Should You Insulate Your Roof Rafters

You are correct and your girlfriend is wrong.

Should you insulate your roof rafters. Other considerations to get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible. On new build or replacement pitched roofs the ideal build up would be insulation fitted over and then between the rafters. This can damage your roof in a number of ways. Before insulating seal any air leaks and make roof and other necessary repairs.

If you decided to use a rigid foam board to help insulate your cathedral ceiling you would install the board on top of the roof sheathing and underneath the plywood at the top of the roof. If your attic is often used or perhaps you plan to convert it in the future you will need to insulate the inner surfaces of the roof. Water is insulation s enemy. Whether or not there is an inner roof lining and the total thickness of the roof structure.

The technically correct approach depends on a number of factors. The first decision is whether to insulate a pitched roof at ceiling or rafter level. Insulate the ceiling of the attic poorly. If it is located in a conditioned part of the house also remember to insulate and air seal your attic access.

The current trend is for a warm roof where insulation is installed between the rafters thereby keeping the roof timbers warm. In my opinion removing the old insulation should be as much a part of putting spray foam insulation on your roof deck as making sure you have whole house ventilation and conditioning the air in the attic. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow. Insulate and air seal any knee walls vertical walls with attic space directly behind them in your home as well.

Insulating between rafters will do no good because the attic should be ventilated and the rafter insulation would be between two unheated spaces. If you use open cell spray foam on your roof rafters you should cover the finished application with a paint or sealant that retards water vapor. Knock these to dos off your list to ensure that your insulation will last for years and keep conditioned air where it belongs. For example if the space beneath the rafters is going to be used for a living area then you will need to insulate the roof rafters.

Other key prep steps before you insulate. Whether you need to insulate your roof rafters will depend on what you intend to do in the space directly beneath the rafters. In which case there would be no economic rationale for spending all that money to insulate the roof deck. I believe the optimum way to insulate your attic is to insulate the floor of the attic very well but allow the air above that to escape ie.