Roof insulation with polyurethane foam

Table of contents:

Roof insulation with polyurethane foam
Roof insulation with polyurethane foam

The nuances of roof protection with polyurethane foam, the advantages and disadvantages of this thermal insulation, preparation, sequence of work, especially the insulation of a flat roof PPU. Insulating the roof with polyurethane foam is a great way to minimize heat loss in the house. A fairly large amount of heat is lost through the roof - about 25% of the total losses. High-quality protection of the structure will help not only reduce heat leakage, but also extend the life of the entire roof. When insulating, it is important to choose the right insulator, since not all thermal insulation materials are equally good in certain situations.

Characteristics and features of polyurethane foam

Polyurethane foam on the roof
Polyurethane foam on the roof

Polyurethane foam is a type of gas-filled plastics, with a minimum solids content of up to 15%, the rest is occupied by gas bubbles. Thanks to this combination, an excellent thermal insulation material is obtained, which is widely used in construction.

According to their main characteristics, there are three types of this insulation:

  • Solid polyurethane foam with a density of 40-80 kg / m3… Produced in plates, sheets.
  • Soft polyurethane foam with a density of up to 40 kg / m3… They are produced in the form of a spray coating.
  • Foam rubber - in rolls.

Hard varieties are used as thermal insulation and sound insulation, soft ones - in the form of padding and coatings in industry and in everyday life.

Polyurethane foam sheets can be produced both uncoated and coated. As protective layers, paper, foil, fiberglass are used, which are applied on one side.

The undoubted advantage of polyurethane foam is the possibility of spraying directly onto the surface, excluding the stage of manufacturing, installation, fitting, etc. This feature distinguishes polyurethane foam from other heat-insulating materials by practically the absence of any special and labor-intensive preparatory work, the insulator forms a high-quality and durable insulating layer that is not exposed to external influences, does not absorb moisture and does not lose its properties over time.

Due to its high adhesion, PU foam can be used on almost any surface - wood, metal, glass. It can be perfectly sprayed on both vertical and horizontal surfaces. Due to the high service life, according to some sources up to 50-60 years, it does not require renovation or repair.

PUF is characterized by low moisture permeability, the higher the density of the material, the less moisture it absorbs. One of the substances that make up polyurethane foam, due to which moisture permeability is reduced, is castor oil.

It is also important that this insulation is practically non-flammable, which is achieved by adding various halogens and flame retardants to the mixture. Polyurethane foam burns only in the presence of an open flame. The features of this material can also be attributed to the ability to prevent the spread of flame, since when exposed to fire, PPU is coked.

For thermal insulation, you can use a cheaper foam, but it is important to take into account that this material can deform at the slightest mechanical stress, in contrast to polyurethane foam, which is not subject to any deformation and does not lose its integrity. Thus, the insulation of the PPU roof is the most expedient solution.

The main methods of application include the method of pouring and spraying:

  1. Most often, the pouring method is used for frame structures and buildings. It consists in filling the space between the rafters. Perfect for insulating a roof of a complex shape, since the insulation fills all possible cracks and cracks in the structure. It differs from spraying in that no air is supplied to the mixture, a jet is formed at the exit, which, falling into the cavities, fills them, giving a certain shape. This method is suitable for creating polyurethane foam boards, sandwich panels. It is recommended to fill in several layers, with a time delay for drying each layer.
  2. The second method differs in that the polyurethane foam is applied already in a foamed form. The constituent ingredients isocyanate and polyol are mixed with air in special installations. The mixture is pumped under pressure into a spray gun and applied to the desired surface. This method is more expensive, since special equipment is needed, but due to the speed of filling and drying, as well as the effectiveness of thermal insulation, the method completely pays for itself. Advantages of the spraying method: high sound insulation, absence of seams and dew point, high adhesion, quick drying of the composition - it hardens within 3 seconds. Equipment for polyurethane foam application is of two types - high and low pressure.

Note! At high temperatures, polyurethane foam foams better, which makes it possible to use material more economically. Therefore, it is best to carry out insulation work in the warm season.

Advantages and disadvantages of polyurethane foam

How is polyurethane foam applied
How is polyurethane foam applied

Like any other type of insulation, polyurethane foam has both strengths and weaknesses.

The advantages of the selected material include:

  • PU foam completely fills any cracks and cracks.
  • The use of this insulation strengthens the roofing system.
  • Due to the low coefficient of thermal conductivity (up to 0.035 W / m * K), the insulation layer decreases, which in turn reduces the load on the structure.
  • Fast and easy performance of insulation works.
  • There are no icing and icicles on the roof.
  • Does not attract rodents and various insects.
  • The surface does not need special preparation before applying insulation.
  • Does not rot, mold and mildew do not form.
  • High adhesion, due to which the material is applied to almost any surface.
  • The formation of a seamless coating, the absence of "cold bridges".
  • PPU waterproof. Moisture absorption - up to 3% of the total.
  • Harmless and non-toxic, fireproof.
  • Does not corrode.
  • Not affected by chemicals.
  • Due to its low weight, it does not form an additional load on the roofing system.

