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How to Properly Insulate Your Roof

Spray foam is an effective way to insulate your roof.
Spray foam is an effective way to insulate your roof.

Your first line of defense against the Seattle area weather is the roof over your head. Your roof alone is not able to keep the serious problem of heat transfer from occurring. The warmth you need in your home during winter will escape out through your roof and likewise, during the hot summer days the heat will find a way into your home. The result is lower efficiency, higher energy bills and a shortened lifespan for your roof.

If you properly insulate your roof and attic space, you can reduce energy loss and help your roof last for many more years. Unfortunately, when it comes to insulating roof and attic space, a lot of people don’t know exactly what they are doing, which can lead to costly air gaps and unsuccessful sealing. Here’s how to avoid these mistakes and insulate your roof properly.


You will need an estimate of how much space you have to insulate. To get a good estimate of how much blown or rolled fiberglass blankets to buy, simply measure the length and width of your attic. Buying a bit more than you think you need is always a good idea.

Sheeting Installation

The first thing you need to do is cover the entire attic floor and several inches up the wall with plastic sheeting. Be sure to seal all the gaps but DO NOT BLOCK ATTIC VENTS. Roof ventilation is vital for your roof’s condition and for preventing mold and mildew growth in your attic.

Installing Blown Insulation

A blower is used to install blown insulation, and each brand may have different instructions so be sure to read the manufacturer’s instructions carefully. Blow a layer between the attic joists and then, once that is done, cover the top with another thin layer. It is a good idea, if you have floorboards in your attic, to blow a full, thick layer beneath the boards. Replace the boards and then, for maximum results, blow another thin layer over the top.

Rolled Insulation

Accuracy is required when installing rolled insulation. As much as a 20 percent loss in heating and cooling efficiency can occur with just a one-inch gap. Make sure your insulation sits flush with the floor joists and has no cracks or gaps. For maximum effectiveness you should put rolled insulation between the roof rafters.

Spray Foam

Because it is both quick to install and extremely effective, spray foam is becoming a popular form of insulation. Special tools are required, and the chemicals have to be mixed accurately to get the best results. This is why we recommend hiring a professional for the job. It’s usually worth the extra cost.

Is your Snohomish area roof in need of repair? Contact Asset Roofing for a service estimate today!