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Energy Efficiency: Understanding R-value, Mass Walls, Continuous Insulation and Air Tightness

R-VALUE ISN’T THE ONLY VARIABLE THAT AFFECTS A BUILDING’S ENERGY EFFICIENCY.

How to talk about mate­ri­als, design and con­struc­tion to help your clients reduce their ener­gy foot­print — and their cost of own­er­ship.


When it comes to ener­gy effi­cien­cy, the indus­try buzz of R‑Value” (ther­mal resis­tance or abil­i­ty to pre­vent heat trans­fer) con­tin­ues to cause con­fu­sion – and false assump­tions. R‑values con­tin­ue to be used syn­ony­mous­ly with build­ing ener­gy effi­cien­cy per­for­mance. In real­i­ty, R‑value is only a par­tial pre­dic­tor of a building’s ener­gy effi­cien­cy, at best.

A structure’s opti­mal ener­gy effi­cien­cy is achieved when impor­tant vari­ables work in har­mo­ny: archi­tec­ture and build­ing sys­tem design, mate­ri­als and con­struc­tion method. Rely­ing on just one is like remov­ing two legs from a three-legged stool. Imper­fec­tions in the instal­la­tion of insu­lat­ing mate­ri­als – includ­ing air gaps and improp­er com­pres­sion of the insu­la­tion – can dra­mat­i­cal­ly reduce the per­for­mance of a wall sys­tem. Oth­er fac­tors, such as ther­mal mass and air infil­tra­tion through the wall enve­lope can also make a sig­nif­i­cant impact on ener­gy per­for­mance – pos­i­tive­ly or neg­a­tive­ly.

While walls are very impor­tant to the ener­gy effi­cien­cy of a build­ing, oth­er crit­i­cal items such as win­dows, doors, roof assem­blies, pen­e­tra­tions through the enve­lope, and the design of the heat­ing, ven­ti­la­tion and air con­di­tion­ing sys­tem will all con­tribute to the ener­gy effi­cien­cy and per­for­mance of a struc­ture.

The Bau­tex Wall Sys­tem, includ­ing Bau­tex Block and Bau­tex Air and Mois­ture Bar­ri­er, cre­ates an extreme­ly ener­gy-effi­cient build­ing enve­lope with greater ther­mal mass, con­tin­u­ous insu­la­tion, and very low air per­me­abil­i­ty.

R-value is a starting point for comparing insulation systems, but remains only one factor. Design, materials and construction science will play a huge role in energy efficiency.


Accord­ing to the Amer­i­can Soci­ety of Heat­ing, Refrig­er­a­tion and Air Con­di­tion­ing (ASHRAE) 90.1 stan­dard*, the e ective” R‑value of a wood-framed build­ing with studs on 16-inch cen­ters, using con­ven­tion­al R‑13 cav­i­ty insu­la­tion (i.e., the actu­al ther­mal resis­tance pro­vid­ed by the insu­la­tion in a giv­en assem­bly), is only R‑9. For a wall assem­bly using light gauge met­al fram­ing and the same R‑13 cav­i­ty insu­la­tion, the e ective R‑value is only R‑6 – more than a 57 per­cent reduc­tion in insu­lat­ing per­for­mance.

This hap­pens because ther­mal bridg­ing occurs through the struc­tur­al fram­ing mem­bers and un- insu­lat­ed design fea­tures of the walls, which reduces the over­all effec­tive­ness of the wall insu­la­tion.

While using more insu­la­tion may appear to increase ener­gy effi­cien­cy, there is a point of dimin­ish­ing return when adding insu­la­tion to a wall sys­tem no longer improves ener­gy per­for­mance. This was demon­strat­ed in a Nation­al Con­crete Mason­ry Asso­ci­a­tion (NCMA) study** com­plet­ed in 2013 that showed for every build­ing, there is an opti­mal amount of insu­la­tion that can be installed in a wall sys­tem. Adding insu­la­tion beyond that opti­mal amount no longer pro­duces any sav­ings in ener­gy con­sump­tion. They sum­ma­rized that mon­ey for excess insu­la­tion would be put to bet­ter use by improv­ing oth­er com­po­nents of the build­ing enve­lope and mechan­i­cal sys­tems.

By spec­i­fy­ing con­tin­u­ous insu­la­tion, archi­tects and con­trac­tors can improve ener­gy effi­cien­cy while meet­ing the speci cations of recent build­ing codes, which strong­ly rec­om­mend con­tin­u­ous insu­la­tion for most wall types.

