Wind Mill - Waterproofing and Thermal Insulation

Here is an 18 metre tall 200 year-old Grade 2 listed wind mill, not very far from the sea. Wind driven rain created major problems, resulting in ongoing water leaks. The wind mill waterproofing and thermal insulation has been resolved with lime plasters - using only breathable, sympathetic, heritage-friendly materials.

The building being situated close to the sea in a very exposed environment, wind driven rain and high salinity were the primary challenge. High speed winds were able to push the rainwater through the lime mortar bed, resulting in significant water ingress throughout the building.

Throughout the years several attempts have been made to resolve the problem of persistent water ingress and to make the building watertight. Rendering the fabric with a modern cement render was also attempted, but that did not resolve the problem long-term.

The present owners went a long way to gradually restore the breathability of the building by removing the cement render and some of the previously added modern materials. Various lime based solutions have also been attempted but they did not last very long.

The problem of water ingress has been finally resolved with with the Rinzaffo MGN Roman waterproofing lime plaster. The volcanic sands and ashes mixed into the lime result in a special lime plaster that once set it becomes waterproof while allowing the wall fabric to breathe. The technical page of the product explains the concept in more details.

We also encountered some challenges during the waterproofing of such a large, exposed building.

• Sustained wind-driven rain: a full week of sustained wind-driven rain during the beginning of the waterproofing phase caused ongoing water leaks, the rainwater washing out the waterproofing plaster before it could set. To stop the water leaks, we used natural cement (also known as Parker's cement). This heritage-friendly material invented in the 19^th century, burnt of limestone with a high clay content with no artificial or synthetic additives, sets in a matter of minutes, being excellent as an instant waterproofing material. Plugging in some cracks and holes with natural cement allowed the continuation of plastering work during the rainy period.   
• Inaccessible areas: some wall areas behind and under the joists were either completely inaccessible or very hard to reach, making very difficult the application of lime waterproofing material. Cutting back some of the joist ends mostly took care of this problem. 

Being a tall, slender building with external walls only, subject to rain, wind and sea spray, addressing the thermal comfort of the building was an important point for the owners. Combination of two thermal plasters have been selected for the building:

1. Coccioterm MGN : a Cocciopesto-based (lime and brick dust) thermal plaster. These type of plasters have been known since antiquity for their excellent moisture regulating and anti-condensation properties. As a result, these plasters have been commonly used in very humid environments such as basements and Roman baths.   
2. Termorasante Aerogel MGN: a super-insulating lime-aerogel plaster with outstanding thermal performance and high breathability. Due to its excellent thermal properties it allows the creation of high performance slim insulations. Due to its excellent heat-reflective properties, it reflects the heat back into the room, resulting in very high thermal comfort.

Here is a wall section before and after the application of the first thermal plaster.

The wind mill had a cement slab floor. To make sure that the floor is without any cracks and thus stays dry under all circumstances, a 20 mm Rinzaffo MGN Roman waterproofing lime coat has been applied on top of the old cement floor, to serve as a lime floor base onto which any floor configuration and finishing can be built.  

Finally, please see below a photo gallery detailing the project.