To say there are a lot of metal roofs in Spokane, Washington would be an understatement.
Since the 60’s pre engineered metal buildings have been installed in Spokane, Washington at a high rate. Metal buildings are cheap, durable, low maintenance and can withstand harsh weather quite well. In one study, metal buildings have an average life expectancy of 77 years.
A old rusted and leaky metal roof in Spokane
There are however, some downsides to the metal roofing on these buildings. The biggest downfall we have seen hasn’t been failures of fasteners, but condensation on the underside of the metal. Condensation occurs when the interior heated air contacts the colder metal and hits the dew point. The moisture will then gather on the underside of the metal and either “run” along the underside until it finds a drip point or soak into the insulation. In some cases where the metal building has blanket insulation, the insulation is squeezed between the framing and the metal roofing, virtually removing all insulative value. In addition, the fasteners used to secure the metal roofing create thermal shorts and allow for another condensation point. The end result is a poorly performing building envelope.
Fortunately, these problems can be fixed!
There are several ways to fix the problems associated with condensation, I will address the 3 I feel would work the best in no particular order.
- Unheated attic space and insulating with blown in insulation.
- Apply 2# closed cell spray foam insulation to the inside.
- Apply 3# closed cell spray foam roofing to the exterior.
Unheated attic space.
Depending upon the framing of your building, this method could be cheap or fairly expensive. If you have rafters, it would be quite simple to install drywall and blow in some insulation. If you have an open style ceiling this would be quite a bit more challenging and costly.
2# closed cell spray foam insulation to metal
2# closed cell foam also known as medium density foam can be applied directly to the underside of the exposed metal roof. As it is sprayed the foam will expand roughly 50 times its size, sealing all air leaks and thermal shorts. 2# spray foam has an average R Value of 6.5 per inch. This is a far superior insulation method than a drop ceiling.
3# closed cell spray foam roof
3# high density spray foam is fluid applied and rises approximately 30 times its size after it is sprayed on. This seals all seams, cracks and fasteners permanently creating a watertight seal. The foam is typically applied in 1/2″ to 1″ “lifts” to the desired thickness. A typical spray foam roof will be 1 1/2″ but can be applied as thick as necessary depending upon the needs and goals desired. Closed cell 3# spray foam has a R value of 6.5 per inch, giving the building tremendous energy savings. In fact, a typical spray foam roof has an average payback of 4.5 years. After the spray foam is applied, a UV protective coating is applied to protect the foam.