Why You Should Insulate the Roof Deck

Roofing is a crucial part of any building. And many builders will put a lot of focus on finding a durable roofing material that will withstand the elements and whatever use the building may need for it. Unfortunately, while an emphasis on the quality of roofing is important, an equally important facet is often overlooked—the application of insulation below the roof deck.

Multi-Faceted Benefits
Most people will agree that insulation is important to any building. And with reports coming in that most homes and buildings are technically underinsulated, a bigger push has been made in recent years to insulate walls, floors, ceilings and upper stories of buildings to increase energy efficiency. When including plans for insulation, however, it’s important not to overlook the underside of the roof deck as an important area not only for the improvement of energy efficiency, but for the protection of the roof itself.

When you insulate the underside of the roof deck, you’re essentially preventing the transfer of heat between the building’s interior and the roof. This barrier has a positive cascading effect on many parts of the building.

First, when the sun’s rays beat down on the roof, without insulation a large portion of this heat can be transferred through the roof deck to the area below. This can cause super-heating of the upper stories of the building in questions. To combat this, the HVAC system, as well as building fans need to work harder to cool this air. This results in higher energy bills for the entire building, as well as a less comfortable atmosphere for those working there.

This heat transfer works both ways, however. Not only does the superheated air just below the roof deck seep down into the floors below, it a portion of it also gets transferred back up to the roof itself. There, the higher temperatures coming from below combined with the direct impact of the sun’s rays cause the roofing material to begin deteriorating at a faster rate than would otherwise happen. So, the roof will require replacement much sooner than it would if there was less heat transfer between the upper stories of the building and the roof itself.

Finally, this heat transfer doesn’t just occur during the warmer months of the year. During the winter, when snow covers the roof, rising heat from the building below can cause the roof to heat up. This escaping heat not only lowers the energy efficiency of the building, raising energy bills, it also causes the snow to melt.

If the roof has any degree of pitch, this melting snow will flow to the edge of the roof where it will refreeze into an ice dam. Ice dams are dangerous because they can cause moisture to back up beneath the roof itself, resulting in leaks and the further deterioration of the roofing material. Ice dams on tall commercial buildings also cause hazards for pedestrians below when the ice inevitably falls.

If the roof is flat, the snow will still melt, and the water will collect on the roof. This freeze/thaw cycle can start to break down the roofing material. It can also force small cracks in the roofing material to expand over time, resulting in leaks to the upper floors of the building, as well as the necessity of roof repairs and roof replacements much sooner than may be anticipated.

Insulating the Roof Deck
Insulating the underside of the roof deck is the building’s first defense against higher energy bills and a weaker, more leak prone roof. Insulation can be applied to the underside of the roof deck at any time, either directly after a roof replacement, or at a later date.

The most common method of insulating this area uses a spray foam insulation. The spray foam is able to stick to and to coat the entirety of the roof deck, including corners, edges, gaps, and other hard to reach areas that might not otherwise be insulated. When the foam expands, it fills and covers all areas of the roof deck, providing superior insulation to the roof and the floors below.

Ventilation
The second component to insulating the underside of the roof deck and providing these benefits to the building is to ventilate the area directly below the roof thoroughly. Most buildings also lack adequate ventilation in this area.

Venting the area just below the roof deck helps to keep the area just below the roof cool year-round. The prevention of superheated air in this area can help keep the building more comfortable, and will help extend the lifespan of the roof itself. Ventilation combined with roof deck insulation is the best defense for preserving the roof and keeping energy bills down.

Insulate Your Buildings
When you undertake the insulation of any commercial building, be sure not to overlook the underside of the roof deck as you do so. Insulating this area will have a profound impact on the comfort, energy usage, and longevity of the building and roof itself. If you’re looking to include architectural roofing shingles to your project, you need to also take the time to insulate the underside of the roof deck to reap these benefits for your buildings.