Austin Design and Construction Conference Makes Clear Case for Airtightness in Buildings

Last month, several Bautex team members had the oppor­tu­ni­ty to attend the 2019 ATX Building Per­for­mance Con­fer­ence in Austin, Texas. This has become a serious regional con­fer­ence that is held every other year, opposite the larger Humid Climate Con­fer­ence (Image Source). The ATX Building Per­for­mance Con­fer­ence is jointly hosted by Passive House Austin, AIA Austin Building Enclosure Council and the 2019 AIA Austin Committee on The Envi­ron­ment (COTE).

The central topic of this year’s con­fer­ence was air­tight­ness of buildings and how imper­a­tive it is for archi­tects, engineers, con­trac­tors and even building owners to under­stand why we, as an industry, must keep pushing for better-per­form­ing buildings. Through­out the day, we heard from a number of speakers rep­re­sent­ing a broad cross-section of con­struc­tion project teams, each with their own per­spec­tives on building air­tight­ness. Yet, all of the speakers rein­forced the theme of the con­fer­ence that air­tight­ness is a critical goal to achieve in all buildings. 

For those of you who could not attend, here are five of the most important takeaways from this year’s ATX Building Per­for­mance Conference.

1. Our buildings cost us trillions extra, and we don’t even know it.

Researchers estimate that improving the indoor envi­ron­ment of buildings could have an annual positive impact of $700 per person. Extrap­o­lat­ing that to the 320 million or so citizens in the United States, it would yield trillions of dollars in worker pro­duc­tiv­i­ty and reduced health­care costs annually. In fact, other than improving our diet, indoor envi­ron­men­tal quality may have the most sig­nif­i­cant impact on reducing health­care costs in this country.

We spend over 85% of our lives indoors, nearly 70% of our lives in our homes, and around 30% of our lives just in our bedrooms sleeping. Buildings are micro­cli­mates, and we are bio­log­i­cal machines that con­stant­ly interact with the climate around us. It’s no surprise, then, that the quality of our indoor envi­ron­ments has a sig­nif­i­cant impact on our physical and mental health. Unfor­tu­nate­ly, the envi­ron­men­tal quality of the buildings we work and live in today is not good. In fact, it can be quite bad.

The problem is that most people aren’t aware of the impact their buildings have on their physical and mental health. They can’t see or hear the mold, bacteria, protozoa, irritants and chemicals that are floating around in the air or laying on the surfaces of our buildings. They don’t realize that moisture and humidity in their buildings are not only uncom­fort­able, they are dangerous because they drive the growth and dis­tri­b­u­tion of all those things that cause us harm.

How confident are you that the buildings you are designing or con­struct­ing are providing indoor envi­ron­ments where people can live healthy, safe and com­fort­able lives? How many trillions of dollars are we costing ourselves when we don’t get the building envelope and indoor envi­ron­men­tal control systems right? As an industry, we need to address this problem head-on and soon, espe­cial­ly before we build the next few million square feet of buildings that will be in service for the better part of this century.

2. “Build Tight, Ventilate Right” is here to stay.

Leaders in building per­for­mance circles have been talking about and promoting tight building con­struc­tion for over 40 years; yet in 2019, many in the con­struc­tion industry are still skeptical of (and sometimes downright hostile to) the idea of building airtight buildings.

For one, these antag­o­nists assume that all buildings will get wet so they need to be con­struct­ed in a way that they can dry out quickly. Secondly, they believe that if the building is too tight, people will get sick due to improper ven­ti­la­tion. And lastly, they argue that it costs sig­nif­i­cant­ly more to build an airtight building which is a non-starter in a cost-conscious world. All of these arguments fall way short.

We could use the same logic in the first statement to say that we should build large holes in the bottom of our walls so that when snakes get in, they have a way to get out. Air migration through the building envelope is the largest source of moisture in buildings and must be con­trolled. Besides, without a tight building envelope, we will sig­nif­i­cant­ly overspend to try and control the indoor envi­ron­ment with our mechan­i­cal systems.

