Roof Purlin Metal Building Air Gap

Warm air holds more moisture than cold air.

Roof purlin metal building air gap.

You would have to seal the ridge vent it isn t working anyhow because your building does not have an air intake from enclosed vented soffits. The colder the climate the more essential the air gap. Research has confirmed that creating an air space under a metal roofing system will increase energy savings during both summer and winter months. This lets any condensation on the underside of the metal roof evaporate.

The metal will be attached to at least 3 4 purlin and 1 2 plywood instead of just 1 2 plywood which should make the overall roofing system stronger. Metal roof coatings with solar reflectance can help building owners save substantially in annual cooling costs. Getting a perfectly sealed vapor barrier under purlins would be nearly impossible to achieve. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern.

You don t even want to go there. Do all roofing projects require purlins. Purlins at a 45 degree angle still provide sufficient support for installation of the metal roof panels. The air space allows natural ventilation when there is a vent at the low part of the roof structure and another at the high part of it.

Metal roof purlins are installed horizontally under metal roofs. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. If you do not completely fill purlin cavities code requires airflow from eave to ridge over top of the insulation. You have no way to achieve this without a major remodel.

Purlins are 2 by 4 feet and are installed much like metal roofing. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Warm air is actually lighter than cold air known as avogadro s law essentially condensation occurs at night when the temperature inside a building is warmer than outside.

Ventilation air follows exactly the opposite path. Warm wet air rises and meets the cold roof and cools. On a sloped metal roof there is a vent at the bottom to allow air in and natural convection takes air at the top out notes wingfield. But probably the best benefit that comes from using purlins is the air gap it creates between the metal roof and the existing shingle roof.

As it cools it can t hold as much moisture.