
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.
