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Exploring House Retrofit Heating Systems: A Closer Look at Heat Pumps

  • Mihai
  • Jan 14, 2024
  • 3 min read

Updated: Jun 3

Comprehensive technical assessment for heat pump grant eligibility, including BER evaluations to assess building energy efficiency, system requirements, and suitability for heat pump installation under government grant programs.
House Retrofit Assessment

As energy efficiency and sustainable living gain traction in Ireland, more homeowners are considering retrofitting their homes with heat pumps. However, the process isn’t as simple as replacing a boiler. It involves evaluating your home’s thermal performance, selecting the right heat pump type, and understanding what retrofitting entails.

In this guide, we’ll walk you through the key considerations and technical requirements for a successful retrofit—whether you’re interested in ground source heat pumps, air source systems, or integrating a hybrid solution.


🌱 Ground Source Heat Pumps: Efficient but Demanding

Ground source heat pumps (GSHPs) are among the most efficient heating options available. However, they come with high installation costs and require significant outdoor space.

Installation Options:

  • Ground Loop System:The most cost-effective method. Pipes are laid in shallow trenches (1.5–2m deep) around the building in a straight or slinky pattern.

    ✅ Best suited for properties with ample land.

  • Vertical Boreholes:Ideal for limited outdoor space. Boreholes are drilled 100–150m deep.

    ⚠️ Higher cost but stable year-round temperatures for consistent performance.

Note: GSHPs work best with underfloor heating systems, which provide gentle, low-temperature heat. However, retrofitting underfloor heating—especially in homes with suspended timber floors—can be costly and invasive.


🔥 Biomass Boilers: Viable but Impractical?

Biomass boilers use organic fuel (e.g. wood pellets), but they come with challenges:

  • Need for regular fuel sourcing

  • Bulk storage space for pellets

  • Higher maintenance and complexity

➡️ These factors make them less practical for most retrofitting scenarios.


🌬️ Air Source Heat Pumps: Popular & Practical

Air source heat pumps (ASHPs) are the most common retrofit option. They:

  • Extract heat from outside air

  • Are more affordable than GSHPs

  • Require less space and disruption


Types of ASHPs:

  • Air-to-Air: Heats the air in your home; best for open-plan layouts.

  • Air-to-Water: Supplies hot water and supports radiators or underfloor heating.

Efficiency Note:ASHPs have a lower Coefficient of Performance (COP) during cold Irish winters due to falling air temperatures, unlike ground source systems, which draw from the stable 8–12°C underground heat.


🏡 Is Retrofitting a Heat Pump Right for You?

Yes—provided your home meets the right conditions. The most critical factor is insulation quality, measured by the Heat Loss Indicator (HLI). For SEAI heat pump grant eligibility, your home’s HLI must be ≤ 2.00.

Poor insulation = inefficient heating + larger (more expensive) heat pumps.In such cases, it may be better to first improve insulation through wall, roof, and floor upgrades.


🔄 Radiators vs Underfloor Heating in Retrofits

  • Radiators:

    ✅ Cost-effective

    ✅ Fast heat-up time

    ❌ Operate at high temps (not ideal for heat pumps)


  • Underfloor Heating:

  • ✅ Ideal for continuous heat at low temps

  • ✅ Higher comfort

  • ❌ More expensive to retrofit


Hybrid Solution:

Many homes install radiators upstairs and underfloor heating downstairs to balance cost and efficiency.


🔧 Can You Pair a Heat Pump with a Boiler?

Absolutely. A hybrid system—especially in colder climates—can offer the best of both worlds. During mild weather, the heat pump handles the load, while the boiler supplements when outdoor temperatures drop significantly.


📐 Heat Pump Sizing: One Size Doesn’t Fit All

Your system should be sized based on:

  • Local climate (especially winter lows)

  • House size and layout

  • Level of insulation

  • Hot water demand

A qualified heating engineer or BER assessor can help determine the right heat pump for your home.


🔁 Common Retrofitting Challenges

  • System Type Selection:GSHPs need large outdoor areas or boreholes.ASHPs require accessible external wall space.

  • Radiator Compatibility:Most radiators need to be oversized for use with a heat pump’s lower output temperature.

  • Hot Water Tanks:May need slight adjustments to ensure compatibility with heat pump water heating.


🧾 SEAI Grants, Technical Assessment & BER Requirements

If you're planning to apply for the SEAI Heat Pump System Grant, your home must:

  • Pass a technical assessment

  • Have an HLI ≤ 2.00

  • Be BER-certified after heat pump installation


📌 For more information on required documents and eligibility, read our post:


👷 Work with Certified Professionals

Every home is unique. To ensure your retrofit is successful and eligible for grant support, always consult a qualified BER assessor and heating engineer.

At MTS DNC Energy Consultants Limited, we guide homeowners through:

  • BER Assessments

  • Technical Inspections

  • Heat Pump Grant Applications

  • Contractor Coordination


📞 Contact us to discuss your project or get started with a professional heat loss assessment.


⚠️ Disclaimer:

This article provides general information. Every retrofit project requires tailored assessments and may need modifications to meet SEAI guidelines. Always ensure compliance with local regulations, manufacturer guidelines, and building codes.


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