Condensing boiler
According to the Non-domestic building services compliance guide, 2013 edition, published by HM Government, a condensing boiler is: '… a boiler that offers a high energy efficiency by recovering heat from the flue gases. This is achieved by increasing the heat exchanger surface area, which recovers extra sensible heat whenever the boiler fires. The boiler becomes even more efficient when system water temperatures are low because the larger heat exchanger area promotes condensation, allowing much of the latent heat to be recaptured. Standard losses (when the boiler is not firing) are low, and part load performance is very good. In multiple-boiler systems, condensing boilers can be used as the lead boiler.'
The Illustrated Guide to Mechanical Building Services, Third Edition (BG 31/2017), by David Bleicher, published by BSRIA in 2017, states in relation to condensing boilers: ‘The flue gases (otherwise known as products of combustion) from a conventional boiler consist primarily of carbon dioxide (CO2) and water vapour, plus other gases such as oxides of nitrogen. The water vapour holds a significant amount of energy, known as latent heat. In a condensing boiler, the flue gases are cooled before being discharged, so the water vapour condenses (turns into liquid water). The latent heat released is used to preheat water returning to the boiler, and so condensing boilers are more energy-efficient than conventional ones. In order for this condensing process to work, the return water must be below a certain temperature. For this reason, and also that the flue gases are cooler and less buoyant, condensing boilers can’t always directly replace non-condensing boilers in existing buildings.’
[edit] Related articles on Designing Buildings
- Balanced flue appliance.
- Biomass boiler.
- Boiler efficiency.
- Carbon monoxide detector.
- CHP boiler.
- Coefficient of Performance CoP.
- Combustion appliance.
- Domestic building services compliance guide.
- Domestic micro-generation.
- Energy related products regulations.
- Fluepipe.
- Gross calorific value.
- Heat generator.
- Heat interface units.
- Heat pump.
- Industrial gas boilers market 2020.
- Non-domestic building services compliance guide.
- Types of domestic boiler
Featured articles and news
Managing building safety risks
Across an existing residential portfolio, a client's perspective.
ECA support for Gate Safe’s Safe School Gates Campaign.
Core construction skills explained
Preparing for a career in construction.
Retrofitting for resilience with the Leicester Resilience Hub
Community-serving facilities, enhanced as support and essential services for climate-related disruptions.
Some of the articles relating to water, here to browse. Any missing?
Recognisable Gothic characters, designed to dramatically spout water away from buildings.
A case study and a warning to would-be developers
Creating four dwellings... after half a century of doing this job, why, oh why, is it so difficult?
Reform of the fire engineering profession
Fire Engineers Advisory Panel: Authoritative Statement, reactions and next steps.
Restoration and renewal of the Palace of Westminster
A complex project of cultural significance from full decant to EMI, opportunities and a potential a way forward.
Apprenticeships and the responsibility we share
Perspectives from the CIOB President as National Apprentice Week comes to a close.
The first line of defence against rain, wind and snow.
Building Safety recap January, 2026
What we missed at the end of last year, and at the start of this...
National Apprenticeship Week 2026, 9-15 Feb
Shining a light on the positive impacts for businesses, their apprentices and the wider economy alike.
Applications and benefits of acoustic flooring
From commercial to retail.
From solid to sprung and ribbed to raised.
Strengthening industry collaboration in Hong Kong
Hong Kong Institute of Construction and The Chartered Institute of Building sign Memorandum of Understanding.
A detailed description from the experts at Cornish Lime.