Following on from the ‘The Americans are like us, but they are different: Framing vs Cavity walls’ post; I was getting ready to criticise the level of insulation in US framed walls compared to that in the UK and Ireland but in terms of Building Regulations they are remarkably similar (Image extracted from Part L Irish TGD Documents):

I’m going to compare equivalent constructions in terms of u-value in SI units to avoid confusion and if we look at a fairly typical US stud wall at 6″ the resultant U-value is in the region 0.21 W/m2K (depending on insulation type etc…) which is spot on the Maximum Elemental u-value in the Irish Building Regulations. Remember: You can’t rely on backstop U-values for Part L compliance anymore:

In comparison to obtain the equivalent U-value in a traditional cavity wall, the cavity would be in the order of 150mm.

Now both of these figures are a long way off meeting the Passivhaus requirements where exterior building elements must have a U-value below 0.15 W/(m2K). In a US framed wall this would mean an insulated frame of 225mm and the cavity wall would need to be in the region of 225mm (excluding any internal insulated plasterboard). What’s interesting is that I guess many people would think the block walls are increasing the insulation in a wall but they actually are doing nothing (in this respect).

I think this will be the last post (for a while) on the US/UK-Ireland differences, if you think of one why not let me know via a comment.

Next weeks post is starting a week of #BIM

So, if you would like me to help you with your drawings (whether you are a potential client or another designer (using Vectorworks) with either cavity or timber walls, if you are in the UK or US, then why not CONTACT ME…