Wrapping a building’s envelope with a continuous layer of insulation (CI) saves money and energy. It also increases the effective R‑value of the structure, eliminates condensation, and creates a comfortable space for the building’s occupants. Continuous insulation is required by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 90.1) and the International Energy Conservation Code (2015 IECC). Also, under the 2015 IECC, Section C103.2.1, a building’s thermal envelope must be represented in the construction drawings. The building envelope components must meet the minimum thermal requirements of envelopes for different climates as defined by ASHRAE.
Five Ways to Continuous Insulation
There are several methods of applying continuous insulation.
- Expanded polystyrene (EPS) rigid foam insulation
- Extruded polystyrene (XPS) rigid foam insulation
- Polyisocyanurate (ISO) rigid foam insulation
- Insulated concrete forms (ICF)
- Insulated concrete blocks (ICB)
These methods are all designed to seal a building’s envelope and prevent the flow of heat and energy through the wall assembly. Ultimately these methods should save money, reduce energy consumption, and make buildings more comfortable for occupants. When selecting a method of CI, builders and designers should evaluate the CI’s thermal performance, fire, ultraviolet (UV) and moisture resistance, the versatility of use, and the cost. Regardless of the method of CI installation, the result should create a comfortable, healthy, and energy efficient structure.
EPS, XPS, and ISO Rigid Foam Continuous Insulation
Application of rigid foam insulation to walls, roofs, and foundations can reduce thermal bridging, raise the R‑value, and reduce air leaks. Tightly fitted wall cavities and properly taped joints between the sheets and boards are essential to preventing air flow problems within rigid foam insulation. Another potential problem is that sunlight and UV rays can damage rigid foam. The most common types of rigid foam insulation used for CI are EPS, XPS, and ISO. All provide CI but vary on R‑value per inch, compressive strength, permeability to water vapor, and cost.
Expanded Polystyrene (EPS) Rigid Foam Insulation (beadboard)
- EPS provides an R‑value of 3.6 to 4.2 per inch of thickness
- EPS is fragile and therefore rarely used for wall sheathing
- EPS is semi-permeable with a permeance (water vapor transmission) of 2.0 to 5.8 perm). It is too permeable for below-grade; however, applying high-density EPS below-grade is acceptable
- The air bubbles inside EPS prevent heat transfer and may collect moisture, which makes it ineffective.
- EPS is the least costly of the rigid foam insulations
Extruded Polystyrene (XPS) Rigid Foam Insulation
- XPS provides an R‑value of 5 per inch of thickness
- XPS a semi-impermeable. One inch of XPS has a permeance of 1.1 perm. Two inches of XPS has a permeance of 0.55 perm
- XPS has high compressive strength and water resistance and is mainly used in walls and below grade
- The cost of XPS is between EPS and ISO
- XPS uses HCFCs in its production, which depletes the ozone layer
Polyisocyanurate (ISO) Rigid Foam Insulation
- Utilization of ISO is mostly on roof assemblies
- At warm temperatures, ISO has higher insulating values (R‑6 to R‑6.5 per inch) than XPS or EPS; however, when temperatures drop, the performance of ISO worsens
- ISO’s R‑value starts at R‑7 per inch of thickness but decreases to R‑6.5 over time as the thermal-enhancing blowing agents used to make ISOs diffuse out of the material
- ISO is the most expensive of the rigid foam insulation
- Because ISO absorbs water, it should not be used under slabs or on the exterior of a foundation wall
Insulated Concrete Forms (ICF) Continuous Insulation
Insulating concrete forms (ICF) are hollow panels or blocks made of expanded polystyrene insulation (EPS) or other insulating foam. Insulating concrete forms are stacked to form the shape of the walls of a building. Steel rebar reinforces the hollow centers which are filled with reinforced concrete to create a layer of continuous insulation; substantially eliminating thermal bridging through the wall.
- ICF walls are energy efficient with whole wall R‑values of 20
- ICF buildings are comfortable, quiet and pest proof
- ICF walls contain no organic materials and won’t support the growth of mold, mildew and other potentially harmful microorganisms
- ICF concrete walls can withstand continuous exposure to intense flames and flying debris with wind speeds of up to 250 mph
- The disadvantage of ICF is the walls can be thick, which reduces the interior space. The structure plus interior finish and exterior cladding can be 14 inches thick
- The extra weight of ICF adds cost to the foundation design and expenses for engineering and materials
Bautex Insulated Concrete Blocks (ICB)
Bautex Block Wall Systems™ are insulated concrete blocks that meet and surpass recommendations for best practices for continuous insulation in exterior walls. The Bautex Block is a lightweight (45 pounds), stay-in-place concrete form that measures 16 inches by 32 inches on the face and 10 inches through the wall. Components of the Bautex Block include custom engineered expanded polystyrene (EPS), regionally sourced Portland cement and regionally sourced recycled cementitious material. Commercial and residential buildings can use Bautex Blocks.
- The Bautex Block Wall System provides a continuous insulation R‑value of 14; far exceeding 2015 IECC recommendations.The Blocks stop thermal bridging and create an insulated and energy efficient building envelope that is compliant with the latest building codes
- The Bautex Air and Moisture Barrier limits thermal convection and thermal radiation by preventing air, moisture and ultraviolet infiltration to the interior of the structure
- The unfinished Bautex Wall System has an ASTM E119 fire rating of four hours, and ASTM E84 values for flame speed of zero and smoke development of twenty. Since the Blocks meet the ASTM E84 and NFPA 286 standards, they meet the NFPA 101 code
- The Bautex Wall System is easy to install, noise reducing and storm-resistant
- Bautex Blocks are lighter than both concrete block (CMU) and ICF. An 8‑inch concrete block (CMU) wall weighs roughly 50 percent more than the Bautex Wall System. A poured traditional ICF wall weighs about 100 percent more than the Bautex Wall Systems
- Bautex Wall System does not move during the pour; unlike ICF that requires extensive and expensive bracing systems
The continuous insulation design of a building should stop the flow of heat, energy, pollution, noise, and moisture through the wall assembly. The method used must take into account the CI’s thermal performance, fire, UV and moisture resistance, along with the type of construction, climate zone, and the wind loads. Regardless of the method of CI installation, the result should create a comfortable, healthy, and energy efficient structure. For more information on continuous insulation, visit Bautex Systems.
The effective R‑value includes all the materials used in its construction: the drywall, studs, fiberglass batts, plywood or OSB sheathing, water control plane, and siding. The larger the R‑value, the lower the conductivities of the wall assembly.
The IECC is a model code which is part of the family of International Codes (I‑Codes) first published by the International Code Council, Inc (ICC) in 2000. The ASHTAE 90.1 is the ICC referenced standard for the IECC. Their purpose of the IECC is to establish codes and standards for the minimum design and construction requirements for energy efficiency, for both new and renovated buildings. The IECC has separate codes for commercial buildings and low-rise residential buildings (three stories or less in height above grade). Revision of the International Energy Conservation Code occurs every three years. The most recent 2015 IECC improves energy efficiency and saves building expenses.