Air conditioning systems for large residential developments: Solutions for new-build apartments and renovations

Residential high-rise buildings regularly suffer from overheating as a result of modern construction methods and materials improving the thermal insulation of the buildings. While this helps to reduce heating energy use and lowers the building’s carbon footprint to achieve a high BREEAM score and allows individual units to be sold with a high EPC rating, it can lead to issues down the line.

The materials used to provide thermal insulation capture and store heat from the sun, which then radiates out into the apartments. This results in hot and stuffy accommodation that can’t easily be relieved. This situation has, in some instances, resulted in residents taking developers to court due to uninhabitable living conditions. 

As a result, many developers are looking at ways in which air conditioning can be installed in both new-build properties and as part of property renovations. This means that property owners can control the temperature of their apartments in summer as well as winter, benefit from cleaner, filtered air and reduce humidity levels. 

However, AC brings with it some added challenges whether you are looking to install in a brand new building or are retrofitting an existing property. Understanding the air conditioning options and the challenges various systems can bring, whether this is outside space availability or planning challenges with listed buildings, can enable you to find the best fit for your project.

Every air conditioning solution has both pros and cons. Keep reading for a breakdown of the current systems available including; (1) Central Four Pipe systems, (2) Constant Temperature systems, (3) Split type systems, (4) VRF systems and the new (5) TRIAC air conditioning systems.

1. Central Four Pipe System

A central four-pipe system is a central-based boiler and refrigerant chiller combination that can provide both hot water for heating and chilled water for air conditioning to all the individual residential units that are connected to it. 

The system works by running four pipes – heating flow and return and chilled water flow and return – which are usually installed in iron barrel pipes around the building. The pipework is lagged to stop condensation and ensure efficiency is maintained. 

Heating is provided by a large boiler or a bank of boilers while a refrigerant-based chiller provides the chilled water for the building’s air conditioning. Each apartment has fan coil units that connect onto the four pipes so heating or cooling valves can be opened to heat or cool a room as required. 

The big issue with a central four-pipe system is the capital outlay needed for installation. Both boilers and chillers have to be large enough to cope with the demand of the building as a whole while the pipework has to run throughout the entire building. 

In addition to the high cost, space also needs to be provided for the central boilers, chillers and plant rooms. This space is not sellable and so potentially reduces the number of units within a development or cuts down on amenities like parking. 

Finally, metering and billing also need to be taken into account so that each residential apartment can be charged for the energy they use for heating and cooling.

Central Four Pipe System – Advantages
  • Heating and cooling provided to all residential units.
Central Four Pipe System – Disadvantages
  • Large initial capital outlay
  • Loss of space due to equipment 
  • Added communal charges due to operation and maintenance of mechanical systems
  • Difficult to meter hot and chilled water usage for owners to pay as per consumed
  • Breakdown of the system would shut down the whole building’s heating and cooling.

2. Constant Temperature Systems

Constant temperature systems are similar to four-pipe systems. There is a central boiler and refrigerant chiller but there are only two pipes – a flow and a return – that run throughout the entire building and to each apartment. 

The water in the system is generally kept at a constant temperature – around 20°C. Each apartment is then cooled or heated via a water-cooled heat pump condenser. These are usually installed in a cupboard and are then connected via refrigeration pipes to internal fan coil units in each room or a central fan coil unit that serves the apartment as a whole. 

As the system serves the entire building, this means that any issues with a communal mechanical component, such as the chiller, will affect the whole building. Standby mechanical components can be designed into the system to reduce disruption in case of a fault, but this will increase capital outlay. 

Constant Temperature System – Advantages
  • Heating and cooling provided to all residential units.
Constant Temperature System – Disadvantages
  • Large initial capital outlay
  • Loss of space due to equipment 
  • Added communal charges due to operation and maintenance of mechanical systems
  • Difficult to meter hot and chilled water usage for owners to pay as per consumed
  • Breakdown of the system would shut down the whole building’s heating and cooling.

3. Split Type Air Conditioning

Split type air conditioning systems are, as the name suggests, split into an internal evaporator unit and an external condenser unit. Refrigerant pipework is run between the internal and external units to provide heating or cooling. 

This type of air conditioning is very effective, as well as incredibly efficient. However, split type systems present some challenges, especially when it comes to high rise buildings. 

The main problem is the installation of the outdoor condenser, which can be noisy and also affect the aesthetics of the building. As most apartments in high rise buildings only have small balconies as outdoor space, this becomes the only place for external condenser units to be installed.

Not only does this further reduce the already limited outside space an apartment has, but it also doesn’t look attractive when multiple balconies have condensers installed. This can reduce the desirability of a property. 

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In some cases, such as in conservation areas or listed buildings, external condensers cannot be installed or require additional planning permission. This means that split type air conditioning systems cannot be used or come with added planning costs. 

Split Type Air Conditioning – Advantages
  • Provides cooling and heating to every apartment
  • Self-contained systems serve one apartment each
  • No costly metering of usage
  • Energy efficient.
Split Type Air Conditioning – Disadvantages
  • Can affect the external aesthetics of the building
  • External condensers are often bulky
  • Uses precious outside space
  • Often not an option for listed buildings or in conservation areas.

4. Variable Refrigerant Flow Air Conditioning Systems

Variable Refrigerant Flow (VRF) air conditioning systems use refrigeration to provide cooling and heating to individual residential units. These systems use single or multiple internal units for each flat – depending on size and the number of rooms to be heated or cooled. 

