|
In accordance
with the
described
methodology,
the Bygone
Collection of
sash windows
has been
simulated
under the
BFRC
calculation
method. The
Bygone
window loses
just 20KW /
per square
metre / per
year.
|
Putting this into Perspective
In order to put this into some
meaningful numbers we must first set
the calculation criteria.
This paper is calculating the costs and
CO² during the winter months, when
heating would be required. For most
households, our figures show that an
average household has their heating on
for, a period of 191 days, just over 6
months, taking into account increased
usage for the colder days of the season,
and shorter lengths of time for the
Autumn / Spring days, and the
difference between week days and
weekends, and for an average of 8
hours a day, with a temperature difference between outside and inside of 15 degrees
It is also necessary to understand how
the heat loss is calculated. What does
W/m2K actually mean, let me explain.
A Watt is a unit of measure for energy,
it is 1 Joule per second. M² is the area
of the window, width x height, and
Kelvin is the difference in temperature
from the inside to the outside, the rest
is just mathematics.
|
The Energy Loss Explained
To benchmark the Bygone window, lets
first calculate how much money is lost
in heat through a old single glazed
timber window at 5.8W/m²K
Using the CEN standard size window as
the standard size this would mean that
the total heat loss would be 242 KW
(5.8 joules per second x 1.82m² x
(191x8) x 15 =241.94KW )
Our average order quantity is 7
windows, and therefore the heat loss
through the windows of an average
house would be in the region of
1,693.58KW
(242KW x 7 = 1,693.58KW)
The costs
Based upon an average cost of 10 pence
per KW (1000 Watts) per hour, the
average single glazed timber sash
window would lose the equivalent of
£24.20 each year.
(241.94KW x £0.10 = £24.20)
However most boilers are only 70% to
80% efficient, consuming energy in the
boiler itself and therefore the output
cost should be factored by an average
25%
Meaning the average property with 7
timber sash windows, spends
approximately £211.25 every year
replacing the heat that is lost through
the windows.
|
