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HEMFHS-TP-07: Calculating cold water and evaporative losses within the Home Energy Model — extracted text
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Calculating cold water and evaporative losses within the Home Energy Model: FHS assessment
A technical explanation of the methodology
March 2026
Acknowledgements
This methodology has been developed for the Department for Energy Security & Net Zero by a number of organisations and individuals, including Sustenic, Quidos, Scene Connect, City Science, Hoare Lea, Oxford Brookes University, University of Bath, 10-x, Building Research Establishment (BRE), AECOM, Kiwa Ltd., Loughborough University Enterprises Limited, Chris Martin and John Tebbit.
Quality assurance has been undertaken by a consortium led by Etude, including Levitt Bernstein, People Powered Retrofit, University of Strathclyde’s Energy Systems Research Unit, Julie Godefroy Sustainability, and UCL.
Document reference: HEMFHS-TP-07
Document version: v1.0
Issue date: March 2026
Home Energy Model version: HEM v1.0
Home Energy Model: FHS assessment version: FHS v1.0
© Crown copyright 2026
This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gsi.gov.uk.
Where we have identified any third-party copyright information you will need to obtain permission from the copyright holders concerned.
Any enquiries regarding this publication should be sent to us at: homeenergymodel@energysecurity.gov.uk
Contents
Background to the Home Energy Model _________________________________________ 4
What is the Home Energy Model: Future Homes Standard assessment? ______________ 4
Where can I find more information? ___________________________________________ 4
Related content ____________________________________________________________ 5
Introduction _______________________________________________________________ 6
Level of losses _____________________________________________________________ 7
Time-of-day profiles _________________________________________________________ 8
Evaporative losses ________________________________________________________ 8
Cold water losses ________________________________________________________ 10
Applying profiles to the average losses _________________________________________ 12
Future work ______________________________________________________________ 14
Annex A – Tables of time of use factors _________________________________________ 15
3
HEMFHS-TP-07 Cold water and evaporative losses
Background to the Home Energy Model
What is the Home Energy Model: Future Homes Standard assessment?
The Home Energy Model: Future Homes Standard assessment is a calculation methodology designed to assess compliance with the Future Homes Standard (FHS). It builds on the government’s Home Energy Model, which will replace the government’s Standard Assessment Procedure (SAP).
Where can I find more information?
This document is part of a wider package of material relating to the Home Energy Model:
Home Energy Model: FHS assessment technical documentation (e.g. this document)
What: This document is one of a suite of technical documents, which explain the approach to developing the standard assumptions and methodology used in the wrapper.
Audience: The technical documentation will be of interest to those who want to understand the justifications and evidence base behind the assumptions used in the model.
The Home Energy Model: Future Homes Standard assessment consultation and government response
What: The Home Energy Model: Future Homes Standard (FHS) assessment consultation sought views on the proposed methodology for demonstrating compliance with the FHS.
Audience: The consultation and response will be of interest to those who want to understand the proposed standardised assumptions around occupancy, energy demand etc. to be used when assessing compliance with the FHS, as well as the methodology for the calculation of the FHS compliance metrics.
The Home Energy Model reference code
What: The full Python source code for the Home Energy Model FHS wrapper has been published as a Git repository. Note the reference code for the HEM core engine is published as a separate repository.
4
| Col1 | Col2 | Col3 |
|---|---|---|
| Home Energy Model: FHS assessment technical documentation (e.g. this | ||
| document) | ||
| **What:**This document is one of a suite oftechnical documents, which explain the | ||
| approach to developing the standard assumptions and methodology used in the wrapper. | ||
| Audience: The technical documentation will be of interest to those who want to | ||
| understand the justifications and evidence base behind the assumptions used in the | ||
| model. | ||
| Col1 | Col2 | Col3 |
|---|---|---|
| The Home Energy Model reference code | ||
| What: The full Python source code for the Home Energy Model FHS wrapper has been | ||
| published as aGit repository. Note the reference code for the HEM core engine is | ||
| published as a separate repository. |
HEMFHS-TP-07 Cold water and evaporative losses
Audience: The reference code will be of interest to those who want to understand how the model has been implemented in code, and those wishing to fully clarify their understanding of the new methodology. It will also be of interest to any potential contributors to the Home Energy Model or those wishing to use it within their own projects.
Future Homes and Buildings Standards Government Response
What: The FHS consultation and response sets out the feedback received to the 2023 consultation on proposed Part L standards, and details the new regulations being introduced.
Audience: The consultation and response will be of interest to those wishing to understand the incoming standards for Building Regulations Part L.
Related content
Some related content can be found in the paper on occupancy assumptions (HEMFHS-TP-02), as well as pipework losses for hot water (HEMFHS-TP-04).
To understand how this methodology has been implemented in computer code, please see the following modules:
future_homes_standard.py
cold_water_loss_profile.csv
evap_loss_profile.csv
5
| Col1 | Audience: The reference code will be of interest to those who want to understand how | Col3 |
|---|---|---|
| the model has been implemented in code, and those wishing to fully clarify their | ||
| understanding of the new methodology. It will also be of interest to any potential | ||
| contributors to the Home Energy Model or those wishing to use it within their own | ||
| projects. | ||
HEMFHS-TP-07 Cold water and evaporative losses
Introduction
This paper reviews HEM’s treatment of heat loss related to incoming cold water and evaporation, as well as the creation of heat loss factors for half hour time periods, for each day of the week.
Heat is lost to cold water entering the home, as the cold water warms towards the internal ambient temperature.
Heat is also lost through evaporation occurring within the home when the water vapour created leaves the dwelling via ventilation or infiltration, rather than condensing and re-releasing the energy of evaporation back into the space.
These losses need to be taken into account in HEM’s core heat balance module when it calculates the heating requirement.
