**4. Results and discussions**

 A benchmark comparison of surveyed buildings was performed; first to provide an indication of how the buildings are performing; second, to identify where energy waste is prominent, and third to identify the areas for improvement. **Figure 3** shows the result of the comparison between the benchmark and annual energy consumption of the buildings surveyed.

 It could be observed that the energy use of the buildings was substantially and simultaneously higher and plateaued than the benchmarked utility consumption, apart from buildings 'B1' which had lowest energy consumption (i.e. better than the benchmarked utility consumption). The energy performance indicator (EPI) for the investigated buildings is depicted in **Table 3**. It can be seen that the total annual energy use per heated floor area ranges from 17 to 730 kWh/m2 /year with a mean of 321.6 kWh/m<sup>2</sup> /year. Building 'B1' was found to have the lowest EPI of 17 kWh/m2 while building 'B5' was found to have the largest EPI of 730 kWh/m2 / year. Accordingly, the CO2 emission from the buildings is shown in kgCO2/m2 per floor area in order of their emissions to allow for comparisons. **Table 4** shows the building characteristics and the pattern of use. It was observed that buildings used for catering services (B2, B3 and B5) recorded high energy use when compared to other uses. Meanwhile, building used for online bookshop (B1) recorded low energy usage per floor area. To facilitate comparison of energy use, according to the building pattern of use, total energy use in each category was determined and given

**Figure 3.**  *Comparison between benchmark and annual energy consumption of the surveyed buildings.* 

*Improving Environmental Sustainability in Reuse of Some of England's Churches: Challenges… DOI: http://dx.doi.org/10.5772/intechopen.81222* 


**Table 3.** 

*Energy performance of surveyed buildings by ranking.* 


#### **Table 4.**

*Building characteristics and pattern of use.* 

overall rank (**Table 3**) according to their performance range (1 = high performance, 5 = low performance). Building 'B1' ranked 1st and the best performing having the least environmental impact.

 Building 'B2' used as community café ranked 2nd with energy use more than twice compared to the benchmark. Energy use became more than tripled with building 'B3' used for dual purpose (i.e. community café and worship) and ranked 3rd. Building 'B4' (397 kWh/m2 ) used for dual purpose (i.e. bookshop and community café) ranked 4th. Meanwhile, building 'B5' with a singular use for community café use the largest amount of energy (730 kWh/m2 ) ranked 5th as the lowest performing building. The fuel type used by the buildings was investigated; the operational energy performance of the building (B2) using only gas energy was poor compared to the building (B1) using electricity only given the similar construction properties of the buildings. To compare and contrast between the performances of the buildings (B2 and B5), the overriding element that makes building 'B5' less performing to building 'B2' could be attributed to the level of demand, its use requires compared to building 'B2' or put another way, how desirable is its use. Further, the building location factors and the energy efficiency characteristics of the building is a key feature that should not be overlooked but instead needs to be better understood. Meanwhile, the risk posed to a building having such a very poor energy efficiency performance could become undesirable with time and become unfit for purpose. Thus, it can be seen that buildings used as a community cafe either as single use type (B2 & B5) or used in combination with other functions (B3 & B4) appears to consume more energy when compared to other uses. Apart from space heating, the high energy use of these buildings is perceived to be as a result

of multiple factors arising from energy end uses. For instance, process plant (e.g. freezers, fridges, etc.) and other equipment (e.g. catering), user's behaviour and attitude, efficiency of heating equipment, etc. It is estimated that around 25% of the energy used for catering operations is expended in the preparation, cooking and serving food. By far the largest proportion of this energy is consumed by cooking apparatus from which much of it is wasted through excessive use, poor utilisation and poor energy management attitude.

 Further observation from **Table 4** show that as the building size (i.e. B3, B4 and B5) decreases, energy consumption increases. This finding is quite surprising and contrary to expectation that smaller size building (B5) would consume less energy. The increase in energy consumption in smaller size buildings could perhaps be attributed to the intensity of energy use and more patronage than the larger ones and operational practices of the building operators. In addition, the preference in the use of smaller buildings may have consequently resulted in their over-use, which could have also been responsible for their high energy consumption. Further findings show that among the investigated buildings, only building 'B1' had a form of energy management strategies apart from the fact that the pattern of use contributes to its low energy use. Generally, there are two methods to effectively reduce the energy demand of a building. The first and the most common approach is the physical improvement to the buildings (i.e. fabric and services). The second approach is to improve the way the building is operated (i.e. through facilities management and users behavioural change). However, the peculiarities of Heritage buildings (e.g. listed churches) such as their thick masonry walls, stained glass windows, traditional organic building materials, lime plasters/lime wash and the way they absorb and release moisture; pose challenges and limitation to modern applications of energy efficiency measures. Therefore, the first approach has limited application in several ways. For instance, application of modern type of insulation could create excessive humidity and dampness damaging the fabric irreversibly. Whilst a balance between air tightness and unwanted heat loss through the envelope and controlled ventilation needs to be found; the second approach, which is more passive would be more appropriate.

