Spray Foam Systems to Protect Your Harvest from Condensation & Temperature Fluctuation
Grain quality in storage depends on two variables above all others: moisture content and temperature. AHDB guidance recommends storing wheat at below 14% moisture content and below 15°C for up to 6 months. These targets exist because mould growth, mycotoxin development, and grain beetle activity all accelerate sharply when temperature or moisture rises above recommended levels.
An uninsulated grain store creates the worst possible conditions for maintaining these targets. The roof absorbs and releases heat rapidly as external temperatures change. During summer days, an uninsulated steel roof can reach 60°C and radiate heat into the grain bulk beneath. During the night, it cools rapidly to near outside air temperature. These diurnal swings drive moisture movement through the grain bulk by convection: warm air rises through the centre of the bulk, cools against the cold roof, and descends around the edges — depositing moisture as it cools.
This moisture migration creates a peripheral band of high-moisture grain around the edges and surface of the store. This grain spoils first, developing mould, mycotoxins and heating that can spread into the bulk. The financial consequence of even partial grain condemnation can easily exceed £50,000 for a 1,000-tonne store. The cost of properly insulating that store is a fraction of this amount.
Unlike livestock buildings — where condensation is obvious with visible drips — grain store condensation is often invisible until the damage is done. Moisture is transported through the grain bulk by convection currents, distributing high-moisture conditions throughout the peripheral grain rather than pooling in one obvious place.
The convection cycle works as follows. The grain bulk retains the temperature at which it was loaded — typically 12–14°C for UK harvest-condition wheat. As autumn and winter temperatures fall, the roof sheet cools to outside air temperature — perhaps 2–5°C on a cold night. Warm air from the grain surface rises to the roof, cools against the cold surface, descends around the periphery, and deposits moisture as it cools below dew point. Over weeks, this cycle creates increasingly moist conditions at the grain surface and edges.
Spray foam insulation breaks this cycle by eliminating the cold surface at the top of the convection loop. With the roof surface insulated, the temperature differential between grain surface and roof is drastically reduced — convection currents slow and stop. The grain bulk remains at stable temperature and maintains its moisture content through the storage season.
Mineral wool and fibreglass both shed loose fibres — completely unacceptable in a food storage environment. They also provide perfect nesting material for rodents and insects, harbour moisture when wet, and lose thermal performance when they absorb water.
Closed-cell spray foam (Nexseal LE) has none of these weaknesses. It sheds no fibres. Its closed-cell structure provides no accessible voids for rodents or insects. It is impermeable to moisture. Applied to the internal roof and upper walls, Nexseal LE raises the surface temperature above dew point and creates a continuous vapour barrier — permanently eliminating condensation-driven moisture migration.
Spray foam must be installed when the store is empty of grain. Once cured (24 hours after application), Nexseal LE is inert and does not off-gas. The store should be cleaned and aired before loading grain. Our completion pack includes material safety data sheets suitable for food storage documentation.
No obligation. Our surveyor visits your farm, assesses the building, and provides a fully itemised fixed-price quotation — usually within 48 hours.
Complete overview of spray foam insulation for all UK farm building types.
Learn moreSpray foam that bonds to every profile of corrugated metal, steel and iron roofing.
Learn moreThe permanent fix for dripping metal roofs — spray foam raises surface temperature above dew point.
Learn moreMaintain optimal temperatures, eliminate condensation and cut heating costs in poultry houses.
Learn moreImprove animal welfare, reduce pneumonia risk, and eliminate condensation in livestock buildings.
Learn moreHSA-compliant spray foam encapsulation of asbestos cement roofing sheets.
Learn moreTell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.
