Wall Materials for 2015 Energy Code Compliance

There are a few products and methods available for achieving con­tin­u­ous insulation.

Under­stand­ing what each of these products offers can help guide how you choose wall con­struc­tion solutions in your projects.

Let’s take a look at the most common kinds of con­tin­u­ous insu­la­tion materials.


1. Poly­iso­cya­nu­rate (Polyiso or ISO)

Polyiso panels are rigid foam panels fab­ri­cat­ed from liquid foam. Polyiso rigid foam panels provide an R‑value of about 6.0 per inch, although insu­lat­ing values can degrade slightly over time. Due to the liquid foam fab­ri­ca­tion technique and the need for addi­tion­al dimen­sion­al stability , polyiso panels must be faced with a secondary liner material.

These panels are not vapor permeable — one man­u­fac­tur­er states its product has a 0.05 perm rating. If the breatha­bil­i­ty of the wall cavity is an issue, polyiso sheathing should be used with caution. These panels are often con­sid­ered less green” than some other exterior sheathing options. They are used more often in roof con­struc­tion than wall construction.

2. Extruded Poly­styrene (XPS)

XPS panels are quite notice­able because they are usually green, pink or blue in color. XPS offers an R‑value of about 5.0 per inch.

XPS is a semi-permeable sheathing with a perm rating of approx­i­mate­ly 1.0. As such, even unfaced XPS is more of a vapor retarder than a vapor barrier. In some instances, XPS can absorb moisture over time, which lowers its R‑value.

The man­u­fac­tur­er of one XPS product cal­cu­lates potential shrinkage of as much as two percent. Undue con­trac­tion can leave gaps and put stress on tape along seams, which impacts its effec­tive­ness as an air/​moisture barrier.


3. Expanded Poly­styrene (EPS)

EPS panels are con­sid­ered a versatile solution for insu­la­tion. With an R‑value of approx­i­mate­ly 4.0 per inch, it often out­per­forms XPS and Polyiso in terms of cost-effi­cien­cy, and tends to retain its R‑value over time.

EPS rigid foam panels are usually applied over house wrap or a suitable alter­na­tive. EPS is typically the foam of choice for use in struc­tur­al insulated panels (SIP) and insulated concrete forms (ICF). EPS can also be used for below grade appli­ca­tions and can be treated to resist insects.

EPS is available faced or unfaced. Faced EPS is con­sid­ered a vapor retardant, and some specialty products are con­sid­ered vapor barriers.


4. Mineral or Rock Wool

You can also design walls with a layer of mineral wool, also referred to as rock wool and stone wool.

Roxul® is a rock wool insu­la­tion panel fab­ri­cat­ed from basalt, an igneous rock. In both com­mer­cial and res­i­den­tial con­struc­tion, Roxul is used in a variety of ways, including as exterior wall insulation.

Since it is a stone-based product, Roxul is very fire-resistant. In fact, it can withstand tem­per­a­tures up to 1,177 degrees C or 2,150 degrees F. It inhibits the spread of fire, and it does not release toxic gases. Moreover, the non-direc­tion­al nature of the rock wool fibers effec­tive­ly absorbs acoustic waves, so it reduces noise and dis­rup­tive echo.

Mineral wool is highly water repellent, so the risk of mold, mildew and bacteria growth is effec­tive­ly elim­i­nat­ed. And Roxul’s vapor-per­me­abil­i­ty allows water vapor trapped inside a wall cavity to escape.

Unlike some types of rigid foam panels, Roxul retains its essential char­ac­ter­is­tics over time. It’s not as prone to expansion and con­trac­tion when there are local shifts in tem­per­a­ture and humidity.

5. Spray Foam

Spray foam insu­la­tion provides an R‑value of 6.0 per inch while both acting as a vapor retarder and offering an air/​water barrier. What makes it stand out from other insu­la­tion products is the flex­i­bil­i­ty afforded by its sprayable form.

The spray appli­ca­tion is far simpler than con­ven­tion­al con­tin­u­ous insu­la­tion methods and entirely elim­i­nates the need for metal fastening. With fewer steps and easy appli­ca­tion, spray foam reduces labor costs. This is espe­cial­ly true for curved walls and other similar designs, which are otherwise difficult to achieve and require addi­tion­al labor hours.


6. Bautex Wall System

For both com­mer­cial and res­i­den­tial struc­tures, a wall system with built-in con­tin­u­ous insu­la­tion is an effective solution to thermal bridging. The Bautex Wall System, for example, is a four-hour fire rated load-bearing system that includes the con­tin­u­ous insu­la­tion required by modern, updated building codes, so no addi­tion­al sheathing or insu­la­tion is required.

Single-con­trac­tor instal­la­tion reduces the chance of worker errors that can com­pro­mise wall integrity. The thermal mass of the wall helps exceed energy code require­ments in Texas and climate zones in nearby states. Moreover, with the appli­ca­tion of a liquid-applied air and moisture barrier, Bautex exceeds both above-grade moisture pro­tec­tion require­ments and air tightness standards.