The most sustainable and available options for heritage buildings is to actively engage users and visitors in an energy saving campaign, introduce energy management systems and making building services such as heating and lighting more efficient. Public building users generally do not have incentives to act in an energy efficient manner. This is the case for all types of users. The result from this study reveals the need for energy management policies and strategies to minimise the energy required to operate rehabilitated Heritage buildings and to ensure their long term sustainability. This is due to their nature as 'hard to treat buildings'. Thus, it is this project's contention that the operational energy efficiency policy should be developed and implemented for sustainable retrofitting of heritage buildings in the world level and not only at EU level.

### **5. Recommendations and implications for sustainable practices**

Existing buildings, particularly those of historical significance, can be transformed with a wide range of interventions, a process which greatly relies on the peculiarities of each case. However, the designer needs to assess what is best for the building and its future users/occupant. A secondary objective of the project should be to investigate and assess proposed functions of the new and upgraded building through the viewpoint of low energy use since energy use of a building is greatly affected by its use and the occupancy patterns that it creates as evidenced by this

#### *Improving Environmental Sustainability in Reuse of Some of England's Churches: Challenges… DOI: http://dx.doi.org/10.5772/intechopen.81222*

 study. Thus, low energy use as a key contemporary demand for better performance and as a response to climate change should be fully integrated into the retrofitting of heritage buildings. In this way, energy use in rehabilitating heritage building projects can also provide insights for the selection of the appropriate future use, and whether that use can be a viable option for its operation. Further recommendations include considering the potential of integrating building management systems into any proposed retrofitting projects. This allows the monitoring and controlling the heating, cooling and lighting systems as well as ventilation systems where it is introduced in different parts of the building at different times of the day.

Generally, the traditional heritage building technology did not tightly seal buildings neither did they use damp-proof courses in walls nor damp-proof membranes below ground floors. This results in high ventilation rate within the building and consequently high energy consumption. Thus, achieving balance between moisture content, water vapour and ventilation within the building is achieved by high ventilation rates through operable windows, doors and different kind of gaps. By adapting historic buildings, this equilibrium is disrupted, as a rule, providing a building with an insulation envelope is accompanied by an increase in air-tightness, with the aim of reducing the heat losses and making the insulation work. In order to achieve a good energy performance, the available and the most inexpensive and effective option is draught proofing. Nevertheless, this disrupts natural ventilation, making a ventilation system essential to secure the necessary air exchange rate and to maintain the interior air quality. Meanwhile, where internal partitions are used, they can be linked to the function room booking system so that lighting, heating and cooling are only switched on when a function is going to be in use.

 Other areas could be fitted with movement or occupancy sensors as part of a wider building management system, so lights come on only when people are present. Similarly, the use of daylight sensors can control artificial lighting according to what is required in different areas of the building, based on natural light entering the building from outside. Building management systems are considered more cost-effective for large Heritage buildings (e.g. churches) used for community and commercial purposes. Further, building owners and corporate building occupiers (i.e. users) and the professionals should be made aware that one of the overriding factors that make a sustainable building is the level of its reduced energy demand when occupied. Therefore, behavioural change of the users should be targeted by making real time information about energy use available. The energy behaviour of employees can also be influenced and changed by providing them with current information about their energy use at their desk, room and/or section within the building. Consumers would also need to be made to understand that lower energy running costs of the buildings means higher operating profits and less impact on the environment.

Additionally, the appointment of personnel trained in energy management as building operators for Heritage buildings retrofitting projects is imperative as this has been known to dramatically reduce energy consumption by 40% and consequently advanced improved operational energy performance of retrofitting projects. More importantly, after all the minimum intervention options have been exhausted for energy saving, consideration for generating on-site energy from renewable (e.g. air-source heat pumps, ground source heat pumps, biomass boilers, etc.) sources could also be sensitively installed on the buildings. Although this option could also be considered earlier where there is already a history of an on-site energy generation, or where boilers are being replaced. The professionals involved in heritage buildings retrofitting projects, such as architects, installation engineers, building surveyors etc., should include services such as analysis of whole life costs and carbon savings in services they provide to support the justification of the

investment. Achieving the levels of improved energy performance in the retrofitting of heritage buildings required would not be likely reached if professionals rely on marketing only the economic benefits and payback periods to potential clients. The retrofitting projects should be seen as an opportunity to reduce long term expenditure on energy use by tackling the two simultaneously.
