Cold and thermally insulated roof hatches – what are the differences between them?

Cold and thermally insulated roof hatches – what are the differences and which one to choose?

At first glance, they may look identical, but the devil is in the construction details. The choice between a cold hatch and a thermally insulated one is not just a matter of price, but primarily depends on the building's purpose and the requirements set out in the Technical Conditions.

Here is a comparison of the most important differences to help you make the right decision.

1. Construction and materials

The difference begins at the construction stage of the base and the dome itself:

• Cold hatches (uninsulated): These have bases made of sheet steel without additional insulation or with a thin layer of padding. Their filling is usually a single layer of polycarbonate or acrylic. They are lightweight and easy to install, but have a high heat transfer coefficient ($U$).
• Thermally insulated hatches (warm): Their bases are filled with a thick layer of mineral wool or polyurethane foam (PUR). The dome consists of several layers of multi-wall polycarbonate (e.g., 16 mm, 20 mm, or more), creating a barrier against escaping heat.

2. Where to use each type of hatch?

This is the most important point when making a decision. The choice must be dictated by whether the building is heated:

• Cold hatches: Ideal for unheated buildings, sheds, detached garages, "cold" warehouses, and non-habitable attics. Where the indoor temperature is close to the outdoor temperature, thermal insulation is not required.
• Thermally insulated hatches: Mandatory in production halls, temperature-controlled warehouses, office buildings, and residential buildings. Using a "cold" hatch in a heated hall is a direct path to massive energy losses and moisture problems.

3. Condensation (water vapor)

Using a cold hatch in a heated room carries the risk of the so-called dew point.

• In cold hatches (in heated halls), water vapor will condense on the inner surface of the metal base or dome. This can lead to the dampening of roof insulation, and even to structural corrosion or water damage to goods stored under the hatch.
• Thermally insulated hatches eliminate this risk by maintaining the appropriate temperature on the profile surface.

4. Economic aspect

Although a cold hatch is cheaper to purchase, it may turn out to be more expensive in the long run for heated buildings.

• Wirmet thermally insulated hatches feature a low $U$ coefficient, allowing them to meet current standards (e.g., WT 2021). As a result, the investment pays off in the form of lower heating bills for the hall.

Summary: What to choose?

The rule is simple: if the project involves heating the facility, the only correct choice is a thermally insulated hatch. Leave cold hatches for unheated infrastructure, where the primary function is roof access rather than protection against the cold.

Are you looking for a hatch that meets energy efficiency requirements for your hall?

Check the technical parameters of our products at wirmet.eu or ask about a version with additional base insulation.