Which insulation is better for a roof under metal tiles – a cake with sheets of foam plastic/polyurethane, fiberglass or foam

Selecting the appropriate insulation for a roof covered in metal tiles is essential to preserving your home’s comfort and energy efficiency. Because temperature extremes can be intensified by metal roofs, insulation is crucial for controlling indoor climate and lowering heating and cooling expenses.

Three popular options for insulation stand out: foam, fiberglass, and polyurethane or foam plastic sheets. Every type has advantages and suitability of its own based on installation requirements, budget, and climate.

Foam plastic and polyurethane sheets are perfect for roofs because they provide superior moisture control and thermal resistance. They offer an uninterrupted layer of insulation that reduces heat transfer and can raise your home’s overall energy efficiency. These materials are long-lasting because they are lightweight, simple to install, and mold- and mildew-resistant.

Another well-liked choice is fiberglass insulation, which is well-known for being widely used and reasonably priced. It effectively reduces heat loss and is made of tiny glass fibers. Fiberglass, however, needs to be installed carefully to prevent gaps or compression that could lessen its effectiveness. When using fiberglass, it’s crucial to make sure there is enough ventilation to avoid moisture buildup.

Depending on the shape and design of your roof, foam insulation—such as spray foam or rigid foam boards—can be applied in a variety of ways and provides excellent thermal performance. By creating an airtight seal, it lowers air leakage and boosts energy economy. Although foam insulation is adaptable, for best results, it might need to be installed by a professional.

The ideal insulation for your roof beneath metal tiles ultimately comes down to your personal priorities and needs. When making your choice, take into account aspects like long-term performance, ease of installation, budget, and climate conditions. In addition to improving comfort, proper insulation can save a substantial amount of energy over time, making it an investment in the sustainability and efficiency of your house.

Multilayer roof insulation

Insulation works wonders to cut down on acoustic noise in addition to heat loss. In order to lower the amount of humidity, vapor barriers are typically added to conventional thermal insulation materials (especially in the area of rafters, sub-rafters and attic spaces).

Because of this, metal tile roofing requires its thermal insulation to be applied in multiple layers, or what roofers refer to as a "pie." How should this kind of "pie" look?

Features of operation

Every layer addresses a different aspect of protection:

• heat insulator – thermal and acoustic;
• waterproofing – against precipitation;
• vapor barrier – from moisture-saturated vapors and waterlogging of insulation and adjacent structures.

Without this pie, metal roofs are more likely to be noisy during rainy seasons, chilly during the winter, and scorching during the summer when the sun is shining and extreme weather is bothersome. Naturally, I would prefer it if a single material could accomplish all of the aforementioned tasks, but sadly, none has been developed as of yet.

Prior to installing the covering, the underlayment needs to be put directly onto the sub-roof. It ought to completely envelop the surface and offer an extra degree of defense against severe weather.

The roof and the remainder of the house are vulnerable to wind and precipitation in the absence of such a pie. To ensure that your home lasts as long as possible, it is crucial to select the best metal roof covering.

Take note: In this instance, the "pie’s" service life needs to match the lifespan of your roofing system. Furthermore, it is made to last for at least 40–50 years.

You’ll discover how to properly make a roofing pie for metal tiles by watching this video:

The key considerations when selecting insulation for a roof covered in metal tiles are cost-effectiveness, moisture resistance, and insulation effectiveness. Foam, fiberglass, or foam plastic/polyurethane are the most common options. For humid climates, sheets made of foam plastic and polyurethane provide excellent thermal performance and moisture resistance. Although less expensive, fiberglass insulation may need additional moisture barriers and may not perform as well in very cold temperatures. Although it can be more expensive, foam insulation offers good thermal resistance. The optimal option for long-lasting and energy-efficient roofing beneath metal tiles ultimately depends on your climate, spending capacity, and unique insulation requirements.

Types of materials and their characteristics

Spray foam insulation, rigid sheet foam or felt, and fiberglass insulation rolls are the common materials used to cover metal tile roofs with insulation. In certain regions, they also employ more antiquated materials, like mineral wool.

It is crucial that the materials chosen are safe for the environment and meet GOST 31913-2011 requirements.

For example, GOST 31913-2011 advises against using phenolic foam for thermal protection in residential buildings because the resins it contains, phenol-aldehyde, can be harmful to human health when heated. Be aware that some efficient heat insulators, such as cork, vermiculite, and basalt wool, have limited applications because they are hard to come by.

