The Ins and Outs of Insulation
Which type of insulation is best for a given project?
Several different types of insulation are being used together in our Mercy Magnuson Place Apartments project. Each was chosen for its particular characteristics in its given application. Having a well thought out system with a quality installation will: improve energy efficiency; control air leakage; improve indoor air quality and occupant comfort; improve the structural strength of the building; and reduce condensation, moisture, and mold problems. While there are countless other materials and application methods, this article highlights those being used on this project.
Closed Cell Rigid Foam
Dow Styrofoam brand closed cell rigid foam board was chosen to insulate the inside of the exterior masonry walls on the project because of its quick and easy installation, and good R value for the cost. In most places we are using the standard 2” thick sheets which provide a R-10 thermal value (the higher the R-value, the greater the insulating effectiveness). In some places we are using 1 ½” thick sheets to keep the wall thinner so that the historic concrete columns in the wall will remain exposed.
In addition to its insulating properties, closed cell foam is non-porous and not moisture-penetrable. By using Great Stuff Pro Series insulating spray foam and 3M seam tape around the wall edges and where panels abut, we are able to complete the air and vapor barrier. In most areas we can use the seam tape in lieu of spray foam as it is a cheaper and quicker alternative.
Closed Cell Spray Foam
To insulate the roof of the building, we are spraying BASF brand SPRAYTITE closed cell foam on the inside of the roof sheathing. This application is a two-part polyurethane expanding foam with the liquid components mixing at the application nozzle. It’s thermal rating is R-6.6 for each inch of thickness as applied. While relatively costly, this application method is a great way to get insulation in hard to reach areas. It has the added benefit of controlling moisture and air infiltration as well as increasing the structural stability of the building where it is applied.
Before spraying on the underside of the roof sheathing, the wood needs to be dried to a moisture level below 12% to prevent mold and mildew from being sealed in. To accomplish this, we use a dehumidification system to circulate air with zero percent relative humidity to dry the wood. So far, we have been able to bring the moisture level down into the 8% range.
On this project, we are applying fiberglass batt insulation over the top of the spray foam insulation in the roof truss cavities. Combined with spray foam, fiberglass batt is an economical way to increase the thermal resistance of the installation.
We are pre-installing this product at locations that won’t be easily accessible later, including where new interior walls meet the existing sloped ceiling.
Rock-Based Mineral Fiber
We are using ROCKWOOL brand acoustical fire batt made from stone. ROCKWOOL is a mineral fiber insulation made up of basalt rock and recycled slag. Basalt is a volcanic rock and slag is a by-product of the steel and copper industry. These minerals are melted and spun into fibers to make the insulation.
On the project, ROCKWOOL is used in the cavities adjacent to the building’s historic windows where the window’s lead weights were. The material is dense and heavy which makes it well suited for small cavity applications. It is also a fire retardent.
Spray-Applied Fire Resistive Material (SFRM)
To protect the structural steel within the building, we are applying Isolatek’s CAFCO Blaze-Shield II commercial density dry mix spray-applied fire resistive material. This is a spray applied mixture of mineral fiber and cement and is used on structural steel as fireproofing. A standard application is 1 ¼ inch thick and provides a 1-hour fire barrier.
The Isolatek product is made from inorganic material which does not promote mold or fungal growth. It meets or exceeds all major fire protection specifications for commercial structures. And it also features a high percentage of recycled content (67% pre-consumer).
What will work best for your project will depend on many different factors as insulation is not a one size fits all product. Taking care in choosing different materials and different applications will help bring together a complete system to ensure your building is comfortable and energy efficient.