Future Homes Carbon Assessment Tool

This tool enables whole-life carbon to be compared between different design options for individual dwellings and informs early-stage decision making. You will need to enter project information, including high-level building geometry inputs and select pre-defined build-ups for one or more elements.

It has been provided for free and whilst every effort has been made to ensure its accuracy the Future Homes Hub can assume no liability for errors or omissions. It is used entirely at the user's own risk. Please review the full disclaimer and terms of use here.

The calculations, assumptions and reporting framework follow the Future Homes Hub Whole-Life Carbon Conventions for New Homes – April 2024 (FHH WLC Conventions), which is available here.

A detailed User Guide, including a list of all the inputs required and pre-defined build-ups, is available here.

Project Details

Provide some general details about your development.

* These properties are recorded in the design summary sheet.

Global Constants

These properties apply to all building design options.

Dwelling Type

Apartment Block

Bungalow

Detached House

Semi-Detached House

Terraced House

Overview

The total number of dwellings in the building.

Further Guidance

For a single detached house input 1

For an apartment block or row of terraces - input the number of dwellings.

Overview

The total number of occupants in the building (across all dwellings).

What is it used to calculate?

Operational Water and Operational Unregulated Energy calculations.

Further Guidance

For a Detached house, enter the total number of occupants in the house. For an Apartment Block or Terraced Housing Block, input the total number of occupants for the building block.

If left blank, number of occupants will be estimated based upon GIA floor area, based on WLC Conventions for New Homes assumptions.

Overview

Number of storeys including ground floor.

What is it used to calculate?

Embodied carbon impact of stairs.

Overview

Gross Internal Area (as defined by RICS Code of Measuring Practice) is the area of a building measured to the internal face of the perimeter walls, at each floor level.

What is it used to calculate?

Embodied carbon of floors and some component benchmarks.

It is also utilised to normalise the total WLC in the output graphs and estimate number of occupants if not specified.

Overview

The combined Gross Internal Area of all existing buildings to be demolished to enable the new building. If there are no existing buildings on site, the value would be 0.

What is it used to calculate?

Impact from A5.1 Pre-construction Demolition.

Overview

Ground Floor Area measured to the internal face of the perimeter walls.

What is it used to calculate?

Embodied carbon of ground floor slabs and upper floors.

Overview

Length of load-bearing ground floor walls (internal and external, including party walls) measured along the wall centreline.

What is it used to calculate?

Embodied carbon of strip foundations and substructure walls.

Overview

Length of internal load-bearing walls at all ground and upper floor levels, measured along the wall centreline. This excludes external walls and party walls.

What is it used to calculate?

Embodied carbon of internal load bearing walls.

Further Guidance

Total length of internal load bearing walls = X metres for L00 + Y metres for L01 + … etc.

Overview

Length of internal stud walls at all ground and upper floor levels, measured along the wall centreline. This excludes all load-bearing walls.

What is it used to calculate?

Embodied carbon of internal stud (non-load-bearing) walls.

Further Guidance

Total length of internal stud walls = X metres for L00 + Y metres for L01 + … etc.

Overview

Roof area in pitch, excluding roof windows, measured externally.

What is it used to calculate?

Embodied carbon of roofs (external covering).

Overview

Roof area in plan, measured to outside of wall plate.

What is it used to calculate?

Embodied carbon of roofs (structure / internal structure).

Overview

Total external wall area excluding windows and doors, measured to the external corners.

What is it used to calculate?

Embodied carbon of external opaque walls (structure/internal, cavity and façade).

Overview

Total area of rough openings associated with windows, roof windows, and glazed doors. Do not include non-glazed doors.

What is it used to calculate?

Embodied carbon of windows.

Overview

Total area of rough openings associated with external doors. Do not include glazed doors.

What is it used to calculate?

Embodied carbon of external doors.

Overview

Total area of party walls (walls between different dwellings) within a terraced housing block or apartment building.

What is it used to calculate?

Embodied carbon of party walls.

