DISCUSSION ABOUT THE RECENT RESEARCHES ABOUT THE USED METHODOLOGIES OF MEASURING THE THERMAL COMFORT IN HISTORIC HOUSES
Controlling the thermal comfort and the energy performance in architectural heritage buildings require different interventions process that are not similar to those used interventions in the other contemporary exiting buildings. The available interventions criteria that aim at energy saving are not suitable for historical buildings. The reason is that the regulations of preservation the architectural heritage and energy saving are not very well connected. CEN issued several standards to define methodologies for energy performance calculation that can be applied for new or existing buildings \citep{Mazzarella_2015}, \citep{Genova_2017}.
Few months ago, CEN presented first law so called “Conservation of cultural heritage – Guidelines for improving the energy performance of historic buildings” (FprEU 16883) that provides the procedures for selecting methods in order to improve the energy performance of historical buildings based on investigations, documents analysis, and heritage significance of a building \citep{CEN2016conservation}. This guideline is compatible with countries that are located in the EU climate regions.
On the other hand, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) considers that energy efficiency retrofitting of historical buildings is the greatest opportunity to preserve the history, and to contribute in the sustainability concept for future. The reason behind is that 75-85 % of buildings that will exist in urban area in 2030 already exist today. Hence, ASHRAE recently proposed first guidance to historic buildings called "Guideline 34P". This guideline aims at providing standards to rehabilitate, restore historic buildings in order to achieve energy efficiency without compromising cultural heritage values. The main visions of ASHRAE are to improve the energy efficiency, to consider long term use, and to preserve historical buildings \citep{Phoenix_2015}, \citep{wonderen2016overview}.
Regarding the hot climate zones historical buildings (as in Egypt), there aren’t applied standards or methodologies up to now for measuring and controlling the thermal comfort and energy efficiency. So, several examples will be analysed in this section for sake of learning from the previous projects that created specific methodology to deal with energy efficiency and thermal comfort, and for extracting suitable methodology that can fit for hot climate zones buildings.
Generally, there are two kinds of researches in this field:
- Analysing a single case study, such as monument, that aims at comparing different retrofit actions that promote the energy conservation and building conservation at the same time. This comparison used to clarify the feasibility of each retrofit action in order to select one and to apply it in future. This approach usually uses “holistic methodology or multi-criteria approach” that includes diagnostic of total energy in the building and suggests improvement of the building envelop. The main goal of this approach is to inspire and spread the experiences to the other restoration projects \citep{Genova_2017}.
- Analysing recurrent characteristics of the historic architecture aims at evaluating energy performance in heritage construction to develop the correct regulations and technical guidelines. This methodology depends on collection of several representative case studies to be analysed in details \citep{Genova_2017}.
For examples:
Ascione suggests multi-criteria approach to study the impact of different retrofitting actions on the building energy demand of Palazzo dell'Aquila Bosco-Lucarelli in Benevento, southern Italy. Different techniques are implemented to achieve this goal as following:
- Field analysis is carried through the endoscopies and core sampling to identify the thermal characteristics of the building,
- Site measurements are done using wireless heat flux meter to measure thermal transmittance of the building envelop,
- “Energy Plus” software is used to simulate and predict the present and possible energy performance of the building and to analyse the five different retrofit actions. Those five actions are as following: Changing indoor temperature set-points, Reducing the present infiltrations due to the fenestration or bad conditions, Increasing the thermal insulation of the vertical walls, Substituting the existing old gas heater with a with heat recovery new system, and Replacement of the present fenestration and adoption of double glazing system with low-emissive coating”.
Finally, the building has been analysed according to "Asset rating" method to measure the impact of retrofit actions on energy performance.
The result shows that the different retrofit actions have various impacts on the percentage of reduction the annual energy demand as following: (2%) reduction by increment of building insulation; from 10% to 11% reduction by changing the indoor temp. set points and improvement the airtight of the windows. The last percentage reduction by reducing building pollution emissions \citep{Ascione_2011}.
Şahin introduce a transdisciplinary methodology to balance between building conservation and energy conservation. This methodology aims at reducing the energy consumption without unacceptable impact on the historical heritage values. The application of this methodology is carried on the historical building called "Basmane Neighborhood Center" in Izmir, Turkey. Three techniques are conducted as the following;
- Building energy simulation using 3D drawing interface of Design Builder software to quantify the shading effects on solar gain calculations,
- validated and calibrated of the result of building simulation tool using data logger and ASHRAE Guideline 14, and
- transdisciplinary strategy to choose the most appropriate retrofit action. These retrofitting actions are weather stripping, temperature control, changing the windows, insulation of the attic floor, additional insulation of the roof, exterior insulation of walls, interior insulation of walls, additional insulation of ground floor, changing the heating system, and renewable energy sources.
The result showed that 34% of energy saving can be achieved through retrofitting without damaging the heritage value \citep{_ahin_2015}. Some parts from this methodology will be used in the PhD topic.
As a conclusion, the projects, in which compromise between thermal comfort control, energy saving, and conservation requirements in historical buildings, consist of six main steps in their methodologies. As shown in (Figure 23), They are; Monitoring, Simulation, Site analysis, Laboratory test, Transdisciplinary & multi-disciplinary discussion, and Calibration with codes and standards.