On 17 Dec, 23:05, "
js.b1" wrote:
On Dec 17, 10:14*pm, robgraham wrote:
convincing a disbeliever that he should insulate his workshop.
Single brick structure
Hahaha... leave it one winter...
1 - Insulate walls AND ceiling AND floor
2 - Not insulating the floor gets calf muscle ache all night long
3 - Vapour barrier is important
U value of wall...
- Find the R value for 1 brick
- Find the R value for various insulation types of various thicknesses
- U = 1 / (R1+R2)
So 20mm marmox (R= 0.60) on uninsulated cavity wall (R=0.73) gives a
combined U of 0.75. An uninsulated cavity wall on its own is 1.37 so
nearly halves the heat loss. Makes warm up very fast, plus when cavity
wall later insulated it jumps further. No point using plaster anymore
on external walls, Marmox is quicker and almost anyone can skim 3mm
with a bit of effort... belt sander... angle grinder... expanding
foam.
Actual wattage differences, for 21oC internal temperature...
- Calculate wall surface area
- Calculate U value of wall
- Heat Loss = Area * U * 21 = Watts
So for example a 5.31m^2 wall with 50mm celotex (U=0.40) has heat loss
is 45W, without the celotex a solid 9" brick wall is 235W. That shows
how even a little insulation helps hugely - consider four such walls
and you've 1kW heat loss BEFORE considering your door, draughts,
windows, floor & ceiling. Doing 50mm celotex on those four walls saves
0.8kW.
Do a Google for "R value" and look for single brick.
You have to do an estimate for the studding re "cold bridging".
Simplest is to stick a piece of 25mm XPS over the studs before the
final plywood or hardboard. B&Q do lots of cheap(ish) insulation at
the moment.
Thanks John, for the pointer - as you say there ought to be one on the
'Insulation' page.
js - I take it that what you are saying is that a single brick, 75mm
stud wall with OSB facing is going to have the same insulation value
as a single brick wall with no lining at all ?
I don't believe that. And what's more that's not going to help my
discussion with the 'Disbeliever' who is expecting figures from me to
satisfy the argument.
Rob