Building Science

Bautex Blocks Create Airtight, Moisture Resistant, Energy Efficient Walls

Energy efficient walls are a key component to the envelope of a high per­form­ing building. Other parts of the envelope include the roof, windows and doors, and foun­da­tion. An energy efficient envelope is a thermal barrier that stops the flow of heat by air, vapor and radiation. The transfer of heat through a wall occurs by three primary mech­a­nisms: thermal con­duc­tion, thermal con­vec­tion, and thermal radiation. An energy efficient wall should be con­struct­ed to prevent the flow of heat by all three of these mechanisms.

Thermal Conduction — Transfer of Heat on the Molecular Level

Thermal con­duc­tion occurs when hot molecules spon­ta­neous­ly move towards and collide with cooler molecules. The collision causes the energy of the hot molecule to transfer to the cooler molecule. Thermal con­duc­tion occurs in a wall when there is warm air on one side of a wall and cooler air on the other side of the wall. The warm air always moves towards the cooler air. The more tightly packed (densely) the molecules are in a substance, the better the substance conducts heat and the faster the hot air will move towards the cooler air. The molecules in metals are tightly packed. Therefore, metal is a good conductor, and heat will quickly move through it. Wood is less dense than metal, so it is a less efficient conductor of heat. So, wood buildings lose less heat and stay warmer than metal buildings. Buildings intended for occupancy typically utilize low-density insu­la­tion in their design, which slows con­duc­tion through the envelope.The effective R‑value1 of a build­ing’s wall assembly is its resis­tance to con­duc­tion. Problems in a wall’s assembly, such as thermal bridging, increase the wall’s con­duc­tiv­i­ty. An energy efficient wall assembly should have low con­duc­tiv­i­ty and a high effective R‑value.

Thermal Convection — Transfer of Heat by the Flow of Air

Thermal con­vec­tion occurs when heat moves from the warmer side to the cooler side of a wall by the flow of liquid or air molecules. When occupants of a building feel a draft, they are expe­ri­enc­ing thermal convection.Thermal con­vec­tion is often the biggest source of energy loss in a building. In wood-frame buildings con­vec­tion occurs through the framing con­nec­tions, wall, floor, roof, and fen­es­tra­tion inter­sec­tions. A tightly sealed building envelope with adequate air and moisture barriers can stop thermal con­vec­tion and create a com­fort­able envi­ron­ment for the occupants.

Thermal Radiation — Transfer of Heat by Solar Energy

Thermal radiation transfers heat from a warm area to a cooler area by elec­tro­mag­net­ic waves, which for buildings is mainly the sun’s rays. Thermal radiation between two surfaces does not require a medium, like air and water, to move through space. The two surfaces need only be in view of each other. All materials absorb, reflect and emit radiant energy. A mate­ri­al’s ability to radiate absorbed energy, or emit energy as thermal radiation, is called emis­siv­i­ty. A high emis­siv­i­ty material has low reflec­tiv­i­ty and will quickly absorb energy that strikes it. The design of an energy efficient wall should incor­po­rate materials with high reflec­tiv­i­ty and low emis­siv­i­ty to limit the absorp­tion of radiant heat.

Bautex™ Walls Stop Thermal Conduction, Convection, and Radiation

The Bautex Wall System delivers a high-level of con­tin­u­ous insu­la­tion and creates a tight energy efficient envelope. Con­tin­u­ous insulation2 in the con­struc­tion of a wall’s assembly stops the flow of heat by con­duc­tion, con­vec­tion, and radiation. Con­tin­u­ous insu­la­tion also prevents thermal bridging, which is a common issue with con­ven­tion­al con­struc­tion like wood and metal framing. Con­duc­tion tests were done on Bautex Blocks in accor­dance with ASTM C 518 – 10. The Blocks have an R‑value per inch: 1.84 and a whole wall R‑value (with concrete) of R‑14. Thus, Bautex Blocks stop thermal con­duc­tion. Also, The Bautex Air and Moisture Barrier reduces thermal con­vec­tion and thermal radiation by pre­vent­ing air, moisture, and ultra­vi­o­let waves from passing through the wall. The Bautex Wall Assembly is energy efficient and meets the thermal per­for­mance required of the IRC and IBC. Bautex Blocks are also easy to install, fire rated, noise reducing and storm-resistant. Bautex Blocks can be utilized in both com­mer­cial and res­i­den­tial buildings and are the ideal choice for energy efficient wall construction. 

The building and con­struc­tion industry use the R‑value as a measure of thermal resis­tance or con­duc­tiv­i­ty. The effective R‑value includes all the materials used in its con­struc­tion: the drywall, studs, insu­la­tion, plywood, siding, etc. The higher the R‑value, the better the thermal per­for­mance the material or system. 

Con­tin­u­ous insu­la­tion covers all parts of building other than the windows, skylights, doors, and building service systems. Con­tin­u­ous insu­la­tion helps create an insulated, airtight, and energy efficient building. The ASHRAE 90.1 and 2015 IECC require con­tin­u­ous insulation.