Thermal displacement

Heat protection in summer

Climate of perfect wellness even at extreme temperatures

As pleasant as summer can be, it's hard to feel at home in rooms with tropical temperatures. FiberTherm wood fiber insulating materials ensure that, even during extremely hot days, inside your four walls remains a pleasant cool - without the expense of an air conditioning system.

Our climate is changing, there is no doubt about this. It is known that in recent decades "tropical days" with temperatures above 30°C have quadrupled. It is therefore no wonder that in the context of new buildings and renovations protection from the summer heat is becoming increasingly important. And on the other hand, who is ever willing to endure sauna temperatures throughout the home? With adequate facilities and careful selection of materials, however, it is possible to achieve a pleasant living climate even in the hottest season of the year - in a completely natural way.

An important point of approach is undoubtedly constituted by non-transparent construction elements, such as walls or roof surfaces. Here FiberTherm wood fiber insulation materials help to keep the heat out - even for attic rooms. This is because the lofts tend to heat up a lot in the summer. The reason is often not simply attributable to insufficient thermal insulation of the roof, but also to the reduced storage capacity of the structural element layers. Many structures can not offer sufficient resistance to the high thermal radiation of the summer sun. The heat can reach the living spaces without major obstacles.

The solution consists of constructive elements with a particularly high thermal mass, such as FiberTherm wood fiber insulation materials. In the afternoon hours they absorb the heat and "dab it" up to the cooler evening hours. When finally the accumulated heat is released, it no longer weighs on the living area, but can be diverted to the outside by airing the premises.

The combination of an intelligent structure and FiberTherm wood fiber materials with heat storage allows to bring temperatures back to a level that guarantees well-being even in the attic.

Material      Apparent specif.
a cm²/h
Spruce, pine 600 0,13 2500 3
FTH Universal 270 0,048 2100 3
FTH Protect 110 to 265 0,037 a 0,048 2100 3
FTH Special 240 0,046 2100 3
FTH Therm 160 0,039 2100 4
FTH Flex60 60 0,036 2100 15
BetonWood 1350 0,26 1880 22,6
Full bricks 1800 0,8 1000 16
Reinforced concrete 2200 1,4 1050 22
Foamed polystyrene 40 0,040 1380 26
Foamed polyurethane 30 0,030 1380 26
Glass wool 30 0,035 800 52
Steel construction 7800 58 600 446

Thermal diffusivity: heat protection

The choice of insulation material is decisive for optimizing construction.
The materials that ensure very slow heat transmission or that have the lowest possible thermal diffusivity value are suitable for summer heat protection. These are materials with good thermal insulation properties, but thanks to their low thermal conductivity they also combine a high storage capacity (high apparent specific weight and high specific heat storage capacity). Many heavy materials, e.g. steel, have poor insulating properties, as they have a high thermal conductivity. With heavy materials, which have a good insulation capacity, it is possible to reduce and significantly delay heat transfer, for example through the roof.

Fibertherm insulating materials in wood fiber have a particularly favorable ratio between thermal conductivity and the product of thermal storage capacity and apparent specific weight and therefore a low thermal diffusivity a.

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Amplitude attenuation and thermal displacement

The equivalent of the U value for insulation in winter, for the thermal protection from the summer heat, is represented by the attenuation of the amplitude and by the thermal displacement. While the amplitude attenuation shows how intensely it is possible to reduce heat transfer through the building component, the thermal displacement indicates how many hours the transition to maximum temperatures is delayed.

With amplitude attenuation the ratio of the external temperature fluctuation to the internal one is defined. If the outdoor temperature fluctuates between 10 and 40°C and the internal temperature is between 18 and 21°C, the external temperature fluctuation corresponds to 30K and the internal temperature fluctuates to 3K. The amplitude attenuation as a ratio of these two corresponds to 10 (= 30K / 3K). In other words: the thermal fluctuation is attenuated by one tenth (10%) in the external path inward through the constructive element. It is aimed at an attenuation of the minimum amplitude of 10.

The thermal displacement corresponds to the time period between the occurrence of the maximum temperature outside and the substitution of the maximum temperature inside. In the above example this corresponds to 12 hours, extending from 2.00pm to 2.00pm. One of the objectives of heat insulation is to delay the passage of heat through the roof or a wall so that in the room the maximum temperature of the day is reached only when the outside is already sufficiently cooled to prevent heating of the room simply with good ventilation.

Amplitude attenuation and thermal displacement Thermal displacement Roof structures compared

A thermal displacement of at least 10 hours should be aimed at. A part of the heat accumulated in the construction element is then again diverted outwards. Consequently on the internal front of the building the same temperature levels are not generated on the external side. Adjustment of temperature attenuation and thermal displacement is particularly important in the roof. In the roof the ratio of the external surface to the cubing is very unfavorable. This is because the attic rooms have a large heat transmission surface compared to the cubic size. In summer, high temperatures (up to 80°C) are generated under the roof covering, which in turn intensify the heating of the rooms below. Moreover, roof structures very often have very low thermal masses, so that they are particularly suitable for use with FiberTherm natural insulating materials.

