The 4-Seasons air inlet is robust, simple and reliable and serving Tulderhof already for more than 20 years.

The frame is constructed out of the highest quality plywood. The valve has a fixed hinge point and is very well insulated with 15 mm insulation foam. This foam also ensures a proper closing at the edges. Therfore the 4-Seasons air inlet is absolutely draught free.

The air flow is as following: when the valve opens, the air can only pass above. This way it steers quite straight into the house. After 10 to 15% the valve opens underneath as well. The air is then deflected downwards, creating a nice rolling effect.