If you're building a new extension on your home then you will probably be aware that the building inspector will expect you to install a certain amount of energy efficient lights to comply with the regulations. In this short post we won't go in to massive details regarding the regulations but we will highlight an issue that seems to occur quite regularly.
A previous version of the rules demanded that 25% of all lights in the extension be 40 lumens per circuit watt and only have the ability to take dedicated low energy bulbs. (Read our blog regarding understanding lumens here http://lowenergylights.blogspot.co.uk/2012/06/understanding-watts-lumens.html) This basically meant only bulbs with pins (typically like PL bulbs) could be used. This part of the regulations was designed to stop someone from using a low energy bulb when the inspector visited and then changing it for an old fashioned incandescent type after they left.
This was all very good until the technology of low energy products improved that rapidly that the newer more efficient items outpaced the regulations and consequently the lighting products with the greater efficiency no longer complied with the rules. A typical example of this would be the LED GU10 bulbs that used half the power of the then current compact fluorescent versions but didnt comply because they were the same size and shape as the halogen GU10 so they were not a dedicated product. (The irony of course being that as they matched the halogen GU10 the LED version could fit in to a greater number of existing lights).
We would imagine that this would have had a bearing on the newer L1A version of the regulations that changed to specify bulbs needed to be 45 lumens per circuit watt but more importantly that you were now required to install a minimum of 75% of these low energy bulbs however they no longer need to be dedicated. So in effect instead of a quarter of all lights needing to be low energy it is now three quarters but the choice of bulb is much easier to understand & choose & consequently the actual light you install can be a lot more basic with a simple bayonet or screw cap lampholder.
The common mistake mentioned in the title of this post that we see quite regularly is the fact that some homeowners (and even building inspectors) still seem to be following and quoting the old 25% dedicated rule which is now long out of date. So if you're in the middle of, or thinking about, building an extension on your home then make sure you understand the current rules regarding energy efficiency and lighting. You can view the current regulations on the governments planning portal website here