The more I get into looking at insulating our house, the more I need to learn! At the moment I’m fighting off a swarm of mismatched R, U, and k values. All I want to know is what type of insulation we need to come close to the PassivHaus standards but everything I see is quoting differing units. So what are all those units? and what’s the relationship between them?

### What are R,U and k

**k**is the Thermal Conductivity of a*material*, so for Insulation**LOWER is better**. Units are W/mK.**R**is Thermal Resistance of a*specific piece of insulation*, we want this to be**as high as possible**. Units are Km²/W. It is calculated as d/k where d is the thickness of the insulation and k is the Thermal Conductivity.**U**is the Thermal Conductivity of a s*pecific piece of insulation or building element*and, as with k,**lower is bett****er**. Its units are W/m²K. It is calculated as 1/R or k/d.

March 22, 2009 at 9:39 pm

[…] to work out what will fit into our budget while giving us the best possible insulation effect (U-Value). The PassivHaus standards state that our windows should have a U value of <= 0.8 W/m2K, so […]