Vault insulation
The restoration of heritage buildings is often overlooked. However, thermally insulating churches and other historical buildings is essential for energy savings, increased comfort, and protecting the structure itself from deterioration.
The importance of this increases when such buildings are repurposed and used more intensively.
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Download (Dutch version)
What does our 'Vault insulation' solution consist of?
1st Layer: Airtight and vapor Barrier
For thermal insulation to perform as expected, airtightness is crucial. Due to the chimney effect (warm air rises), a lot of energy will escape through air leaks. The higher the space, the stronger this effect becomes.
- A smoothed mortar layer on top of the masonry vaults or a crack-free plaster layer applied on lath or the underside of the masonry vaults can provide the necessary airtightness.
- Unplastered masonry vaults, even those one and a half bricks thick, are NOT airtight on their own. Gypsum boards can only form an airtight layer if there are no cracks or gaps—neither between the boards themselves nor between the boards and adjacent construction elements like walls or access hatches.
A practical method to make such structures airtight is to coat or spray them with pro clima AEROSANA VISCONN (FIBRE).This forms a strongly adhesive and highly elastic layer on the surface. AEROSANA VISCONN (FIBRE) is also a vapor retarder (with variable moisture permeability), although this is less relevant for vaults.
2nd Layer: iQ3-cellulose insulation
When insulating vaults, iQ3 cellulose-insulation is usually sprayed with a fine water mist.
To prevent dune-like shifting caused by wind blowing between the insulation and roof structure, it is important that the fibers at the surface of the cellulose layer are sufficiently bonded.
Products used
- iQ3 cellulose insulation
- AEROSANA VISCONN (FIBRE)
Airtight coating (fiber-reinforced)
Benefits of vault insulation with iQ3
- Cellulose insulation easily conforms to the shape of the surface to be insulated, even if it is three-dimensionally curved, uneven, or has electrical wiring.
- Even at the sides, where the cellulose comes into contact with exterior walls, partition walls, and other adjoining construction elements, as well as within the material itself, there are no gaps or cracks. The material fits seamlessly.
- When insulating vaults, another benefit is that the cellulose maintains continuous contact with the substrate due to the strong fiber bonding with the added water. It won't sag or shift over time.
Protection against water infiltration
While it is assumed that the existing roof structure (roof covering and possibly under-roof) provides sufficient protection against infiltration, any minor water intrusion can be easily absorbed and temporarily stored by the cellulose insulation. This reduces stress on the underlying structure and minimizes the risk of damage or aesthetic degradation.
Protection of masonry vaults from cracking
Churches were rarely heated in the past, so brick vaults were not originally intended to endure large temperature differences between their upper and lower sides. When repurposed, these buildings are often more intensively heated, warming the vault over its full thickness and surface. To avoid localized thermal stress and potential cracking, it is advisable to have a continuous, well-adhered insulation layer that remains intact over time.
Protection of wood in vaults from rodents and fungi
When wood is enclosed in insulation, visual inspection is no longer possible. It is therefore important to create a safe system that naturally protects the wood from degradation.
- iQ3 cellulose protects the wood from insect damage: thanks to the tight fit, insects cannot easily reach the wood. Insects already present in the wood will be unable to exit through the cellulose at the end of their life cycle and thus cannot reproduce.
- Fungal damage is also limited: any unwanted moisture in the structure is largely buffered by the cellulose, and due to the extremely vapor-open construction outward, drying remains perfectly possible.
Protection of interior finishes
Due to the highly hygroscopic nature of cellulose and its strong bond with the substrate, occasional moisture in plaster or gypsum board will be quickly absorbed and dispersed.
- The installation is very quick. Even with complex shapes, nothing needs to be cut to size—no cutting waste or sawdust.
- The binding agent used in spraying is water—the cheapest option.
- iQ3 cellulose insulation is transported in a highly compressed form, reducing transport costs. At the construction site, there's no need to carry insulation upwards: the iQ3 bags are emptied into a machine, usually set up on the contractor’s truck.
- Recycled newspaper makes up 90% of the raw materials used.
- Compared to other insulation materials, the production of cellulose flakes requires very little energy.
- iQ3 cellulose has a full B-EPD (Belgian Environmental Product Declaration), showing that its overall environmental cost is very low compared to other insulation materials.
We have documented this effective vault insulation solution in a comprehensive document (available in Dutch and French), including installation guidelines, project examples, and more background information. Download the complete “Vault Insulation” solution below (Dutch version).
Still have questions? Don’t hesitate to contact our free technical helpdesk. We’re happy to share our expertise and knowledge.
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