Examples of events which lead to cold water losses:
- Toilet flushing – leading to cold water entering the cistern and feed pipework.
- Cold water use (showers, baths, taps) – leading to cold water entering the feed
pipework. 3. Hot water use – leading to cold water entering the feed pipework.
Regarding item 3, the calculation of the energy required for water heating already includes the energy required to heat incoming cold water from its cold temperature to the required hot water temperature, so the energy required to heat from cold temperature to room temperature is excluded to avoid double counting.
Examples of sources of evaporative loss:
- Physical presence of humans (evaporation from skin and from breathing)
- Drying clothes and towels indoors
- Watering indoor plants
- Cleaning activities
- Spillages
This list is unlikely to be exhaustive.
Item 1 is not considered further here because this is dealt with elsewhere as part of the consideration of metabolic gains (see HEMFHS-TP-02 for details).
Cooking also results in evaporative losses, but this is factored in the cooking energy consumption/gains calculation, so is also not treated here.
6
HEMFHS-TP-07 Cold water and evaporative losses
Level of losses
No existing methodology or standard was identified which provides an approach suited to HEM for establishing losses to cold water or via evaporation.
Similarly, no new dataset stating or implying the level of losses from these sources was found. The only reference values identified were from Passive House Planning Package (PHPP) documentation1.
The physics of determining the magnitude of losses of these types are straightforward – heat transfer from/to pipes as a function of pipe/air temperature is implemented elsewhere in HEM and evaporative losses are easily calculated from the volume of water evaporated. But to calculate these losses directly in HEM would require a lot of detail about the system and how it is used. For example, to work out cold water losses the layout of the pipework to all outlets would need to be known, as would a schedule of individual outlet use (for which we have no data – unlike for hot water use). Direct modelling of this within HEM was therefore deemed impractical in terms of the data available and the input data requirements that would be required for HEM.
There are standards describing how to calculate heat loss from pipework, such as the method used elsewhere in HEM taken from 2021 ASHRAE Handbook2, Section 4.4.2. There are also system design guidance standards (e.g. CIBSE Guide B) which are relevant for estimating pipework lengths and diameters. However, as noted above, this is only useful if a realistic temperature profile can be applied to that pipework, on which there is no data, and which would not be practical to use in HEM.
This leaves the PHPP basis as the only usable source for the level of these losses. PHPP assumes a fixed 25 W/person for evaporative losses (from non-metabolic sources) and a value of around 20 W/person for cold water losses from this equation3456.
Losses to incoming cold water (W/person) = 70 x 1.16 x 0.5 x (Tint – Tground) / 24
Where:
Tint is the internal air temperature °C – assumed to be 22 degrees.
Tground is the incoming cold water temperature in °C - assumed to be 10 degrees7
The FHS wrapper has adopted these figures as the average level of losses.
1 SAP applies value of 40 W/person, but this is in turn based on PHPP.
2 https://www.ashrae.org/technical-resources/ashrae-handbook/ashrae-handbook-online
3 Internal heat gains in relation to living area [Passipedia EN] (sections 7and 9)
4 70 Litres per day PHPP assumption on per person hot water consumption
5 1.16 Wh per litre per Kelvin = 4.186 kJ/kg·K (the specific heat capacity of water)
6 PHPP assumes the cold water will only heat to 50% of the internal temperature before new cold water is added.
7 PHPP assumes cold water comes in at the ground temperature (hence the variable name), but HEM receives
cold water temperatures from the input file, so this does not have to be the ground temperature.
7
HEMFHS-TP-07 Cold water and evaporative losses
Time-of-day profiles
No specific data relating to the timing variation of evaporative and cold-water losses was found (it is not needed for PHPP/SAP), but some insight can be gained from considering occupancy and occupant activity data8 held by the Office for National Statistics (ONS).
Evaporative losses
Evaporative losses due to household activities (drying, cleaning, plant watering, etc.) are predominantly related to active occupancy – such that new sources of moisture will largely cease to be created when occupants are asleep or away from home.
ONS data on householder activities tells us both the level of occupancy by time of day and the types of activity being undertaken.
The profile shown in Figure 1, when occupants are both in and not asleep (labelled ‘in-and- awake’), is used as the basis for a time-of-day profile for evaporative losses. Note that only the weekday profile is shown here – there is a different profile for the weekend.
Most sources of moisture generation will have considerable ‘tails’ on them. While these may be initiated by events that take place at times of active occupancy, evaporation will not suddenly cease when occupants are out or asleep, meaning a direct link with the in-and-active occupancy profile above would underestimate evaporative losses at other times.
Therefore, a decay-style smoothing is applied so that evaporation is assumed to continue after the causal event. For example, it is assumed that drying evaporation falls exponentially, such that this can be characterised by a halving time. To apply this smoothing, a set of 24 factors9 was generated which halve in a defined time and sum to a total of 1, as shown in Figure 2.
8 Time Use In The UK: March 2023, Office for National Statistics, https://www.ons.gov.uk/peoplepopulationandcommunity/personalandhouseholdfinances/incomeandwealth/bulletin s/timeuseintheuk/march2023 9 Since the ONS activity data has one value per hour.
8
HEMFHS-TP-07 Cold water and evaporative losses
Weekday occupancy profile
100%
90%
80%
Proportion of occupants
70%
60%
50%
40%
30%
20%
10%
0%
0 2 4 6 8 10 12 14 16 18 20 22 24
Hour of the day
In-and-awake In
Figure 1 – Weekday occupancy profile based on ONS data.
Tail function with 4-hour halving time
0.18
0.16
0.14
0.12
Factor applied
0.1
0.08
0.06
0.04
0.02
0
0 2 4 6 8 10 12 14 16 18 20 22 24
Hours since causal event
Figure 2 – Tail function to be applied to occupancy profile.
