The Insulation Atlas helps you find the right insulation method and material for your building. To ensure you can interpret the information correctly, you should be familiar with a few basics.
Key technical terms
| Term | Meaning |
|---|---|
| Lambda value (λ) | The thermal conductivity of a material. The lower the value, the better the material insulates. Typical values for good insulation materials: 0.032 to 0.045 W/(m·K). Please note: the design value for thermal conductivity applies! The nominal value (which is lower and is prominently advertised by many manufacturers) must not be used by energy advisers or architects for U-value calculations – and therefore must not be used for subsidy applications either! A formula for comparing the insulating properties of different insulation materials or converting between them: Insulation thickness (old) : thermal conductivity (old) x thermal conductivity (new) = insulation thickness (new). Example: 12 cm : 0.040 (W/mK) x 0.023 (W/mK) = 6.9 cm. Or: the insulating performance of a 6.9 cm thick polyurethane board (aluminium-faced) is the same as that of a 12 cm thick softwood fibreboard. |
| WLS / WLG | Thermal conductivity class or group: the lambda value in abbreviated form (e.g. WLS 035 = λ 0.035). Commonly used as a quality specification on packaging and data sheets. |
| U-value | Thermal transmittance coefficient of an entire building component (wall, roof, window). The lower the value, the less heat is lost. The U-value is the reciprocal of the sum of the R-values (of the individual insulation layers) plus the internal and external thermal resistance. |
| R-value | Thermal resistance of a single layer: thickness divided by the lambda value. The higher the value, the better the layer insulates. |
| Insulation thickness | The actual thickness of the insulation layer — together with the lambda value, it determines the U-value. |
| Blown-in insulation | Loose-fill insulation material (e.g. cellulose, mineral wool granules, polystyrene beads, SLS20, in-situ foams, etc.), which is blown into cavities — often the simplest and therefore most cost-effective retrofit option. For this reason, it is highlighted here. Of course, it is also possible, for example, to insulate upper floor slabs with all kinds of board insulation – but this comes at a much higher cost. |
| Forms of insulation | Insulation materials are available in panels, mats, loose-fill and blow-in granules. Blow-in and mat insulation materials adapt to uneven structural elements – panel insulation materials do not. For this reason, we do not recommend installing any type of board insulation, for example, in sloping roofs or timber-frame buildings. |
| Seamless installation | The following applies to all insulation scenarios: joint-free installation! ‘Ventilated’ insulation is more or less ineffective! (For internal insulation, joint-free installation is absolutely essential, as otherwise there is a risk of condensation and, consequently, mould problems |
| The environmental impact of insulation materials | ALL insulation materials are environmentally friendly! This is because they help to: 2. to lower heating costs 3. and to reduce energy dependence on problematic countries. The energy used in the manufacture of almost all insulation materials pays for itself in less than a year (in some cases in just a few days). And they remain effective for a further 50 years |
Good to know: Insulation can also be applied flexibly
- It is possible to insulate individual sections. If only two out of four walls can be insulated, it’s still worth doing — every insulated area reduces heat loss.
- Different insulation thicknesses and grades are permitted. You don’t have to use the same thickness or the same material everywhere — for example, where space is limited.
- Insulation materials can be combined. If, for example, there is already old insulation on the top floor ceiling, it can be left in place and simply doubled up with new insulation.
- It doesn’t have to be an ‘all or nothing’ approach. Carrying out partial renovations in stages often makes sense — the important thing is to plan the order sensibly.
- Insulate as thickly (and effectively) as possible. Either – if space is limited – use very high-quality insulation materials with low lambda values, or - if there is plenty of space available, e.g. in the top floor slab – use cost-effective (blown-in) insulation materials such as cellulose or glass wool to a thickness of 40 cm (or more)
- Insulate only the heated envelope! If the loft space under the roof is unoccupied – i.e. unheated – there is no point in insulating the sloping roof surfaces right up to the ridge.
- Identify any air gaps and have them insulated. For example, external insulation (composite thermal insulation system) on (ventilated) double-skin masonry is severely limited in its insulating effect due to rear ventilation effects.
Please note: The Insulation Atlas is no substitute for individual expert advice on site. For definitive advice regarding your building, we recommend an independent energy assessment.