The answer to the second objection is properly designed and balanced ven­ti­la­tion systems. The answer is not to let air come into a building anywhere it can, but to build tight and ventilate right.” Ven­ti­la­tion should be designed into a building from the beginning, taking into account the building design, envelope per­for­mance and all sources of ven­ti­la­tion, including make-up air ven­ti­la­tion, bath and kitchen vents, and dryers. Ideally, the active ven­ti­la­tion systems would be designed to balance outflow and inflow so that the building is not pos­i­tive­ly or neg­a­tive­ly pressurized.

The cost argument is always the toughest one to address, at least in the beginning. This argument assumes there are no economies of scale or tech­no­log­i­cal effi­cien­cies that make costs decrease as improved tech­nolo­gies come to market and we learn how to build better. This argument also fails to address the huge long-term, con­se­quen­tial cost of low-per­form­ing buildings discussed above. Besides, getting to a moderate level of air­tight­ness isn’t as hard as people make it out to be.

To put things in per­spec­tive, the national average of existing com­mer­cial buildings is 1.55 cubic feet per minute per square foot of building envelope at 75 pascals of pressure (CFM75). Here are the infil­tra­tion rates of several other current standards in use today:

0.40 CFM752015 Inter­na­tion­al Energy Con­ser­va­tion Code (IECC)

0.25 CFM75 United States Army Corps of Engineers (USACE)

0.15 CFM75 Canadian Building Code

0.08 CFM75 Passive House US (PHIUS)

At the con­fer­ence, we heard about an architect in Austin who is building his own home to the Passive House standard and who achieved a 0.02 CFM75 air infil­tra­tion rate! That is 20 times less air infil­tra­tion than the current energy code in Texas and 77.5 times less than the average existing building in this country. Meeting current building code is not difficult. Going 50% better is also quite achiev­able. Here’s how Joe Lstiburek put it to the audience:

To get to 0.4 CFM, just get rid of all the big holes in the envelope.

To get to 0.25 CFM, get rid of all the small holes.

To get to 0.6 CFM, get German (Passive House).

This argument that it is too expensive to build airtight buildings might have held a bit of truth in the 1980s, but it is certainly not true today. Besides, building codes now require more airtight con­struc­tion. These building code require­ments will soon become the new normal,” at least until they change the codes again.

The con­struc­tion of the Ironsight Office Building in San Marcos was a great example of airtight con­struc­tion that achieved a 0.25 CFM blower door score simply using Bautex Blocks and Bautex Air and Moisture Barrier.

Are you measuring the air­tight­ness of your buildings? Are you testing new tech­nolo­gies and methods to see what it will take to continue to drive down air infil­tra­tion in all of the buildings you design and build?

3. Air barriers aren’t about energy efficiency (at least not in the beginning).

Joe Lstiburek has been in building science for several decades and par­tic­i­pat­ed directly in the spec­i­fi­ca­tion and adoption of energy effi­cien­cy and air quality building codes and standards in the U.S. and Canada. One inter­est­ing story he shared was the history of air­tight­ness standards.

Common per­cep­tion is that air­tight­ness came about as an energy effi­cien­cy measure; however, the initial drive to require more air­tight­ness was the pre­ven­tion of moisture infil­tra­tion into buildings.

Framed wall assem­blies are fragile and sus­cep­ti­ble to rotting and mold growth when humidity is high. As stated earlier, the biggest source of moisture in a building is air infil­tra­tion through the building envelope. As energy code standards increased the amount of insu­la­tion required in building assem­blies, the drying potential of the assem­blies were reduced. To coun­ter­act this, building codes needed to reduce the wetting potential by reducing the flow of moisture-laden air into a building. Hence, lower air infil­tra­tion standards.

While vapor barriers are often a topic of con­ver­sa­tion in building circles, it did not get much attention here except as a way to compare the degree of the problem rep­re­sent­ed by air infil­tra­tion versus vapor diffusion. This is largely because water vapor diffusion through materials is a weak and slow force. As a result, the amount of moisture that comes into a building through air infil­tra­tion can be 30 – 50 times larger than what can come into or exit a building through vapor diffusion.

As we learned, there are many arguments for airtight con­struc­tion. Air barriers are more about building resilien­cy and occupant health and only sec­on­dar­i­ly about energy effi­cien­cy. Regard­less of your position on these goals, air­tight­ness in buildings is critical.

