Rated heat output and rated heat input of combustion appliances
A combustion appliance is an apparatus where fuel is burned to generate heat for space heating, water heating, cooking or other similar purpose.
According to Approved document J, Combustion appliances and fuel storage systems:
The rated heat input (or ‘rated input’) for a gas appliance is the maximum heat input rate at which it can be operated, as declared on the appliance data plate.
The heat input rate is the maximum rate of energy flow into an appliance, calculated as the rate of fuel flow to the appliance multiplied by either the fuel’s gross or net calorific value. Traditionally, the UK has used gross values, most European standards use net values. Thus for gas appliances it is now the norm to express this rating as a net value (kW (net))
The rated heat output for an oil appliance is the maximum declared energy output rate (kW) as declared on the appliance data plate.
The rated heat output for a solid fuel appliance is the manufacturer’s declared nominal energy output rate (kW) for the appliance. This may be different for different fuels.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
A change to adoptive architecture
Effects of global weather warming on architectural detailing, material choice and human interaction.
How big is the problem and what can we do to mitigate the effects?
Overheating guidance and tools for building designers
A number of cool guides to help with the heat.
The UK's Modern Industrial Strategy: A 10 year plan
Previous consultation criticism, current key elements and general support with some persisting reservations.
Building Safety Regulator reforms
New roles, new staff and a new fast track service pave the way for a single construction regulator.
Architectural Technologist CPDs and Communications
CIAT CPD… and how you can do it!
Cooling centres and cool spaces
Managing extreme heat in cities by directing the public to places for heat stress relief and water sources.
Winter gardens: A brief history and warm variations
Extending the season with glass in different forms and terms.
Restoring Great Yarmouth's Winter Gardens
Transforming one of the least sustainable constructions imaginable.
Construction Skills Mission Board launch sector drive
Newly formed government and industry collaboration set strategy for recruiting an additional 100,000 construction workers a year.
New Architects Code comes into effect in September 2025
ARB Architects Code of Conduct and Practice available with ongoing consultation regarding guidance.
Welsh Skills Body (Medr) launches ambitious plan
The new skills body brings together funding and regulation of tertiary education and research for the devolved nation.
Paul Gandy FCIOB announced as next CIOB President
Former Tilbury Douglas CEO takes helm.
UK Infrastructure: A 10 Year Strategy. In brief with reactions
With the National Infrastructure and Service Transformation Authority (NISTA).
Ebenezer Howard: inventor of the garden city. Book review.
Airtightness Topic Guide BSRIA TG 27/2025
Explaining the basics of airtightness, what it is, why it's important, when it's required and how it's carried out.