On Wed, 27 Oct 2004 13:16:32 +0100, "TheScullster"
phil-at-dropthespam.com wrote:
Following previous message "Central Heating Design - Help Please", can
anyone comment on U Values for the following features please?
I have two sources of reference, the Screwfix site and Plumbing and Heating
by Treloar.
These seem to conflict and, when I research other sources, I find these
don't tally with either of the above. Is there a definitive source for this
information? If so can someone please confirm or revise the following
feature values for me (W/m2 Deg C)?
Walls
U Value
External Wall - 11" brick-block cavity uninsulated. 1
My table (from HVAC guide) has 0.87 for this assuming 13mm plaster
Internal Wall - plaster, 4.5" brick, plaster 2.2
1.76 for this one
Plasterboard, 2" eggcrate cavity, plasterboard 2 (guessed)
Generous, possibly a bit less
External Wall - 11" brick-block cavity insulated. 0.7
If it's aerated blocks and mineral wool slab, 0.42
Floors
Ground Floor - Solid Concrete
0.8
You have to take external walls into account separately here.
I have tables of U values for this which are determined from the
number and lengths of external walls and their positions.
Assuming uninsulated floor, the worst case is 1.15.
Best can be as low as 0.39
You could assume the worst case for this purpose if you want.
Alternatively, if you post the relevant room wall lengths and what
joins what, I can look up the numbers for you.
Int Floors - Floorboard, 8" joist, Plasterboard 1.7
(heat flow up)
Int Floors - Floorboard, 8" joist, Plasterboard 1.5
(heat flow down)
Yes.
Roof
Pitched with felt - 100mm insulation
0.34
Yes
Pitched with felt - 50mm insulation
unknown
Doubling the above to 0.7 would be a reasonable assumption for this.
Flat roof - no insulation
1.2
I have 1.6
DG Windows/doors uPVC
3
Yes for a wooden door. For a DG unit about 2.8 for standard glass, 2.1
for low-E.
Thanks again for all help given previously
Don't forget that the internal surfaces are not going to be that
important unless you are going to have huge temperature differences
between rooms. Heat gain and loss room to room will not usually be a
lot; so don't sweat for the last 10W.
..andy
To email, substitute .nospam with .gl
|