Have a look at this diagram:

The drawing shows continuous insulation, representing each of the major elements in a residential building, with prescribed U-VALUE (top decimal # = lambda value in W/mK) and the equivalent R-Value (bottom # in brackets). It's important to know that the U-VALUE is the critical number because the R-Value may change depending on where the building is located.

Why?

Because when we group everything together in an assembly - the air inside, dry wall, studs, insulation, siding, and the air outside - we get the EFFECTIVE thermal conductivity of the whole wall, floor or roof. This means that we're calculating the whole thing together to find out HOW MUCH HEAT WILL BE LOST BY THE ASSEMBLY...or the EFFECTIVE U-VALUE. This value will be measured as how many watts of heat energy (btu's) are lost across each square metre (square foot) of an assembly every hour.

This means that we want a LOW U-VALUE for all of the assembly elements, including windows. For somewhere warm like Vancouver, the assemblies might not need much insulation to achieve Passive House U-Values. For a colder place like Saskatoon, the insulation would be much thicker to achieve the Passive House U-Value.

Here's the key consideration: The difference in temperature between INTERIOR and EXTERIOR will change the required amount of insulation!