What would you do to prevent rework on your next jobsite? The cost of rework on a commercial construction project can run anywhere from 2 to 20% of the total contract, including labor, materials and equipment. So, if you have a $50 million job, rework could cost an additional $1 to 10 million!
Let’s look at the top 10 building enclosure concerns I have come across in my 25+ years of construction, and how to avoid them to protect your future projects from potential disaster. Read to the bottom to get your free infographic!
Coordination of CM/GC
I don’t want to point fingers, but sometimes CMs and GCs cause their own problems. They want to meet the building owner’s deadlines and may cut corners to achieve it. For example, I often see substrates not ready to receive an air barrier material, but CMs and GCs will push to make it happen. You need proper substrate preparation and detailing first. Another simple thing that often gets overlooked during site walks is exterior screw spacing. Do you know what it is supposed to be? See the full video below for the answer. It may seem elementary, but it doesn’t always happen.
Designers’ Lack of Building Science Knowledge
The construction industry and building science knowledge is advancing rapidly. With many design professionals having received their degrees prior to the year 2000, they may find themselves without the knowledge of current research. Think about it, air barriers were not mentioned in any code or standard at that time, and today we know they are critical for durability, energy efficiency, and moisture control. Items frequently missed or not addressed in details due to this lack of awareness are thermal bridging, a lack of a continuous air barrier throughout the building envelope, and a lack of redundancy at primary interfaces.
My recommendation is to continue learning about building science through various avenues and educational groups. Many of these are free and led by our industry's top experts. Thoroughly review your enclosure details (especially at the connections: roof to wall, wall to window, or wall to foundation) and include performance specifications that require mockups, field testing and a good quality assurance program.
Lack of Modeling
The use of modeling can significantly aid in the design and understanding of requirements for your project, but we don’t see it as often as we should. Using software like Therm, WUFI, or eQuest, can help with understanding how your system will handle a range of climates and may provide warnings for potential issues. These simulations can predict energy-efficiency and the likelihood of issues such as condensation by challenging or validating designs.
Improperly Insulating Existing Buildings
Retrofitting buildings is more complex than it might appear, so make sure you do the necessary upfront testing to validate the proposed restoration solution. Adding interior insulation to an existing brick building, for example, can impact the dew point and freeze/thaw abilities of that brick, threatening the success of the façade. Use of modeling and testing of some of the existing materials is a good first step.
Thermal Insulation Expectations/Understanding
Continuous insulation is now a requirement per the energy codes and ASHRAE standards, yet designers are still trying to find ways to maintain the old wall design. By moving the insulation outward of the stud cavity, we generally move the dew point outside of the studs, which provides a more energy-efficient and durable design.
One area of misconception in the use of exterior insulation is the impact of vertical z-girts. By running the vertical Z girt in line with the metal stud, studies have shown this could lead to 60 to 80% reduction in the building’s thermal efficiency. Thermal bridging from steel lintels/relieving angles being directly applied to the structure can reduce the nominal R value of the insulation by 30 to 50%, as you just created a radiator fin for your enclosure. There are numerous options to obtain continuous insulation and greatly reduce thermal bridging.
Spray Polyurethane Foam Insulation (SPF) Installation Issues
Spray Foam is a fantastic product if it is installed correctly. However, there are numerous ways to mess up the installation. When spraying the product, the Air Barrier Association of America (ABAA) recommends the thickness be no greater than 2 inches per pass. The application creates an exothermic reaction, giving off heat upwards of 240 °F (116 °C). If you apply the product too thick at one time, the heat could become so great that surrounding materials melt or burn. Always follow the manufacturer’s application instructions.
Another area of concern is improperly specified and installed thickness of foam. Specifiers should always provide a minimum thickness requirement and require a quality assurance process to ensure the project is receiving a good product.
The cell structure of the foam also needs to be correct. During application, if you do not follow the instructions and deviate the chemical ratio, applied or remove heat and/or pressure, the foam will have the incorrect density and not perform as designed. ASTM D1622, Standard Test Method for Apparent Density of Rigid Cellular Plastics, is an easy test you should perform daily to check the density of your foam. The alternative is having a failed product and painstakingly removing all the foam and reapplying.
Improper installation of Air/Vapor Barrier Materials
When dealing with mechanically fastened or self-adhered membranes, watch out for common errors. To start, I often see improper fastening as the spacing and fasteners used are often not per manufacturer requirements. Penetrations through these products need to be properly detailed, including if fasteners are removed. Another concern with these materials, is fish mouths. Following the application instructions, using primer (if required) and rolling self-adhered membranes properly can prevent this problem. Reverse shingle or lap can also cause issues after construction, along with improper or forgotten flashings.
For fluid-applied air/vapor barriers, familiarize yourself with the necessary substrate preparation and know the conditions under which the product can be applied before applying it. Refer to manufacturer’s instructions on the proper wet mil-thickness and check it on multiple areas along the wall. I highly recommend you understand the expected cure time of the product and look at the incoming weather conditions of the jobsite to ensure the fluid is not washed away by precipitation.
When considering any air barrier material, confirm if it is compatible and will adhere to adjacent materials. The general rule of thumb is that whichever manufacturer’s product is on top in the sequencing, that manufacturer needs to provide the letter of compatibility
No Pre-installation Meeting
Pre-installation meetings are critical for all the building’s stakeholders. They allow the team to review details, sequencing and acceptable “hand offs” during construction. During this meeting, you can also clarify the owner’s expectations and discuss the plans for inspections and testing, ensuring that the design/build team, as well as the trades and manufacturers are all on the same page. This meeting can mitigate significant miscommunications and issues during construction and should be a requirement in the front-end specifications.
No Mockup or site testing
Mockups are your opportunity to test, adjust and validate your design at various connections prior to jobsite constructions. A national testing lab reported that 93% of mockups they were involved in and tested -- failed. By analyzing those areas of air or water infiltration, you can reevaluate the design, materials being used, sequencing and installation practices. Even if you aren’t testing the mockup, it still offers a custom training opportunity for your crews to get their hands on the materials and familiarize themselves with the specific details, so they are more comfortable on the actual project. Don’t pass up your chance to discover potential issues ahead of time to avoid expensive repairs down the line.
Transitions are the most common area where I see critical errors. Whether it’s the below grade to above grade, window to wall, wall to roof, or penetrations, properly sealing these connections will save 99% of your potential building envelope failures. Seemingly minor gaps or holes can lead to substantial water and air intrusion. If you run into complex details or have installation questions, talk to your product manufacturer for an appropriate solution.
With the cost of rework so high, why would you not spend the extra time to make sure things are done right the first time? By reviewing the common areas of concerns, you can help your building become more air and water-tight and lessen the chance of devastating callbacks.
Dive deeper into this topic by watching Brian's full presentation from BEC-Cleveland 2018.