How Does an Oast House Work: Explained in Simple Terms
Updated: Aug 2
The oast houses scattered across Kent and Sussex are beautiful pieces of vernacular architecture. However they were originally designed as highly efficient agricultural machines.
Before modern factories existed local farmers needed a fast and reliable way to dry massive amounts of fresh hops for the brewing industry. To do this they built the oast house. It is essentially a giant and incredibly clever drying oven.
Here is exactly how the traditional hop kilning process worked.
1. Preparing the Hops
The hop growing season runs from late spring to early September. Once the hops were ready they were picked by hand and brought immediately to the oast house.
The Drying Floor: Inside the main roundel of the building there was a special slatted wooden floor.
Spreading the Load: The fresh hops were spread out evenly across these wooden slats in a thick layer.
2. The Heating Process
To dry the hops without burning them the farmers needed a steady and controlled flow of heat.
The Furnace: At the very bottom of the oast house on the ground floor a large furnace was lit. Historically this was fuelled by wood or charcoal.
Rising Heat: Because hot air naturally rises the heat would float up from the ground floor and pass directly through the slatted wooden ceiling where the hops were resting.
Removing the Moisture: As the hot air passed through the green hops it gently removed all the moisture. This process could take up to 24 hours to complete perfectly.
3. The Magic of the Oast Cowl
This is where the iconic wooden cowl at the very top of the roof comes into play. It was the most important piece of engineering on the entire building.
Catching the Wind: The weather vane on top forced the cowl to constantly rotate so its back was always facing the wind.
Creating a Vacuum: As the wind blew past the opening it created a powerful draught. This essentially acted like a giant vacuum cleaner.
Pulling the Air: This vacuum actively sucked the hot humid air up from the furnace, through the hops, and out into the sky. Without the rotating cowl the hops would just go soggy!
4. Cooling and Brewing
Once the hops were perfectly dry they were moved to a cooling floor above the kiln. After they had cooled down they were packed tightly into large jute sacks called bushels and sent straight to the local breweries to flavour the beer.
Preserving the Mechanics of History
Today the vast majority of oast houses have been converted into stunning residential homes. While they no longer dry hops the mechanics of the building still need to function. If the wooden cowl seizes up and stops turning in the wind it can cause severe structural damage and let rainwater flood into your home.
At G&S Oast Cowl Refurbishment we specialise in keeping the mechanics of these historic structures working perfectly.
Does the cowl on your historic property need expert maintenance or structural repairs? Contact Glynn and Scott today for a free site visit and professional quotation!
