The actual specification required for a compliant building and necessary building fabric u value targets may vary depending on the actual overall proposed specification and the outcome of the energy.
Flat roof minimum u value.
Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value.
Insulation for walls including cavity walls solid walls and timber or steel framed walls.
The below drawing shows the u value requirements set out for new properties in the building regulations for each element walls floors and roofs.
State applicable energy ashrae zone minimum r value state local ms mississippi ashrae 90 1 2010 2 r 20 3 r 20 state local mo missouri 2012 iecc.
The current legal limits under building regulations part l are as follows.
Floor 0 25 w m2 k.
To comply with part l of the building regulations 2010 all roofs to rooms except those in unheated buildings should be thermally insulated to a maximum u value of of 0 18 w m k.
U value of a flat roof.
Insulation for flat roofs pitched roofs and balconies and terraces.
A lower u value indicates better insulation properties hence u value requirements usually specify a maximum value.
Walls 0 30 w m2 k.
Ground floor no underfloor heating 0 18w m k.
0 039 12 fiberglass insulation.
0 05 8 fiberglass insulation.
0 16 3 fiberglass insulation.
Ground floor underfloor heating 0 15w m k.
R value of various materials.
Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces.
A u value of 0 55 w m k is used for cavity insulation and 0 30 w m k for internal or external wall insulation.
0 48 1 fiberglass insulation.
0 26 2 fiberglass insulation.
Cold roof ceiling level 0 16w m k.
0 11 4 fiberglass insulation.
Flat metal roof.
0 90 1 fiberglass insulation.
All new projects must prove themselves to be reasonably energy efficient.
However in new builds u values are part of the overall goal for energy efficiency.
Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials.
You should of course see the manufacturer provided technical data sheet for the r value of specific products.
Minimum r value state local al alabama 2015 alabama commercial energy code 2 r 25 3 r 25 state local ak alaska 2012 alaska building energy efficiency standard 7 r 35 8 r 35.
Pitched roof sloping ceilings.
For a very good introductory overview article on r value see r values over at the website of.
Get a u value calculation from our free online u value calculator or our technical department.
