What is the best way to thermally improve our farm buildings, to maintain the best growing and breeding conditions while making significant savings on heating?
"Agricultural buildings" is a blanket term for facilities used for the production and storage of agricultural produce, and a commonplace feature of the countryside today, still used for traditional tasks, but now featuring the latest thermal insulation.
Farmers are becoming increasingly interested in construction materials that boast superior thermal insulating performance, which last decades and require no tedious maintenance, rework or refurbishment.
Modern thermal insulating solutions include sandwich panels with thermal insulation cores made from a selection of materials (including mineral wool, EPS, and PUR foam), state-of-the-art Thermano panels with the core made from modified polyurethane with a gas-tight and durable cladding, and another version dedicated specifically for agriculture and made from PIR (rigid polyisocyanurate): Thermano Agro panels.
Thermano Agro, the solution for thermal insulation of agricultural buildings
Storage rooms, freezers and cold stores are all essential environments for sandwich panels, used to create thermal insulation layers, with PUR-core sandwich panels taking an increasing segment of the market.
These are most often chosen for an essential and very unique performance parameter, one which leaves competitive materials far behind. This is the best-in-class thermal insulation performance: both PIR and PUR foam share one of the lowest thermal conductivity coefficient values for existing thermal insulators λPIR/PUR≈ 0.023 W/(m²·K).
This implies that thermal insulation based on these materials can be used to make construction partitions for walls, roofs and floors, which are thinner than was possible before. In comparison to polyurethane, the average value of thermal conductivity coefficient of typical, commercially available thermal insulators is approximately λwm≈ 0.040 W/(m²·K), for mineral wool and λEPS≈ 0.032 W/(m²·K) for expanded polystyrene.
IACSC (International Association for Cold Storage Construction), a renowned global organisation of cold storage design engineers, specifies the essential criterion for effective thermal insulation thickness selection in the work “Design, Construction, Specification and Fire Management…”..
This is based on years of practical observations and dedicated testing. What it states is that the minimum thickness of a thermal insulating layer for a building must be estimated at the value at which the heat flux transported through the building's partition does not exceed 10 W/m2. This means that the condition expressed by the following simple relation must be met:
Φ = (Te - Ti) · U < 10 W/m2
Φ – heat flux transmitted through the partition;
Te – outdoor temperature (outside the partition);
Ti – indoor temperature (under the partition);
U – heat transfer coefficient of a sandwich panel with thickness d [m] and heat transfer coefficient λ[W/(m²·K)].
In a different notation:
dmin> (Te - Ti) · λ/10
The estimates derived from the above suggest that the designed insulating rate of a partition can be achieved with sandwich panels using different core materials, if the inversely proportional ratio of sandwich panel thickness to the heat transfer coefficient values of the sandwich panels is met, as in"
λwm /λPIR/PUR= 0.040 /0.023 = 1.74
This means that an energy equivalent partition layer made from mineral wool must be nearly twice as thick (≈ 1.74) as a Thermano layer for the same type of partition.
This is the prime argument for choosing polyurethane as our thermal insulating material. However, there is also another, one which is considered by wise design engineers.
This uses a closed-cell/pore foam structure, which is the most resistant to all types of moisture ingress. The latter often occur at the discontinuities in the thermal insulation layer, including the panel joint locks, interfaces with the ceiling and walls, etc. Moisture ingress is a common feature of agricultural buildings, more so than in typical structures in 'normal' temperature ranges, due to a number of extreme operating conditions, such as low temperature or controlled atmospheric parameters.
There are two main sources of damage to thermal insulation materials in such locations: the highly volatile relative humidity (which often reach almost 100%) and the almost ever-present extreme chemical and biological aggression of the air inside livestock buildings.
Hallebrand, 1993, lists a massive 136 gas substances that may be present in locations involving animal rearing. The air in the ventilation system of the average livestock building features many of these gases, and for most part they are chemically aggressive to the point of being vitriolic.
The most significant of these are:
Ammonia NH3 (max. 14 mg/m3)
Nitrous oxide, N2O
Hydrogen sulphide, H2S (do 10 mg/m3)
Volatile fatty acid particles
Aggressive particulates and other airborne factors
Many of these chemicals are not neutral to EPS (expanded polystyrene), which heavily restricts the long-term application of the material.
The exposure of EPS to many organic chemicals results in premature loss of the elementary performance characteristics, especially mechanical strength, with a markedly accelerated weathering of the thermal insulation.
Mineral wool also fails to perform well in long-term agricultural applications. The fibres in the mineral wool are chemically resistant, unlike their organic binder compounds; however, when exposed to extremely high moisture, trouble ensues. Damp mineral wool is a thermal and biological nightmare.
Rooms in which animals are kept form a very complex ecological system, with an extremely unstable microclimatic. In the simplest descriptions, the thermal and humidity conditions of animal buildings are modelled using the classical thermal dimensioning method, where ventilation heat losses are calculated from the amount of steam or carbon dioxide emitted (as in the simplified thermal properties index method, or the WWT method developed by Wolski).
Without going into too much detail, it is sufficient to understand the basic assumptions of the WWT method. The conditions for water vapour condensation are determined in two variants, with the following inputs:
a stable indoor temperature of 8oC,
a stable indoor air humidity of 85%,
a variable outdoor air humidity between 50 and 100%.
a stable indoor temperature of 8oC,
a stable outdoor air humidity of 85%,
a variable outdoor air humidity between 50 and 100%.
The relative humidity of the air and the temperature on either side of the partition (the building shell) in the WWT model undergo extremely dynamic changes. This means that the heat transfer through the partitions is governed by transient conditions.
The variability of the conditions makes the probability of water condensation beneath a partition (or on its outer surface) very likely and hard to estimate. As the proverb says, “Here be dragons”.
Under these conditions, thermal insulating materials having a low diffusion resistance to water vapour give poor results. This means that the effectiveness of insulating solutions made from mineral wool or open-pore spray foam is limited under real-life conditions. Thermano Agro has none of these disqualifying properties.
Thermano Agro is a system of purpose-designed PIR (rigid polyisocyanurate) sandwich panels, each featuring reinforcement of the outer layers based on 50 µm aluminium foil, providing a marked improvement in both the mechanical strength and chemical resistance of the thermal insulation system in practice.
One side of every Thermano Agro panel features a chemically resistant decorative finish, based on a lacquer. This feature is important for the well-being of the animals kept in buildings insulated with the product: it can be cleaned easily with high-pressure washing equipment in order to maintain microbiological cleanliness.
Thermano Agro panels are soffit lining layers, intended for livestock buildings. Thermano Agro features the best insulating performance parameters of all commercial products (λ=0,023 [W/m·K]). This provides tangible cost savings and optimised temperature control within the livestock buildings.
The core density of Thermano Agro is just 30 kg/m3, on average. In comparison with rigid mineral wool, the mechanical load applied by the product is up to 5 times less, and when corresponding thickness values of both thermal insulation materials are considered at the same U-values, the load drops by a factor of 7 to 8.
The panels are quick and easy to install, even by direct bolting to the rafters or collar ties without PVC profiles, or in suspended ceiling systems on PVC profile gratings. Thermano Agro is a revolution, bringing state of the art, energy-efficient and healthy thermal insulation to farming, for the benefits that have been enjoyed elsewhere in Europe for many years.