Disadvantages of polyurethane foam:

  1. Relatively high cost.
  2. Destruction by direct sunlight.
  3. The use of special equipment when applying.
  4. The thermal insulation layer must be at least 5 centimeters, otherwise the proper thermal insulation effect will not be achieved.
  5. Low vapor permeability, as a result of which dampness can form on the inside of the floors.
  6. When applying by pouring, it is important to take into account the amount of the mixture, since deformation and destruction of the structure are possible during expansion.

Regarding the destruction of the material by ultraviolet radiation, it is important to take into account that this drawback is easily removed when the finished layer is coated with paints, mastics. Ultraviolet rays do not penetrate deep into the insulation and have a negative effect by about 1-2 millimeters in the absence of a protective paint layer.

As you can see, this insulation has an order of magnitude more positive properties than disadvantages. Compliance with the above recommendations for work, safety precautions with this material will allow you to get a high-quality and durable heat-insulating roof covering, extend the service life of the entire roofing system, which will have a beneficial effect on the microclimatic indicators of the dwelling.

PPU roof insulation technology

Due to its characteristics, polyurethane foam is considered to be the most effective material for insulation, sound insulation, and roof seams. Due to the diverse form of release, PPU is applied in various ways that are suitable both for structures under construction and for the reconstruction of already finished buildings and structures.

Preparatory work

PPU spraying equipment
PPU spraying equipment

Before directly insulating the roof with polyurethane foam, it is necessary to carry out preparatory work. It is enough to clean the roof from debris and dust, if necessary dry the surface.

An important advantage is that there is no need to cut off the insulation itself with a waterproofing layer, since polyurethane foam itself is an excellent insulator and does not absorb moisture.

When choosing polyurethane foam for roof insulation, you should pay attention to its density. With increased density, the number of voids decreases. For the roof, a density of 40-50 kg / m is suitable3, which in turn will not place additional stress on the roof structure.

When using polyurethane foam, there is no need for a standard roofing cake, which includes a hydro and vapor barrier layer. This completes the preparatory work, and you can proceed directly to the insulation.

Important! For the effectiveness of thermal insulation, the insulation layer must be at least 5 centimeters.

Installation instructions for polyurethane foam

Roof insulation with polyurethane foam
Roof insulation with polyurethane foam

When insulating the roof with polyurethane foam, it is necessary to adhere to safety rules and a certain order of work. They should be carried out in a protective suit with a respirator and goggles, rubber gloves.

The order of work:

  • Surface preparation - elimination of dust, dirt, old heaters;
  • Installation of the battens, in accordance with the desired thickness of thermal insulation;
  • Bringing the composition of polyurethane foam to the desired consistency;
  • Application of the first layer (from 5 to 8 centimeters);
  • If necessary, applying a second layer;
  • After the layer has solidified and dried, excess material is trimmed;
  • Cosmetic finishing with chipboard, plywood, lining panels.

Compliance with these recommendations will ensure high-quality work and an effective thermal insulation coating.

Insulation is carried out from the inside, in the intervals between the rafters. Spraying is carried out from the bottom up, paying attention to the corners and joints of the roof. After application, PUF hardens for about 30 seconds, complete drying occurs in 1-2 days. After installation, the material fills with gas bubbles and expands, which provides the required thermal insulation. Due to the expansion, PUF fills the entire space, penetrating into all cracks and irregularities, closing them and thereby creating an airtight layer.

The spraying method is more in demand, despite the need to use special equipment. This is due to the ability to select the thickness of the coating depending on the situation, as well as the speed and ease of work. There will be no problems with the choice of devices, at present the market provides a wide range of disposable equipment, simple and economical, which does not require special skills to work with it.

When insulating a flat roof, it is first necessary to determine whether the surface will be used or not. If so, then a concrete screed must be made over the insulation.

The process of applying polyurethane foam will not be difficult if you follow the requirements for working with spray equipment. Such installations should be located at a distance of 2 meters from the surface. In addition, the hoses and the unit itself should be heated.

Finishing the roof

Polyurethane foam on the roof of the house
Polyurethane foam on the roof of the house

After the insulation work has been carried out, you can do the final finishing. No special technologies or any complex manipulations are required. If the insulation was carried out inside the building, then the surface should be sheathed with any available material - fiberboard, lining. In addition, the final stage can be the coating of the insulation layer with paint or plaster for additional protection. This completes the finishing work.

If the insulation is made from the outside on a flat roof, then the main stage of finishing is the application of a protective coating to prevent the destruction of the insulation under the influence of sunlight. To do this, after drying, the surface is cleaned of debris, a layer of acrylic, facade or latex paint is applied. You can use special mastics that cut off the ultraviolet spectrum.

Pitched roof finishing consists of the following stages:

  • A vapor barrier layer is applied to the truss structure (roof frame);
  • The cornice is being mounted;
  • The initial crate is installed;
  • A layer of polyurethane foam is applied;
  • A counter-lattice is installed;
  • If necessary, install additional waterproofing;
  • Roofing is laid (as an option - shingles).

How to insulate the roof with polyurethane foam - see the video:

Taking into account the main characteristics of polyurethane foam, as well as the procedure for carrying out the work, we can conclude that it is quite possible to carry out insulation with this universal material on our own, and the roof of the building after thermal insulation will be reliably protected from the penetration of cold air.