Z E M C H 2 0 1 2 I n t e r n a t i o n a l C o n f e r e n c e
240
Insulated rigid ducts (OPT 1) help reduce energy use when compared to uninsulated
flexible ducts (OPT 19) or insulated flexible ducts (OPT 17). Flexible ducts offer more
resistance and tend to increase energy demand. Uninsulated rigid ducts (OPT 18) are
unsuitable as they increase heat loss. Seemingly, uninsulated flexible ducts are the
worst option among these options (OPT 19). It is important to measure heat loss through
building envelopes including openings to consider the amount of heating load required.
The more the fabric heat loss, the higher the space-heating demand. The U-values are
an indicator which is generally used for the measurement (Fig.22).
Figure 22: Fabric heat loss for openings with different U-values
NRGStyle is currently considering the application of a steel modular building system to
ZEMCH 109. The high thermal performance prefabricated building envelope is being
produced by Powerwall Space Frame Systems based in Wishaw, Scotland. The U-
values in the building envelope achieved 0.8W/m
2
K in windows and 0.15Wm
2
K in floors.
Structuring the Cost-effectiveness Model
In addition to the SAP assessment for the energy use, cost and CO
2
emissions of 34
design options, the future value of the operating costs identified were further identified by
making of the future worth method based on the time value of money concept (White,
Case and Pratt 2010). In this study, the period of the assessment was considered to be
10 years while the interest rate was estimated at 10%.
The future worth is the value of an asset in the future. It determines the worth for a given
sum of money at a specific time to which an assumed rate of interest is applied. In this
study, the future worth of each design option was estimated using the following formula:
FW = AC (1 +i)
n
(1)
Where,
FW = future worth of the option selected
AC = annual energy cost
i = interest rate
n = number of the year in question
66.06
72.53
69.29
70.55
64.44
65.39
60
62
64
66
68
70
72
74
OPT 1 OPT 12 OPT 13 OPT 14 OPT 15 OPT 16
Fabric Heat Loss (W/K)
