APC 2026 > Case Study- Cost Control > Flashcards

Case Study- Cost Control Flashcards

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1
Q
A
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2
Q

What buildings were included in the mechanical services design on this project?

A

• Custodian’s Lodge – approx. 122 m² • Post Room – approx. 71 m² • Both buildings formed part of the same construction package

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3
Q

What was the original mechanical services strategy for the Custodian’s Lodge?

A

• Air Source Heat Pump (ASHP) system • Underfloor heating for space heating • Fan coil units in reception for cooling

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4
Q

What heating strategy was used for the Post Room?

A

• Electric radiators • Acceptable because: • Low occupancy building • Low energy demand

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5
Q

What alternative mechanical system was proposed during Stage 4 design development?

A

• Variable Refrigerant Flow (VRF) system • Provided heating and cooling through indoor units

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6
Q

What was the role of the Quantity Surveyor in the ASHP vs VRF comparison?

A

• Review capital costs of both options • Advise the design team on cost implications • Support the design decision

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7
Q

What saving was identified when comparing VRF with the ASHP system?

A

• Approximate saving of £83,211

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8
Q

What were the primary drivers of the £83k saving?

A

• Removal of underfloor heating system • Removal of ASHP plant equipment • Simpler installation using refrigerant pipework

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9
Q

What is an Air Source Heat Pump (ASHP)?

A

• System that extracts heat from outside air • Transfers that heat into the building • Provides space heating

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10
Q

How does an Air Source Heat Pump work?

A

• Heat absorbed from external air • Refrigerant is compressed to increase temperature • Heat transferred to water heating system

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11
Q

What heating emitters can be used with an ASHP system?

A

• Radiators • Underfloor heating • Fan coil units

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12
Q

What type of ASHP was likely used in this project?

A

• Air-to-water heat pump

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13
Q

What are the two main types of Air Source Heat Pumps?

A

• Air-to-water heat pumps • Air-to-air heat pumps

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14
Q

What does an air-to-water heat pump do?

A

• Extracts heat from outside air • Transfers heat into water heating system • Water distributed through radiators or underfloor heating

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15
Q

What does an air-to-air heat pump do?

A

• Transfers heat directly into air • Provides heating or cooling through indoor units

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16
Q

Can ASHP systems provide cooling?

A

• Some systems can produce chilled water • Used with fan coil units • Underfloor heating generally cannot provide cooling

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17
Q

Why were fan coil units used in the original Lodge design?

A

• To provide cooling in the reception area

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18
Q

What is a fan coil unit (FCU)?

A

• Terminal unit containing: • Coil • Fan • Blows air across coil to heat or cool the space

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19
Q

How does an FCU work with an ASHP?

A

• Hot water flows through coil • Fan blows air across coil • Warm air distributed into the room

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20
Q

What is a Variable Refrigerant Flow (VRF) system?

A

• Heat pump system that circulates refrigerant • Connects outdoor condenser to multiple indoor units

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21
Q

How does a VRF system work?

A

• Refrigerant compressed in outdoor unit • Refrigerant flows through pipework • Heat exchanged through indoor units

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22
Q

What are the main components of a VRF system?

A

• Outdoor condenser unit • Refrigerant pipework • Indoor units • Controls

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23
Q

What are the two main types of VRF systems?

A

• VRF heat pump systems • VRF heat recovery systems

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24
Q

What is a VRF heat pump system?

