Warming of the pitched and flat roof: the choice of materials and different technologies for the installation of insulation

Roof insulation is a critical decision that affects how comfortable and energy-efficient your home can be. No matter if your roof is flat with a practical layout or pitched with noticeable slopes, choosing the appropriate materials and installation methods can make a big difference in your comfort level and heating costs.

Pitched roofs present special opportunities and challenges for insulation because of their traditional triangular shape. Materials like fiberglass, mineral wool, or spray foam can be used in the attic space or between rafters, depending on the climate and the design of your home. In addition to keeping heat in during the winter, proper installation also aids in controlling summertime temperatures.

Conversely, flat roofs are renowned for their effectiveness in modern architecture and urban environments. Specialized spray-applied products or rigid foam boards are frequently used for flat roof insulation. Selecting the appropriate vapor barrier and insulation thickness is crucial to avert heat loss and possible moisture problems.

Why should you warm the roof

The roof lets in one-third of the house’s heat loss. As a result, the main financial savings from high-quality roof insulation are for home heating.

Moisture forms as a result of inadequate subcutaneous space insulation and waterproofing. It pierces through to the roof frame’s supporting components, shortening their lifespan.

You can convert the attic into a complete house thanks to the pitched roof’s insulation.

Common materials for roof insulation

There are two categories into which all materials used for insulation fall:

  1. Cotton (or fibrous). This group includes basalt (stone) cotton wool, glass wool, slag. Products of this type have different characteristics of hardness, density, resistance to crushing and are produced in the form of rolls or plates. Cotton heaters are considered unloaded materials.
  2. Foamy. These materials are produced from foamed polymers and are produced only in the form of plates. Have high stiffness and belong to loaded materials.

Features of cotton materials

Cotton heaters can transfer moisture vapors, but they shouldn’t get wet in the process. The fibers of the material are coated with a hydrophobisator to prevent water condensation from remaining in the thickness of the material. Because of this, moisture escapes or is removed by air streams rather than being absorbed by fibers.

Mineral wool

Mineral wool is thought to be the ideal material for warming roofs with wooden rafters because of its vapor permit capacity, which promotes the natural exchange of moisture between wood and air.

However, there is a drawback to being able to pass moisture vapors: in order to protect the insulation from the roof side, you need to use a waterproofing film, and in order to prevent warm, moist air from residential premises, you need to use a vapor barrier film.

The waterproofing film will get accumulated with condensation. Should it be situated in close proximity to a cotton heat-insulator, moisture will seep through its thickness. This will cause the insulation to get wet and start to grow mold. As a result, a 2-3 cm space must be left on each side when employing traditional vapor-permeable films between the insulation and the waterproofing film. We refer to this area as a ventilation gap. Natural air circulation will eliminate moisture from the waterproofing membrane’s surface following condensation.

A superdiffusion membrane can be used for waterproofing in place of traditional films. Installing insulation will be made easier with this material since it eliminates the need for ventilation clearance. By using such a film, you can save space and ensure that the insulation fills the cells all the way up to the rafter beam’s height.

Basalt insulation

Mineral wool frequently refers to the insulation made of basalt. However, basalt wool has a higher level of heat protection and is virtually immune to mold and fungi because of the unique location of the fibers. This dense material is resistant to burning, compacting, and merging over time.

Most frequently, basalt cotton wool is mounted in the rafter structure’s cells to insulate pitched roofs. The potential for a complete cell filling without cracks or cold bridges is the benefit of all cotton materials when using this laying technique.

Glass wool

Comparing this material to insulation made of basalt, it is also widely used. It is made from mats and rolls with varying thicknesses (up to 150 mm). To reduce waste when cutting, you can therefore always select the material based on how the roof frame’s cells are arranged. However, basalt insulation outperforms it in terms of density, thermal conductivity, and resistance to compressing glass wool.

The primary factor enabling glass wool to rival basalt insulation is its affordability. Because of this, even though glass wools are well known for their ability to gradually slide down a slope with the formation of cracks and cause severe skin irritation when handled, many masters prefer this material.

