How to choose lighting for an interior design project?

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Have you gone to those fancy restaurants, read through the food menu, a hundred different ingredients on dishes you never heard before, so you end up ordering the waiter’s recommendation? Please don’t do this when choosing your lighting. It is true that there are so many terms to know that make it a complex, tangled, tortuous topic for many, so we end up making decisions based on what the neighbour did. Instead, keep reading and you will be one step (or many) closer to mastering the complexity of lighting design.

LIGHTING TYPES

In interior design, we categorize lighting in four types:

General Lighting is used to light up a room in a uniform way and provide you with a safe walk through, we achieve this using recessed downlights, sometimes called pot lights or can lights.

Task Lighting as the word says is used to illuminate a working surface where a task is performed. This could be for example in the kitchen when you are chopping vegetables, task lighting would be under cabinet lighting also called puck lights or a pendant above a kitchen island. Task lighting for reading could be a floor lamp or table lamp. Task lighting for applying on makeup could be a wall sconce. So you get the point, it's basically lighting that is close enough to illuminate a task being done. 

Accent lighting is used to light up a key object or a feature, in interior spaces, a feature could be an artwork, a textured wall or a waterfall. In the exterior it's typically used for landscape. Accent lighting fixtures could be track lighting or directional recessed downlights (these ones will aim towards the direction of the feature).

Decorative lighting is the jewelry of the home. Unlike the other types which main function is to illuminate, decorative lighting main function is to decorate a space. For this type, we use chandeliers, pendants, scones, etc., you can have them anywhere but most commonly seen in living rooms, kitchens, bedrooms, and anywhere you want to show off the fixture. If you are choosing decorative lighting you need to know which is the style of your design, so that you buy a fixture that coordinates with the other elements in the room.

Pro Tip: having more than one lighting type in the same room is the key to a pro lighting job, and it's always done by those mastering the interior design industry, designers refer to this as layered lighting.

PLACEMENT AND QUANTITY

The placement as well as the number of your lighting fixtures is critical, and although there aren't any fixed rules, there are general guidelines that can help you distribute your lighting correctly.

General Lighting

The first thing you want to do is measure the area of the room. (ie. 12 ft. x 20 ft. = 240 square feet). If you are working with an open floor plan, where the kitchen and living room are not divided by any wall, imagine there is a wall between them and measure them separately.

Then, you need to calculate the total watts to illuminate the space, to do this you will need to multiply the area of the room by 1.5. (240 square feet x 1.5 = 360). You may wonder where this 1.5 comes from, 1.5 is the average watt per square foot for general lighting. For tall ceilings or areas where you need more illumination like the kitchen, you may want to multiply it by 3 instead. After you have figured out your total wattage needed, you want to divide it by the bulb wattage you plan on using. (40 watts, 60 watts, 75 watts, 100 watts). This will give you the total number of recessed lights you will need, I will do 60 watts for this example (360 / 60 = 6). So 6 is the number or fixtures for our room. If you want to understand watts better, keep reading as I will explain it in further detail.

Pro Tip: A pro lighting placement practice is to try to always align your recessed downlights vertically as well as horizontally, creating rows. For the light spacing in a row, you want to take the length of the room and divide it by the number of lights that you want in a row, for our example since we have 6 total lights we will do 2 rows of 3 lights each. I always convert to inches to avoid wrong calculations, so 20 ft. or 240 inches divided by 3 (the number of pot lights we want to be in each row = 80 inches, however this would mean that you would have the same distance between each pot light and away from the wall, and this will create brighter spots between the lights and darker spots near the walls, creating cast shadows. Having said that, the spacing between the wall and a pot light should be around half the space between the other pot lights. If you think this is getting too complex, a good rule of thumb is to have 30 to 36 inches from the wall to the nearest pot light, and from there calculate the spacing for the lights in the centre of the row. So if we have 30 inches from the wall to the first light on both sides, we end up with 180 inches in between those corner lights, because we said we wanted 3 lights, we will divide this 180 by 2 to place the third light right in the middle. You want to do this for the width of the room as well. You can be a little more flexible on placement as long as your fixtures are evenly distributed across the ceiling area.