With the exception of the roof covering and the paneling of the rooms, the thermal mass of the roof structure is generated exclusively by the insulating material. It follows the great importance of defining the amplitude attenuation and thermal displacement with an insulating material that has a low thermal diffusivity. The value must be 10 (10% TAV) for the amplitude attenuation and the thermal phase displacement of at least 10 hours. With an external temperature of 35°C under the roof covering, values of up to 80°C can occur. Through a good structuring of the constructive elements it should be ensured that with this thermal load it influences the climate of the internal rooms in the most damped and delayed way possible.

If, in the presence of these summer heat conditions, two roofs are compared with the same thermal transmittance of 0.18 W (m ²·K), the roof with a mineral fiber insulation belongs to the thermal conductivity group 035 with a specific weight of 20 kg/m³, an attenuation of the mathematical amplitude of 6 and a thermal displacement of 6.8 hours. On the side of the roof facing the premises it is calculated an increase in temperature of 29°C at 20. It is a temperature far too high for a restful sleep. At that time the outside temperature will still be at a similar level; consequently aeration will not lead to any sensitive relief. If you replace the mineral fiber-based insulation material with FiberTherm flex wood fiber insulation with the same thermal conductivity and a specific weight of 50kg/m³, the heat storage volume of the insulating layer will quintuple, thanks in part to the higher specific thermal mass of the insulating material. For the roof itself, the attenuation of the amplitude doubles to 12, while the thermal displacement improves by 4 hours, passing to 11 hours. Here the temperature curve to be expected appears completely different on the front of the premises: the temperature increases to a maximum of 21°C and reaches the inside of the roof only at 1 am. At this time the outside temperature is already so low that if these 21°C should be disturbed, they could be further reduced by ventilation of the premises.

Hypothesis of progress during the day

Hypothesis of progress during the day

With an external temperature of 35°C at 2 pm and 15°C at 2 am below the roof cover, a maximum temperature of around 80°C is generated, which at night can at best be reduced to 15°C.

Temperature trend as a function of the roof insulation change

Temperature trend as a function of the roof insulation change

With FiberTherm wood fiber insulating materials, extreme thermal peaks are prevented, creating an ideal temperature for the wellbeing of people both at night and during the day.

Heat protection for subsequent installation

What hopefully for new buildings is part of the state of the art, in old buildings can only rarely be found: a protection from functional heat. However, also for this BetonWood offers an ideal renovation system.

Rehabilitation of roof from the outside
Rehabilitation of roof from the outside

The ideal renovation variant, if the attic has already been made habitable and you do not intend to compromise the environment inside.

Once the old roof is removed, the gaps in the beams are insulated with a flexible insulating material such as FiberTherm flex50 or FiberTherm flex60. To maximize the insulating effect, a FiberThermSpecial rehabilitation panel is also laid directly on the beams. The panel is hydrophobed (water repellent), so that with a simple intervention it is possible to obtain a triple functionality: second non-hydrophilic layer, windproof and insulating effect.

Example calculation:
with 160 mm FiberTherm flex50 and 60mm of FiberTherm special we have:
U=0,20 W/m²*K
Thermal displacement: 14,1 hours.

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Rehabilitation of roof from the intside
Rehabilitation of roof from the intside

In this rehabilitation variant, neither a scaffolding nor a renewal of the existing roofing is required.

Once the old internal lining (if present) is removed, the gaps of the beams are insulated with a flexible insulating material such as FiberTherm flex50 or FiberTherm flex60. To maximize the insulating effect, an additional insulation can be mounted using a transversely applied batten. Double advantage: This layer can be used as an installation plane, e.g. for laying electric cables for ceiling lights.

Example calculation:
with 160 mm FiberTherm flex50 complessive we have:
U=0,24 W/m²*K
Thermal displacement: 9,8 hours.

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Rehabilitation of walls
Rehabilitation of walls

Long-lasting restoration of the façade with many design advantages - and summer heat protection is also included.

The great advantage over traditional polystyrene facades: the superior thermal mass also actively acts against the proliferation of algae on the facade. The facade cools slowly at night, so that the humidity of the air can not settle on the surface in the form of dew. In this way, any growth substrate is less algae. For wood or clinker facades, vice versa, FiberTherm universal or FiberTherm special are proposed in combination with the flexible insulation such as FiberTherm flex50 or FiberTherm flex60.

Example calculation:
with 100 mm FiberTherm flex50 and 60mm of FiberTherm special we have:
U=0,24 W/m²*K
Thermal displacement: 22 hours.

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