Metal Roof Insulation – How To Insulate Under Metal Roof Panels?


Metal roof insulation helps eliminate two problems that they often face – condensation and loss of heat. Metals are good conductors of heat and so, whenever there is a difference of temperature between the interiors of the building and the exteriors there is a heat transfer. Same way, when the temperature drops, water condenses on the metal panels. Adding a layer of insulation can eliminate this problem. There are different methods of insulating metal roofs.

Fiberglass Batts or Glass Mineral Wool Insulation

Commonly used insulation till recently these fiberglass batts formed a physical barrier between the metal roof and the interiors of the building. These are placed side to side on the roof rafters. The batts do not form a continuous barrier and hence air can flow through them causing heat loss. The insulation batts themselves are not closed systems and hence flows through the batts but a little slowly. These batts need a vapor barrier. They can not be placed directly underneath the metal roof as the condensation formed under the metal roof can seep into the metal roof insulation material and can ruin it. Water is an excellent heat transmitter, so, if gets into the insulation batts, you will need to replace it. So, a gap of about 15 cm allows the air to freely circulate under the metal roof and above the insulation barrier preventing condensation of water. But, this allows some amount of heat loss. This type of insulation is not too great for metal roofs as neither condensation nor heat loss problems are addressed effectively. Also, building this intricate fiberglass insulation system adds to cost of your roofing.

Polyurethane Spray Foam

Spraying the undersides of the metal roofing with a thick layer of polyurethane spray foam insulates the roof, eliminating the problems very cold buildings in winter and hot interiors in summer. As it is a spray unlike a physical barrier like batts the foam gets into all the crevices and gaps and forms a complete seal preventing any thermal leakage. The spray can either be applied to bottom surface or top surface of the roofing metal. This is a much better metal roof insulation than fiberglass batts. The thickness of the spray applied will give you the U rating of the insulation – which indicates the thermal value. The thicker the layer the better the insulation. Just one-inch of the foam will prevent the formation of condensation under the metal roofing. If the roof needs to be renovated and insulated then polyurethane spray insulation is a effective option but financially speaking and also has an effective heat barrier. To achieve the same insulation capacity you will need 20 cm thickness of batts which can be achieved by 10 cm of polyurethane foam.

Radiant Barrier Spray

The world is facing the stark reality of energy shortage in a few decades time. It is only financially and environmentally in our favor to reduce our energy usage to the minimum possible. An effective layer of insulation to seal the home and prevent unnecessary loss of conditioned air – whether hot or cold is in our best interests as it reduces energy loss. A reflective insulation and radiant barrier layer will help keep the home comfortable with a lower energy use and save money on the electricity bills. All buildings whether home or office can benefit with a layer metal roof insulation under the panels. The insulation can be done over open rafters, over new roof decking or over existing shingles. A layer of felt paper, waterproofing layers should be placed below the reflective insulation. The foil can be placed horizontally or vertically on the roof deck as needed. A double layer of horizontal and vertical layer is also sometimes done in very hot or cold places. Nail it down in place using felt nails of 4′ length. This prevents the ripping away of the insulation in very windy conditions or stormy weather. Make sure to overlap the foil when laying it down on the roof. The foil seams have to be taped down to effectively seal it off against water seepage and as a vapor barrier. This metal roof insulation can be installed either on top over a older roof deck or under a new roof.

Here we have touched upon 3 methods of installing insulation under the metal roofs. When re-roofing or installing a new roof, adding the optimum metal roof insulation is much easier than when your renovating it. Office buildings and businesses need to do this without disrupting the work and loss of valuable business days. Experienced and well-trained roofing and insulation experts will be able to advice on the most effective way to add the insulation without too much hassle for the business.



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