Heat Pumps in Flats: Challenges and Solutions for Multi-Occupancy Buildings

As the UK moves away from gas boilers and embraces heat pumps to meet its Net Zero targets, one significant challenge remains: how do you install heat pumps in flats and multi-occupancy buildings? While heat pumps are well-suited to standalone houses with gardens or exterior walls, the logistics of installation become more complex in apartment blocks, particularly older or high-rise buildings.

This comprehensive guide explores the different approaches to installing heat pumps in flats, including collective systems, individual solutions, and the potential for heat networks.

The Challenges of Heat Pumps in Flats

Why Are Flats Hard to Retrofit with Heat Pumps?

Flats are often considered “hard-to-treat” buildings when it comes to decarbonizing heating. The main challenges include:

• Lack of Exterior Space: Unlike houses, flats typically don’t have gardens or private outdoor areas for the heat pump unit.

• Building Regulations and Restrictions: Installing a heat pump on a balcony or external wall can require planning permission.

• Shared Ownership and Management: In multi-occupancy buildings, getting agreement from all leaseholders or tenants can be difficult.

• Existing Infrastructure: Many flats have combi gas boilers, which don’t require hot water tanks, making the transition to heat pump systems more complex.

Heat Pump Solutions for Flats

Despite these challenges, there are several viable solutions for integrating heat pumps into flat buildings. These solutions can be categorized based on whether they involve collective systems or individual installations.

1. Collective Heat Pump Systems in Flats

New Builds with Integrated Heat Pump Systems

The easiest scenario is when heat pumps are integrated from the start, particularly in newly built apartment blocks. In these cases:

• Central Heat Pumps on the Roof: Large air-source heat pumps (ASHP) are installed on the building roof, distributing hot water through a centralized system.

• Individual Controls: Each flat has a Heat Interface Unit (HIU), allowing residents to control their own heating and hot water.

• Billing and Management: Heating costs are typically billed through a building management system, where individual usage is metered and billed by the building manager or an energy service company.

Example: London New BuildsThe Greater London Authority (GLA) has mandated lower carbon emissions for new developments. As a result, many buildings that initially planned for gas CHP (Combined Heat and Power) have switched to centralized ASHP systems.

Retrofitting Centralized Systems in Older Flats

Older buildings, especially those from the 1970s and 80s, present unique challenges. However, if the residents collectively agree, a central heat pump system can be retrofitted.

Key Steps:

1. Agreement Among Residents: The management company or freehold owners must agree to the change.

2. System Design: A centralized ASHP on the roof or ground-source heat pump (GSHP) in a communal area.

3. Infrastructure Upgrades: Using existing vertical risers to distribute heated water.

4. Heat Interface Units (HIUs): Installed in each flat to ensure individual control.

Example: Social Housing ProjectsMany social housing blocks are adopting shared ground-source heat pump systems, where boreholes are drilled in communal areas, like car parks. These systems offer high efficiency and can integrate well with existing communal heating networks.

2. Individual Heat Pump Installations

In cases where collective agreement is not possible, some residents may still opt for individual heat pump solutions.

Balcony Heat Pumps

Balcony heat pumps are designed specifically for flats with balconies. These compact units:

• Take in air from the side and expel cold air at a 90-degree angle, minimizing disruption.

• Are compact and vertical, fitting easily on most balconies.

• Work well for single apartments, especially in moderately sized flats.

Manufacturer Focus:Many European manufacturers are leading the way in designing balcony-friendly heat pumps, as apartments are more common on the continent.

Portable and Modular Heat Pumps

Some companies are experimenting with portable heat pump units, which resemble window air conditioners:

• Easy Installation: No major structural changes are needed.

• Reversible Operation: Can be used for both heating and cooling.

• Condensate Management: Requires proper drainage, which can be a limiting factor.

Electric Boilers as an Alternative

If a heat pump is not feasible, some residents are opting for electric boilers:

• High Electricity Usage: Less efficient than heat pumps.

• Good for Time-of-Use Tariffs: Charge at night when electricity is cheaper and store heat in thermal batteries.

• Useful in Flats: Where space and external venting are issues.

Heat Networks: A City-Wide Solution

In densely populated urban areas, heat networks (district heating) are emerging as a long-term solution:

• Shared Infrastructure: Large centralized heat pumps or waste heat from industry.

• Efficient Distribution: Hot water piped to multiple buildings.

• Government Initiatives: Projects like the South Westminster Area Network (SWAN), using heat from the River Thames, are paving the way.

Example: ParisParis has been using district heating for decades, drawing heat from the River Seine to warm residential and commercial buildings.

Summary: Finding the Right Heat Pump Solution for Flats

There’s no one-size-fits-all approach to heat pumps in flats, but solutions exist for nearly every scenario:

1. New Build Apartments: Centralized ASHP on the roof with individual HIUs.

2. Retrofit in Older Blocks: Centralized systems using vertical risers for distribution.

3. Individual Solutions:

   • Balcony Heat Pumps: Compact, air-source units for single apartments.

   • Electric Boilers: Paired with thermal batteries for efficiency.

   • Portable Heat Pumps: Suitable for short-term or lower-demand use.

4. Heat Networks: City-scale solutions for densely populated areas.

While flats present unique challenges in adopting heat pump technology, the increasing variety of solutions means that decarbonizing heating in multi-occupancy buildings is becoming more feasible. Whether through central systems, individual units, or heat networks, there’s a pathway to sustainable heating for every type of flat.