PIR insulation
What makes a home energy efficient and how do you assess its environmental impact?
A home can use little energy in operation and still have significant environmental impacts from its materials, maintenance or replacement work. Reducing heat loss and choosing durable, repairable components helps address both questions. PIR can provide high thermal resistance in a thin layer when the design also accounts for moisture, ventilation and summer comfort. The energy used while a building is occupied depends on its envelope, its services and how people use it. A wider environmental assessment also includes manufacturing, transport, construction, refurbishment and what happens at the end of service life. Consider both perspectives when comparing designs.
In this article
How do energy efficiency and environmental impact differ?
Comparing houses requires more than insulation thickness. Floor area, shape, occupancy and the level of comfort expected all matter. A large building that performs well per square metre can consume more in total than a smaller one. Consider the efficiency of the design alongside its total size and actual use.
Why start with the building envelope?
A well-insulated, airtight envelope limits uncontrolled heat loss, making it easier to size the heating system. Pay close attention to roof-to-wall junctions, plinths and window reveals. Performance at the centre of a wall or roof tells only part of the story. The insulation and airtightness layers must also meet continuously at junctions.
This applies to retrofits too. Locate losses before selecting the work. Replacing a heating appliance leaves a leaking roof unresolved, while insulation alone cannot correct poor controls. Choose the scope and sequence for the building’s actual condition.
Where is a thin PIR layer particularly useful?
PIR is useful where high thermal resistance is needed and space is limited, for example above rafters, under a floor being refurbished or at a terrace junction. A 100 mm board with a thermal conductivity of 0.022 W/(m·K) gives a calculated resistance of about 4.55 m²·K/W. This value is for the insulation layer alone. The performance of the whole assembly also depends on the other layers and thermal bridges.
A smaller build-up can help a design, but other requirements also matter. For fire performance, check the classification of the complete assembly. Check loads for floors and the intended finish for walls. EPS, XPS and mineral wool also have appropriate uses. Select materials according to the properties the location actually needs.
How do airtightness and good indoor air work together?
Airtightness limits air leakage through the envelope. Ventilation supplies fresh air at a controlled rate. Coordinate the two, including after sealing an existing home. Cooking, bathing and drying laundry continue to release moisture. Size and detail the ventilation for the number of occupants and the use of each room.
In summer, sunlight through the windows and heat generated indoors affect comfort. Bedrooms can overheat despite low insulation conductivity. Solar shading, how and when the building is ventilated, and its thermal mass all matter. A prediction of a particular indoor temperature needs an assessment of the specific house.
How do you read an environmental product declaration?
An environmental product declaration provides data for a specific product and a specified scope. To compare products, check the reference unit, thickness and life-cycle stages covered. Insulations with different conductivities should be compared at a similar thermal resistance: the same volume may deliver different performance. A declaration alone does not establish which product has the lowest impact.
Consider durability and service access. A protected waterproofing membrane, an accessible outlet and well-made flashings can reduce later replacement work. Account for waste during installation as well. These decisions all affect the real environmental balance of the project.
What should you check when construction or renovation is complete?
At handover, inspect materials and junctions and check the settings of the building services. Keep records of the layers installed and their maintenance requirements. Monitor energy use alongside indoor temperature. For a fair comparison also allow for weather, energy prices and changes in how the home is used.
A well-designed home should have understandable controls, accessible filters and repairable components. Energy efficiency lasts when the construction is sound and occupants can use the systems easily. Assessing environmental performance also requires looking at the full period over which those systems and materials serve the building.