This study investigated the effects of three pore-forming agents on the properties of the fired clay body applied in the production of lightweight bricks for the building envelopes. Test samples were made from clay raw material already containing two combustible pore-forming agents (sawdust and cellulose sludge). A part of this research was focused on studying the influence of adding two combustible pore-forming agents (molasses and cornstarch) and a chemical additive Vuppor to the claw raw material. Testing of the material properties showed that although the three samples had almost the same pore volume, their thermal conductivities varied. These findings led to an important conclusion. The pore size of 1–200 µm (filled with not only air but also biomass ash) reduced the thermal conductivity, and conversely, an increase in the small pore size less than 1 µm increased the thermal conductivity of the fired clay body.

A plan to reduce CO2 emissions is a priority these days. Brick industry contributes to the increase of these emissions mainly through the use of combustible pore-forming agents such as sawdust, cellulose, and coal sludge. These agents are used to improve the thermal insulation properties of brick products, and the suppliers regularly increase the prices of these agents based on their high consumption. Therefore, in an effort to reduce raw material expenses and CO2 emissions, brick manufacturers are looking for new possibilities while maintaining the quality of their products. This article discusses the possibility of using industrially manufactured product Vuppor as an additive as a replacement for combustible poreforming agents. The presence of this additive in the fired clay body increases the proportion of pores, especially with a size range between 0.1 and 5 µm, having a positive impact on the reduction of its thermal conductivity. With a 0.5 wt.% dose of Vuppor additive, the brick production costs and thermal conductivity can be reduced by 20 % and 12 %, respectively, while also achieving reductions in CO2 emissions over 60 %. Consequently, the combustible pore-forming agents can be used in a more environmentally friendly manner, for example in the furniture industry, the biogas production, and the like.