Task lighting

This one is more flexible on placement and using your common sense is what works best. For puck lights under kitchen cabinets some designers will recommend spacing them somewhat between 6-10 feet apart, however, there are puck lights spaced out as little as 3 feet. For pendants above a kitchen there isn't a rule on the right number of pendants, the size of the island as well as the size of the pendant will rather determine the number of pendants that work best. The best thing to do is to aim for visual balance and to well illuminate the whole counter surface. You could have anywhere from 2 bigger pendants to 5 smaller ones. For bathroom vanity lights which are typically sconces, placement typically goes from 65 to 70 inches from the floor, if the users are taller or shorter the height can be slightly adjusted. The distance between the wall sconces is typically between 36 to 40 inches apart.

Accent lighting

When using recessed fixtures, the number will be determined by the size, shape and number of pictures, in case you are illuminating artwork. For small to medium size pictures, one recessed downlight would be enough. If the picture is rectangular or quite large, you may require two, and if you have a bunch of picture frames displayed on the wall, more than two may be required. The placement is critical also, you want to place the fixture from 18 to 36 inches away from the wall and aimed at a 30 degree angle to the vertical surface. Make sure that the fixture that you are installing has an adjustable trim of at least 30 degrees of adjustment.

Decorative Lighting

Placing decorative lighting is one of the easiest ones, as you normally want your decorative fixture to be in the centre of the room, in the case of it being a chandelier or pendant. For larger spaces you may opt for two fixtures instead of one, placed evenly across the space.

THE TECHNICAL STUFF

This may not be the most exciting part of choosing lighting, but it's highly important if you want to master your lighting, so take a deep breath and read carefully ahead:

You've figured out what lighting types you need and you've chosen the right fixtures for your space, that is great but your fixture(s) need bulb(s) inside them, do we all agree on this? The bulb you choose can be an incandescent, halogen, fluorescent, or LED. Your bulb will have wattage, lumens, CRI, kelvins. Now you are thinking “what the heck is that?” If yes, keep reading.

Watts is the amount of energy used by a bulb, lower wattage bulb = lower light output alias less light, however, this only applies for incandescent and halogen bulbs, not LED, read until the end to find out why.Wattage of a bulb can be 40, 60, 75, or 150. The bulb wattage that you need will be dictated by the fixture itself! So take your fixture, whether it's a can light, lamp, pendant, etc., and look for a label that indicates the wattage rating of the fixture. Fixtures carry a maximum wattage rating, so all I can say is: don’t mess up with electricity and try higher wattage than noted in the fixture because it can lead to serious trouble.

Lumens is the way to find out how bright a lighted bulb or integrated LED light fixture is. Lumens is the brightness, easy, huh?. But, to know how many lumens you need is the tricky part. First you need to know how many lumens you need per square foot, otherwise called "foot candles". The lumens per square foot will not be the same for all rooms, as you may need more light in some rooms than others, depending on the use. Generally speaking a room needs 10-20 lumens per square foot while a kitchen or laundry room needs 70-80 lumens per square foot. So, all you do at this point is multiply the square footage of the room by the lumens per square foot and voila, you have the lumens needed for your room.

Chromaticity is the colour temperature and it’s measured in kelvins. The higher the kelvin number the bluer the light will look, the lower the kelvins, the more yellow. If you ask, somewhat between 2700K and 3000K is the ideal warm white for an interior space, though opinions differ.

CRI (Colour Rendition Index) is a scale from 0 to 100, the higher the number the truer the colour, you always want to keep the CRI the highest you possibly can. I wouldn’t go lower than 90 CRI.

Tip: The advantage of choosing LED over other types is very simple: an LED can deliver the same amount of lumens (brightness) than an incandescent 60-watt bulb, using only 10 watts, which makes it an energy efficient option.

So, there you go, that was quite a lecture on lighting. Please remember that these are general guidelines, and there are also other factors that play a big role in how your lighting will be reflected in the space. Other common factors are the wall colour, room orientation, amount of natural light, floor tone, other colours used in the room, etc. I’ve always believed that the best way to learn is by doing so get your hands working and you will keep learning on the go.