This was then applied10 to the 24-hour profile of in-and-awake data to give an adjusted profile. The impact of applying a tail function of this type, with a 4-hour halving time, to the in-and- awake occupancy rate is shown in Figure 3.
10 Each hourly figure was spread over the following 24 hours according to the tail function then the total for each hour was summed.
9
HEMFHS-TP-07 Cold water and evaporative losses
The choice of a 4-hour halving time is an estimate based on a working group’s experience that, during the heating season, clothes left to dry on a rack indoors typically take about a day to dry to an acceptable level – consistent with the graph. In practice this time would vary with case- specific factors, like air circulation in the specific location.
4-hour halving tail smoothing for evaporative losses
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Proportion
0 24 48 72 96 120 144 168
Hour of the week
In and active Smoothed
Figure 3 – Impact of smoothing occupancy profile (before and after)
There is a slightly different profile on the last two days shown in figure 3 as these are based on the weekend ONS profile data.
The difference caused by applying the tail function is most obvious at night, where the in-and- awake rate falls close to zero, but the smoothed data falls much more gradually, reaching a minimum of just over 20% in the morning. This gives the intended behaviour – that moisture generated during the day continues to generate evaporative losses during the night.
Cold water losses
Losses to incoming cold water are directly linked to the volume of water used, so it is assumed this would also reduce when people are out or asleep. Therefore, basing this profile on the in- and-awake occupancy dataset is again assumed to be suitable. It will take time for cold water to warm up towards room temperature, a ‘tail’ of the sort described for evaporative losses was also applied here. In the case of cold water in uninsulated copper pipes, this is likely to warm up quite quickly; but due to their larger volume and compact shape, cold water entering toilet cisterns will take longer.
A simple heat loss model was developed in a spreadsheet to consider likely warm up times. It was assumed cold water pipework was made up of uninsulated 15mm copper pipe11. Heat
11 The length of pipework can be ignored for this purpose – the time taken is independent in the length assumed, for the chosen calculation method.
10
HEMFHS-TP-07 Cold water and evaporative losses
transfer from air to pipework was based on the 2021 ASHRAE Handbook methodology, assuming a cold-water temperature of 10°C and room air temperature of 20°C. The toilet cistern was modelled as a rectangular box made up of sides with a U-value of 5 and a total volume of 8l but only assumed to be filled ¾ full for calculating the heat capacity. The results of these models are shown in Figures 4 and 5. Note the substantial differences in the scale of the time axes of the two graphs.
PipeTemp
20
19
18
Pipe temperature (°C)
17
16
15
14
13
12
11
10
00:00 00:10 00:20 00:30 00:40 00:50 01:00 01:10 01:20
Time (HH:MM)
Figure 4 – Modelled warm-up profile of water in uninsulated 15mm pipework
Cistern
20
19
18
Cistern temperature (°C)
17
16
15
14
13
12
11
10
00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00
Time (HH:MM)
Figure 5 – Modelled warm-up profile of water in a toilet cistern
The modelled halving times for heat loss (i.e. where the temperature has risen halfway to the ambient air temperature) for pipework and a toilet cistern were about 14 minutes and 57
11
HEMFHS-TP-07 Cold water and evaporative losses
minutes, respectively. Toilet flushing is the single largest user of cold12 water in homes13, so weighting more heavily towards this halving time by using a figure of 45 minutes gives the adjusted profile shown in Figure 6.
Figure 6 – Impact of smoothing on occupancy profile (before and after)
This makes a fairly subtle difference to the in-and-active profiles (much less than the 4-hour halving smoothing profile applied for evaporative losses), but it reduces peaks slightly and shows some non-negligible differences during in the night.
Applying profiles to the average losses
Multiplying the time-of-day profiles described above by the flat/average figures for evaporative and cold-water losses based on PHPP (25 and 20 W/person), does not yet give the correct outcome (since the average of the ‘in-and-active’ data is not 1). This is because the PHPP figure already have inherent assumptions about occupancy that we would result in double counting. Therefore, before application of each profile, the proportions were rescaled to give an average of 1.
A further subtlety relates to the fact that the weekend occupancy profile is different from the weekday profile. Because smoothing used, the factor for any given time depends to some extent on the occupancy profile for each point in the previous 24 hours. This means the smoothed profile is different on Monday from Tuesday, for example, because Monday contains
12 Total water use is higher for showers, but the ‘hot’ component of that is out of scope of this work because this is
included in the calculation of hot water energy directly – where it is assumed water is directly heated from cold.
13 According to the EST’s At Home With Water report:
https://energysavingtrust.org.uk/sites/default/files/reports/AtHomewithWater%287%29.pdf?utm_source=chatgpt.c
om
12
HEMFHS-TP-07 Cold water and evaporative losses
the tails of Sunday’s different activity profile. To allow for these intraday differences, a full week’s set of profiles is provided in the data files used by the FHS wrapper code (cold_water_loss_profile.csv and evap_loss_profile.csv).
Finally, the 24-hourly values (based on there being 24 values in the ONS data) are interpolated to give the 48 half-hourly figures needed when using a 30-minute timestep.
The final data tables incorporating these adjustments are shown in Appendix A, with graphs shown here (Figures 7 and 8). These values are applicable directly to the flat loss figures.
The FHS wrapper calculates the evaporative and cold-water losses for each half hour of the year and writes these to the input file that is sent to HEM’s core calculation.
Evaporative loss time of day factor
1.8
1.6
1.4
1.2
Time of day factor
1
0.8
0.6
0.4
0.2
0
0 4 8 12 16 20 24 28 32 36 40 44 48
Half-hour of the day
Mon
Tue Wed Thu Fri Sat Sun
Figure 7 – Final evaporative loss time-of-day profile used for FHS wrapper.