Slag cotton wool

Made using dollhouse furnaces for domains. Its operating temperature range is the widest of all cotton materials (up to 300 o C). The slag is not used to warm the facades because it has the highest hygroscopicity.

Since the slag has the dirtiest base, using it in residential settings is not advised. Pipelines and industrial buildings are typically insulated using this material.

Slab materials

Slab materials are manufactured using a variety of polymer types. Polystyrene, polystyrene, and polyurethane are these.

Vapor permeability and stiffness are crucial properties of plate materials. This also affects the technology used to use insulation in the warm roofing pie. The process used in production to form the foam polymer plates determines the capacity to pass moisture vapors:

  1. Extruded materials have high stiffness and do not miss moisture. They do not need vapor barrier films. A weak place with continuous styling – these are joints between panels. Therefore, many plates are produced with shaped edges, which when they form a castle and make the surface of a monolithic. This type of insulation is used for laying a continuous layer on top of the rafters when warming the pitched roofs or to arrange the upper part of a multi -layer pie on flat roofs.
  2. Materials for forming whose extrusion was not used. Typical heat insulator of this type – foam. The cells in the thickness of the material do not fit tightly to each other, so moisture can penetrate through it. Such materials are always mounted with ventilation ducts.

Since it is challenging to cut the material precisely in the size of the cell, plate foams are not used to warm the roof between the rafters. The inevitable fissures will turn into the cold’s bridges. Furthermore, a significant quantity of waste will be produced during cutting if the rafters are not installed with consideration for the size of the material.

"We examine the critical decisions regarding materials and techniques for both pitched and flat roofs in our in-depth guide to roof insulation. It’s crucial to comprehend the various insulation technologies available, from more contemporary options like spray foam and rigid boards to more conventional ones like fiberglass and mineral wool, whether you’re building a new roof or renovating an old one. We dissect the advantages, installation methods, and factors of each material to assist you in making decisions that will improve your roof’s longevity, comfort, and energy efficiency."

Naling roof insulation technology

The following methods can be used to insulate a pitched roof:

  1. Installation of insulation between rafters.
  2. The formation of a continuous layer of insulation on top or under the rafters.
  3. Combined method.

Insulation between rafters

Installing insulation with single-layer ventilation using a superdiffuse membrane is the simplest method. They purchase insulation for this method, the thickness of which is determined by the cell’s depth:

  1. First, the heater slabs are cut to the sizes of the cells, after adding 2 cm per side. Allowance is necessary so that the stove sits tightly in the cell.
  2. In this situation, it is assumed that there is no waterproofing film, so it is necessary to fix the superdiffusal membrane. The rafters are enveloped with the membrane and attached to the crate under the roofing material with a stapler. The edges of the membrane around the perimeter of the room are removed under the ovum of the roof.
  3. Then the chopped insulation is inserted into the cells. If the slabs have a foil coating on one side, the material is laid in foil inside the room.
  4. If the lower vapor barrier is made of a superdiffusal membrane, then it is immediately attached on top of the insulation.
  5. If a regular film is used, you need to create a lower ventilation gap. For this, the insulation is knocked out with a thin rail.
  6. The inner vapor barrier film is fastened over these racks. The joints are glued with tape.
  7. Fill the rails for the installation of interior finishes.

The space between the insulation and the waterproofing film should be on both sides if the old film is to be replaced with a low vapor permeability (microperfined) film for bottom tagging. In order to accomplish this, the panel must be inserted with an indent of two to three centimeters from the edge rather than all the way into the cell. The attic side must leave an identical space. The insulation should be five centimeters thinner than the cell’s depth. A panel expiration can be tucked under cells or along wire segments that are hung on nails:

  1. A thin rail (2 cm) is stuffed along the upper edge of the cell, and the nails are driven with an indent 2 cm from the upper edge of the beam.
  2. Cross-crusts are wrapped in nylon threads or wire to nails. Now, when laying the insulation in the cell, the necessary gap between it and the film will remain.
  3. Exactly the same operation is performed after installing the panels of the mineral wool. The threads on the bottom will not let the material sag or move in the cell.

