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
Internal Wall - plaster, 4.5" brick, plaster 2.2
Plasterboard, 2" eggcrate cavity, plasterboard 2 (guessed)
External Wall - 11" brick-block cavity insulated. 0.7


Floors

Ground Floor - Solid Concrete
0.8
Int Floors - Floorboard, 8" joist, Plasterboard 1.7
(heat flow up)
Int Floors - Floorboard, 8" joist, Plasterboard 1.5
(heat flow down)

Roof

Pitched with felt - 100mm insulation
0.34
Pitched with felt - 50mm insulation
unknown
Flat roof - no insulation
1.2


DG Windows/doors uPVC
3



Thanks again for all help given previously

Phil

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

Andy

Many thanks for your time on this.
From the figures you give I am a little more reassured.

However I would appreciate it if you could look up the following:

Floors

All floors are uninsulated ie plain concrete (due to pipe leaks we even had
to lift all the original vinyl tiles!)
The basic house dimensions a
8m square in plan with front elevation facing approx east
There is also a single storey kitchen extension to the north which has three
exposed walls - north wall 5.5m long and east/west walls 4m long.
Finally, our room is over a garage, constructed in an extension before we
bought the property. Do you know the likely floor construction for this
room bearing in mind building regs requirements and hence the likely U Value
for heat flow down from this room?
The garage ceiling has been plastered with a plaster board "return" down the
wall which adjoins the original house about 2 ft deep. Presumably the joist
cavities will have been insulated to meet regs (it certainly doesn't feel
like it as the cold weather arrives!)

Thanks again

Phil