PIR or EPS for the roof of a pavilion used all year round?

Record the sources of moisture. Wet items, washing and processes carried out indoors can increase its amount. A panel should not be selected on the basis of air temperature alone. An assessment of the tightness of the joints and the possibility of removing vapour from the room is also needed.

If the function of the building is to change, take this into account before purchase. Moving more humid work into the pavilion may require different ventilation and linings. Changing the heating appliance alone does not confirm the suitability of the entire existing roof.

In an example PIR roof panel with a 100/140 mm section, the U-value is 0.20 W/(m²·K). The section notation takes the profile height into account. In the selected EPS panel family, a thickness of 200 mm has a Uc of 0.19 W/(m²·K). This is a comparison of two specific variants with a similar thermal result.

For the same EPS family, the 100 mm variant has a Uc of 0.37 W/(m²·K). The price of two 100 mm panels should therefore not be compared as if they provided equal insulation. First establish the project objective, then select the thicknesses that correspond to it.

A simple auxiliary calculation can be made. For an area of 42 m² and a temperature difference of 25 K, a coefficient of 0.20 gives a heat flow of 210 W, and 0.19 gives approximately 199.5 W. This is not the demand of the entire pavilion. The calculation omits, among other things, joints, ventilation and door opening.

The mass depends on the core, profile and facings. In the PIR 100/140 mm variant under consideration with 0.5 and 0.4 mm steel sheets, it is 12.4 kg/m². An example EPS panel of 200 mm has a mass of 11.5 kg/m² in the configuration specified for it. Thickness alone therefore does not determine weight.

This does not mean that both panels have equal load-bearing capacity. The mechanical parameters must be read separately from the data for the relevant section. The support spacing and the structural scheme are important. A lighter element is not automatically approved for a larger span.

Also check the transport dimensions and details. A thicker panel may require different flashings and fixings. In a small building, the space at the eaves and above openings is particularly important. The whole assembly should be installable without accidental compression or shortening of the required terminations.

The cladding is in direct contact with the operating conditions. With regular cleaning, the approved agents, concentrations and application method must be known. The choice of core does not ensure resistance to every substance. The coating and the way the edges are finished are separate issues.

Moisture can reach the joint through a leak. Therefore, the perimeters of openings and service penetrations require proper detailing. Water should not remain in places without a drainage path. A well-chosen panel needs equally well-executed connections.

Check the fire requirements for the entire roof. Reaction to fire, fire resistance and external fire performance are not a single assessment. The same properties must not be attributed to both cores without documentation. The selection must meet all requirements, not only the thermal objective.

Compile variants that meet the same operational objective. For each, count the panels, fixings and flashings. Add the effect of thickness on openings and installation cost. The difference in core price is not automatically the difference in the cost of the finished roof.

Check the required quantity of material and the delivery conditions. A different cover width may change the number of runs. Also do not assume that every variant is available in a small batch. The lead time and feasibility of the order must be confirmed for the specific specification.

Finally, compare the maintenance plan and the scope of future changes. If the pavilion is to operate all year round, the decision should take into account the actual moisture, temperature and cleaning frequency. Price is important, but it refers to a solution that is to meet these conditions over the service life.