The internal units in each apartment are connected by refrigerant pipework to a large single or multiple condensers, which are usually located on the roof or in the basement of the building. 

As a refrigeration-based system, VRF systems are very effective at temperature control, providing fast heating and cooling for individual apartments and flats. They are also very energy efficient. 

However, there are downsides to this type of system, with the main issue being the oil levels in the condenser units’ compressors, which can limit pipe runs and the number of connectable units. This is because a sufficient amount of oil must return to the compressors with the refrigerant to keep a constant level of oil available to lubricate the compressors. 

Manufacturers of VRF systems typically state the maximum pipe runs and pipe diameters that a system can use. The manufacturer calculates this by running the connected capacity and elevation between indoor units and the condenser units through a software program. Unfortunately, this means that there is no VRF system that can serve a large high rise building, so the system has to be designed to meet each building’s requirements. This can mean that multiple systems are needed within one building. 

While the use of multiple VRF systems can be good in that one system going down doesn’t affect the entire building, it does come with added installation costs. Multiple main runs of refrigerant pipework have to be connected to each condenser, which dramatically affects capital outlay. 

There is also the concern that VRF systems require a large amount of refrigerant for them to run effectively. This in itself is not an issue, but if a leak in the pipework were to happen and be located in an apartment, there is a risk that all of the refrigerant can leak into that apartment. This can cause suffocation if not detected in time. 

All internal units within the VRF system also need to communicate with the condenser units for the system to correctly function. If a fault appears or if power to an internal unit in one apartment is turned off, the whole system can suffer from a communication error or go into a protection stop fault. 

VRF Air Conditioning – Advantages
  • Provides heating and cooling to every residential apartment in a building
  • No individual external condensers needed
  • Very energy efficient
VRF Air Conditioning – Disadvantages
  • Large initial capital outlay
  • Loss of space due to equipment 
  • Added communal charges due to operation and maintenance of mechanical systems
  • Difficult to meter hot and chilled water usage for owners to pay as per consumed
  • Power outages in part of the system will cause issues across the whole system
  • Possible large loss of refrigerant in a small apartment

5. TRIAC Air Conditioning Systems

This new air conditioning system from Urban Cooling remodifies the simple air conditioning split system to allow for apartments to benefit from fully internal air conditioning. TRIAC air conditioning systems remove the need for external condenser units with each system located within an individual apartment. 

The unique system operates with three essential components instead of two. Our condensers are split into two parts – a compressor housing and a condenser housing. These parts connect by refrigerant pipework and are then connected to the indoor units. 

Typically, the compressor housing is installed in a utility cupboard while the condenser housing is installed in a false ceiling, between the concrete slab and plasterboard. Air from an external grille is then ducted over the condenser housing and is discharged externally via a second external grille. 

There are multiple unit types available for this style of air conditioning, allowing it to easily work with property designs. Wall-mounted, ducted and floor-mounted units can all be connected to a TRIAC system, each of which can come in a range of capacities to suit different room sizes. 

Currently, our TRIAC air conditioning systems only provide cooling to apartments, so separate heating will be needed. However, a cooling and heating version is expected to be available in 2022.

TRIAC Air Conditioning – Advantages
  • Low capital outlay per apartment
  • Separate, fully internal systems
  • All flats and apartments benefit from air conditioning
  • No costly communal machinery needed
  • No metering and usage requirements
  • No external condenser required.
TRIAC Air Conditioning – Disadvantages
  • Currently only cooling available – heating version expected in 2022.

Deciding On The Right Air Conditioning System

When it comes to deciding between different air conditioning system types, there are a few things to consider:

Type of Development

The type of development – high rise apartments or smaller buildings – will have an impact on available space while the category of the development – luxury apartments or affordable housing, for example – will affect the available budget. For redevelopments, you’ll also have to factor in planning permission, especially within listed buildings or conservation areas. 

Aesthetic Requirements

Is it possible to install multiple outdoor condensers? Can they be installed at every level or be clustered on one level? Looking at how air conditioning systems will affect the look of the building, as well as what space they will take up for each apartment and the development as a whole will have an impact on the best air conditioning system for your project.

Capital Outlay / Maintenance Costs

The initial cost for installing air conditioning is a key consideration. Central four pipe systems, Constant temperature systems and VRF systems all require a considerable capital outlay upfront due to the fact they are single systems designed to service all apartments. In comparison, Split type and TRIAC air conditioning systems serve individual apartments so capital outlay is significantly reduced for the overall development.

Higher ongoing maintenance costs must also be factored in when considering systems that utilise communal machinery and interconnecting pipework to provide the air conditioning system for all apartments. Typically, maintenance costs are higher because isolating and fixing the problem is more difficult. The fault also impacts part or all of the building, rather than an individual apartment. 

How can Urban Cooling Help?

Whether you are installing air conditioning in a new residential development or as part of a renovation, we can help you find the right air conditioning solution. 

With our broad range of air conditioning options, every building can benefit from AC. We work with you to design systems based on the size and requirement of the building as a whole and each unit. 

Urban Cooling - commercial air conditioning solutions for large residential developments and property renovations.
To find out more details about our internal air conditioning systems, download our brochure or call the Urban Cooling construction team on 0208 080 9708.

If you have any questions about our solutions you can also connect with me (Tony Ellerker) on LinkedIn and I’d be happy to help.