The efficiency of 2×4 stripping your metal roof

We have installed metal roofing on residential homes for many years. This has been my main source of income for the past several years. I have learned some important techniques to make your roof system more efficient. Pulling 2x4s every two feet seems to be the most cost effective.

We’ve laid metal directly on singles, laid it on tar paper, and laid it on 1×4, 2×4, etc. There are some important benefits of stripping 2x4s that you may be aware of. For one thing, the space between the metal and the original roofing material acts as an insulation gap (like storm windows) that doesn’t allow the sun’s heat to penetrate the attic space. This allows for easier cooling during the summer months.

On most raised rib panels (not standing seam panels) there is an open raised rib space every nine inches or so for warm air to rise from below on the eve to your ridge and out the vent from the ridge by the metal ridge. A ventilated roof system.

An important fact here is not to overfill the space created by the 2x4s with insulation, thereby blocking airflow from the eve to the ridge vent.

* In fact, we ran our own myth busting test on this theory. We built 2 identical wooden boxes with a pitched roof, completely sealed from the outside. Both roofs were covered with singles.

On a roof, we placed the metal roof directly over the singles.

The other 2×4 roof was added, then the metal roof was placed on top of the 2x4s.

A digital thermometer was installed in both boxes. In the first test on a sunny 85 degree day, the box without the 2×4 stripping rose to 112 degrees, while the box with the 2×4 stripping peaked at about 95 degrees. That’s about a 17 degree difference in the two attic spaces,

That’s justification enough to spend the extra bucks to dismantle your new 2×4 roof.