Do-it-yourself PPU roof insulation

Among the most efficient things you can do to keep your house warm and energy-efficient is to insulate your roof. Many homeowners choose polyurethane foam (PPU) due to its superior insulating qualities and ease of application. You’re in the right place if you want to take on this project on your own.

Although DIY PPU roof insulation may seem difficult at first, it’s actually a very simple process if you follow some instructions. This method can drastically lower your energy bills in addition to helping you keep your home at a comfortable temperature.

We’ll walk you through every step of successfully using PPU to insulate your roof in this guide. You’ll receive comprehensive instructions to guarantee that you complete the task correctly, from setting up your workspace to applying the foam. Together, let’s make your house a cozier and more energy-efficient space.

Characteristics, pros and cons of PPU

A polyol (manufacturers refer to it as component "A") and polyisocyanate (component "B") react chemically to form a stiff, foamed plastic mass that is the end product, which is polyurethane foam (PPU). It is made up of 97% air and about 3% dense matter. Because of its structure, the material is lightweight, highly thermally insulating, and less hygroscopic.

Types of polyurethane foam

There are various varieties of polyurethane foam, which vary in terms of cell structure, elasticity, and aggregation state. As a result, the current classification separates polyurethane foam into four categories:

• elastic. Presented by well-known foam rubber. Has a density of 15-20 kg/m3, good vapor permeability, open cells, high elasticity. Completely restores its form with deformation of more than 90%. For insulation of the roof is not used. Although, rather, as an exception, you can find the attic;

• hard. Consists of two components, when mixing which foam is formed. Has a closed structure of cells, in connection with which a vapor perme. Density 30-60 kg/m3, which allows you to withstand various kinds of deformations (therefore hard). It is widely used for thermal insulation, both inside the building and outside;

• Semi -rigid. One -component insulation with open cells. Steamoproke. Density 20-30 kg/m 3 . Used only for thermal insulation of walls, roof and ceiling. Requires a standard procedure for steam and waterproofing the insulated surface. Known to many, like mounting foam;

• liquid. Used for insulating a space closed on all sides or when installing soft roofing on flat roofs. Density – 20 kg/m 3 or less.

Adding DIY PPU roof insulation to your home is an easy and affordable way to improve its energy efficiency. You can build a robust, seamless barrier that stops heat loss in the winter and keeps your house cooler in the summer by using polyurethane foam (PPU). This approach reduces energy costs and requires less work to produce high-quality insulation, making it a great project for homeowners who want to increase the comfort and value of their home.

Insulation characteristics

In polyurethane foam, the primary insulating properties are determined by the type of cell. The signs of rigid polyurethane foam and polyurethane foam (single-component, with open cells of insulation) are displayed in Tab 1.

Table 1 lists the primary attributes of insulation made of polyurethane foam.

Types of cells / Indicators	Closed cell insulation	Open cell insulation
Thermal conductivity coefficient, W/(m×°K)	0.022-0.035	0.025-0.045
Number of closed cells, %	More than 90.0	Less than 50.0
Increase in foam volume compared to the beginning of polymerization	1 in 40	1 to 70-90
Vapor permeability, mg/(m*h*Pa)	0.02-0.05	0.07-0.17
Density, kg/m3	20.0-80.0	8.0-18.0
Water absorption,%	1.0-3.0	10.0-60.0
Compressive strength, kgf/cm2	1.53-10.19	About 1.02
Bending strength, kgf/cm2	3.3-19.37	About 17.0

There are numerous benefits associated with insulation made of polyurethane foam. Not every benefit, though, is like that. Let’s examine more closely to determine which benefits are genuine and which are just marketing gimmicks.

Pros and cons

Among the unquestionable strengths are:

• low thermal conductivity;
• long service life;
• good adhesion to all wall materials;
• absence of cold bridges coming through the seams;
• ecological purity of the applied spraying;

• fire safety (combustion class G1 – self-extinguishing);
• low density;
• ability to insulate the most complex surfaces;
• low moisture absorption;
• inertness to all chemicals used in everyday life;
• is not a basis for the growth of mold and mildew;
• preservation of thermal insulation properties in a wide range of temperatures – from -160 o C to +150 o C;
• versatility.

