3 Case Studies
Introduction
The heater rating model can be used to develop advice for householders on heating options. As part of this project, 10 case studies were developed to illustrate the type of conclusions and information that can be obtained from the output of the model and the heating literature review.
These case studies were developed for a range of heating situations in a variety of different types of households with differing lifestyles, in different types of dwellings, and in different geographic locations. The case studies represent a cross-section of some of the possible heating scenarios that are likely to be encountered in New Zealand, but are only a small sample of the potential heating scenarios that can be explored using the heater rating model.
The objective in producing the case studies was to illustrate the type of information that might be developed by the Ministry for the Environment concerning heating options. A standardised set of weightings of the heater performance criteria was used to produce the case studies. These case studies will need to be reviewed, and the model weightings revised, in light of the priorities of the Ministry for the Environment before they are made available to the public.
The method of developing the case studies was as follows.
- A range of heating scenarios was developed, which attempted to represent the spread of heating situations that might be encountered in New Zealand. These ranged from low heating requirements in well-insulated dwellings in the north, to high heating requirements for poorly insulated dwellings in the south.
- Each heating scenario was then entered into the heater rating model and the default performance weightings applied. The resulting heater ratings and performance information were then extracted from the model. This process was repeated for further heating scenario inputs.
- The heating scenarios and heater rating results were then written up. To make the case studies more readable, descriptions of the households and dwellings were used to explain the heating scenarios. The case studies present the preferred heating option, based on the overall rating given by the model, together with three or four additional heating options. The advantages of the preferred heating option are explained and compared to other heaters. These explanations often rely on both the output of the model and general information concerning the operation of the heaters, much of which is contained in the heating options literature review.
Case Study 1
Description
The household consists of a family with children. Both parents work and the children are at school during the day. During the working week heating is only used in the evenings. The whole house is heated so that the children can do homework and play comfortably in their own rooms.
The house is of medium size with two storeys, about 20 years old and situated in Auckland. It is insulated to Building Code standard.
Heating model inputs
Table 2: Case Study 1: Heating model inputs
| Geographic area | Northern |
|---|---|
|
City or regional/rural |
City |
|
Natural gas available |
Yes |
|
Type of house |
Two storeys |
|
Insulation |
Code |
|
Heating behaviour |
Evenings only |
|
Size of house |
Medium |
|
Whole house versus main living room heating |
Whole house |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- pellet-fired burner
- diesel-fired burner
- electric heat pump – ducted.
There are minimal differences in the operating costs of the three heaters but the electric heat pump will have a higher initial cost.
A critical issue will be whether the house design allows for the effective heat transference throughout the house from the pellet- or diesel-fired burners. A heat-transfer system may be needed, and this would increase the installed cost of the burner options, making them more comparable with the electric heat pump option.
Model output
The model indicated that a 12.0 kW peak heat output would be needed and 1555 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 3: Case Study 1: Heating options
View Case study 1 heating options (large table).
Case Study 2
Description
The household consists of children, parents and grandparents sharing a small home. The youngest and oldest family members are usually at home during the day. The whole house is heated throughout the day to help keep the occupants healthy.
The house is in Northland, about 50 years old, and is not insulated.
Heating model inputs
Table 4: Case Study 2: Heating model inputs
| Geographic area | Northern |
|---|---|
|
City or regional/rural |
Regional/rural |
|
Natural gas available |
Yes |
|
Type of house |
Single storey |
|
Insulation |
None or poor |
|
Heating behaviour |
Available 24 hours per day |
|
Size of house |
Small |
|
Whole house versus main living room heating |
Whole house |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump – ducted
- pellet-fired burner
- gas-enclosed flame effect heater.
There are minimal differences in the operating costs of the three heaters, but the electric heat pump will have a higher initial cost.
A critical issue will be whether the house design allows for the effective heat transference throughout the house from the pellet-fired burner or gas-enclosed flame effect heaters. A heat-transfer system may be needed, and this would increase the initial cost of the pellet-burner and gas-heater options.
Model output
The model indicated a 10.6 kW peak heat output would be needed and 6674 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 5: Case Study 2: heating options
View case study 2 heating options (large table).
Case Study 3
Description
The household consists of a family with children. Both parents work and the children are out at school during the day. Heating is used only in the evenings during the working week. The whole house is heated so that the children can do homework and play comfortably in their own rooms.
The house is of medium size with two storeys, about 20 years old and situated in Wellington. It is insulated to Building Code standard.
