One of the most important decisions that will need to me made when designing your metal building is how you decide to insulate. Long term heating and cooling costs should be the driving factor of this decision. Because energy costs to run your AC and furnace aren't going down anytime soon, many businesses and barndominium designers are choosing to use spray foam insulation instead of fiberglass insulation.
Advantages of Spray Foam Insulation
The main advantage of Spray foam insulation is it's ability to completely fill gaps and air seal. Spray foam insulation is a product formed from the mixing of specific chemicals that when sprayed onto a surface quickly expands. Unlike fiberglass insulation, spray foam will make it's way into the small gaps between sheets of metal and wrap itself around metal framing members. This gives the structure a more continuous insulation system.
Another advantage that Spray foam has over Vinyl backed fiberglass is that it isn't subject to compression. The active ingredient in fiberglass insulation, that makes it a great insulator, is air. Because the air particles are surrounded by fiberglass particles, heat energy cannot travel efficiently from one side of the wall to the other. This makes fiberglass a great insulator. However, in new construction, most fiberglass insulation is installed by sandwiching it between the exterior sheet metal and the structural iron members. This causes the insulation to compress at every framing member. When fiberglass insulation is compressed, you have fewer air particles to create resistance to heat exchange. Therefore, your insulation is reduced at every framing member that the insulation is in contact with.
This is another advantage of Spray Foam over Fiberglass. Application is performed after the framing and sheet metal is installed, so you don't have a loss of performance due to insulation compression.
Fiberglass insulation is similar to going camping with a sleeping bag with holes in it. Heat loss will occur everywhere the insulation is compressed and anywhere there are gaps. Having a continuous insulation system with more efficiently prevent heat from moving from the outside of the building to the inside.
Another advantage if you are using Closed cell foam, is that your structure will be much stronger. Open cell foam dries soft and spongy, but closed cell foam dries hard and rigid. This creates a stronger wall system. When the closed cell foam is applied to the metal R panels and structural columns and girts, the foam bonds strongly to the surfaces. It creates a sort of glue that strengthens the entire building structure and protects against impacts and high wind events.
Disadvantages of Spray Foam
The cost of Open Cell Spray Foam is usually 2-3 times higher than fiberglass, and the cost of Closed Cell foam is 4-5 times higher. If you are on a tight budget, spray foam may be cost prohibitive. However, if you are building a residence, or a commercial building, it is smart to weigh the costs now vs what you will save over time in heating and air conditioning costs. Typically ventilated warehouses aren't the type of building that you need to have spray foam.
For appearance, the white vinyl backed insulation is a very smooth and clean look. The surface that you see is bright and reflects light back into the room efficiently. For warehouses, lighting design can be reduced because of the reflectivity of the vinyl. Foam isn't as attractive. And the foam is often an off white, yellow or orange color. It's not as reflective as the vinyl. Also, there will be over-spray on the framing members, so if the ceiling or walls of your building is exposed , you'll need to take into consideration how you will feel about the appearance of the spray foam.
Most spray foams are flammable and require a flame retarder sprayed over the top of the foam after it is applied. One of the advantages of a metal building shell, is that on it's own, the building has no chance of burning down. However, if you apply spray foam, you now have a building that can go up in flames very quickly. The solution is to apply a flame retardant that is sprayed over the foam like paint.
Closed cell foams don't let any water in... or out. If you have applied closed cell spray foam and you get a leak in the roof. The water will run between the roof panel and the foam all the wall down until it comes out at the bottom. If there is a leak, the trapped water will quickly degrade the metal roof panel, causing it to rust and fail. If our customers want closed cell foam, I generally recommend going with a standing seam metal roof. This eliminates the exposed fasteners and greatly reduces the chance that there will be a leak.
Residential Standing Seam Double-Lok Roof.
For open cell foam, if the roof leaks, you will know immediately, because the water can pass right through. You will know if you get a leak.