Understanding the Difference Between Warm and Cold Roof Insulation

There are two main types of insulated roof systems in building construction, warm roofs, and cold roofs. Do you want to know which is better: a warm roof or a cold flat roof? Let's understand the similarities and differences between warm and cold roof insulation.

Warm roof vs Cold roof

Understand Similarities and Differences Between Warm and Cold Roof Insulation

When it comes to insulating a flat roof, there are two options - Warm Roof vs Cold Roof. If you're considering which is the best type of roof insulation for your flat roof and are unsure of the difference between these two options, keep reading.

In this article, we’ll look at the similarities and differences between Warm and Cold Roof insulation and their advantages and disadvantages.

What is a Cold Roof?

A cold roof is when insulation is laid in-between the ceiling joists and the space between the insulation and the roof deck remains empty. This results in the living space below the insulation staying warmer than the space above it (i.e. the roof.)

Advantages of a Cold Roof

One of the major advantages of a Cold Roof is that it utilises existing space between the rafters that already exists and would otherwise be wasted. It can also be a simple way to add insulation to your home without the creation of additional space or building height.

A Cold Roof can also have an advantage if you live in a country that experiences cold winters with low temperatures and high levels of snowfall. As a Cold Roof will maintain the external temperature, it prevents snow from melting and so reduces the risk of ice dams and leaks.

Disadvantages of a Cold Roof

Unfortunately, Cold Roof insulation does have disadvantages too. Though the ceiling has an insulation cover, the rafts themselves are left exposed, and as adequate space is needed to encourage airflow and prevent condensation, this means a lot of unoccupied space above the insulation.

The air in this space can become very cold when outdoor temperatures are low, which means that the building itself will lose heat. This will require additional heating to compensate and can reduce your home’s energy efficiency and lead to increased energy bills.

Furthermore, the construction of a Cold Roof can in itself present a challenge and be both costly and time-consuming.

What is a Warm Roof?

A Warm Roof, as its name suggests, is a form of roof insulation designed to keep the entire roof structure warm. In this case, insulation is laid on top of the actual roof deck itself. The insulation is sandwiched between a vapour control layer (to prevent condensation) and the external roof covering.

Advantages of a Warm Roof

There are several advantages of Warm Roof insulation. The first is that, unlike Cold Roof insulation, it acts to keep the entire property warm, improving the energy efficiency of your home and reducing the overall costs of heating your home. This makes it a cost-effective option that is better for the environment.

A Warm Roof also removes the need for adequate ventilation to prevent the accumulation of moisture from condensation. This keeps your home drier and protects building materials in your home, such as roof timbers, for example.

Additionally, a Warm Roof is typically easier to install than a Cold Roof and doesn’t require the demolition of your existing flat roof.

Disadvantages of a Warm Roof

The main disadvantage of a Warm Roof is that it increases the building height of your flat roof, as the insulation is added on top of your existing roof structure. It also requires that your roof decking is in good condition, to enable the insulation to be retrofitted. If your roof is in poor condition or in need of extensive repairs, it may not be possible to fit Warm Roof insulation until these are carried out.

Which is best?

In summary, when it comes to deciding between Warm and Cold Roof insulation, you need to consider the advantages and disadvantages of both as well as the particulars of the building itself. A Warm Roof can help keep your energy costs lower but if you experience harsh winters, a Cold Roof has its advantages when it comes to protecting your home from heavy snowfall and the dangers of ice.