Halogen Lighting 101
It's a staple of modern lighting. You have seen it glowing magnificently from ceiling light fixtures, outdoor light fixtures, and patio lights. But how well do you know this ubiquitous light source?
Halogen lighting is really just another form of incandescent lighting Both have tungsten filaments, which heat up and give off light. The main difference is that halogen lights have halogen gas inside their lamp glass envelopes, while traditional incandescent use nitrogen or argon gas.
Halogen gas does something very interesting: It combines with the tungsten that evaporates from the filament, so that the evaporated tungsten gets deposited back onto the filament when the light is turned off. So what? You know how traditional incandescent light bulbs sometimes turn black before they burn out? Halogen lights don't do that. That residue inside the glass envelope of the old school light bulb is evaporated tungsten. Now, you are getting it.
The envelopes of halogen light bulbs don't darken, and this helps them last longer and provide clearer light for the long haul. Speaking of their envelopes - halogen lights are sometimes called "quartz halogen lights" because their envelopes are often made of quartz instead of glass in order to withstand the high heat. Not all halogen lamp envelopes are made of quartz anymore: There are high-melting-point glass envelopes as well.
Just remember that because halogen lights have smaller envelopes closer to the filament, they get extremely hot. If you are using halogen, just remember not to touch the light bulb until it has cooled off.
In fact, you may not want to touch the light bulb at all with your bare hand. Because halogen light bulbs tend to get quite hot, oil from your hand can make the glass envelope get hotter where you touched it. This can prevent halogen lamps from achieving their maximum life span, so consider using a cloth or glove between your hand and the glass when installing these bulbs.
After all, if you are using halogen lamps, you are probably doing so at least in part because they typically last longer than their standard incandescent cousins. But this does not mean that the two types of light bulb have nothing in common. Like traditional incandescent light bulbs, halogen don't need to be "warmed up," which means they can be turned on and instantly achieve full brightness. Plus, they are dimmable.
PAR vs. MR
The main thing to remember about PAR and MR lights is that the "R" stands for reflector. The reflectors in these lamps control the direction of the light, in contrast to the standard tungsten light bulb, which can be thought of as omnidirectional.
A significant difference between PAR and MR halogen lamps has to do with these reflectors. More so than MR lights, PARs direct heat toward the front of the lamp and therefore toward the object that is being illuminated. For this reason, PARs are generally recommended for high ceilings or spotlight applications in which the light fixture will not be too close to the accented object, if it is sensitive to heat.
MR lamps have reflectors that disburse their heat a little bit, so that it does not ALL get directed forward. Because of this, and the fact that MR lamps are often smaller than PARs, they can be placed a little closer to the things the are spotlighting.
PARs generally run on line voltage and use medium screw bases, just like standard household bulbs. Because they typically give a broad range of light, they are great for floodlights and recessed lighting.
MRs, while they can come in line voltage varieties, more often run on low voltage. They typically have bi-pin inserts and are increasingly popular, in part because they can emit narrow beams of light. Their ability to achieve a tight beam spread makes them great for landscape lighting, for example.
Choosing between PAR and MR halogen is really all about fixture design. Smaller, low voltage MRs typically fit into smaller light fixtures than PARs, and this is often a significant determining factor. But it is still useful to know the difference.
Halogen and the "Light Bulb Ban"
You have probably heard a lot about the "light bulb ban." First, allow us to clarify that incandescent light bulbs - which include halogen lamps - are not being banned altogether. Rather, the Energy Independence and Security Act (EISA) has set new efficiency standards that incandescent lamps must meet in order to be legally manufactured.
Traditionally, the standard tungsten 40-watt light bulb has produced between 310 and 749 lumens. Now, an incandescent bulb that produces the same amount of lumens can use a maximum of only 29 watts of energy. So, light bulbs simply must be more efficient in order to meet new, higher efficiency standards.
One way manufacturers are making their light bulbs more efficient is by adding halogen gas. So, we are seeing halogen light bulbs replace standard A-19s more and more. Additionally, halogen lamps are increasingly designed to be extra energy-efficient.