Among the supposed benefits that don’t exist are:

• good level of noise absorption;
• resistance against rodents;
• a simple method of insulation;
• savings on vapor and waterproofing.

Cons include:

• intolerance to ultraviolet radiation;
• lack of vapor permeability;
• complex application technology;
• the need to use complex equipment, which makes it difficult to do the work yourself;
• high final cost of roof insulation with polyurethane;
• the slightest deviation from the instructions leads to a change in the spraying characteristics;
• sharp increase in thermal conductivity during compression.

Apart from the previously mentioned drawbacks, it is imperative to acknowledge the following drawbacks: the incapacity to precisely determine the quantity of components needed, and the uneven surface of the solidified foam, resulting in an 8 cm discrepancy between the peak and valley.

Further information on polyurethane foam can be found in the article "PPU Insulation."

Limitations when insulating polyurethane foam

The insulation technology of polyurethane foam is intricate. requires proficiency with spraying techniques and component mixing. Furthermore, there are several limitations when thermal insulation work cannot be completed.

• The absence of any adhesion between polyurethane foam and polyethylene makes it impossible to insulate surfaces covered with polyethylene film.
• One-component insulation should be applied only to a moistened surface, two-component insulation – to an absolutely dry one.
• Before use, the cylinders must be heated to a temperature of +18 to + 20 o C. Going beyond the specified limits reduces the quality of insulation.
• You cannot start insulating a roof with polyurethane foam from the inside if it is not heated enough. Minimum temperature – +5 o C.

Necessary materials and tools

Polyurethane foam insulation for roofs requires the purchase of a set of tools in addition to the necessary materials. In this instance, rigid polyurethane foam requires one kind of equipment, while one-component polyurethane foam requires a different kind.

You can purchase professional or semi-professional equipment to insulate with rigid polyurethane. The expert kit consists of:

• polyol – poured into a metal barrel with a volume of 50 or 100 l. There is a large letter “A” on the container;
• polyisocyanate – in the same barrel, but of a different color. The component designation is “B”;
• compressor station. Buying is very expensive, even if you cooperate with a neighbor or friend. Therefore, only rent;

• connecting hoses;
• spray gun;

• gun attachments;
• water in a bucket;
• flame retardants;
• lubricant.

A compressor station is not needed if you purchase a semi-professional polyurethane foam spraying kit because the parts are supplied in high-pressure cylinders. With the exception of water, the rest of the kit is identical; the gun is not cleaned and the kit is disposable.

You’ll need the following when using single-component insulation:

• cans of liquid polyurethane foam;
• spray gun;

• vapor barrier film (type B);
• windproof membrane (type A);
• water spray;
• gun cleaner (pressurized water bottle);
• flame retardants;
• water.

Furthermore, in every situation, personal protective equipment will be necessary:

• costume;
• glasses;
• respirator;
• gloves.

Thickness of applied layer

It only takes a 60–70 mm thick layer of thermal insulation to adequately insulate the roof. But it won’t be feasible to spray with such accuracy across the whole surface. Professionals therefore advise operating in the 50–100 mm range, where 50 mm is the minimum and 100 mm is the maximum thickness of the thermal layer.

Insulation density

Every gun has an adjustable bolt, or valve, that lets you get a specific density of sprayed layer. The ideal value of this indicator for a roof is 40 kg/m3.

Preparatory work

It’s easy to get the roof ready for insulation:

• the entire space between the rafters is covered with OSB (otherwise there will be nothing to spray insulation on). This is done either on top of the rafter system, or between the rafters, but so that the insulation layer does not extend beyond their plane;

Important: theoretical authors recommend installing sheathing instead of sheathing in all roof insulation work.

• the surface is cleaned of dirt, debris, mold;

• existing gaps more than 6 mm wide are sealed. If this is not done, the foam will actively expand on the other side of the skin;
• dormer windows are sealed with plastic film and tape – the foam that gets on them is unlikely to be completely removed;
• the sheathing and rafters are primed;
• equipment is assembled and then adjusted;

• its performance is checked, as well as the density of the insulating layer. If necessary, additional adjustments are made.

It’s important to wet the surface with water before applying one-component polyurethane foam (in cans).

PPU roof insulation technology

Using polyurethane foam for roof insulation involves a number of sequential steps (we’ll use one-component polyurethane foam as an example).