13
HEMFHS-TP-07 Cold water and evaporative losses
Cold water loss time of day factor
2.5
2
Time of day factor
1.5
1
0.5
0
0 4 8 12 16 20 24 28 32 36 40 44 48
Half-hour of the day
Mon
Tue Wed Thu Fri Sat Sun
Figure 8 – Final cold water loss time-of-day profile used for FHS wrapper.
Future work
There remains a good deal of uncertainty in this area both regarding the level of losses and how they vary over the day and year. Should suitable data become available, the level and time-of-day profile, and possibly the whole calculation approach, should be reassessed.
14
HEMFHS-TP-07 Cold water and evaporative losses
Annex A – Tables of time of use factors
Table A1 - Evaporative losses time of day factor
Half hour
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
0 1.2311
1.1595
1.1595
1.1595
1.1595 1.1673
1.2389
1 1.1430
1.0771
1.0771
1.0771
1.0771 1.0846
1.1505
2 1.0549
0.9947
0.9947
0.9947
0.9947 1.0019
1.0621
3 0.9783
0.9229
0.9229
0.9229
0.9229 0.9283
0.9837
4 0.9017
0.8511
0.8511
0.8511
0.8511 0.8547
0.9053
5 0.8373
0.7906
0.7906
0.7906
0.7906 0.7924
0.8390
6 0.7728
0.7302
0.7302
0.7302
0.7302 0.7301
0.7727
7 0.7155
0.6763
0.6763
0.6763
0.6763 0.6766
0.7158
8 0.6582
0.6224
0.6224
0.6224
0.6224 0.6230
0.6589
9 0.6152
0.5821
0.5821
0.5821
0.5821 0.5811
0.6141
10 0.5721
0.5419
0.5419
0.5419
0.5419 0.5391
0.5693
11 0.5611
0.5331
0.5331
0.5331
0.5331 0.5131
0.5412
12 0.5501
0.5242
0.5242
0.5242
0.5242 0.4872
0.5131
13 0.5793
0.5550
0.5550
0.5550
0.5550 0.4949
0.5191
14 0.6084
0.5858
0.5858
0.5858
0.5858 0.5025
0.5252
15 0.6450
0.6242
0.6242
0.6242
0.6242 0.5475
0.5684
16 0.6816
0.6626
0.6626
0.6626
0.6626 0.5925
0.6116
17 0.7196
0.7023
0.7023
0.7023
0.7023 0.6520
0.6693
18 0.7577
0.7421
0.7421
0.7421
0.7421 0.7115
0.7271
19 0.7903
0.7763
0.7763
0.7763
0.7763 0.7675
0.7815
20 0.8229
0.8105
0.8105
0.8105
0.8105 0.8235
0.8360
21 0.8464
0.8352
0.8352
0.8352
0.8352 0.8705
0.8816
22 0.8698
0.8600
0.8600
0.8600
0.8600 0.9174
0.9272
23 0.8896
0.8809
0.8809
0.8809
0.8809 0.9557
0.9643
24 0.9094
0.9018
0.9018
0.9018
0.9018 0.9939
1.0014
25 0.9280
0.9214
0.9214
0.9214
0.9214 1.0217
1.0284
26 0.9467
0.9409
0.9409
0.9409
0.9409 1.0496
1.0554
27 0.9640
0.9589
0.9589
0.9589
0.9589 1.0761
1.0812
28 0.9814
0.9770
0.9770
0.9770
0.9770 1.1026
1.1070
29 1.0010
0.9973
0.9973
0.9973
0.9973 1.1311
1.1348
30 1.0206
1.0175
1.0175
1.0175
1.0175 1.1595
1.1626
31 1.0483
1.0457
1.0457
1.0457
1.0457 1.1953
1.1979
32 1.0760
1.0739
1.0739
1.0739
1.0739 1.2311
1.2331
33 1.1133
1.1116
1.1116
1.1116
1.1116 1.2731
1.2747
34 1.1505
1.1494
1.1494
1.1494
1.1494 1.3152
1.3164
35 1.1977
1.1968
1.1968
1.1968
1.1968 1.3609
1.3618
36 1.2449
1.2443
1.2443
1.2443
1.2443 1.4066
1.4072
37 1.2930
1.2925
1.2925
1.2925
1.2925 1.4456
1.4462
38 1.3411
1.3407
1.3407
1.3407
1.3407 1.4847
1.4851
39 1.3925
1.3921
1.3921
1.3921
1.3921 1.5216
1.5221
40 1.4440
1.4436
1.4436
1.4436
1.4436 1.5585
1.5590
41 1.4809
1.4805
1.4805
1.4805
1.4805 1.5862
1.5866
42 1.5178
1.5174
1.5174
1.5174
1.5174 1.6139
1.6143
43 1.5024
1.5021
1.5021
1.5021
1.5021 1.5934
1.5937
44 1.4871
1.4869
1.4869
1.4869
1.4869 1.5729
1.5731
45 1.4134
1.4133
1.4133
1.4133
1.4133 1.4990
1.4991
46 1.3398
1.3398
1.3398
1.3398
1.3398 1.4251
1.4251
47 1.2496
1.2496
1.2496
1.2496
1.2535 1.3320
1.3281
15
| Col1 | Table A1 - Evaporative losses time of day factor | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 | Col15 | Col16 | Col17 | Col18 | Col19 | Col20 | Col21 | Col22 | Col23 | Col24 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Half hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday | ||||||||||||||||
