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
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effective placement of openings. Double and triple glazed windows are desirable for
homes built in cold and cool climates to reduce the heat loss. The U-value plays a key
role in identifying the type of openings. In this study, triple glazed windows with U-values
of 0.8Wm
2
K and 1.2Wm
2
K were considered in addition to the window size variations.
Ventilation system
: Ventilation systems can fall widely into two approaches: natural and
mechanical ventilation. The former does not require the use of electricity while the latter
has a clear linkage to electricity consumption when the house comes into operation. “In a
balanced system with heat recovery both the extract and supply air are provided via
ducting, with a heat exchanger between the outgoing and incoming air” (BRE 2009). The
specific fan power, efficiency and ductwork have impact on energy consumption when
an MVHR system is applied to housing.
Heating system:
A variety of devices to heat buildings are available in the market today.
In this study, a comparison between various systems using mains gas and electricity
was carried out. The systems were examined according to the CO
2
emission, efficiency
and affordability levels. A combi (or combination) boiler is a compact system applied for
heating water and space, saving space as a separate hot water cylinder can be excluded.
Also, in this study, two types of heat pumps were considered: ground source and air
source heat pump systems. The ground source heat pump with COP of 250%-300%
utilises solar energy stored in the ground, applied to space and water heating (Energy
Saving Trust 2012a). It can also provide domestic hot water to 50°C (Bayfield Energy
2012). According to Energy Saving Trust (2012a), the installation of a typical ground
source heat pump system costs around £9,000 to £17,000. The air source heat pump
has the efficiency of 220%-300% and absorbs heat from the outside air even when
outside temperature is as low as -15
°
C (Energy Saving Trust 2012b). According to the
data from Energy Saving Trust, in Scotland, the installation of a typical system of an air
source heat pump system costs around £6,000 to £10,000. Biomass heaters can be
fuelled up by wood pellets, logs and chips. Wood chips can be used to heat larger
dwellings or a group of houses. Wood pellets can be easily handled if compared to logs
and the boilers can run automatically. Pellet costs depend mainly on the size and
method of delivery. If a few bags are bought at a time, it costs more than buying in a bulk.
If there is enough storage space to store the bulk of pellets and then the cost can be
lowered down to £190 per tonne in most parts of the UK (Energy Saving Trust 2012c).
This study focuses on the use of wood pellets as a biomass heating system and the
performance will be compared to one of other non-bio heating systems.
Photovoltaic (PV) power generating system
: PV applied to the roofs and walls of a
dwelling unit can generate electricity. The amount of electricity generation depends on
the number of solar panels, PV type and the orientation and sloping angle in addition to
the availability of sunlight.
The above design components and approaches can be combined to create a set of
design solutions. The following section aims to structure the cost-effectiveness analysis
matrix which helps visualise the value of each design option which consists of the design
solutions identified in the previous sections. The tool is proposed to assist stakeholders
to make proper design decision based on the value visualisation represented in a
comparative manner.
Structuring a Cost-Effectiveness Analysis Matrix
In this study, 34 design options were developed based on selected design parameters
that are influential in energy use, cost and CO
2
emissions of housing in view of SAP
2009 calculation method (Table 1). Option 1 was considered as the benchmark value