Step 1: The gun’s control valve opens to its maximum setting. After giving the can a good shake, it is turned upside down. It is necessary to apply the first layer from bottom to top. There are 35 to 45 centimeters separating the gun from the casing.

Step 2: After using the first can, a spray bottle is used to moisten the foam-covered surface. They go to work with the second canister.

Step 3: The first can’s thermal insulation layer is covered with a second layer of polyurethane foam after 25 to 35 minutes.

Be advised that holding the can head down vertically is not possible at the highest point of the roof. In this instance, the gun has unique nozzles that alter the foam jet’s movement at a 45-degree angle.

Step 4: The rafters themselves must be covered with foam in order to attain the tightness of the insulation layer.

Step 5: Using a pressure cylinder that screws onto the spray gun, water is used to clean the tool. The adjusting screw is tightened once all foam has been removed from the gun’s interior. In this state, the gun can be kept for a very long time in storage.

Step 6: To lower the flammability class of polyurethane foam, the insulating layer is treated with a fire retardant prior to the polymerization process, which takes around 40 minutes to complete. A basic spray gun is used to apply it, and the earlier you do it, the more effective it is.

Taking everything into consideration, it is easy to conclude that the roof should be insulated piecemeal rather than all at once.

Step 7: A vapor barrier film (type B) is applied inside the insulation, and a windproof membrane (type A) is applied outside, along the skin, to cover the insulation. The work "Installing a vapor barrier with your own hands" contains instructions on how to complete the task correctly and, most importantly, which side to lay the vapor barrier material on.

Caution: Vapor barrier work is not done when using hard polyurethane foam.

Step 8: Plasterboard or OSB sheets are used to sheathe the insulation layer in the attic room.

It is slightly simpler to insulate using semi- or professional-grade equipment.

The equipment is debugged before spraying is done, working from bottom to top in multiple layers. The procedure is comparable to using a spray gun to paint a surface. Until the desired thickness is reached, layers are applied.

Upon completion of work, the equipment is cleaned. The surface is sprayed with fire retardants. A construction knife is used to cut off any excess sagging. Attic space interior lining is being installed.

Insulation of a flat roof with liquid polyurethane foam

Installing liquid polyurethane foam on a flat roof is probably more of a soft roof installation than insulation because liquid rubber is added to the polyurethane. When it’s dry and warm (no more than +15 o C), the following procedures are carried out in order:

1. the surface is cleaned of debris and dust;
2. primed;
3. insulation is applied, manually or using equipment.

Strong pumps are used to apply the second layer of insulation after the first has dried. Usually, three layers suffice.

Step	Description
1. Prepare the roof	Clean the surface and ensure it is dry and free from debris.
2. Install a vapor barrier	Lay down a vapor barrier to prevent moisture from getting into the insulation.
3. Set up the equipment	Prepare the spray foam machine according to the manufacturer"s instructions.
4. Apply the foam	Spray the PPU foam evenly across the roof surface, covering all areas.
5. Allow to cure	Let the foam cure completely as per the recommended time.
6. Trim excess foam	Cut off any excess foam to create a smooth and even surface.
7. Install a top layer	Apply a protective top layer, such as roofing felt or shingles, to finish the insulation process.

Adding polyurethane foam (PUF) insulation to your roof is a useful way to increase the energy efficiency of your house. If you prepare ahead of time and have the necessary supplies, you can complete the project by yourself. By doing this, you’ll help create a more comfortable living space in addition to saving money on energy costs.

Always keep in mind that working with PUF requires caution. Make sure the work area has adequate ventilation and wear the proper protective gear. Apply the foam slowly and evenly, taking care to fill in all the spaces and gaps.

This do-it-yourself project can be satisfying, improving the insulation in your house and providing you with a sense of accomplishment. You can successfully finish this project on your own with careful planning and execution, but don’t hesitate to consult experts for advice if necessary.

Video on the topic

Vapor barrier with plywood and polyurethane foam / StroyKhlam approves / Sealed rigid frame without jibs and films!

The hangar rotted under the foam! This is a violation of the application technology and an error in choosing the layer thickness.

How to properly insulate an attic? How to insulate an attic? Insulating the attic roof. PPU insulation

Roof insulation – Penoizol