| 0<br> | <br> | 1.2311<br> | 1.1595<br> | 1.1595<br> | 1.1595<br> | 1.1595<br> | <br> | 1.1673<br> | 1.2389<br> | <br> | |||||||||||||
| 1<br> | <br> | 1.1430<br> | 1.0771<br> | 1.0771<br> | 1.0771<br> | 1.0771<br> | <br> | 1.0846<br> | 1.1505<br> | <br> | |||||||||||||
| 2<br> | <br> | 1.0549<br> | 0.9947<br> | 0.9947<br> | 0.9947<br> | 0.9947<br> | <br> | 1.0019<br> | 1.0621<br> | <br> | |||||||||||||
| 3<br> | <br> | 0.9783<br> | 0.9229<br> | 0.9229<br> | 0.9229<br> | 0.9229<br> | <br> | 0.9283<br> | 0.9837<br> | <br> | |||||||||||||
| 4<br> | <br> | 0.9017<br> | 0.8511<br> | 0.8511<br> | 0.8511<br> | 0.8511<br> | <br> | 0.8547<br> | 0.9053<br> | <br> | |||||||||||||
| 5<br> | <br> | 0.8373<br> | 0.7906<br> | 0.7906<br> | 0.7906<br> | 0.7906<br> | <br> | 0.7924<br> | 0.8390<br> | <br> | |||||||||||||
| 6<br> | <br> | 0.7728<br> | 0.7302<br> | 0.7302<br> | 0.7302<br> | 0.7302<br> | <br> | 0.7301<br> | 0.7727<br> | <br> | |||||||||||||
| 7<br> | <br> | 0.7155<br> | 0.6763<br> | 0.6763<br> | 0.6763<br> | 0.6763<br> | <br> | 0.6766<br> | 0.7158<br> | <br> | |||||||||||||
| 8<br> | <br> | 0.6582<br> | 0.6224<br> | 0.6224<br> | 0.6224<br> | 0.6224<br> | <br> | 0.6230<br> | 0.6589<br> | <br> | |||||||||||||
| 9<br> | <br> | 0.6152<br> | 0.5821<br> | 0.5821<br> | 0.5821<br> | 0.5821<br> | <br> | 0.5811<br> | 0.6141<br> | <br> | |||||||||||||
| 10<br> | <br> | 0.5721<br> | 0.5419<br> | 0.5419<br> | 0.5419<br> | 0.5419<br> | <br> | 0.5391<br> | 0.5693<br> | <br> | |||||||||||||
| 11<br> | <br> | 0.5611<br> | 0.5331<br> | 0.5331<br> | 0.5331<br> | 0.5331<br> | <br> | 0.5131<br> | 0.5412<br> | <br> | |||||||||||||
| 12<br> | <br> | 0.5501<br> | 0.5242<br> | 0.5242<br> | 0.5242<br> | 0.5242<br> | <br> | 0.4872<br> | 0.5131<br> | <br> | |||||||||||||
| 13<br> | <br> | 0.5793<br> | 0.5550<br> | 0.5550<br> | 0.5550<br> | 0.5550<br> | <br> | 0.4949<br> | 0.5191<br> | <br> | |||||||||||||
| 14<br> | <br> | 0.6084<br> | 0.5858<br> | 0.5858<br> | 0.5858<br> | 0.5858<br> | <br> | 0.5025<br> | 0.5252<br> | <br> | |||||||||||||
| 15<br> | <br> | 0.6450<br> | 0.6242<br> | 0.6242<br> | 0.6242<br> | 0.6242<br> | <br> | 0.5475<br> | 0.5684<br> | <br> | |||||||||||||
| 16<br> | <br> | 0.6816<br> | 0.6626<br> | 0.6626<br> | 0.6626<br> | 0.6626<br> | <br> | 0.5925<br> | 0.6116<br> | <br> | |||||||||||||
| 17<br> | <br> | 0.7196<br> | 0.7023<br> | 0.7023<br> | 0.7023<br> | 0.7023<br> | <br> | 0.6520<br> | 0.6693<br> | <br> | |||||||||||||
| 18<br> | <br> | 0.7577<br> | 0.7421<br> | 0.7421<br> | 0.7421<br> | 0.7421<br> | <br> | 0.7115<br> | 0.7271<br> | <br> | |||||||||||||
| 19<br> | <br> | 0.7903<br> | 0.7763<br> | 0.7763<br> | 0.7763<br> | 0.7763<br> | <br> | 0.7675<br> | 0.7815<br> | <br> | |||||||||||||
| 20<br> | <br> | 0.8229<br> | 0.8105<br> | 0.8105<br> | 0.8105<br> | 0.8105<br> | <br> | 0.8235<br> | 0.8360<br> | <br> | |||||||||||||
| 21<br> | <br> | 0.8464<br> | 0.8352<br> | 0.8352<br> | 0.8352<br> | 0.8352<br> | <br> | 0.8705<br> | 0.8816<br> | <br> | |||||||||||||
| 22<br> | <br> | 0.8698<br> | 0.8600<br> | 0.8600<br> | 0.8600<br> | 0.8600<br> | <br> | 0.9174<br> | 0.9272<br> | <br> | |||||||||||||
| 23<br> | <br> | 0.8896<br> | 0.8809<br> | 0.8809<br> | 0.8809<br> | 0.8809<br> | <br> | 0.9557<br> | 0.9643<br> | <br> | |||||||||||||
| 24<br> | <br> | 0.9094<br> | 0.9018<br> | 0.9018<br> | 0.9018<br> | 0.9018<br> | <br> | 0.9939<br> | 1.0014<br> | <br> | |||||||||||||
