! 14 Dec 2018: New version (1.3.0) of XCC now released. Click here to see what's changed

Frequently Asked Questions (FAQs)

BRE Excess Cold Calculator

1. Why do we need an Excess Cold Calculator?

The Excess Cold Calculator is a tool to support decisions about Excess Cold hazards made by Environmental Health Practitioners and Technical Officers. In the past some decisions have been legally challenged and it has sometimes proved time consuming and expensive to provide the evidence needed to justify decisions made. Often running costs based on Energy Performance Certificates (EPCs) have been used, which are not always appropriate. There are also some dwelling types which cannot be dealt with using EPCs, such as homes in multiple occupation. The Excess Cold Calculator allows a more specific calculation to be carried out which can be made specific to the type of occupant when considering the required mitigation work. For example, the occupant may be a vulnerable person who requires a different pattern of heating from that assumed in the EPC. The data inputs required are limited to just those which are most relevant to the assessment of Excess Cold hazard.


2. Why isn't it free to use?

No funding from government or any other source has been provided to BRE to support the development of the Excess Cold Calculator. We hope to recoup the costs of development through a modest cost to users.


3. Why do I have to enter so much information about the dwelling?

There are a lot of factors that affect the energy consumption of a dwelling, some physical, some human. We have tried to limit the number of inputs to the most important ones to reach the best compromise between accuracy and ease of use. By removing many inputs collected for an RdSAP calculation (as used to create Energy Performance Certificates) and adding a few new ones, we believe we have reached the most suitable balance for this type of assessment.


4. What are the default fuel prices assumed by the calculator?

Where no fuel prices are entered for a case, typical defaults are used. These are taken from the same database used for SAP calculations (e.g. for creating Energy Performance Certificates). They represent national averages and are updated regularly.

The current set of fuel prices is as follows:

FuelS. charge (£)  Unit price (pence)  
mains gas883.92
LNG883.92
LPG subject to Special Condition 18883.92
bulk LPG566.51
bottled LPG010.56
heating oil04.04
appliances able to use mineral oil or liquid biofuel04.04
B30K04.53
biodiesel from any biomass source05.67
biodiesel from used cooking oil only05.67
rapeseed oil05.67
bioethanol from any biomass source047
house coal04.17
anthracite04.21
manufactured smokeless fuel05.21
wood logs04.65
wood pellets (in bags for secondary heating)06.09
wood pellets (bulk supply for main heating)05.51
wood chips03.48
dual fuel appliance (mineral and wood)04.53
Electricity - standard tariff016.96
Electricity - 7-hour tariff (high rate)019.99
Electricity - 7-hour tariff (low rate)87.86
Electricity - 10-hour tariff (high rate)018.35
Electricity - 10-hour tariff (low rate)710.48
Electricity - 24-hour heating tariff3010.02
Community heating884.78
Community CHP03.35



5. What is the difference between www.excesscold.com and uat.excesscold.com?

www.excesscold.com is the live, public version of the Excess Cold website. To ensure undisrupted service, different environments are used for development and testing of new features. Although they may look the same uat.excesscold.com is an entirely seperate website. UAT stands for User Acceptance Testing and is where test users try out new features before they are released to the live environment. Users must register seperately on the www and uat environemnts. Projects, passwords, etc will be completely seperate for each website. Cases for real properties should always be created using the live environment.



6. There is no option for electric ceiling heating. How should I deal with that?

Apart from storage heaters and heat pumps (which have their own categories to choose), all types of electric heating should be modelled as 'Electric fires'. There are lots of types of electric heater out there, but they are all much the same from an energy consumption point of view (despite what manufacturers might claim). This includes electric fan heaters, oil-filled electric radiators, electric underfloor heating, electric ceiling heating, radiant electric heaters (and probably others). In all cases these should be modelled as 'Electric fires'.



7. Why are my existing cases showing as incomplete after the update on 07 November 2013?

One of the updates in version 0.8.0 is the addition of two new fields; property age and type. The new fields can be found at the bottom of the first section 'General Parameters' and need to be completed before you can continue to the case results. This data will be used for statistical and categorisation purposes and does not affect the calculations so if you are unsure of these details please just estimate as best you can.



8. What happens if I choose to share a case?

Allowing a case to be shared means that it can be easily recreated by other users. If you choose to make a case sharable then a sharing link and QR code will be printed on the last page of the pdf report (not to be confused with the QR code in the report banner that is used for admin purposes). By following the link, scanning the QR code or entering the RRN into the Import a Case section of the New Case page the case will be recreated in your account. Importing a case that was created by a user from your local authority or company will import all case details, while importing a case that was created by someone outside your local authority or company means that identifying details, such as the address, will be removed to preserve anonymity.



9. I read in the paper the other day that a government study has shown that actual savings from energy efficiency measures are lower than predicted by models like SAP? Does this affect the Excess Cold Calculator?

The research is correct, but the XCC is able to deal with this. Energy efficiency improvements like cavity wall insulation have indeed been found to save less than predicted by models. There are a number of reasons for this, but in under-heated homes the dominant cause is ’comfort taking’. In most savings calculations an average level of heating is assumed both before and after an efficiency measure is installed. However, in circumstances where occupants can’t afford to heat their homes properly they are very likely to be under-heating to start with. Following insulation, they may find that they can afford to heat their homes better; so rather than taking the benefit in the form of lower energy consumption, they may choose to take some or all of it in the form of improved comfort. Looking at this from a purely financial point could suggest the efficiency measure was a failure, but if the benefits to the health and happiness of the occupants and the reduction in damage to the property are taken into account this may be a very desirable outcome.

It is possible to use the XCC to consider how much warmer occupants could afford to heat their home for a given level of fuel cost, so XCC users are well placed to consider this kind of issue, which couldn’t possibly be done with a normal SAP calculation.



10. What is the typical range for u-values of the elements of a dwelling?

Currently the Excess Cold Calculator does not place restrictions on the u-values entered for the various elements of a dwelling. However, if unrealistic u-values are entered then you may see some very strange results. A future release the tool may only allow u-values within a certain range to be entered in order to reduce errors. For now, please make use of the u-value help box on the right of the input page to estimate your dwelling u-values and note that the values below represent a range that is unlikely to be exceeded for any UK dwelling:

  • Walls: 0 - 3.5 W/m2K
  • Roofs: 0 - 3.5 W/m2K
  • Floors: 0 - 3.5 W/m2K
  • Windows and doors: 0.5 - 6.0 W/m2K
  • Party walls: 0 - 1.0 W/m2K