Study of heating/cooling, domestic hot water and ventilation for small-scale houses

Study of heating/cooling, domestic hot water and ventilation for small-scale houses

In the Housing 4.0 Energy (H4.0E) project, small-scale houses are built with the aim of reducing the overall CO2 impact of buildings by 60%. An important component of this impact is the technology which is used for heating, cooling, domestic hot water (DHW) and ventilation.

Each technology will have a different impact on the CO2 footprint, but this selection also has an impact on the installation of the heat distribution system, and the way inhabitants should use the system with energy consumption in mind.

Therefore, it was decided to ask energy specialists to perform a study to determine the impact of multiple combinations of systems, so each partner in the project can make a well-informed decision when selecting the technologies they will apply in the small scale houses.

Below you can find the main findings of the study.

Study:

A simulation was done for 2 sizes of small-scale houses:

  • 42m² with 2 occupants
  • 67m² with 3 occupants

1. Heat loss:

A heat loss simulation was performed, as this is the starting point for the heating requirement. 2 conclusions were made:

  • The specific heat loss (W/m²) of small-scale houses is higher than larger residential houses due to the higher ratio between windows and walls, so the commonly used standard values 30-50W/m² aren’t achieved.
  • Although type D ventilation uses a lot of useful space, a heat loss reduction of 25% is achieved compared to type C ventilation. However, in practice it’s seen that tenants don’t replace the filters in type D system, which makes the ventilation system inefficient. Therefore it might be considered to implement type C to get over this hurdle, and gain some useful room at the same time, as these houses are small already. Also, at the moment there are very few products on the market which are dimensioned for small-scale houses.

2. Radiators:

When connecting radiators to a heat pump, due its low temperature regime (40/35), large radiators would have to be used, since radiators normally run on high temperature regimes (75/65). When using active ventilo radiators to increase the heat exchange, the size of the radiators can be reduced which is beneficial in small houses, but an electrical cable needs to be run to each radiator to provide power to the fan. It goes without saying that special care should be given to the dimensioning of the radiators in the living room and bathroom.

3. Floor heating:

Floor heating is ideal to combine with heat pump, as it also works on low temperature regime. Since the specific heat losses are rather high, a “dry” system should be used with a small creed layer, to enable a lower response time. The system control should take this into account to intelligently steer the heating.

As with radiators, special care should be given to the dimensioning of the radiators in the living room and bathroom. In the bathroom it’s usually a good idea to put an additional radiator to ensure sufficient thermal comfort. For this reason, it’s equally important not to increase the water temperatures in order to avoid too warm floor surfaces.

4. Heating/cooling profile:

For heating and cooling the following setpoint assumptions were made:

Heating during the year:

  • 20°C from 00:07 – 24:00
  • 16°C from 00:00 – 07:00

Cooling:

  • 26°C from 31/April to 30/August

A simulation was made to determine the energy profile over the entire year, and came to the conclusion that there are few hours per year where there would be cooling requirement (over 26°C in summer), so it can be concluded that these houses probably won’t require a cooling system.

5. Systems analysis:

Different combinations of technical solutions were compared to each other on primary energy consumption, CO2 emission, energy cost, TCO over 20 years. Systems that were compared are the following (performed for 2 sizes of small-scale houses):

 

Heating

Domestic hot water

1

Gas boiler

Gas boiler

2

Air/water heat pump

Air/water heat pump

3

Air/air multi-split heat pump

Ventilation heat pump boiler

4

Direct electric

Direct electric

5

Direct electric

Ventilation heat pump

6

Ventilation heat pump

Ventilation heat pump

 

Embedded CO2

In this study only the operational CO2 footprint was taken into account. It is also important that when selecting a certain technology, the embedded CO2 (CO2 throughout the entire life cycle) is also included in the CO2 calculation. Only then the total CO2 footprint can be shown correctly.

Maintenance:

When selecting a technology, the maintenance aspect should also be considered. Heat pumps and ventilation systems require higher maintenance, where direct electric heating needs no maintenance as they have no moving parts which fail or filters that need to be changed.

Conclusion:

When selecting a technology for the small-scale houses, it’s important to look at a lot of factors. This is the reason why the study was performed, so all partners can make a calculated decision to make the selection which they believe is most suitable for their situation.

 

 

Author:

Bart Vannoppen

Technology Advisor (Volta)

 

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