Heating model inputs
Table 6: Case Study 3: Heating model inputs
| Geographic area | Central |
|---|---|
|
City or regional/rural |
City |
|
Natural gas available |
Yes |
|
Type of house |
Two storeys |
|
Insulation |
Code |
|
Heating behaviour |
Evenings only |
|
Size of house |
Medium |
|
Whole house versus main living room heating |
Whole house |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- gas-central heating
- enclosed wood burner
- enclosed multi-fuel burner.
There are minimal differences in the operating costs of the three heaters, but the gas central heating will have a higher initial cost.
A critical issue will be whether the house design allows for the effective heat transference throughout the house from either of the burners. A heat-transfer system may be needed, and this would increase the installed cost of the burner options, making them more comparable with the central heating option.
Model output
The model indicated an 18 kW peak heat output would be needed and 3640 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 7: Case Study 3: heating options
View case study 3 heating options (large table).
Case Study 4
Description
The household consists of a retired couple in a small house. The house is occupied most of the day and one room is heated during the day and in the evenings.
The house is situated north of Wellington, about 40 years old, and has no insulation.
Heating model inputs
Table 8: Case Study 4: Heating model inputs
| Geographic area | Central |
|---|---|
|
City or regional/rural |
Regional/rural |
|
Natural gas available |
Yes |
|
Type of house |
Single storey |
|
Insulation |
None or poor |
|
Heating behaviour |
Day and evenings |
|
Size of house |
Small |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump
- electric night-store heater
- gas convection.
There are minimal differences in the operating costs of the three heaters and all three have relatively low capital costs. The electric heat pump and gas convection heater may be more convenient because their heat output can be controlled more effectively than for the night storage heater.
Model output
The model indicated a 6.4 kW peak heat output would be needed and 4049 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 9: Case Study 4: heating options
View case study 4 heating options (large table).
Case Study 5
Description
The household consists of a group of people sharing a large house. They all work, so the house is usually empty during week days. Heating is used only in the evenings and only for one room.
The house is in Wellington, about 40 years old, with one storey and no insulation.
Heating model inputs
Table 10: Case Study 5: Heating model inputs
| Geographic area | Central |
|---|---|
|
City or regional/ rural |
City |
|
Natural gas available |
Yes |
|
Type of house |
Single storey |
|
Insulation |
None or poor |
|
Heating behaviour |
Evenings only |
|
Size of house |
Large |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- gas central heating
- enclosed wood burner
- enclosed multi-fuel burner.
There are minimal differences in the operating costs of the three heaters, but the gas central heating will have a higher initial cost. The gas central heating is recommended due to the high peak heating load that is required, but a single room is being heated so it may be possible to get a larger gas convection heater to heat the space at a lower capital cost.
Model output
The model indicated a 15.1 kW peak heat output would be needed and 4804 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 11: Case Study 5: heating options
View case study 5 heating options (large table).
Case Study 6
Description
The household consists of a couple in their small first home. Since both of the occupants are at work during the day, they only use heating in the evenings and only heat the living room area.
The house is in Christchurch, about 20 years old, and insulated.
Heating model inputs
Table 12: Case Study 6: Heating model inputs
| Geographic area | Southern |
|---|---|
|
City or regional/ rural |
City |
|
Natural gas available |
No |
|
Type of house |
Single storey |
|
Insulation |
Code |
|
Heating behaviour |
Evenings only |
|
Size of house |
Small |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump
- gas convection heater
- pellet burner.
There are minimal differences in the operating costs of the three heaters, but the electric heat pump will probably have the lowest installed cost.
Model output
The model indicated a 5.7 kW peak heat output would be needed and 2019 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 13: Case Study 6: Heating options
View case study 6 heating options (large table).
Case Study 7
Description
The household in this scenario consists of a retired couple or a family with young children living in a small house and spending most days at home. The living room area is heated during the day and evenings.
The house is in Christchurch, about 40 years old, and un-insulated.
Heating model inputs
Table 14: Case Study 7: Heating model inputs
| Geographic area | Southern |
|---|---|
|
City or regional/rural |
City |
|
Natural gas available |
No |
|
Type of house |
Single storey |
|
Insulation |
None or poor |
|
Heating behaviour |
Day and evening |
|
Size of house |
Small |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump – ducted
- pellet burner
- electric distributed ceiling panels.
The electric heat pump and pellet burner have the lowest operating costs, while the ceiling panels are considerably more expensive to operate and install. Given that only a single room is being heated, a way to reduce the capital costs of the heat pump option might be to install a sufficiently powerful non-ducted heater pump, or even two standard heat pumps.
