In Norway, during the last decade, several dual purpose rock installations have been constructed. In time of peace they are serving as sports halls and swimming pools and in war events as public shelters. Running experiences have shown remarkable low energy consumption and maintance costs compared to conventional installations. A sports hall built in 1972 and a swimming-pool built in 1975 are referred to.
Since the last World War, Norway has had ambious plans in building wartime shelters for greater part of the population. However, if the constructions cannot be given a reasonable application in time of peace, this would be a very expensive, if not impossible task. During the last decade, several large dual purpose rock installations have been erected. In 1972 a sport hall was taken into use in the western part of Norway, and in 1975 a swimming pool in the inland north of Oslo. For the swimming pool an extensive study was carried out to eludicate the energy aspects compared to a conventional indoor swimming pool. The calculations indicated very low energy consumption for the rock alternative. The running experiences have been very satisfactory, and have fully confirmed the theoretical estimates. In the following I will give a short summary of the theoretical and practical results and try to eludicate the reason why a rock installation is so favourable compared to a freestanding alternative.
A conventional building is influenced by following main factors, determining the heating demand:
-Heat transmission through building structures owing to the difference between inside and outside temperatures.
-Heating of ventilation air volume.
-Heating of infiltration air volume, owing to the leakages through building structures windows and doors.
-Solar heat gain.
-Electric illumination and motors.
By meanse of modern insulation materials, it is possible to obtain very low heat tranmission through walls and roofs. The windows, however, will always be a tangible problem, especially where a high indoor air humidity is desirable, par example in a swimming pool. In a swimming pool, owing to high indoor air humidity and temperature in combination with low environmental temperatures during the winter, special attention has to be paid to the vapor barriere in walls and roof. Undesired ventilation owing to infiltration is practically propotional to wind velocity. In Norway, the highest wind velocities occure during the winter in combination with low ambient temperatures. The heat loss due to infiltration cannot be recovered. In theory it is not difficult to handle the infiltration problem. Most of the constructions suffer from unfortunate technical solutions and bad workmanship. And a present leakage has a tendenct to be constantly increasing as the time elapses. In building with high air humidity contents and temperatures, the leakage air transports large guaranties of vapour condensing into the insulation layer. Primarely this in causing reduction of the heat resistance of the structure, secondarely the building structure is damaged. The heat dissipation from electric illumination and motors are considered as integrated parts of the heating system.