| 25<br> | <br> | 0.9280<br> | 0.9214<br> | 0.9214<br> | 0.9214<br> | 0.9214<br> | <br> | 1.0217<br> | 1.0284<br> | <br> | |||||||||||||
| 26<br> | <br> | 0.9467<br> | 0.9409<br> | 0.9409<br> | 0.9409<br> | 0.9409<br> | <br> | 1.0496<br> | 1.0554<br> | <br> | |||||||||||||
| 27<br> | <br> | 0.9640<br> | 0.9589<br> | 0.9589<br> | 0.9589<br> | 0.9589<br> | <br> | 1.0761<br> | 1.0812<br> | <br> | |||||||||||||
| 28<br> | <br> | 0.9814<br> | 0.9770<br> | 0.9770<br> | 0.9770<br> | 0.9770<br> | <br> | 1.1026<br> | 1.1070<br> | <br> | |||||||||||||
| 29<br> | <br> | 1.0010<br> | 0.9973<br> | 0.9973<br> | 0.9973<br> | 0.9973<br> | <br> | 1.1311<br> | 1.1348<br> | <br> | |||||||||||||
| 30<br> | <br> | 1.0206<br> | 1.0175<br> | 1.0175<br> | 1.0175<br> | 1.0175<br> | <br> | 1.1595<br> | 1.1626<br> | <br> | |||||||||||||
| 31<br> | <br> | 1.0483<br> | 1.0457<br> | 1.0457<br> | 1.0457<br> | 1.0457<br> | <br> | 1.1953<br> | 1.1979<br> | <br> | |||||||||||||
| 32<br> | <br> | 1.0760<br> | 1.0739<br> | 1.0739<br> | 1.0739<br> | 1.0739<br> | <br> | 1.2311<br> | 1.2331<br> | <br> | |||||||||||||
| 33<br> | <br> | 1.1133<br> | 1.1116<br> | 1.1116<br> | 1.1116<br> | 1.1116<br> | <br> | 1.2731<br> | 1.2747<br> | <br> | |||||||||||||
| 34<br> | <br> | 1.1505<br> | 1.1494<br> | 1.1494<br> | 1.1494<br> | 1.1494<br> | <br> | 1.3152<br> | 1.3164<br> | <br> | |||||||||||||
| 35<br> | <br> | 1.1977<br> | 1.1968<br> | 1.1968<br> | 1.1968<br> | 1.1968<br> | <br> | 1.3609<br> | 1.3618<br> | <br> | |||||||||||||
| 36<br> | <br> | 1.2449<br> | 1.2443<br> | 1.2443<br> | 1.2443<br> | 1.2443<br> | <br> | 1.4066<br> | 1.4072<br> | <br> | |||||||||||||
| 37<br> | <br> | 1.2930<br> | 1.2925<br> | 1.2925<br> | 1.2925<br> | 1.2925<br> | <br> | 1.4456<br> | 1.4462<br> | <br> | |||||||||||||
| 38<br> | <br> | 1.3411<br> | 1.3407<br> | 1.3407<br> | 1.3407<br> | 1.3407<br> | <br> | 1.4847<br> | 1.4851<br> | <br> | |||||||||||||
| 39<br> | <br> | 1.3925<br> | 1.3921<br> | 1.3921<br> | 1.3921<br> | 1.3921<br> | <br> | 1.5216<br> | 1.5221<br> | <br> | |||||||||||||
| 40<br> | <br> | 1.4440<br> | 1.4436<br> | 1.4436<br> | 1.4436<br> | 1.4436<br> | <br> | 1.5585<br> | 1.5590<br> | <br> | |||||||||||||
| 41<br> | <br> | 1.4809<br> | 1.4805<br> | 1.4805<br> | 1.4805<br> | 1.4805<br> | <br> | 1.5862<br> | 1.5866<br> | <br> | |||||||||||||
| 42<br> | <br> | 1.5178<br> | 1.5174<br> | 1.5174<br> | 1.5174<br> | 1.5174<br> | <br> | 1.6139<br> | 1.6143<br> | <br> | |||||||||||||
| 43<br> | <br> | 1.5024<br> | 1.5021<br> | 1.5021<br> | 1.5021<br> | 1.5021<br> | <br> | 1.5934<br> | 1.5937<br> | <br> | |||||||||||||
| 44<br> | <br> | 1.4871<br> | 1.4869<br> | 1.4869<br> | 1.4869<br> | 1.4869<br> | <br> | 1.5729<br> | 1.5731<br> | <br> | |||||||||||||
| 45<br> | <br> | 1.4134<br> | 1.4133<br> | 1.4133<br> | 1.4133<br> | 1.4133<br> | <br> | 1.4990<br> | 1.4991<br> | <br> | |||||||||||||
| 46<br> | <br> | 1.3398<br> | 1.3398<br> | 1.3398<br> | 1.3398<br> | 1.3398<br> | <br> | 1.4251<br> | 1.4251<br> | <br> | |||||||||||||
| 47 | 1.2496 | 1.2496 | 1.2496 | 1.2496 | 1.2535 | 1.3320 | 1.3281 |
HEMFHS-TP-07 Cold water and evaporative losses
Table A2 - Cold water losses time of day factor
Half hour Monday Tuesday Wednesday Thursday Friday
Saturday Sunday
0
0.5256
0.5032
0.5032
0.5032 0.5032
0.5324 0.5547
1
0.4044
0.3888
0.3888
0.3888 0.3888
0.4102 0.4258
2
0.2833
0.2744
0.2744
0.2744 0.2744
0.2880 0.2969
3
0.2255
0.2193
0.2193
