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Bathroom Lighting Basics

Bathroom Window DesignThere are several factors that make lighting for a bathroom different than other rooms. Space constraints, privacy concerns and task lighting needs are the most important. A well though out bathroom strikes a balance between natural lighting and artificial lighting but there can be challenges getting there.

Natural Lighting

A good bathroom design will include suitable windows and optionally a skylight. Natural lighting is obviously energy efficient, and provides a welcome feel of openness and freshness to a small space. Not to mention the exterior view possibilities. The challenge is finding a good location for a window. Bathroom walls are often crowded with mechanical systems.

Bathroom plumbing lines, ventilation and electrical cables all have to share the available envelope, which sometimes dictates filling the only exterior facing wall. Some advance planning here is possible with new construction, but for remodeling, not so much.

Window placement is also dictated by structural concerns. If the adjoining walls have other windows, then there may not be much flexibility for placement of a bathroom window, either. Nonetheless, it is recommended by the National Kitchen and Bath Association’s planning guidelines that every bathroom includes a window or skylight equal in area to no less than 10 percent of the floor area.

Although plenty of natural light is a good thing, a bathroom with too much window glass can make you feel too exposed, which you well may end up being, particularly with a window on the front side of the house. Consider installing a glass block window, or one of frosted or etched glass.

Convertible frosted glass windows are available, which transform from translucent frosted to clear glass at the push of a button. Another option is to situate the window higher up on the wall, if the space exists, in which case an arched-top shape provides a pleasing appearance.

Bathroom Skylight

Skylights have their pluses and minuses to consider as well. On the plus side, a skylight can let in up to five times as much light as the same size window. There are also no privacy concerns to worry about, unless you have very low flying aircraft passing over your house on a regular basis. Another benefit is the dramatic break of the ceilings’ dull visual plane that a skylight provides, along with the striking effect of a floor to ceiling shaft of light at mid-day.

On the minus side, condensation can be a problem with skylights, and the humid environment of a bathroom exacerbates the problem. Heat loss is also an issue, even with high energy efficiency models, and the juxtaposition of warm indoor air with cool outside air can create drafty felling convection currents. The type of light a skylight produces is also highly dependent on roof location, orientation and type of shaft.

Skylight Placement

Eastern facing exposure will give you lots of warm morning light. Northern exposures create soft diffuse light throughout the day, while south and west exposures can let in too much light and create a stuffy room, but can be moderated with shades or glass tint coatings. Straight vertical skylight shafts are simpler and more economical to build and paint, but a flared shaft can provide even more light and visual drama.

If the skylight’s drafty currents and condensation issues are a deal breaker, then a tubular skylight is a great alternative. It’s basically a reflective shaft with a clear plastic dome at the top and a diffuser lens at the bottom. They work well in a bathroom where the distance between the roof and ceiling is long, the room has no exterior facing walls, and you don’t need the ventilation an operable skylight gives. They also have a much better insulation rating than a regular skylight, so heat gain and loss is less of a problem.

Artificial Light

Well placed task lighting is important in a bathroom, where we spend a lot of time looking at ourselves in the mirror. Harsh overhead lighting can make anyone look bad, with the deep shadows under the chin, nose and eyes reminiscent of a 1930’s horror movie. One way to fix this is to install translucent diffusers on the lighting, which will soften the shadows somewhat. You can also improve things with multiple light locations, spreading the light out so it is not so sharp.

The best solution is side lighting on the mirror, Broadway backstage style. Vertically installed light bars with frosted lamp bulbs mounted on wither side of the mirror; at least 30 inches apart are ideal for lighting the face evenly and naturally. It is called vertical cross illumination by lighting experts, who often recommend including a dimmer switch for controlling the light level for optimal effect.

General Lighting

This task lighting will need to be supplemented in all but the smallest of bathrooms by general illumination, usually by ceiling mounted lighting. A good rule of thumb is to plan for 1 watt of incandescent lighting per square foot for surface mounted light, and 2-4 watts per square for recessed lighting. For fluorescent light, ½ watt per spare foot for both cases is good. Recessed lighting does use more energy, but the effect produced is one of reduced glare due to the shadowing created in the upper areas of the room.

General lighting from wall mounted sources, such as sconces, is even more diffuse and has a pleasantly natural feel to it. If you opt for wall lighting, a light colored finish to the ceiling is a must to enable the light to diffuse throughout the room.

Other Requirements

Another bathroom lighting consideration is to ensure adequate lighting in each functional area. If your bathroom has separate toilet or bathtub areas, these should each receive their own individually controlled light. Be aware that building codes usually specify wet and humid locations like showers have fixtures moisture-rated for these applications.

Many building codes also call for a GFCI (ground-fault circuit interrupter) at each outlet, light fixture and switch. Additionally, no lighting fixture or switch should be within reach of someone standing or sitting in the bathtub or shower.

Provision for night lighting should be included, whether it is an outlet in an accessible location for simple plug-in night lights, or building in a dimmer switch control for the general lighting. The primary concern should be safety followed by comfort.

Bulb Types

Compact fluorescent lighting (CFL) bulbs are now a widely available alternative to incandescent bulbs, and use much less energy. They run at a higher color temperature, and provide a subtly cooler, whiter light. The overall effect is one of cleanliness and efficiency, and some find it somewhat cold at first. But they do save energy and last many times longer. Tungsten halogen lighting is also energy efficient, giving up to 25% more light per watt and has a brighter, neutral feel to it.

Incandescent bulbs, the old standby are becoming less and less of a viable option for lighting as energy costs and environmental concerns mount. Despite their cost and relatively short life span, they do still provide the warmest and most intimate feel lighting at this time. Color temperature of lighting is specified in degrees Kelvin.

Abbreviated as K, the Kelvin scale is a means of measuring temperature, like the Celsius or Fahrenheit scale, and begins at absolute zero, which is -273.2 degrees Celsius. For comparison, an incandescent bulb emits light of around 2550 degrees K, compact fluorescent bulbs 2700 K, halogen bulbs are 3000 K, fluorescent tubes are at 3600 K, and natural sunlight is around 5000 degrees K.

Photo: StopnLook, Creative Commons License