def _get_materials(material_members):
    """
    Function to extract the material information from EnergyADE files.

    :param material_members: lxml Object
            CityGML EnergyADE FeatureMembers - SolidMaterial, Gas
    :return: material_dict
            python dictionary containing the material information
            Solids -> {mat_id: [solid, name, conductivity, density, specific heat capacity]}
            Gases -> {mat_id: [gas, name, is vetilated, r Value]}
    """

    material_dict = {}

    for material in material_members:
        mat_id = material.attrib['{http://www.opengis.net/gml}id']
        material_dict[mat_id] = []
        if material.tag == "{http://www.sig3d.org/citygml/2.0/energy/1.0}SolidMaterial":
            for mat_info in material.iter():
                if mat_info.tag == '{http://www.opengis.net/gml}name':
                    mat_name = mat_info.text
                    material_dict[mat_id].append(mat_name)
                elif mat_info.tag == '{http://www.sig3d.org/citygml/2.0/energy/1.0}conductivity':
                    conductivity = mat_info.text
                    material_dict[mat_id].append(conductivity)
                elif mat_info.tag == '{http://www.sig3d.org/citygml/2.0/energy/1.0}density':
                    density = mat_info.text
                    material_dict[mat_id].append(density)
                elif mat_info.tag == '{http://www.sig3d.org/citygml/2.0/energy/1.0}specificHeat':
                    specific_heat_capacity = mat_info.text
                    material_dict[mat_id].append(specific_heat_capacity)
        elif material.tag == "{http://www.sig3d.org/citygml/2.0/energy/1.0}Gas":
            for mat_info in material.iter():
                if mat_info.tag == '{http://www.opengis.net/gml}name':
                    mat_name = mat_info.text
                    material_dict[mat_id].append(mat_name)
                elif mat_info.tag == '{http://www.sig3d.org/citygml/2.0/energy/1.0}isVentilated':
                    is_ventilated = mat_info.text
                    material_dict[mat_id].append(is_ventilated)
                elif mat_info.tag == '{http://www.sig3d.org/citygml/2.0/energy/1.0}rValue':
                    r_value = mat_info.text
                    material_dict[mat_id].append(r_value)

    return material_dict