0.2193 0.2193
0.2243 0.2305
4
0.1677
0.1642
0.1642
0.1642 0.1642
0.1606 0.1641
5
0.1446
0.1421
0.1421
0.1421 0.1421
0.1338 0.1363
6
0.1215
0.1201
0.1201
0.1201 0.1201
0.1071 0.1085
7
0.1007
0.0997
0.0997
0.0997 0.0997
0.0920 0.0930
8
0.0799
0.0793
0.0793
0.0793 0.0793
0.0769 0.0775
9
0.0909
0.0905
0.0905
0.0905 0.0905
0.0825 0.0829
10
0.1020
0.1017
0.1017
0.1017 0.1017
0.0882 0.0884
11
0.2008
0.2007
0.2007
0.2007 0.2007
0.1267 0.1269
12
0.2997
0.2996
0.2996
0.2996 0.2996
0.1652 0.1653
13
0.4837
0.4837
0.4837
0.4837 0.4837
0.2927 0.2927
14
0.6678
0.6678
0.6678
0.6678 0.6678
0.4201 0.4201
15
0.7880
0.7880
0.7880
0.7880 0.7880
0.6150 0.6150
16
0.9082
0.9082
0.9082
0.9082 0.9082
0.8099 0.8099
17
0.9844
0.9844
0.9844
0.9844 0.9844
0.9684 0.9684
18
1.0605
1.0605
1.0605
1.0605 1.0605
1.1268 1.1268
19
1.0934
1.0934
1.0934
1.0934 1.0934
1.2121 1.2121
20
1.1263
1.1263
1.1263
1.1263 1.1263
1.2974 1.2974
21
1.1244
1.1244
1.1244
1.1244 1.1244
1.3303 1.3303
22
1.1226
1.1226
1.1226
1.1226 1.1226
1.3633 1.3633
23
1.1221
1.1221
1.1221
1.1221 1.1221
1.3718 1.3718
24
1.1217
1.1217
1.1217
1.1217 1.1217
1.3803 1.3803
25
1.1288
1.1288
1.1288
1.1288 1.1288
1.3677 1.3677
26
1.1359
1.1359
1.1359
1.1359 1.1359
1.3551 1.3551
27
1.1449
1.1449
1.1449
1.1449 1.1449
1.3618 1.3618
28
1.1540
1.1540
1.1540
1.1540 1.1540
1.3684 1.3684
29
1.1768
1.1768
1.1768
1.1768 1.1768
1.3943 1.3943
30
1.1996
1.1996
1.1996
1.1996 1.1996
1.4202 1.4202
31
1.2510
1.2510
1.2510
1.2510 1.2510
1.4753 1.4753
32
1.3023
1.3023
1.3023
1.3023 1.3023
1.5304 1.5304
33
1.3756
1.3756
1.3756
1.3756 1.3756
1.5977 1.5977
34
1.4489
1.4489
1.4489
1.4489 1.4489
1.6650 1.6650
35
1.5377
1.5377
1.5377
1.5377 1.5377
1.7310 1.7310
36
1.6264
1.6264
1.6264
1.6264 1.6264
1.7971 1.7971
37
1.6929
1.6929
1.6929
1.6929 1.6929
1.8263 1.8263
38
1.7594
1.7594
1.7594
1.7594 1.7594
1.8555 1.8555
39
1.8271
1.8271
1.8271
1.8271 1.8271
1.8828 1.8828
40
1.8949
1.8949
1.8949
1.8949 1.8949
1.9101 1.9101
41
1.8978
1.8978
1.8978
1.8978 1.8978
1.9081 1.9081
42
1.9007
1.9007
1.9007
1.9007 1.9007
1.9060 1.9060
43
1.7266
1.7266
1.7266
1.7266 1.7266
1.7394 1.7394
44
1.5524
1.5524
1.5524
1.5524 1.5524
1.5727 1.5727
45
1.2536
1.2536
1.2536
1.2536 1.2536
1.2919 1.2919
46
0.9548
0.9548
0.9548
0.9548 0.9548
1.0111 1.0111
47
0.7290
0.7290
0.7290
0.7290 0.7436
0.7829 0.7683
16
| Col1 | Table A2 - Cold water losses time of day factor | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 | Col15 | Col16 | Col17 | Col18 | Col19 | Col20 | Col21 | Col22 | Col23 | Col24 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Half hour | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday | ||||||||||||||||
| 0 | 0.5256 | 0.5032 | 0.5032 | 0.5032 | 0.5032 | 0.5324 | 0.5547 | ||||||||||||||||
| 1 | 0.4044 | 0.3888 | 0.3888 | 0.3888 | 0.3888 | 0.4102 | 0.4258 | ||||||||||||||||
| 2 | 0.2833 | 0.2744 | 0.2744 | 0.2744 | 0.2744 | 0.2880 | 0.2969 | ||||||||||||||||
| 3 | 0.2255 | 0.2193 | 0.2193 | 0.2193 | 0.2193 | 0.2243 | 0.2305 | ||||||||||||||||
| 4 | 0.1677 | 0.1642 | 0.1642 | 0.1642 | 0.1642 | 0.1606 | 0.1641 | ||||||||||||||||
| 5 | 0.1446 | 0.1421 | 0.1421 | 0.1421 | 0.1421 | 0.1338 | 0.1363 | ||||||||||||||||
| 6 | 0.1215 | 0.1201 | 0.1201 | 0.1201 | 0.1201 | 0.1071 | 0.1085 | ||||||||||||||||
| 7 | 0.1007 | 0.0997 | 0.0997 | 0.0997 | 0.0997 | 0.0920 | 0.0930 | ||||||||||||||||
| 8 | 0.0799 | 0.0793 | 0.0793 | 0.0793 | 0.0793 | 0.0769 | 0.0775 | ||||||||||||||||
| 9 | 0.0909 | 0.0905 | 0.0905 | 0.0905 | 0.0905 | 0.0825 | 0.0829 | ||||||||||||||||