A

• Provides heating OR cooling • Cannot provide both simultaneously

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25
What is a VRF heat recovery system?
• Allows **simultaneous heating and cooling** • Used in larger buildings
26
Why might heat recovery VRF systems be used in large buildings?
• Different zones may require **heating and cooling at the same time**
27
What indoor units are commonly used with VRF systems?
• Wall mounted units • Ceiling cassette units • Concealed ducted units • Floor mounted units
28
What indoor units were used in the Lodge reception area?
• **Concealed fan coil units within bulkhead**
29
Why were concealed units used in reception?
• To maintain **architectural appearance**
30
What regulation governs building energy performance in the UK?
• **Building Regulations Part L**
31
Why does electric heating perform poorly in Part L calculations?
• High **primary energy consumption**
32
Why were electric radiators acceptable in the Post Room?
• **Low occupancy space** • **Low heating demand**
33
What is the Coefficient of Performance (COP)?
• Measure of **heat pump efficiency** • Ratio of **heat output to electrical input**
34
Why are heat pumps considered efficient?
• They **transfer heat rather than generate it**
35
What is a 2-pipe fan coil system?
• Provides **heating OR cooling**
36
What is a 4-pipe fan coil system?
• Allows **heating AND cooling simultaneously**
37
Why are 4-pipe systems more expensive?
• Additional pipework • More plant • Greater installation complexity
38
Why might ASHP systems require more plant equipment?
• Pumps • Buffer tanks • Pipework distribution
39
Why might VRF systems require less plant space?
• Only require: • Outdoor condenser • Indoor units
40
What advantage did VRF provide compared with ASHP?
• Provided **heating and cooling in one system**
41
Why does underfloor heating improve comfort?
• **Even heat distribution**
42
Why is underfloor heating quiet?
Uses circulating water rather than fans
43
Why might VRF indoor units generate noise?
Fans blow air across the coil
44
Why can VRF simplify installation?
No large underfloor pipework networks
45
Why can VRF reduce plant requirements?
Fewer secondary plant components
46
At what RIBA stage was the review undertaken?
RIBA Stage 4 – Technical Design
47
Why is it important for QSs to review design alternatives?
Understand cost implications of design changes
48
What coordination issues were considered for VRF units?
Architecture Maintenance access Acoustic impact External plant location
49
What is a condenser unit in VRF systems?
Outdoor unit that compresses refrigerant
50
What does refrigerant do in a VRF system?
Transfers heat between indoor and outdoor units
51
What is a terminal unit in building services?
Device that delivers heating or cooling into a room
52
What APC competency does this example demonstrate?
Commercial management of construction
53
Why should QSs understand building services systems?
To understand cost implications
54
What key difference exists between ASHP and VRF systems?
ASHP generally heats water VRF circulates refrigerant
55
What heating method was originally used for the Lodge?
Underfloor heating
56
What cooling method was originally used in reception?
Fan coil units
57
What heating and cooling method did VRF use?
Indoor units providing heating and cooling
58
Why are VRF systems flexible?
Allow individual room temperature control
59
Why might building services systems be reviewed during Stage 4?
Improve design coordination and cost optimisation
60
What was the purpose of the cost comparison exercise?
Inform the client and design team of cost implications
61
What was the outcome of the review?
VRF identified as lower-cost alternative
62
What principle do VRF systems operate on?
Reversible refrigeration cycle
63
What is the main component in the outdoor VRF unit?
Compressor
64
What does the compressor do?
Compresses refrigerant into high-pressure hot gas
65
What controls refrigerant flow to indoor units?
Electronic expansion valves
66
What is the purpose of an expansion valve?
Reduces pressure Controls refrigerant flow
67
What role does the indoor coil play?
Allows refrigerant to exchange heat with room air
68
What does the fan do in an indoor unit?
Blows air across the coil Distributes conditioned air
69
What component switches heating and cooling modes?
Reversing valve
70
How does VRF cooling mode work?
Heat absorbed from indoor air Heat rejected outdoors
71
What happens to heat during VRF cooling?
Heat removed from building
72
How does VRF heating mode work?
Heat extracted from outdoor air Released inside building
73
What happens to heat during VRF heating?
Heat transferred into the building
74
Why are VRF systems energy efficient?
They move heat rather than generate it
75
Why is it called Variable Refrigerant Flow?
Refrigerant flow varies depending on demand
76
What technology allows VRF systems to vary refrigerant flow?
Inverter compressors Electronic expansion valves
77
What is the main difference between heating and cooling modes?
Direction of refrigerant flow reverses
78
What happens to the indoor coil in cooling mode?
Coil becomes cold
79
What happens to the indoor coil in heating mode?
Coil becomes hot
80
In simple terms how does VRF cooling work?
Removes heat from inside building
81
In simple terms how does VRF heating work?
Transfers heat from outside air into building
82
What does UFH stand for?
Underfloor Heating
83
What is underfloor heating (UFH)?
Hydronic heating system where pipes are installed within the floor slab or screed Warm water circulates through pipe loops Heat radiates upward into the space Provides even heat distribution across the room
84
What are the main components of an underfloor heating system?
Heat source (e.g. ASHP or boiler) Manifold distributing water to loops PEX pipe loops embedded in the floor Circulation pumps Thermostats and controls
85
Why does UFH work well with air source heat pumps?
Heat pumps operate most efficiently at low flow temperatures UFH typically uses 30–45°C water Lower temperatures improve heat pump efficiency
86
What are typical flow temperatures for different heating systems?
Radiators: 60–75°C Fan coil units: 45–55°C Underfloor heating: 30–45°C
87
What are the advantages of underfloor heating?
High energy efficiency Even heat distribution No visible radiators Works well in large open spaces
88
What are the disadvantages of underfloor heating?
Slow response time Takes longer to heat or cool a space Installation within floor build-up required Typically heating only unless additional systems used
89
What plant is typically associated with a VRF system?
Outdoor VRF condenser units Refrigerant pipework Branch selector boxes (in some systems) Fan coil units (indoor units) Controls system
90
What plant is typically associated with an ASHP system with UFH and FCUs?
Air source heat pump unit Buffer tank or thermal store Circulation pumps Manifolds for UFH loops Water pipework distribution Fan coil units Control valves and thermostats
91
What is the key difference between VRF and ASHP distribution systems?
VRF distributes refrigerant through copper pipework ASHP systems distribute hot or chilled water
92
Why may VRF require less central plant space than ASHP systems?
VRF distributes refrigerant directly to indoor units Does not require pumps, tanks, or hydronic pipe systems
93
Why may ASHP systems require more plant room equipment?
Need circulation pumps Often require buffer tanks or headers Require water pipe distribution systems
94
When an ASHP system includes fan coil units, what does this allow?
Provides both heating and cooling Hot or chilled water circulates through the FCU coil Air is blown across the coil to condition the room
95
In a comparison between VRF and ASHP + UFH + FCU systems, which may be cheaper for a small number of zones (e.g. 3 indoor units)?
VRF is often cheaper on capital cost Requires less hydronic plant and infrastructure
96
Why may ASHP + UFH + FCU systems cost more to install?
Installation of underfloor heating pipe loops Manifolds and pipe distribution Pumps and buffer tanks Additional labour and coordination
97
Which system is typically quicker to install: VRF or ASHP with UFH?
VRF systems are typically quicker to install
98
Why are VRF systems faster to install?
Install outdoor unit and indoor fan coil units Run refrigerant pipework Connect electrics and controls No floor construction work required
99
Why does UFH installation extend the construction programme?
Pipe loops must be installed within the floor slab or screed Pressure testing required before screeding Screed must cure before floor finishes are installed
100
What is the main programme delay associated with underfloor heating systems?
Floor screed curing period, often 2–4 weeks
101
APC style comparison answer for VRF vs ASHP + UFH + FCU (cost and programme)
VRF generally cheaper and quicker to install for small numbers of zones ASHP + UFH introduces wet plant infrastructure and floor installation VRF involves packaged indoor units and refrigerant pipework
APC 2026
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