PIR and fibrous insulation in industrial buildings: choosing by zone

Rigid boards may suit repeated roof bays, while a fibrous fill may suit enclosed cavities in the framed section. Each zone needs a section drawing and acceptance criteria before a substitution can be assessed. Listing these tasks separately allows the project to use more than one installation method where appropriate.

An office beside sunlit glazing and a workstation beside a hot machine gain heat from different sources. For each room, record the hours of sun exposure, equipment operation and ventilation. Use those schedules when comparing how a change in roof insulation affects summer temperatures.

Insulation reduces heat exchange through the envelope. Heat generated by machinery and people still needs a way out. Door opening and ventilation during production can materially affect the hall’s summer heat balance. The heat capacity of the layers influences how fast conditions change, but storage is finite. Include periods when night-time cooling is unavailable.

If raising the roof would mean rebuilding a dozen rooflight upstands, measure the clearance at the lowest one first. Calculate the resistance of the proposed PIR board at the thickness that fits. This checks whether it can deliver the specified thermal resistance beneath the existing flashing.

A fibrous product may fit the shape of framed cavities more readily. On a large refurbishment a small increase in roof height can affect many identical flashings, making thinner PIR a practical choice. In a prefabricated frame the time needed to fill prepared cavities can matter more. Estimate labour for each geometry separately. A price per square metre of insulation alone will conceal the difference.

On a section through the timber frame, mark the sheathing, faced PIR board and fibre-filled cavity. Trace how moisture might reach the timber during construction and which way the timber could dry once the wall is closed.

An office wall detail may be unsuitable for a humid process room. Partitions between zones experience different conditions from outside walls. Temperatures and humidity on both sides influence vapour flow and drying. Allow for periodic washdown or intensive use when selecting the PIR facing and fibrous layer. A hall-wide specification can overlook these local conditions.

For the wall between the hall and offices, assemble two sets of evidence. The fire documentation should identify the specified product and the required layer arrangement. To assess protection against production noise, obtain data for sound transmission through the wall and along flanking paths at its junctions.

Thermal performance of an individual layer does not establish acoustic or fire performance. Distinguish product properties from the classification of the complete element, especially where it protects the structure or separates zones. Acoustic data should cover the installed assembly and its junctions. Check evidence for the actual combination of materials before specifying it.

Ask installers to price two defined sections: an open roof slope over the hall and a row of cavities above the staff rooms. Give the dimensions, required thermal resistance and access conditions for each. The installation price can then account for preparing the cavities or moving boards up to roof level.

Crew availability and the sequence in which the enclosure is closed affect cost. The blow-in crew needs cavities with their boundaries in place. Board installers need an accessible work area and the correct board sizes. Match these prerequisites to the construction programme. A higher unit price may still reduce downtime, but the benefit depends on the actual sequence of trades.

One square metre of insulation 80 mm thick has a volume of 0.08 m³. At an assumed density of 160 kg/m³ it weighs 12.8 kg. With a specific heat capacity of 2,100 J/(kg·K), a one-kelvin change throughout the layer corresponds to about 26.9 kJ per square metre, or about 806 kJ across 30 m². This compares heat storage for layers of known construction. Predicting office temperatures during a shift also requires a heat balance for the entire room.