What is U-value and why is it important?

Understanding U-value: Thermal transmittance unveiled

In simple terms, a U-value is a measure of thermal transmittance. It's occasionally mistaken for a K-value, which gauges thermal conductivity. So, what does this mean? A U-value refers to the rate of heat transferred per second, per square meter, and per degree of temperature difference across a wall surface. Now, let's break that down further.

Defining the U-value

Expressed as W/m²K (Watts per Square Meter Kelvin), the U-value essentially informs us about the effectiveness of a wall as an insulator. The rule of thumb is that the lower the U-value, the better the insulation, and vice versa. This measurement is crucial for certifying construction materials.

For instance, the average U-value of an insulated sectional door measuring 5 x 5 meters is 1.0 W/m²K. A value close to 1 is good, below 1 is excellent, and as the value increases, the material becomes less effective.

Although a door isn't a wall, when closed, it functions similarly. Therefore, it should effectively maintain indoor temperatures for comfort and energy savings.

The formula for calculating U-value

For those inclined towards DIY calculations, here's a simple formula:

Qw = (Ta – Tb) x A / Rw

Where:

• Qw is your U-value (in W/m²K)

• Ta is the temperature on the inside of the door

• Tb is the temperature on the outside of the door

• A is the surface area of the door in m²

• Rw is the thermal resistance expressed as (m²K)/W

Why U-values matter: Compliance and beyond

Now, you might be wondering why you should care about U-values. While doing the calculations yourself can be challenging, it's usually provided on the information sheet delivered with your door.

However, paying attention to the U-values of your entrances is gaining importance due to the rise in regulations aimed at reducing building emissions. As of the end of 2020, new buildings are expected to be nearly zero energy, with specific U-value requirements for various components. For instance, industrial doors must not exceed a U-value of 1.4 W/m²K.

Therefore, keeping an eye on your U-values ensures optimal door performance, and it also ensures compliance with evolving regulations.

Conclusion

U-values play an essential role in determining the efficiency of doors and their insulation capabilities. As we've explained, the lower the U-value, the superior the insulation, making it a crucial factor in certifying construction materials. The simplicity of the formula for calculating U-values, coupled with its inclusion on door information sheets, empowers consumers to make informed choices about their doors. Beyond personal considerations, the increasing significance of U-values in compliance with building regulations emphasizes their role in contributing to energy efficiency and sustainability goals. So, next time you stumble upon the term 'U-value' while exploring automatic door options, remember it's not just a technicality; it's a key to unlocking doors that align with both comfort and environmental responsibility.