What is The Best Wall Construction for a Passive House?

Pas­sive design of a home must include an exte­ri­or wall sys­tem con­struct­ed with a supe­ri­or lev­el of con­tin­u­ous insu­la­tion a com­plete air- and mois­ture bar­ri­er, and a high degree of ther­mal mass. Con­tin­u­ous insu­la­tion keeps heat ener­gy inside a home in the win­ter and heat ener­gy out­side in the sum­mer. The air- and mois­ture bar­ri­er pre­vents air infil­tra­tion through the walls which caus­es more work for heat­ing and cool­ing sys­tems and more ener­gy use. Ther­mal mass walls absorb and delay the impact on inte­ri­or tem­per­a­tures of a home caused by changes in exter­nal con­di­tions, mak­ing occu­pants more com­fort­able and fur­ther reduc­ing ener­gy use.

The pri­ma­ry goal of pas­sive design is to reduce a home’s depen­den­cy on mechan­i­cal ener­gy. How­ev­er, pas­sive design must also ensure a healthy indoor envi­ron­men­tal qual­i­ty and pro­vide a high lev­el of com­fort to its occu­pants. Suc­cess­ful pas­sive design of the whole house requires that the wall sys­tem and oth­er ele­ments of the build­ing enve­lope work in com­bi­na­tion with the home’s ori­en­ta­tion, room and win­dow place­ment, ven­ti­la­tion, and shad­ing. The best wall con­struc­tion for a pas­sive design home includes con­tin­u­ous insu­la­tion, an air and mois­ture bar­ri­er, and a high ther­mal mass build­ing sys­tem.

Continuous Insulation for Passive Wall Design

Con­tin­u­ous insu­la­tion in pas­sive exte­ri­or wall design is essen­tial to cre­at­ing a qual­i­ty build­ing enve­lope and ener­gy-effi­cient home. The ASHRAE Stan­dard 90.12013 defines con­tin­u­ous insu­la­tion as insu­la­tion that is uncom­pressed and con­tin­u­ous across all struc­tur­al mem­bers with­out ther­mal bridges oth­er than fas­ten­ers and ser­vice open­ings. Wrap­ping a building’s enve­lope, includ­ing the exte­ri­or walls, with a lay­er of con­tin­u­ous insu­la­tion increas­es the effec­tive R-val­ue of the home and is a key ele­ment of a pas­sive wall design.

A Vapor Permeable, Weather-Resistant Barrier for Passive Wall Design

A pas­sive wall design must include a weath­er-resis­tant bar­ri­er to pre­vent the infil­tra­tion of both air and wind-dri­ven rain. The selec­tion of weath­er bar­ri­er on wood-framed homes is espe­cial­ly crit­i­cal, because the use of con­tin­u­ous insu­la­tion can block a wall’s capac­i­ty to release mois­ture from with­in the wall assem­bly. High mois­ture lev­els with­in a wall sys­tem can cause wood rot (due to fun­gi) and mold growth, which is unhealthy to the occu­pants of the house. There­fore, wood-frame pas­sive wall design must include a vapor per­me­able air and mois­ture bar­ri­er to allow mois­ture to escape. Mass wall sys­tems are much more resilient than wood, there­fore vapor per­me­abil­i­ty of the air and mois­ture bar­ri­er is not as crit­i­cal.

A high-qual­i­ty vapor per­me­able air and mois­ture bar­ri­er shields the walls of a home from water and air infil­tra­tion, along with mois­ture accu­mu­la­tion with­in the wall sys­tems. It also con­tributes toward cre­at­ing an ener­gy-effi­cient, healthy and com­fort­able home. Essen­tial to wood-frame pas­sive wall design is a vapor per­me­able air and mois­ture bar­ri­er.

High Thermal Mass Material for Passive Wall Design

An essen­tial com­po­nent of pas­sive wall design is the use of high ther­mal mass prod­ucts. High ther­mal mass mate­ri­als sta­bi­lize tem­per­a­ture shifts with­in a home by absorb­ing and stor­ing heat ener­gy. For exam­ple, in a warm cli­mate, con­crete walls absorb cool air at night and store it with­in its mass. Dur­ing the day, these walls will stay cool longer and so will the inte­ri­or of the home. Steel and wood have low ther­mal mass and are not good mate­ri­als for pas­sive wall design. Con­crete, stone, and brick have high ther­mal mass and are good choic­es for pas­sive wall design.

Utilize the Bautex Block Wall System for Best Wall Construction for a Passive House

The Bau­tex Block Wall Sys­tem is a high-ther­mal mass mate­r­i­al that pro­vides con­tin­u­ous insu­la­tion and the air- and mois­ture-resis­tance required for pas­sive wall design. The Bau­tex insu­lat­ed con­crete block has an R-14 con­tin­u­ous insu­la­tion that stops ther­mal bridges and exceeds the stan­dards and codes of the ASHRAE 90.1 and 2015 IECC. Also, appli­ca­tion of the Bau­tex AMB 20 air and mois­ture bar­ri­er to the Bau­tex Block wall cre­ates a mois­ture resis­tant and air­tight house that is ide­al for pas­sive house design.

The best wall con­struc­tion for a pas­sive design cre­ates a tight build­ing enve­lope with con­tin­u­ous insu­la­tion, a vapor com­plete air and mois­ture bar­ri­er, and high ther­mal mass sys­tems. A suc­cess­ful pas­sive design also con­sid­ers the home’s ori­en­ta­tion, room and win­dow place­ment, ven­ti­la­tion, and shad­ing. Pas­sive design reduces a home’s depen­den­cy on mechan­i­cal ener­gy. Pas­sive design also pro­duces a healthy indoor envi­ron­men­tal qual­i­ty and a high lev­el of com­fort to its occu­pants.