U-Value Insulation: How Does It Work?

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Have you ever wondered; what is a U-value in insulation? Simply put, the U-value of a material shows us the rate of how effective a material is at resisting heat transfer. Also called thermal transmittance, the value assigned to a material shows the heat transfer rate. This means that the lower the U-value, the better it resists heat transfer.

With the UK’s ambitious goal of reaching Net Zero by 2050, the thermal efficiency of home insulation has become a very important focus. This ultimate guide by GreenMatch UK is here to break down everything important you need to know about insulation U-value, what is a good value, how to calculate it, and how to improve it.

Ready to insulate your home? Let GreenMatch UK be your one-stop solution for all your needs. Simply spend 30 seconds filling out our online form and receive up to 3 free home-tailored quotes straight from our network of professional installers. No charges or obligations. Click the button below to begin!

The U-value of insulation indicates the rate at how good a material is resisting the transfer of heat. Therefore, a lower insulation U-value means it takes longer for heat to transfer through. Your chosen insulation material should have low U-value insulation, ensuring that your home will be thermally enveloped.

The U-value in insulation should not be confused with the R-value. While the U-value shows us the rate of heat transfer, the R-value is considered to be the inverse, which shows us how good a material is at resisting heat transfer.

There is no best U-value for insulation, but most effective materials will have a U-value somewhere in the range of 0.04 - 0.01 W/m2K, with more effective materials closer to 0.01. 

For example, mineral wool has a U-value range of 0.030 - 0.040 W/m2K, whereas PIR insulation boards have a more impressive 0.022 - 0.028 W/m2K, making them better thermal insulators.

Also, the expected U-value for loft insulation will differ from that U-value for insulation of other home areas such as walls and floors. 

The formula for calculating the U-value of a material is U = 1/(Sum of all R-value). 

In comparison, the R-value of a material is considered to be the opposite of the U-value. So if you were to calculate the R-value, you would use the formula R = 1/(Sum of all U-values). They are inverses of each other. Sounding a bit confusing? Let’s try to break it down.

While the U-value tells us the rate of how good a material is at resisting heat transfer, the R-value shows us the inverse of how good a material is at resisting heat transfer. Being the flipped version, this means a higher R-value means a material is better at resisting heat. 

Still confused? Don’t worry if it doesn’t make sense. It’s most important to understand what these values represent when you are on the market for effective insulation materials. Keep an eye out for low U-values and high R-values for the most effective insulation.

Current building regulations in the UK have been updated since 2022, and outline a series of expectations, including the thermal efficiency of insulation materials exemplified through the minimum expected U-values, highlighted in The Approved Documents L (ADL).

These insulation regulations outline the specific thermal efficiency expectations, for example regarding cavity wall insulation U-value, and exist to make sure that insulation measures around the UK are living up to standards expected to achieve the nationwide Net Zero target by 2050. 

As of current, the expected minimum U-values for various insulation measures are as follows:

New builds are properties that are being built from scratch and tend to have stricter U-value expectations in place as a result. This is because it's more possible to bring up a newly built property to efficient standards than an old one.

The expected U-values for older property renovations and upgrading of existing elements are far more lenient, as they take into account the challenges and complexities that come with retrofitting older properties.

The cost of insulation can also differ based on whether you are a new building or an existing property. This is especially the case if you have outdated and inefficient insulation in place that still needs removal. Still, insulation grants exist to help qualifying households with fronting the investment needed for proper home insulation.

Ready to insulate your home? Let GreenMatch UK free you from burdensome hours of researching and vetting installers. Instead of spending the time stuck on websites and phone calls, spend just 30 seconds filling out our simple online form and get up to 3 free home-tailored quotes from professionals in your area free of charge. Click the button below to begin!

The best way to improve the U-value of your home insulation is to simply use insulation materials with lower U-values. There’s very little you can do to existing insulation, however, if it is in good condition, then perhaps it can be topped up to a larger thickness.

For example, for an acceptable loft insulation U-value, materials such as mineral wool should be expanded to a thickness of at least 270mm to achieve the expectations set by UK regulations. 

With all things considered, effective house insulation is an upgrade with a wealth of benefits for your home comfort, savings, environmental standing, and even property value. 

Here are just a few of the key benefits you could enjoy:

Ready to insulate your home? We’re glad! The next step will be finding the right installer at the right bargain. Many homeowners often get stuck spending endless hours researching and vetting installers with no choices in sight. Luckily, GreenMatch UK can free you from the burden.

By filling out our simple 30-second online form, you can receive up to 3 free home-tailored quotes directly from our network of pre-vetted professionals. The best part? Our services are completely free of charges and obligations. Click the button below to begin!