Further Guidance

If there are no party walls, set this value to 0 or leave blank.

Overview

Total length of all lintels in the building.

What is it used to calculate?

Embodied carbon of lintels.

Overview

Number of bathrooms and en-suites including a Sink, WC, and bath/shower. Not including WCs.

What is it used to calculate?

Embodied carbon of bathrooms (component benchmark).

Overview

Total number of WCs in the building including a Sink and WC. Not including bathrooms and en-suites.

What is it used to calculate?

Embodied carbon of WCs (component benchmark).

Overview

Number of stair cores within the building.

What is it used to calculate?

Embodied carbon of stairs.

Uncertainty Factor

Please provide values for the contingency, carbon data uncertainty, and quantities uncertainty factors.

*See the icons for help with these values.

Overview

To account for uncertainty, the WLC assessor must consider contingency for the project based on the uncertainty at the time of the assessment.

Default Contingency Factors

Early design stage: 15%
Technical design and construction: 6%
Post-completion: 0%

Overview

The carbon data uncertainty factor is based on how accurately project carbon data represents the products and materials being used in the asset.

Remarks

At early design - the carbon data uncertainty should be 0%, as this is accounted for within the contingency factor.

At technical design and construction, and post-completion - the carbon data uncertainty should be calculated based on the top 10 most impactful products (in terms of embodied carbon), in line with RICS PS 2.0 Section 4.10.2.

Overview

The quantities uncertainty factor for key products (the most impactful products and materials used) provides an indication of the uncertainty associated with the quantities used for the WLCA.

Remarks

At early design the quantities uncertainty should be 0%, as this is accounted for within the contingency factor.

At technical design and construction, and post-completion - the quantities uncertainty should be calculated based on the top 10 most impactful products (in terms of embodied carbon), in line with RICS PS 2.0 Section 4.10.3.

Add Your Own Buildups

Optionally upload your completed spreadsheet to augment the default FHH buildups collection.

Click here to download the spreadsheet template.

Design Wizard

Give your design a name. Then, click configure.

Option Name

Design Wizard

Option:

Regulated Operational Energy

Click here to download the WLC pre-calculator – Regulated energy from SAP outputs

Regulated Energy

Overview

Total annual operational energy consumption from regulated uses (i.e. those covered by Building Regulations Part L). This equates to total demand net of any generation by renewables.

If your building has multiple dwellings, please aggregate the total regulated energy for all dwellings in the building.

What is it used to calculate?

Operational carbon from regulated uses.

Further Guidance

To make it easy to extract the right information from the SAP worksheet, please refer to the WLC pre-calculator – Regulated energy from SAP outputs on the Hub’s website (https://futurehomes.org.uk/wlc-tool) link.

Provide a numerical value equal to or greater than zero. KWhr/yr % Regulated Energy From Gas

Overview

Gas consumption as a proportion of total energy demand excluding any contribution from renewables. If your building has multiple dwellings, please aggregate the gas consumption and total energy demand before calculating the proportion.

What is it used to calculate?

Operational carbon from regulated uses.

Further Guidance

Refer to the WLC pre-calculator – Regulated energy from SAP outputs on the Hub’s website

Provide a value from 0 to 100. % % Regulated Energy From Electricity

Overview

Electricity consumption as a proportion of total energy demand excluding any contribution from renewables. If your building has multiple dwellings, please aggregate the electricity consumption and total energy demand before calculating the proportion.

What is it used to calculate?

Operational carbon from regulated uses.

Further Guidance

Refer to the WLC pre-calculator – Regulated energy from SAP outputs on the Hub’s website.

Provide a value from 0 to 100. %

Design Wizard

Option:

Unregulated Operational Energy

Cooking & Appliances Assumption

Overview

Assumed fuels for cooking and appliances.

What is it used to calculate?

Operational carbon from unregulated uses (cooking and appliances), based on the WLC Conventions for New Homes assumptions.

Further Guidance

Cooking relates to the hob and oven only (i.e all-electric and all-gas cooking mean that both hob and oven have the same fuel, and mixed gas/electric means that they have different fuels).

