On Thu, 14 Sep 2006 05:17:55 -0700, Lobster wrote:

TBH I suspect that the cost difference between my largest
"guesstimated" rad wouldn't be vastly different to the ideal size, so
that's not my main motive - would just rather keep it neat and not clog
up the room with more hardware than required.

Anyone know of a Noddy guide to calculating U-values?

Google :-)

There are a few standard U values used in the calculators and you can pick
up some others online

Here are some I made up earlier :-)

Surface Construction U source
Wall Brick 220 + plaster 13 2
Brick 335 + plaster 13 1.6
Block heavy 200 + air 25 + pboard 10 1.8
Block heavy 200 + air 25 + exp poly 25 + pboard 10 0.79
Block light 200 + air 25 + exp poly 25 + pboard 10 0.46
brick + cavity + brick 1.68 Warmfill
brick + cavity + concrete block 1.55 Warmfill
brick + cavity + clinker block 1.4 Warmfill
brick + cavity + insulation block 1.05 Warmfill
brick + bead-filled cavity + brick 0.49 Warmfill
brick + bead-filled cavity + concrete block 0.47 Warmfill
brick + bead-filled cavity + clinker block 0.45 Warmfill
brick + bead-filled cavity + insulation block 0.42 Warmfill

Windows Wooden SG 5
Wood/uPVC DG 2.9
Low-emissivity Double Glazed 1.9 Pilkington 12mm gap, Pilkington 'K' glass
Argon filled/low-e glass DG 1.6 Pilkington
Aluminium, no thermal break, single 6.4
Aluminium, no thermal break, double 4.3
Aluminium, thermal break, single 5.8
Aluminium, thermal break, double 3.7

Floor Suspended, 1 air brick, bare 0.61
Suspended, 1 air brick, covered 0.59
Suspended, 1 air brick, bare 0.82
Suspended, 1 air brick, covered 0.68
Solid on earth 0.36

Roof uninsulated 0.7 guess
fibre 60mm 0.55
fibre 80mm 0.43
fibre 100mm 0.36
fibre 60mm + sarking underlay 0.51
fibre 80mm + sarking underlay 0.4
fibre 100mm + sarking underlay 0.34
fibre 60mm + felt on sarking board 0.48
fibre 80mm + felt on sarking board 0.39
fibre 100mm + felt on sarking board 0.32


For the purpose of rad sizing/U-value calcs, does it matter whether the
sloping area is considered as "wall" or "ceiling"?

Nope