It is about time we change the way we look at doors and energy savings

It is no secret that choosing the right automatic door saves energy. But surprising as it might seem, U-value should only be a small part of that choice.

Change can be slow in coming, especially in our line of business. For all the technical and stylistic innovation in recent decades, doors themselves are nothing new. And most often, neither is the way we door manufacturers think about them.

But a change is overdue. We have been hinting at it for years, and even our own company name reflects it. When we chose to call ourselves ASSA ABLOY Entrance Systems, rather than ASSA ABLOY Door Systems, we took the position that the door was only one part of a total entrance solution.

So why is the door still in focus, both for us and for the industry as a whole? And why is the door's U-value, in particular, often our only metric when looking at building energy costs?

What U-value overlooks

Doors are naturally important when it comes to a building's energy profile. In fact, they are far more important to energy consumption than most of us realize. But they are not always important in the way that we think.

As an industry, we have made huge advances in door designs and materials in recent years. Above all, we have made great improvements in U-value, which is the measure of a door's insulating properties. And as pressure to reduce building energy use has risen, U-value has become something of an industry mantra.

But as we have been looking at U-value, there is something very important we have been missing: insulation only matters when the door is closed.

Time is the deciding factor

Just how quickly does the door standing open outweigh a door's U-value? The answer is somewhat shocking. According to recent studies, it takes just three minutes of opening time per hour to make U-value irrelevant.

If that is the case, our trust in U-value is very often misplaced. After all, most doors are meant to be opened. Many doors, such as those of retail stores or supermarkets, are opened very frequently. And any door used for logistics is likely to be open more than three minutes at a time.

As a result, the energy-efficient door choice may be counterintuitive. A less insulated door – but one that opens quickly – may actually be the best energy alternative.

Saving energy is a balancing act

So from an energy perspective, how do we make sure that our door choices are good ones? To put it simply, we have to consider all of the key factors. In addition to U-value, these include:  

  • Air permeability(leakage)
  • Power consumption
  • Air infiltration (opening/closing speed) 

The last of these, air infiltration, is closely tied to the door's automation. It is also the biggest factor by far, as it helps determine the amount of time the door will spend open each cycle. Yet all of these factors, together with U-value, must be taken into account in order to find the most energy-saving solution.

Want to know more about saving energy with the right automated door?  Contact us