"Andy Hall" wrote in message
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On Fri, 23 Jan 2004 11:15:14 -0000, "IMM" wrote:
"Neil Jones" wrote in message
...
"IMM" wrote in message
...
"Andy Hall" wrote in message
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It does!!!!!!!!!! The upstairs then is much more well insulated,
warmer
and
consumes less fuel to heat. The upstairs rooms benefit greatly by
heavy
insulation in the loft.
Do I need to do the sums again for
you to demonstrate the point?
Well do them by having a before and after of the ground floor and the
1st
floor.
Here's my house as an exercise:-
Foot print ~ 70m2
Downstairs wall height ~ 2.1m
Upstairs wall height ~ 2.2m
Wall construction:-
downstairs 27 m solid wall construction U-val ~ 2.0
+ 8 m timber clad cavity wall construction U-val ~ 0.6
upstairs 27 m tile hung lath/plaster construction U-val ~ 2.0
+ 8 m timber clad cavity wall construction U-val ~ 0.6
Ground floor :- thick concrete + screed + covering U-val ~ 0.3
Ceiling Floorbaord/Joist/Plaster U-val ~ 1.6
Loft currently insulated with ~ 100mm mineral wool U-val ~ 0.5
Windows:-
Downstairs
2.2 m2 single glazed timber frames U-val ~ 4.8
5.9 m2 sealed double glazed units in plastic and metal U-val ~ 3.8
Upstairs
2.2 m2 single glazed timber frames U-val ~ 4.8
5.9 m2 sealed double glazed units in plastic and metal U-val ~ 3.8
Doors:-
6 m2 mixed construction U-val ~ 3.0
Air changes :- 1.5 per hour
Design parameters
=================
Outside temp -3 C
Downstairs temp 21 C (delta-T = 24)
Upstairs temp 18 C (delta-T = 21)
Heat loss - downstairs
======================
Floor = 70 x 0.3 x 24 = 504 W
Walls = (27*2.1 - 5.9 - 3) * 2.0 * 24 ~ 2295 W
+( 8*2.1 - 2.2 - 3) * 0.6 * 24 = 167 W
Walls Total = 2462 W
Windows = 2.2 * 4.8 * 24 = 254 W
+5.9 * 3.8 * 24 = 538 W
Windows Total = 792 W
Doors = 6 * 3 * 24 = 432 W
Ceiling = 70 * 1.6 * 3 = 336 W
Air changes = 70 * 2.1 * 0.36 * 1.5 * 24 = 1896 W
Downstairs losses = 6422 W
Heat loss - upstairs
====================
Floor = 70 x 1.6 x -3 = 336 W
Walls = (27*2.2 - 5.9) * 2.0 * 21 ~ 2247 W
+( 8*2.2 - 2.2) * 0.6 * 21 = 194 W
Walls Total = 2441 W
Windows = 2.2 * 4.8 * 21 = 222 W
+5.9 * 3.8 * 21 = 471 W
Windows Total = 693 W
Ceiling = 70 * 0.5 * 21 = 735 W
Air changes = 70 * 2.2 * 0.36 * 1.5 * 21 = 1746 W
Upstairs losses = 5951 W
Total losses for house = 12.3kW
Downstairs losses are 51.9% of total losses from house.
Losses through:-
Ground floor 4%
Downstairs solid wall 19%
Downstairs cavity wall 1%
Downstairs windows 6%
Ceiling to upstairs 3%
Roof 6%
Upstairs solid wall 18%
Upstairs cavity wall 2%
Upstairs windows 6%
Increase the loft insulation to 350-400mm and do the calcs again.
The U value for 100mm of mineral fibre in a pitched roof construction
is 0.36 according to BS 5449.
So in fact Neil's heat loss via this route is less than suggested and
more like
70 x 0.36 x 21 = 529W.
This is about 4% of his total 12.3kW
Increasing the insulation to your suggested level might achieve a U
value of 0.15 taking the heatloss down to 220W.
This represents a difference of 2.4%
Not very interesting in the context of 20% going out through the solid
walls.
Also what
about the hallway which is also upstairs and downstairs.
The only effect that can happen there is to assume that the hallway
downstairs is at downstairs temperature and that the landing above
will achieve the same temperature via convection.
In most houses the upstairs landing might be 15-20% of the total
upstairs area, so in essence the landing becomes 3 degrees warmer than
the bedrooms. the impact is demonstrably marginal. Another corner
case.
Look specifically
at the upper rooms and see the difference.
They look remarkably similar, even accounting for convection from
downstairs.
Also there is the matters of
keeping the upper rooms cool in summer too. 400mm does that wonderfully.
It is a win, win situation.
If you think that that is a win, win then you are missing out on much
bigger prizes.
You really haven't got it have you?
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