We investigated the possibilities of a new design of flat-plate solar collectors where the main idea is to replace the air inside the conventional design by a low conducting gas, even applying vacuum insulating techniques. During the report we outlined the basic principle of solar thermal collectors, the conventional design of flat-plate collectors and investigated the loss mechanism of these appliances in order to create the proper background for the steps we made and to reveal the importance of reducing heat losses by the mean of using insulating gases and/or vacuum in general. Similar solutions, such as insulating glass units, have been introduced to get another aspects on the problems we have with during the project. Design alternatives and different solution related to gas filling, sealing and various measurements have been placed inside the report, to reveal the possibilities; however many of these solutions was not proper for our purposes, mainly due to the financials. Hence, in most cases we fall back upon the simplest solution, however even with this, good results can be shown. Three experimental setup have been built form the materials what was collected in order to carry out heat loss measurements by using Carbon Dioxide, Argon and Argon+Vacuum insulation inside the setups. By proper tests we showed significant change in the overall heat losses. The main result is there is a 17% reduction in the overall heat losses while applying alloying Argon and vacuum, which is about 15% while having only Argon inside, compared to case when the same experimental setup was filled with air.