Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials.
Flat roof minimum u value.
The below drawing shows the u value requirements set out for new properties in the building regulations for each element walls floors and roofs.
0 48 1 fiberglass insulation.
0 027 wood roof.
Ground floor underfloor heating 0 15w m k.
R value of various materials.
0 16 3 fiberglass insulation.
Flat metal roof.
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.
0 05 8 fiberglass insulation.
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.
Insulation for walls including cavity walls solid walls and timber or steel framed walls.
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 11 4 fiberglass insulation.
0 039 12 fiberglass insulation.
Floor 0 25 w m2 k.
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.
U value of a flat roof.
0 071 6 fiberglass insulation.
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.
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.
Roofs 0 20 w m2 k.
Pitched roof sloping ceilings.
Ground floor no underfloor heating 0 18w m k.
You should of course see the manufacturer provided technical data sheet for the r value of specific products.
0 26 2 fiberglass insulation.
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.
For a very good introductory overview article on r value see r values over at the website of.
Cold roof ceiling level 0 16w m k.
0 90 1 fiberglass insulation.
However in new builds u values are part of the overall goal for energy efficiency.
All new projects must prove themselves to be reasonably energy efficient.
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.