Appliances are always assumed to be electric. These include: fridges, dishwashers, washing machines, kettles, microwaves, IT devices and other plug loads.

To understand the assumptions behind this calculation, please refer to the WLC pre-calculator – Unregulated energy on the Hub’s website (https://futurehomes.org.uk/wlc-tool) link

All-Electric Cooking & All-Electric Appliances
Mixed-Gas/Electric Cooking & All-Electric Appliances
All-Gas Cooking & All-Electric Appliances

Note: Unregulated energy will be estimated based on the Total Floor Area and Number of Occupants. If the user has not provided these inputs, the tool will not calculate a carbon value for Unregulated Operational Energy.

Design Wizard

Option:

Renewable On-Site Energy Generation

Renewable On-Site Energy Generation (Total)

Overview

Total annual on-site renewable energy generation. Energy generation includes on-site: PV, wind, hydro-electric, and micro-CHP.

What is it used to calculate?

Operational carbon from regulated uses.

Further Guidance

Refer to the WLC pre-calculator – Regulated energy from SAP outputs on the Hub’s website

Provide a numerical value equal to or greater than zero. kWh/yr Renewable On-Site Energy Generation
(Used on-site, at time of generation)

Overview

Total annual on-site renewable energy generation used on site at time of generation.

What is it used to calculate?

Allocation of electricity generated and used on site, exported then re-imported, and imported only – in line with RICS carbon conversion factor Set 2 – WLC benchmarking.

Further Guidance

Refer to the WLC pre-calculator – Regulated energy from SAP outputs on the Hub’s website

Provide a numerical value equal to or greater than zero. kWh/yr

Design Wizard

Option:

Operational Water

Water Use

Overview

Mains water consumption in litres of water used per person, per day. If your building has multiple dwellings, please input the average water consumption across all occupants in the building.

What is it used to calculate?

Operational carbon associated with water supply and treatment.

Further Guidance

If project specific information is not available, 120 litres/person/day can be used as an indicative assumption. This is in line with Approved Document Part G.

Provide a numerical value equal to or greater than zero. litres/person/day

Design Wizard

Option:

Foundations

Select one type

Design Wizard

Option:

Substructure

Select one type

Design Wizard

Option:

Ground Floor

Select one type

Design Wizard

Option:

Internal Load Bearing Walls

Select one type

Design Wizard

Option:

Internal Stud Walls

Select one type

Design Wizard

Option:

External Wall (Structure / Internal)

Select one type

Design Wizard

Option:

External Wall (Cavity)

Select one type

Design Wizard

Option:

External Wall (Facade)

Select one type

Design Wizard

Option:

External Doors

Select one type

Design Wizard

Option:

Upper Floors

Select one type

Design Wizard

Option:

Roofs (External Covering)

Select one type

Design Wizard

Option:

Roofs (Structure / Internal)

Select one type

Design Wizard

Option:

Lintels

Select one type

Design Wizard

Option:

Windows

Select one type

Design Wizard

Option:

Party Wall

Select one type

Design Wizard

Option:

Building Services - Heating and DHW

Select one type

Design Wizard

Option:

Building Services - Bathroom and Ensuite

Select one type

Design Wizard

Option:

Building Services - WCs

Select one type

Design Wizard

Option:

Fixed FF&E - Kitchen

Select one type

Design Wizard

Option:

Building Services - Electrical Installations

Select one type

Design Wizard

Option:

Building Services - Water Systems

Select one type

Design Wizard

Option:

Stairs

Select one type

Design Wizard

Option:

Wall Finishes

Select one type

Design Wizard

Option:

Floor Finishes

Select one type

Analysis Results

Blank and/or unselected fields could lead to unintended gaps in the WLC Results.

Results rely on user inputs and build-up selections - for example, Ground Floor Area and the Ground Floor build-up are both needed to calculate the WLC of ground floor slabs.

Compare carbon performance between your design options.

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