Foam slab insulation needs to be done in two layers. The purpose of doing this is to seal the joint cracks. The second row’s joints should be docked in relation to the first row’s docking at the same time.

The thickness of the foam insulation must be chosen carefully to ensure that it does not extend past the rafters. Should the substance (or a pair of its layers) emerge from cells, the rafters need to be reinforced with wood.

Video: laying mineral wool between rafters

The existence of cold bridges around the cell perimeter is caused by the lack of insulation between the rafters. As a result, a lot of owners combine different insulation techniques, adding equipment to the layer above or below the rafters.

Insulation on top of the rafters

Foamed slabs with enough rigidity are ideal for use as insulation above rafters. Since this material can withstand the load placed on it by roofing material, new construction typically has a continuous layer of insulation installed from the outside on top of the rafters. Compared to fastening the panels from the inside, this is far more convenient. You can also preserve the internal space. Furthermore, the exposed portions of the attic beam will remain an original feature of the interior if the rafters’ insulation and plate styling are not combined.

It is not necessary to apply a vapor barrier to the insulation and apply waterproofing on top if extruded slabs are being used. The following principle is followed when performing the work:

  1. Before laying, it is necessary to perform a continuous flooring from OSB on top of the rafters.
  2. On top of it, the heater slab is attached to the rafters using long self -tapping screws. Self -tapping screws are screwed through a continuous flooring. As a rule, foam is laid in two layers, blocking the joints.
  3. A bar is screwed on top of the location of the rafters, to which a crate for the roof is attached and which will simultaneously create a gap for ventilation.

Combined insulation technologies

Underneath and between rafters is the most popular combination of insulation used in repair. One ventilation duct and an additional continuous layer from below are used in this option’s insulation method.

Cotton materials are used in this technology:

  1. Initially, a superdiffuase film is packed or an emphasis is emphasized for arranging a ventilation duct according to the technology described above.
  2. Then the insulation is cut and inserted into the cells. It is advisable to use the material of the same type, but with different density. The thermal resistance of the lower layer should be 80% less than the thermal resistance of the material of the main layer. A vapor barrier film will be mounted between them, and if you do not adhere to this condition, then condensation will appear on the film.
  3. For the installation of the second layer of insulation, a transverse beam is filled. The cross section is equal to the thickness of the insulation.
  4. Then a rail is filled for fastening the material of the interior decoration.

This design is the most straightforward, affordable, and easy to implement. It is most convenient to install a second layer over the rafters when the roof is deeply revised and new roof material is installed afterwards. Combining the three methods will result in the most effective insulation for homes located in harsh climates.

Video: insulation of the roof of the cottage with a layer of foam with a thickness of 20 cm

Materials Technologies for Installation
Fiberglass insulation Loose-fill blown-in insulation
Mineral wool Spray foam insulation
Polyurethane foam boards Rigid board insulation
Reflective foil insulation Insulated panels

Selecting appropriate insulation materials and installation methods for your pitched or flat roof is essential for both comfort and energy efficiency. Every material has advantages and disadvantages, whether you choose more modern alternatives like spray foam or rigid foam boards or more conventional ones like fiberglass and mineral wool. It’s critical to take into account elements like moisture resistance, installation ease, and insulation R-values.

Techniques like insulated roof panels or blanket insulation between rafters can successfully stop heat loss from occurring on pitched roofs and lower energy costs. Maintaining the lifespan of your roof structure and avoiding moisture buildup also depend on adequate ventilation. In contrast, specific methods such as tapered insulation may be needed for flat roofs in order to facilitate water drainage and avoid ponding.

The type of insulation selected and the roof design influence the wide range of installation techniques. Do-it-yourselfers who want to attain maximum performance should closely adhere to manufacturer instructions to avoid common pitfalls such as thermal bridging or insufficient sealing. By hiring a professional roofer, you can be sure that insulation is installed correctly and that any unique challenges presented by the architecture and climate of your roof are addressed.

Video on the topic

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Warming of a flat roof. Part 3

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Alexandra Fedorova

Journalist, author of articles on construction and repair. I will help you understand the complex issues related to the choice and installation of the roof.

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