The ceiling panels are recommended as a backup to underfloor heating, so they may not be suitable in this case.
In addition, a diesel burner and a gas enclosed flame-effect heater received similar ratings to the three most highly rated heaters and have lower capital costs than all but the pellet-burner option. So if capital costs are important, then probably a diesel burner and a gas enclosed flame-effect heater should also be considered.
Model output
The model indicated an 8.5 kW peak heat output would be needed and 6057 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 15: Case Study 7: Heating model inputs
View case study 7 heating model inputs (large table).
Case Study 8
Description
The household consists of a couple or family who are usually out during the middle of the day. They heat the whole house in the mornings and evenings.
The house is two storeys, located in Christchurch, about 10 years old, and insulated to above Building Code standard.
Heating model inputs
Table 16: Case Study 8: Heating model inputs
| Geographic area | Southern |
|---|---|
|
City or regional/rural |
City |
|
Natural gas available |
No |
|
Type of house |
Two storey |
|
Insulation |
Good |
|
Heating behaviour |
Morning and evening |
|
Size of house |
Medium |
|
Whole house versus main living room heating |
Whole house |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- enclosed burner – wood
- enclosed burner – multi-fuel
- gas central heating.
There are minimal differences in the operating costs of the enclosed burners, but the gas central heating will be more expensive to operate and install. A critical issue will also be whether the house design allows for the effective heat transference throughout the house from either of the burners. A heat-transfer system may be needed and this would increase the installed cost of the burner options.
However, given the concerns in some cities in the South Island, local air quality restrictions may prohibit the use of enclosed burners and other alternatives may need to be explored. These would include pellet-fired and diesel-fired central heating, which have similar operating costs but higher initial installation costs.
Model output
The model indicated a 20 kW peak heat output would be needed and 5918 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 17: Case Study 8: Heating model inputs
View case study 8 heating model inputs (large table).
Case Study 9
Description
This is a family household where the residents are often out during the middle of the day. They require heating in the morning and again in the evenings, but only in the main living-room area.
The house is in a rural location, 25 years old, and insulated to Building Code standard.
Heating model inputs
Table 18: Case Study 9: Heating model inputs
| Geographic area | Southern |
|---|---|
|
City or regional/rural |
Regional/rural |
|
Natural gas available |
No |
|
Type of house |
Two storey |
|
Insulation |
Code |
|
Heating behaviour |
Morning and evening |
|
Size of house |
Medium |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump – ducted
- pellet burner
- electric distributed ceiling panels.
The electric heat pump and pellet burner have the lowest operating costs, while the ceiling panels are considerably more expensive to operate and install. Given only a single room is being heated, a way to reduce the capital costs of the heat pump option might be to install a sufficiently powerful non-ducted heater pump or even two standard heat pumps.
The ceiling panels are recommended as a backup to underfloor heating, so they may not be suitable in this case.
In addition, a diesel burner and a gas enclosed flame-effect heater received only slightly lower overall ratings to the three most highly rated heaters, and they have lower capital costs than all but the pellet burner option. So if capital costs are important, then probably a diesel burner and a gas enclosed flame-effect heater should also be considered.
Model output
The model indicated a 9.6 kW peak heat output would be needed and 3027 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 19: Case Study 9: Heating model inputs
View case study 9 heating model inputs (large table).
Case Study 10
Description
This household consists of a retired couple who are at home most of the day. They require heating in the main living room only.
The house is 60 years old, situated in Gore, and is un-insulated.
Heating model inputs
Table 20: Case Study 10: Heating model inputs
| Geographic area | Southern |
|---|---|
|
City or regional/rural |
Regional/rural |
|
Natural gas available |
No |
|
Type of house |
Single storey |
|
Insulation |
None or poor |
|
Heating behaviour |
Day and evening |
|
Size of house |
Small |
|
Whole house versus main living room heating |
Main living room |
Preferred heating options
The three heating options most highly rated by the model for this scenario are:
- electric heat pump – ducted
- pellet burner
- diesel burner.
The electric heat pump has the lowest operating costs, but has a higher capital cost than the two other alternatives. Given only a single room is being heated, a way to reduce the capital costs of the heat pump option might be to install a sufficiently powerful non-ducted heat pump, or even two standard heat pumps. The pellet burner and diesel burner heaters will still have a lower capital cost than the heat pump, though they may not be as convenient to use.
Model output
The model indicated an 8.5 kW peak heat output would be needed and 6057 kWh per year of heating energy required. The ratings of the heating options are displayed below.
Table 21: Case Study 10: Heating model inputs