In wall sys­tems with fram­ing mem­bers that span the width of the wall (such as wood fram­ing, steel fram­ing, CMU, tilt pan­el), adding a lay­er of con­tin­u­ous insu­la­tion to the out­side of the wall becomes absolute­ly crit­i­cal for ener­gy effi­cien­cy. For exam­ple, in a com­mer­cial build­ing locat­ed in Cen­tral or South Texas (2012 IECC cli­mate zone 2) built with wood fram­ing, the pre­scrip­tive R‑value tables require either an R‑20 cav­i­ty insu­la­tion, or a com­bi­na­tion of R‑13 cav­i­ty insu­la­tion and an addi­tion­al R‑3.8 of con­tin­u­ous insu­la­tion on the out­side of stud mem­bers.

In build­ings with met­al-stud con­struc­tion in the same region, the pre­scrip­tive code requires an R‑5.0 con­tin­u­ous insu­la­tion in addi­tion to the R‑13 cav­i­ty insu­la­tion that is usu­al­ly spec­i­fied.

The Bau­tex Wall Sys­tem pro­vides any build­ing with an R‑14 con­tin­u­ous­ly insu­lat­ed wall sys­tem. Bau­tex enables archi­tects and con­trac­tors to be con dent that the build­ing will sur­pass the ener­gy effi­cien­cy demands of even the most strin­gent build­ing codes. And build­ing own­ers will real­ize years of sub­stan­tial, reli­able sav­ings from reduced ener­gy costs.


When designed to work together, mass walls and continuous insulation create buildings that provide extraordinary levels of energy efficiency.

Mass walls have been used for cen­turies. From mud huts to stone cas­tles, build­ings con­struct­ed with thick and dense walls have always been val­ued for their ther­mal prop­er­ties. In parts of the south­west Unit­ed States adobe build­ings have been the hous­ing of choice for as long as peo­ple have resided in that area. Adobe build­ings pro­vide excep­tion­al ther­mal bene ts, keep­ing res­i­dents inside cool on even the hottest sum­mer days, and warm at night in spite of win­ter tem­per­a­tures that can drop below freez­ing.

This ther­mal mass, or ther­mal iner­tia, e ect is well under­stood in the archi­tec­tur­al world and is also fea­tured promi­nent­ly in recent build­ing codes. While insu­lat­ing mate­ri­als in the build­ing enve­lope help to slow down the rate of trans­fer of ener­gy through a wall sys­tem, ther­mal mass ampli es the ener­gy effi­cien­cy of the sys­tem by absorb­ing a sig­ni cant amount of heat ener­gy that reach­es the insu­la­tion. This boost in ener­gy per­for­mance is strongest in cli­mates and sea­sons where there are large swings in tem­per­a­tures through­out the day.

In the 2015 Inter­na­tion­al Ener­gy Con­ser­va­tion Code (IECC), for exam­ple, the amount of added insu­la­tion required for a com­mer­cial build­ing in Dal­las, Texas (IECC Zone 3, Pre­scrip­tive R‑value Method) con­struct­ed of light gauge fram­ing is R‑13 in the wall cav­i­ties – plus an addi­tion­al R‑7.5 con­tin­u­ous insu­la­tion on the out­side of the wall. For the same build­ing con­struct­ed of a mass wall sys­tem, the code only requires the addi­tion of R‑7.6 of con­tin­u­ous insu­la­tion to achieve the same lev­el of per­for­mance.

While wood and light-gauge steel fram­ing are still very pop­u­lar, they have become more com­plex and cost­ly to con­struct. New build­ing codes with stricter ener­gy-effi­cien­cy require­ments are forc­ing builders to add more and more lay­ers of expen­sive insu­la­tion, as well as pay for the addi­tion­al labor and costs of adding these mate­ri­als. In the end, the new build­ing might pass code, but it will fail to pro­vide near­ly as much ener­gy effi­cien­cy as a mass wall sys­tem. Just as impor­tant, cav­i­ty wall build­ings fail to pro­vide the lev­el of re and storm safe­ty that has been demon­strat­ed by many mass wall sys­tems.

In con­trast to light-frame cav­i­ty-wall sys­tems, Bau­tex Block is a light­weight, insu­lat­ed con­crete block that, when used to con­struct a build­ing, pro­vides struc­ture, enve­lope, re and storm resis­tance, an air and mois­ture bar­ri­er, and con­tin­u­ous insu­la­tion – all in a sin­gle inte­grat­ed assem­bly. It’s a mod­u­lar, mor­tar­less wall sys­tem where blocks are stacked and then lled with rein­forced con­crete to cre­ate an insu­lat­ed struc­tur­al wall. The wall sys­tem is con­struct­ed using the same labor, tools and tech­niques as those used in tra­di­tion­al con­crete mason­ry con­struc­tion. Plumb­ing and elec­tri­cal sys­tems are typ­i­cal­ly added a er the walls are con­struct­ed.