| 10 | 0.1020 | 0.1017 | 0.1017 | 0.1017 | 0.1017 | 0.0882 | 0.0884 | ||||||||||||||||
| 11 | 0.2008 | 0.2007 | 0.2007 | 0.2007 | 0.2007 | 0.1267 | 0.1269 | ||||||||||||||||
| 12 | 0.2997 | 0.2996 | 0.2996 | 0.2996 | 0.2996 | 0.1652 | 0.1653 | ||||||||||||||||
| 13 | 0.4837 | 0.4837 | 0.4837 | 0.4837 | 0.4837 | 0.2927 | 0.2927 | ||||||||||||||||
| 14 | 0.6678 | 0.6678 | 0.6678 | 0.6678 | 0.6678 | 0.4201 | 0.4201 | ||||||||||||||||
| 15 | 0.7880 | 0.7880 | 0.7880 | 0.7880 | 0.7880 | 0.6150 | 0.6150 | ||||||||||||||||
| 16 | 0.9082 | 0.9082 | 0.9082 | 0.9082 | 0.9082 | 0.8099 | 0.8099 | ||||||||||||||||
| 17 | 0.9844 | 0.9844 | 0.9844 | 0.9844 | 0.9844 | 0.9684 | 0.9684 | ||||||||||||||||
| 18 | 1.0605 | 1.0605 | 1.0605 | 1.0605 | 1.0605 | 1.1268 | 1.1268 | ||||||||||||||||
| 19 | 1.0934 | 1.0934 | 1.0934 | 1.0934 | 1.0934 | 1.2121 | 1.2121 | ||||||||||||||||
| 20 | 1.1263 | 1.1263 | 1.1263 | 1.1263 | 1.1263 | 1.2974 | 1.2974 | ||||||||||||||||
| 21 | 1.1244 | 1.1244 | 1.1244 | 1.1244 | 1.1244 | 1.3303 | 1.3303 | ||||||||||||||||
| 22 | 1.1226 | 1.1226 | 1.1226 | 1.1226 | 1.1226 | 1.3633 | 1.3633 | ||||||||||||||||
| 23 | 1.1221 | 1.1221 | 1.1221 | 1.1221 | 1.1221 | 1.3718 | 1.3718 | ||||||||||||||||
| 24 | 1.1217 | 1.1217 | 1.1217 | 1.1217 | 1.1217 | 1.3803 | 1.3803 | ||||||||||||||||
| 25 | 1.1288 | 1.1288 | 1.1288 | 1.1288 | 1.1288 | 1.3677 | 1.3677 | ||||||||||||||||
| 26 | 1.1359 | 1.1359 | 1.1359 | 1.1359 | 1.1359 | 1.3551 | 1.3551 | ||||||||||||||||
| 27 | 1.1449 | 1.1449 | 1.1449 | 1.1449 | 1.1449 | 1.3618 | 1.3618 | ||||||||||||||||
| 28 | 1.1540 | 1.1540 | 1.1540 | 1.1540 | 1.1540 | 1.3684 | 1.3684 | ||||||||||||||||
| 29 | 1.1768 | 1.1768 | 1.1768 | 1.1768 | 1.1768 | 1.3943 | 1.3943 | ||||||||||||||||
| 30 | 1.1996 | 1.1996 | 1.1996 | 1.1996 | 1.1996 | 1.4202 | 1.4202 | ||||||||||||||||
| 31 | 1.2510 | 1.2510 | 1.2510 | 1.2510 | 1.2510 | 1.4753 | 1.4753 | ||||||||||||||||
| 32 | 1.3023 | 1.3023 | 1.3023 | 1.3023 | 1.3023 | 1.5304 | 1.5304 | ||||||||||||||||
| 33 | 1.3756 | 1.3756 | 1.3756 | 1.3756 | 1.3756 | 1.5977 | 1.5977 | ||||||||||||||||
| 34 | 1.4489 | 1.4489 | 1.4489 | 1.4489 | 1.4489 | 1.6650 | 1.6650 | ||||||||||||||||
| 35 | 1.5377 | 1.5377 | 1.5377 | 1.5377 | 1.5377 | 1.7310 | 1.7310 | ||||||||||||||||
| 36 | 1.6264 | 1.6264 | 1.6264 | 1.6264 | 1.6264 | 1.7971 | 1.7971 | ||||||||||||||||
| 37 | 1.6929 | 1.6929 | 1.6929 | 1.6929 | 1.6929 | 1.8263 | 1.8263 | ||||||||||||||||
| 38 | 1.7594 | 1.7594 | 1.7594 | 1.7594 | 1.7594 | 1.8555 | 1.8555 | ||||||||||||||||
| 39 | 1.8271 | 1.8271 | 1.8271 | 1.8271 | 1.8271 | 1.8828 | 1.8828 | ||||||||||||||||
| 40 | 1.8949 | 1.8949 | 1.8949 | 1.8949 | 1.8949 | 1.9101 | 1.9101 | ||||||||||||||||
| 41 | 1.8978 | 1.8978 | 1.8978 | 1.8978 | 1.8978 | 1.9081 | 1.9081 | ||||||||||||||||
| 42 | 1.9007 | 1.9007 | 1.9007 | 1.9007 | 1.9007 | 1.9060 | 1.9060 | ||||||||||||||||
| 43 | 1.7266 | 1.7266 | 1.7266 | 1.7266 | 1.7266 | 1.7394 | 1.7394 | ||||||||||||||||
| 44 | 1.5524 | 1.5524 | 1.5524 | 1.5524 | 1.5524 | 1.5727 | 1.5727 | ||||||||||||||||
| 45 | 1.2536 | 1.2536 | 1.2536 | 1.2536 | 1.2536 | 1.2919 | 1.2919 | ||||||||||||||||
| 46 | 0.9548 | 0.9548 | 0.9548 | 0.9548 | 0.9548 | 1.0111 | 1.0111 | ||||||||||||||||
| 47 | 0.7290 | 0.7290 | 0.7290 | 0.7290 | 0.7436 | 0.7829 | 0.7683 |
This publication is available from: https://www.gov.uk/government/publications/home-energy- model-future-homes-standard-assessment-technical-documentation