Low-Carbon Retrofit Buildings

Retrofit is the process of making existing buildings more energy efficient by upgrading the building fabric or heating systems as well as adding new low-energy technologies.

Retrofitting a basement
Retrofitting works such as wall insulation are important ways to reduce the energy consumption of your home

What is retrofit?

The word Retrofit is defined as "to add (a component or accessory) to something that did not have it when manufactured." Apply this to the world of buildings from an energy efficiency perspective and it's about adding the new materials and technologies designed for energy efficiency to existing homes thus making them cheaper to run and reducing environmental impact – a win all round!

Why retrofit existing buildings?

With the recognised drive towards net-zero, the focus on energy efficiency and sustainability has never been greater. Whilst we're now building better and more energy-efficient homes, that doesn’t account for the millions of existing dwellings that are already built. In order to achieve targets we need to bring these existing buildings up-to-date, and this is what retrofit is all about.

How to improve building performance by retrofitting

Every building is different so surveys must be carried out before retrofitting to determine what retrofit improvements are possible. Specific retrofit measures to improve building performance can include:


  • Replacing old boilers with high-efficiency ground or air source heat pumps.
  • Fitting underfloor heating and zone controls.

Hot Water

  • Cylinder jackets to reduce heat loss from hot water cylinders.
  • Tank jackets to help prevent against cold water and expansion tanks freezing.
  • Wastewater heat recovery devices to extract heat from the water that goes down the drain when you have a shower or bath.


  • Replacing all lights with low energy LED bulbs.
  • Fitting smart controls to turn lights off when rooms are unoccupied.


  • Installing cavity wall insulation and loft insulation wherever possible.
  • Adding additional internal/external wall insulation to solid walls.
  • Draught-proofing all windows and doors.

Windows and Doors

  • Energy-efficient triple glazing and thermally separated frames.
  • Modern insulated external doors.

Renewables & Micro Generation

  • Biomass boilers replacing oil-fired systems.
  • Solar PV and solar thermal water heating.
  • On-site wind generation.

Retrofit performance monitoring

We have unique tools for helping your retrofit project successfully improve the buildings performance. Take measurements pre- and post-retrofit to determine the performance improvement.

SmartHTC on an In Home Display with temperature sensors

SmartHTC Heat Loss API

Unique algorithm and software that calculates an accurate and reliable measurement of whole building fabric heat loss (also known as a Heat Transfer Coefficient or HTC).

Learn more about SmartHTC Heat Loss API
Heat3D mobile app and FLIR ONE Pro on an iPhone

Heat3D Infrared U-value Measurement

An innovative mobile app that allows you to precisely measure heat flow and U-values of walls using a low-cost, quick and non-invasive method.

Learn more about Heat3D Infrared U-value Measurement

How to measure retrofit performance improvement?

To support this program of energy efficiency measures Build Test Solutions have developed a suite of accessible and affordable building performance measurement solutions to take the guesswork out of improvement measures.

Pulse Air Permeability Measurement System

Pulse is a new way of measuring just how airtight your home is. A simple two-minute air tightness test during the retrofit assessment stage can identify any issues and set a benchmark for improvements. Test again post works to measure the improvements against projections.

Measure retrofit airtightness using Pulse

Leak Checker Diagnostics Fan

Used in conjunction with Pulse at the assessment stage, Leak Checker cab identify key air leakage paths enabling targeted measures to combat specific issues. Again, it can also be used post works to ensure installed measures have corrected any specific issues.

Find air leakage paths using Leak Checker

U-value measurement and Heat3D

When retrofitting insulation measures the objective is to improve the U-value (the rate of transfer of heat through a structure). Build Test Solutions can measure the actual U-value both pre and post works to identify improvement targets and to provide quality assurance on installed measures. There are two types of tests, the traditional U-value test using heat flux plates and a new system called Heat3D which works using infrared technologies and 3D imagery. It can provide accurate results in just one hour.

Accurately measure U-values of buildings prior to retrofitting Rapidly check U-values post-retrofit works using Heat3D

SmartHTC Thermal Performance Test

At Build Test Solutions we have a saying “you can manage what you don’t measure” and SmartHTC will accurately measure the thermal performance of your entire property. It doesn't simply make assumptions, instead, it uses actual temperature and energy data from the property to calculate an accurate and reliable measurement of heat loss through the fabric of the entire building.

Working from small sensors and energy data SmartHTC is a very simple and cost-effective way of measuring overall thermal performance. It can also assess any risk of damp, mould or overheating.

Use it as part of the retrofit assessment process, post works to measure the impact of works carried out and on an ongoing basis.

Retrofit performance test using SmartHTC

Retrofit Assessment

Retrofit works can make a real and positive impact on energy efficiency and the environment as a whole. Build Test Solutions can help you take the guesswork out of any Retrofit program by providing accurate performance data to support all energy efficiency measures and retrofit assessment.

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