The result is a sim­ple, sin­gle, inte­grat­ed wall assem­bly that cre­ates an air­tight, R‑14 con­tin­u­ous­ly insu­lat­ed mass wall for the build­ing enve­lope with high­er ener­gy effi­cien­cy per­for­mance than most cav­i­ty-wall or tra­di­tion­al mass wall sys­tems – all with­out any addi­tion­al insu­la­tion – while pro­vid­ing sub­stan­tial­ly improved lev­els of per­for­mance and safe­ty.

Air and moisture barriers improve more than just energy-efficiency. They create a healthier indoor environment.

Air Tight­ness” refers to the abil­i­ty of a build­ing enve­lope sys­tem to resist the infil­tra­tion of air – and the mois­ture it brings – into the con­di­tioned spaces of a build­ing. Air tight­ness is impor­tant because, accord­ing to the DOE, air leak­age accounts for between 25 — 40 % of the ener­gy used for heat­ing and cool­ing a build­ing.

Air infil­tra­tion can be caused by the nat­ur­al air per­me­ance of the mate­ri­als used to con­struct the build­ing enve­lope, as well as by gaps, cracks or oth­er inter­rup­tions in the air bar­ri­er sys­tem. Even small improve­ments in air-tight­ness can lead to sig­ni cant reduc­tion of air in ltra­tion, min­i­miz­ing the amount of ener­gy con­sumed in order to main­tain the prop­er indoor cli­mate and decreas­ing the amount of mois­ture – warm, dense, humid air — that can come into the build­ing. The con­se­quences of air leak­age go far beyond the loss of ener­gy effi­cien­cy. Air in ltra­tion can be harm­ful to build­ing occu­pants, with molds, aller­gens and pol­lu­tants pen­e­trat­ing indoor envi­ron­ments.

An air-tight build­ing enve­lope sig­ni cant­ly reduces the amount of work that the HVAC sys­tem has to do in order to main­tain the desired inte­ri­or tem­per­a­ture and humid­i­ty.

Walls built with Bau­tex Block also pro­vide a rm and sta­ble sub­strate on which to apply the air and mois­ture bar­ri­ers. As a result, there is no move­ment, vibra­tion or decay, like that which occurs in light fram­ing sys­tems over time. It’s also much eas­i­er to get a good instal­la­tion of the air and mois­ture bar­ri­er on the Bau­tex Block wall than many oth­er sys­tems.


Bring­ing togeth­er the right design with the right build­ing mate­ri­als has enabled archi­tects and builders to make great strides in improv­ing the lev­el of air tight­ness in struc­tures of every size and pur­pose. Today, it’s pos­si­ble to con­struct a new build­ing with lev­els of air tight­ness that would have been incon­ceiv­able even a decade ago.

ENERGY CONSERVATION BEGINS WITH THE BUILDING ENVELOPE

Bau­tex Block is ide­al for any archi­tect or con­trac­tor inter­est­ed in con­struct­ing air-tight build­ing envelopes that pro­vide unprece­dent­ed lev­els of ener­gy effi­cien­cy.

A prime exam­ple of a build­ing with unprece­dent­ed lev­els of ener­gy effi­cien­cy would be the Bau­tex head­quar­ters, a 3,900 square-foot, light‑o ce build­ing con­struct­ed with Bau­tex Block in San Mar­cos, Texas. It’s one of the most ener­gy-effi­cient office build­ings in the state.

A build­ing of this size usu­al­ly has ener­gy bills of more than $385 per month. On aver­age, month­ly ener­gy bills for heat­ing and cool­ing of the Bau­tex head­quar­ters are $120. Reduc­tion of air in ltra­tion con­tributed sig­ni cant­ly to achiev­ing this high lev­el of ener­gy effi­cien­cy. In fact, our build­ing received a test­ed air in ltra­tion score of two air changes per hour at 50 Pas­cals (ACH50). That is 300 per­cent bet­ter than con­ven­tion­al­ly con­struct­ed build­ings of this type.


While the Bau­tex head­quar­ters build­ing uses sig­nif­i­cant­ly less ener­gy than oth­ers in our region, just as impor­tant is the fact that the indoor air qual­i­ty and com­fort is out­stand­ing. Employ­ees ben­e­fit from even tem­per­a­tures and an extreme­ly qui­et work­ing envi­ron­ment, even though we’re locat­ed near an inter­state high­way. What is per­haps most impres­sive is that our build­ing was con­struct­ed at com­pet­i­tive mar­ket costs by stan­dard trades and labor­ers using tra­di­tion­al build­ing prac­tices.

We invite you to learn more about the unprece­dent­ed lev­el of ener­gy effi­cien­cy that can be achieved with Bau­tex Block at bau​texsys​tems​.com.