10(D) requires all fixtures with the footprint of a shower to be at least damp location rated. Fixtures outside the footprint of the shower are not required to be damp location rated, even though they may be exposed to about as much water vapor as those over the footprint of a shower.

Cheers, Wayne
 
The NEC makes this distinction clear. A roofed open porch is listed in the Informational Note as a damp location. That is not a regional interpretation; it’s in the code text.

The reason is simple: a vented porch ceiling is continuously exchanging air with the exterior environment. In South Florida or anywhere on the East Coast in summer, that means constant humidity, condensation potential, and occasional wind-driven rain. That is not the same as an attic.

An attic is an enclosed cavity that, while vented, is separated from direct exterior exposure by roof decking and other construction. That’s why the NEC allows NM-B in attics but not in porch ceilings.

For wiring in porch ceilings, the correct method is NM-C or UF, both of which are recognized for damp locations. NM-B is prohibited. This isn’t about interpretation; it’s about applying the definitions consistently with the environment.
 
jar546 said:
Never said that. I used it descriptively, and you ran with that part of the sentence. I should know better.
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Well, explain. You seemed to say the attic of a porch was damp and now am not sure about the attic if a house

I also don't know if it's different where you are versus where I am. Florida seems like a humid place. Here on the border with Canada, it's usually very dry, except out in the rain.
 
jar546 said:
it’s in the code text.
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Since when is an informational note code text.

The damp area described in the informational note is the space under the porch ceiling. It has nothing to do with the enclosed area above the ceiling. Beyond that, informational notes are there for edification purposes only. Suggestions as it were. You can like them and ignore them with aplomb.
 
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jar546 said:
The NEC makes this distinction clear
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You are misinterpreting the definitions.

jar546 said:
A roofed open porch is listed in the Informational Note as a damp location.
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Actually it says "partially protected locations under . . . roofed open porches." If your porch has a ceiling, the area above it is fully protected, and not a damp location. Likewise, I'd say a location exposed on (the bottom face of) the ceiling sufficiently far from any of the roof edges is fully protected. While it is at least plausible that a location on the ceiling right next to the roof edge is only partially protected.

jar546 said:
The reason is simple: a vented porch ceiling is continuously exchanging air with the exterior environment. In South Florida or anywhere on the East Coast in summer, that means constant humidity, condensation potential, and occasional wind-driven rain. That is not the same as an attic.

An attic is an enclosed cavity that, while vented, is separated from direct exterior exposure by roof decking and other construction. That’s why the NEC allows NM-B in attics but not in porch ceilings.
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A porch has a roof, and if it has a ceiling, the space between the roof and ceiling meets all the conditions of an attic you mention in the second paragraph. You have not demonstrated a material difference between such a vented, enclosed space with conditioned space under the ceiling (the attic of the the house) or unconditioned open space under the ceiling (the attic of an open porch).

Cheers, Wayne
 
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