Strategies for Code-Compliant Continuous Insulation 2018 Edition

Recent build­ing code require­ment changes and the grow­ing demand for ener­gy-effi­cient build­ings are dri­ving archi­tects to search for a bet­ter solu­tions for con­tin­u­ous insu­la­tion.

Con­tin­u­ous insu­la­tion is required by the Inter­na­tion­al Ener­gy Con­ser­va­tion Code (IECC), The Ener­gy Stan­dard for Build­ings Except Low-Rise Res­i­den­tial Build­ings, and, in most cas­es, ASHRAE 90.1.

Know­ing how to best select and spec­i­fy mate­ri­als for con­tin­u­ous insu­la­tion is key. But it’s also impor­tant to under­stand the meth­ods used to pre­vent ther­mal bridg­ing and improp­er instal­la­tion of mate­ri­als: this ensures that you’re able to deliv­er the most ener­gy effi­cient and high-per­form­ing build­ings to clients.

Addressing Thermal Bridging

Ther­mal bridg­ing occurs when heat pass­es through the path of least resis­tance, like through steel or wood studs. It’s the ene­my of ener­gy con­ser­va­tion.

Effec­tive con­tin­u­ous insu­la­tion stops ener­gy waste and effec­tive­ly address­es the prob­lem of ther­mal bridg­ing. Any gaps in the insu­lat­ing lay­er are sim­ply unac­cept­able. Wast­ed ener­gy also increas­es car­bon emis­sions, so aggres­sive­ly attack­ing the prob­lem is more impor­tant than ever before.

Ther­mal bridg­ing may also allow unwant­ed mois­ture flow, result­ing in con­den­sa­tion with­in the wall cav­i­ty. Wet insu­la­tion can quick­ly lose R-val­ue, and mois­ture inside the wall may lead to mold growth, mildew odors and wood rot.

These are all prob­lems that can com­pro­mise the health and com­fort of build­ing occu­pants, and they may also lead to expen­sive repairs or a struc­ture with a short­ened life cycle.

The Problem with Traditional Methods

Of course, insu­la­tion batts or spray foam insert­ed between studs are not con­tin­u­ous. To counter the prob­lem of ther­mal bridg­ing, steel and wood-frame con­struc­tion requires the instal­la­tion of con­tin­u­ous insu­la­tion over the studs.

But tra­di­tion­al sheath­ing and cladding requires fas­ten­ers that may cre­ate a new threat of ther­mal bridg­ing, par­tic­u­lar­ly when fas­ten­ers are improp­er­ly installed.

Installation Failures

Any instal­la­tion fail­ures that cre­ate gaps or crevices in the lay­ers of con­tin­u­ous insu­la­tion can com­pro­mise the integri­ty of the wall sys­tem.

Even when build­ing designs com­ply with cur­rent codes, instal­la­tion fail­ures may com­pro­mise the con­tin­u­ous insu­la­tion lay­er, lead­ing to addi­tion­al cool­ing require­ments in the sum­mer and heat­ing needs in the win­ter.

The impor­tance of prop­er­ly installed con­tin­u­ous insu­la­tion in mod­ern build­ing con­struc­tion can’t be under­es­ti­mat­ed. Mass air migra­tion in a poor­ly sealed build­ing enve­lope wastes ener­gy and increas­es car­bon emis­sions.

Available Solutions for Continuous Insulation

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 their projects.

1. Polyisocyanurate (Polyiso or ISO)

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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)

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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)

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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

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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

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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.

Safeguarding the Future of Our Buildings

By under­stand­ing the solu­tions and meth­ods avail­able to archi­tects for con­tin­u­ous insu­la­tion, we’re one step fur­ther to more ener­gy-effi­cient, suc­cess­ful and safer build­ings.

A con­tin­u­ous insu­la­tion bar­ri­er is a very big deal,” Carl Wein­schenk said in Ener­gy Man­ag­er Today. In addi­tion to sav­ing mon­ey by improv­ing insu­la­tion, con­tin­u­ous insu­la­tion safe­guards the health of the peo­ple with­in the struc­ture.”

Build­ing with con­tin­u­ous insu­la­tion in mind means archi­tects deliv­er struc­tures that per­form effi­cient­ly, save their clients mon­ey and pro­tect the peo­ple who use it.

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