On Tue, 23 Nov 2004 19:47:33 GMT, (Brad
Awl) wrote:


Hi Folks,
I want to install a second front door in my house, and need to make a
choice between a hansome-looking hardwood door and a white UPVC one
costing three times as much. Can anyone list a few pros and cons of
each?

I can't think of any advantages of a uPVC front door especially
considering the cost difference in this case.


The main thing I'd like to know is: is the heat loss through a heavy
hardwood door significanly more than through a UPVC one? In other
words is it really worth paying an extra £200 for the UPVC door? How
long would it take to recoup the £200 on saved heating expenditure?

If you put it into the context of the house as a whole, the difference
is negligible.

A solid wooden door has a typical U value of 3 W/m^2.K

Let's say it has an area of 2 square metres.

If the temperature in the hallway behind is 18 degrees and the outside
temperature is -3 degrees (normal ones used for heating calculations)
then the heat loss is

21 x 2 x 3 = 126 Watts

This is worst case. A more reasonable assessment would be to go for
10 degrees outside for 6 months of the year and 12 hours heating out
of 24. Substitute your own numbers if you prefer.

Using those numbers, the temperature difference is 8 degrees and the
heating period is a quarter of continuous.

So this would come to

8 x 2 x 3 /4 = 12 watts continuously.

With gas at 3p/kWh it will take approximately 63 years to spend
£200.



I vastly prefer the look of the hardwood item (it looks in keeping
with the age and style of the property) and I guess I can install it
myself, having hinstalled a door or two in the past. I understand that
building regs now require that UPVC items have to be installed by
qualified installers these days (?)

Only if more than 50% is glass, AIUI.




Cheers,
Brad


--

..andy

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