Roof Purlin Metal Building Air Gap

If an open grid framed roof or widely spaced old solid roofing planks as the sheathing it is important to tightly stretch this so it does not sag down and hold water between the framing roof sheathing boards and the metal roofing obviously far better to put down a solid sheet sheathing first when doing a reroof in that sort of situation.

Roof purlin metal building air gap.

It provides a solid flat surface to attach the new metal roof to. This gap allows some vertical eave to ridge movement of air between the purlins and the metal roof. Purlins are 2 by 4 feet and are installed much like metal roofing. So much information has been devoted to the subject of roof venting that it s easy to become confused and to lose focus.

So i ll start by saying something that might sound controversial but really isn t. Metal roof coatings with solar reflectance can help building owners save substantially in annual cooling costs. In other words it s put on last the cap to the job. Metal roofing ridge cap is the trim placed along the roof s ridge the peak where two roof slopes meet up.

Most ridge cap comes in pieces 10 6 long. These clips have height to them we don t know how much which provides a gap between the roof and the purlin. 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. Purlins at a 45 degree angle still provide sufficient support for installation of the metal roof panels.

Ventilation air follows exactly the opposite path. A vented attic where insulation is placed on an air sealed attic floor is one of the most underappreciated building assemblies that we have in the history of building science. Installing the metal roofing over 1 4 s allows the ability to also install additional insulation under the metal roof that can t be done the other two ways. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

It creates an air gap between the back of the metal and the shingle roof which allows for airflow. Metal roof purlins are installed horizontally under metal roofs. Rising along the underside of the angled purlin until it reaches a gap then rising up to the next purlin and so on to exit at the ridge or gable. Research has confirmed that creating an air space under a metal roofing system will increase energy savings during both summer and winter months.

They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.