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165mm Celotex XR4165 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 12
165mm XR4165 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
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165mm Insulation Board XR4000
A 165mm insulation board is designed to reduce heat loss. You will often find this thickness in new builds, large extensions, and upgrade work. It helps improve energy efficiency and support compliance with UK Building Regulations Part L, depending on the full build-up and calculation.
What is a 165mm thick insulation board?
The 165mm thick insulation board is made using high-performance insulating materials, commonly PIR or phenolic foam. The material traps low-conductivity gases within its closed-cell structure, which restricts free heat movement. Thermal resistance increases because heat must travel through a greater thickness of low-conductivity material.
The panel itself is factory-produced to a consistent depth of 165mm. That accuracy matters on site because uneven thickness can lead to a poor fit and reduce thermal performance, even where the calculated U-values appear compliant.
What is the thick 165mm insulation board used for?
A 165mm insulation thickness board is used where space allows and thermal targets are demanding. Final installation depends on structural constraints and detailing requirements:
- Floors – Used above concrete slabs or between joists where depth is available. On ground floors, this thickness significantly reduces heat loss into the ground and helps limit edge heat loss when perimeter detailing is correct.
- Pitched roofs (ceilings and rafters) – Often fitted between and below rafters. This depth may help achieve target roof U-values within some build-ups. Ventilation gaps and correct vapour control remain critical at this thickness.
- Walls – May be used in wide-cavity wall systems where the full wall design allows.. It’s also used internally where external insulation is not possible.
- Framing walls – In timber or metal stud walls, boards can be fixed internally over studs or combined with between-stud insulation to control both heat loss and condensation risk.
- Internal masonry walls – Used as insulated dry lining where solid walls need upgrading. The thickness delivers good thermal improvement but requires careful detailing around reveals and services.
At Insulation Wholesale, you can purchase 165mm Insulation Board at low wholesale prices with fast delivery for most of items within 2-5 days. Competitive rates guaranteed.
FAQ
Where to buy 165mm insulation board?
You can buy your 165mm insulation boards online from Insulation Wholesale. We offer trade discounts, pallet deals, a streamlined quote process, and nationwide delivery straight to your site.
How to cut 165mm thick insulation panels cleanly?
Use a fine-tooth handsaw or insulation saw for straight cuts. A long straightedge or guide rail may be required to guide your cuts. For accuracy, mark both faces and cut in stages instead of forcing the blade through in one go. On deep boards like this, cutting too quickly can result in rear-edge tearing, which creates gaps when fitted.
How to fix 165mm insulation board?
Fixing depends on the location.
- Floor build-ups vary by system. Mechanical fixings can be used in suspended floors, depending on the product.
- Walls and ceilings require mechanical fixings sized for the thickness. These are often combined with a suitable adhesive.
Always follow the board manufacturer’s fixing specification because under-fixing can cause bowing or movement over time.
What are the advantages of 165mm rigid insulation boards?
The main advantage is thermal performance without complex build-ups. Fewer layers mean fewer interfaces where mistakes happen. Rigid 165mm insulating boards also:
- Hold their shape over time
- Resist moisture uptake when the appropriate board type is selected
- Deliver predictable results when installed properly
What is the thermal conductivity of 165mm insulation?
Thermal conductivity (λ) is a material property and does not change with thickness; increased thickness improves overall thermal resistance (R-value).
Most PIR boards are around 0.022 W/m·K, while phenolic boards can be lower. The benefit of 165mm thickness is that this low conductivity is maintained over a greater distance, resulting in much lower heat loss overall.