4. Building envelope details continue to be complex and challenging.

Based on what we heard at the con­fer­ence, there is no question that building envelope designs are getting more complex and more expensive over time. Increased building code and owner per­for­mance require­ments have caused sig­nif­i­cant changes in building designs which have increased costs and con­struc­tion chal­lenges in the field.

One factor driving this increased level of com­plex­i­ty in building envelope design is the addition of new materials and layers to tra­di­tion­al wall assem­blies. The instal­la­tion of these materials is more technical, and often the sequenc­ing and scope overlap between trades aren’t imme­di­ate­ly clear or explicit. In addition, many of the con­di­tions in a project are not detailed in the plans or spec­i­fi­ca­tions, which causes more back-and-forth between the con­struc­tion and design teams.

A second factor is the challenge of hiring, training and retaining competent and skilled trades. The increased com­plex­i­ty of building designs is a challenge for much of the labor force who don’t have a lot of training or expe­ri­ence. Problems are going to happen in the field and the per­for­mance of the building envelope will suffer.

Roof-to-wall tran­si­tions tend to be the toughest to detail in designs and to work out in the field. This is the area where multiple layers of materials in the wall assembly meet multiple layers of materials in the roof assembly. With all of these layers, main­tain­ing a con­tin­u­ous air barrier in this tran­si­tion area is a real challenge.

Another area that is a real challenge to design and construct are party walls in multi-family con­struc­tion. Most of the attention on air infil­tra­tion is focused on the exterior walls of the structure, but less time is spent studying the walls between units as well as adjacent interior uncon­di­tioned spaces such as trash chutes and plenum spaces.

While specific solutions to these chal­lenges were not discussed at the con­fer­ence, it was clear that sim­pli­fy­ing the building envelope design and reducing the number of materials used in the assembly was the most effective way to improve per­for­mance and control con­struc­tion costs for future building projects.

5. Just “nibbling” on innovation doesn’t solve anything.

During the afternoon Lightning Round” where attendees were given a throwable padded micro­phone to pass around and a chance to make a brief statement or ask a question, the theme of inno­va­tion came up several times.

It is clear that how we are building today is all new, despite the fact that the basic building systems we are using may be over a century old and may feel quite familiar. The materials are different, the layers are different, the sequenc­ing is different and the tran­si­tions between assem­blies are different. The way we are building today is NEW!

There was general agreement that we need to be more strategic and system focused in how we approach building designs today. This approach means looking at inte­grat­ed and tested building systems rather than relying on dis­in­te­grat­ed assem­blies of stand-alone building materials that are often supplied by multiple man­u­fac­tur­ers. But whose job is it to do the inte­gra­tion of these systems?

Ideally, it would be building materials man­u­fac­tur­ers. And when inno­v­a­tive building systems like these come to market, the design and con­struc­tion community must do their part to test, deploy and help make the most suc­cess­ful tech­nolo­gies part of the main­stream way of building.

There is a cost to doing new things, but we are doing new things today and every day. However, the return on invest­ment of different solutions varies sig­nif­i­cant­ly. Iron­i­cal­ly, the new things that appear to offer the least amount of change are, in many cases, more costly to implement and provide fewer benefits. Many times, the seemingly bigger change is simpler to implement and, in the end, provides sig­nif­i­cant­ly greater per­for­mance gains.

As one audience member who shared their per­spec­tive in the Lightning Round, the real risk is not in adopting new tech­nolo­gies, but in going part of the way and only nibbling on inno­va­tion” but never expe­ri­enc­ing any real benefit. We couldn’t agree more.

For the Bautex team that attended the 2019 ATX Building Per­for­mance Con­fer­ence, all of these points spoke to the heart of what we do and why we do it. The theme of the con­fer­ence fit perfectly with our company mission to develop building systems that simplify, and, as a result, simul­ta­ne­ous­ly reduce con­struc­tion costs and improve building performance.

Our company motto is Con­struc­tion. Sim­pli­fied.” The Bautex Wall System is both structure and complete building envelope in one inte­grat­ed solution that is quickly and effi­cient­ly installed by a single trade. Bautex makes designing and con­struct­ing resilient, healthy, com­fort­able, safe and energy-efficient buildings easier.

If you are wanting more infor­ma­tion or need some help getting started with The Bautex Wall System, let us know what you are working on.


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