R-Values or U-Values? How do you choose?
When you’re looking at buying insulation you may have seen the terms ‘U-value’ and ‘R-value’ mentioned, but what do they mean, and what is the difference between the two?
Basically, it’s all about measuring just how effective the insulation is - the better the thermal performance, the thinner the layer of insulation needs to be - however, the U-value and R-value measure this in different ways, and it’s important to understand the difference.
What is the U-value?
The U-value tells you how effective a material is at preventing heat from transferring as part of a whole building element, such as wall or roof, taking into account the other materials used. The value is based on the thickness of the material and the temperature difference that occurs between inside and outside of the material.
A U-value, therefore, measures thermal transmittance and is expressed as Watts per square metre - Kelvin - (W/m2 K) – measuring how much heat passes through 1 square metre of the wall etc, per degree Kelvin of temperature difference between the inside and the outside.
The important thing to remember is that the lower the U-value is, the better insulated the building element is. A high performing insulation material such as PIR means that you can get a low U-value without having to make the wall too thick.
What is the R-value?
By comparison, the R-value measures a material’s resistance to the transference of heat, so the higher the value, the better the material is at stopping heat getting in or out of a building. The R-value is measured as square metre-Kelvin per Watt (m²·K/W), indicating how much energy it would take to raise the temperature of the material by a certain amount.
Factors affecting R-Value
· Thickness: The R-value increases with the thickness of the insulation material.
· Material Type: Different insulation materials have different intrinsic R-values. For example, insulating materials, such as PIR, have higher R-values, per a given thickness, than materials like mineral fibre or EPS.
· Temperature: Insulation performance can vary with temperature, slightly changing the R-value. You will see in our Conqueror CQ12001B PIR insulation board literature that the R-value is quoted in accordance with AS/NZS 4859.1:2018 at 15°C.
How are R-values used?
R-values are used to compare the insulating properties of materials used in walls, roofs, floors and other parts of a building, to help you choose which will work best for your project. The R-values of insulation materials are typically declared in millimetres (mm) so you can see how thick different insulation materials would need to be to achieve the same R-value. The National Building Code for New Zealand currently specifies a minimum R-value of 2.0 for wall insulation - just 50mm of our Conqueror PIR board can give you an R-value of 2.10.
Why does the R-value matter?
There are several ways the right R-value can improve your home:
· Energy Efficiency: Proper insulation with a good R-value can help to reduce your heating and cooling costs by maintaining indoor temperatures.
· Comfort and Space: Because higher R-value insulation materials can help maintain a consistent temperature with less material, it helps to keep walls slimmer and could reduce the impact on a building’s internal space if you are adding it to an existing building.
· Environmental Impact: We all need to think about climate change. Efficient insulation reduces energy consumption, helping to lower greenhouse gas emissions.
Find out more about why you should think about insulating your building, and visit our Buy Now page to find solutions with high R-values.