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Warm roof vs cold roof: what’s the difference?

18 February 2020

The roof is a vital part of a construction structure. It protects the occupants and items inside a building from harsh weather and other threats. Two of the most critical functions of a roof is to provide insulation and drainage.

Generations have used diverse materials to build roofs. Thermal insulation is critical in buildings considering the number of fatalities caused by adverse weather.

There are two main types of insulating roofing systems in building construction namely cold roof and warm roof. Both of them achieve insulation, but they differ in the mode of installation.

Keep on reading to learn more!

Cold Roof

A cold roof results from placing the insulation material between the ceiling joists. The result is that the living space below the insulation material stays warmer than the space above the insulator. Warm and damp air from the room rises to escape through the ceiling.

When warm and moist air reaches the low-temperature zone at the cold roof space, condensation could occur. This outcome is undesirable as the resultant moisture can cause the rafts to rot. Therefore, the builder has to install adequate ventilation to allow the humid air to escape the room.

Application of Cold Roofs

Cold roofs have a unique advantage during winter. They prevent ice dams and the leaks which would result from the buildup of snow on the roof.

Without a cold roof, the heat generated in the house radiates to all areas, including the attic. The warmth at the attic heats up the roof and melts the snow above. The water runs down the roof and gets trapped between the eave and the snow above.

The snow at the eave will not melt immediately because the area is much cooler. Hence, it traps the water. With time, an ice dam forms on your roof.

Ice dams can be a concern on extensive flat roofs. The stagnant water collected on the roof can sip through the wall and cause rotting. Similarly, the ice floating on the water can break off and cause injury or destroy property.

If you are to build a house in a region prone to snowing, a cold roof can save you the mess of ice dams. The roof maintains the outside temperature. Therefore, it does not melt the ice.

Cold roofs are good for keeping the snow in place until when it will melt and drain away.

An efficient cold roof model should withstand the weight of the accumulated snow. A cold roof professional can install a snow retention structure which will hold the ice to melt naturally.

Challenges of Cold Roofs

Ice retention may not be a priority for most people since snow is not present throughout the year. Furthermore, some regions never experience winter.

Although the ceiling has an insulation cover, the rafts are exposed, and there is a lot of unoccupied space above. Therefore, the rafts act as a thermal bridge making the building to lose heat when temperatures are low.

Heat loss is the major drawback of cold roofs since you have to compensate for it with a heating system. The cost of regulating the temperature in a home with a cold roof far exceeds that of a warm roof.

Constructing a cold roof on an existing roof can be challenging and time-consuming. It requires you to rip the roofing material apart to lay the insulation on the surface above the ceiling. You must also replace the roof or install a new one, making it an expensive task.

Warm Roof

Installing a warm roof is straightforward. It involves laying the insulation material on top of the roof. You can secure the insulation boards with an adhesive before laying a waterproofing cover.

For effective insulation of the room, the constructor needs to seal the structural deck with a watertight membrane. The next step is to lay a rigid insulation cover and to fill any gaps left with a nonporous coat.

This method of roofing ensures that the entire structure of the roof is insulated. Therefore, the house becomes more energy sufficient. The superior thermal insulation technique of warm roofs makes the installation budget a bit higher than fixing a cold roof.

However, the total cost depends on the building materials required and labor charges among other variables.

Advantages of Warm Roof

Insulation on the entire roof structure keeps all the components in the roof space at the same temperature. Therefore, there is reduced thermal bridging which prevents heat loss from the living room. Houses with warm roofs are less expensive to keep warm than those with cold roofs.

Secondly, there is no need for roof space ventilation. The ceiling space is as warm as the room below, so the dew point is outside the house.

Since condensation does not occur within the house, there is no need to worry about the accumulation of moisture. In turn, building materials like timber stay dry which enhances their longevity.

It’s easy and quick to set up a warm roof whether on a new or existing roof. Unlike installing a cold roof, demolition of the roof surface is not necessary.

The Distinction

Warm roofs and cold roofs can take different forms depending on the nature of the roof form. On flat roofs, the insulation layer of a warm roof is usually on the outer surface of the roof structure. The structural deck and the supporting structure are at a temperature close to the interior of the building.

A cold roof in a flat roofing scenario is the one whose thermal insulator is below or inside the structure of the roof. The temperature of the roof structure is almost the same as the outside.

The definition of a warm roof on pitched roofs relates to the space between the pitch of the roof and the ceiling. Here, a warm roof can be one whose insulation is in line with the rafters instead of above the roof. The space beneath the pitch is warm and insulated.

On the other hand, a cold roof would have the thermal insulator laid at the upper surface of the ceiling. The attic or loft space maintains a temperature close to that of the rest of the building.

If you have cold, unused space in your home, replacing your current roof with a warm roof can help.

Just contact us, and we’ll be happy to work with you.

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