The so-called R-value criterion, which bases a material’s effectiveness on its capacity to withstand cold, has become widely accepted in global practice. A material’s capacity to transfer heat to the outside environment diminishes as R value rises. It is advised that the R-value for thermal insulation be at least 7…9.

Fiberglass rolls

Fiberglass composite-based thermal insulation materials are among the most widely used roofing substrate types. These materials come in a variety of R values and are reasonably priced.

Fiberglass insulation for metal roofs is a great choice because it’s reasonably priced for developers. Conversely, there are a few issues as well:

• Firstly, roll insulation is not so easy to shape in corners or on rafters.
• Secondly, fiberglass does not have high vapor barrier properties. The consequence is that if the humidity of the roll coating increases, the moisture will not dissipate, which will lead to an almost complete loss of R-value.

Since a vapor barrier is installed concurrently with the professional installation of a fiberglass layer, the risk is minimized. The flow of air, either from the outside or the inside, will ensure that the required dispersion of water vapor is provided by the presence of a moisture-proof layer.

Fiberglass insulation is made up of structures that resemble threads that are woven together and mixed with other materials. These particles can cause serious illness if inhaled.

Citation. The R-value of fiberglass insulation determines its cost, which varies from 2700 to 5000 rubles per roll. The higher the cost, the higher the insulation’s thermal resistance.

Rigid sheet

This kind of material is regarded as universal since it is utilized for uses other than thermal insulation on roofs. offered in a broad variety of thicknesses and cross-sectional sizes.

Although rigid foam insulation costs more than felt or glass wool insulation, its higher R-value makes up for this. Additionally, the materials’ capacity to insulate sound well is noteworthy.

However, there are issues with this kind of insulation as well. It requires a great deal of labor to work around intricate roof configurations because it is not flexible. Pre-installing a vapor barrier layer is imperative because thermal insulation made of rigid foam or polyurethane will decrease roof ventilation.

Sheet insulation is preferred by homeowners for two reasons:

• The sheets can be tightly fitted to each other, and the joints can be carefully sealed, then the thermal resistance becomes maximum;
• Foam/polyurethane is denser and thinner than rolled types of insulation, so there will be fewer joints and gaps, which will help reduce air leakage.

One of the drawbacks of sheet insulation is that it requires additional sealing compounds and has a relatively weak resistance to ultraviolet radiation.

Regarding a note. The thickness and manufacturer of the insulator determine the sheet’s cost. The price range is 450–600 rub/m2 (installation included).

Foam

Compared to rigid foam/polyurethane, spray foam insulation has a lower R-value and is more costly than roll insulation. However, the use of such technology is advised and justified if the roof needs to be completely insulated, particularly if the building is already occupied.

You can squirt foam practically anyplace. Since foam acts as an internal heat insulator, it is important to consider the expansion that will occur naturally after use. In this manner, you won’t need to be concerned about a small area that wasn’t able to be treated lowering the R-value of your roof.

Note: Foam is used for both repairs and thermal insulation on small roofs. It is more expensive per unit; additionally, the entire cost has to account for the expense of buying spraying equipment, which still requires practice.

There are two varieties of aerosol foam: closed-pore and open-pore. Efficiency will drop in the first scenario since the real R-value will be lower. As a result, this choice is inappropriate in cold climates. Conversely, closed cell insulation is more costly; however, in northern climates, it offers the best performance when used as roofing.

It is important to make clear the compatibility and viability of foam thermal insulation with respect to particular roofing material types when selecting an aerosol method of thermal insulation for a metal tile roof. The price range for the square meter is 400–1000 rubles.

Installation technology

The type of material selected will dictate how thermal insulation is arranged. You need to carefully check the lower portion of the roof to see if the rafters and sub-rafters are damaged or defective before you start the insulation process. Installing the roofing membrane and fastening it with nails or staples comes next.

• Using roll material to insulate an existing roof – start with the gaps between the horizontal beams and the roof deck. The rolled material should not be laid too tightly, as this may impair its performance.
• Option with sheet insulator – the material is pre-cut to size using a universal roofing knife, and then secured in place using mechanical (staples) or chemical (glue) methods. To install the heat insulator, it is not recommended to use mechanical fastening with nails or self-tapping screws: possible gaps can cause leaks. Sheets of rigid foam or polyurethane are laid, pressing them tightly together, but not allowing them to overlap. Next, using construction tape, eliminate possible gaps and leaks.
• Foam insulation requires the purchase of appropriate equipment. The kit includes the spraying device itself and the required consumables, the quantity of which must be specified based on the standard foam consumption per unit of surface to be treated. Don"t forget to buy a respirator! To begin work, it is necessary to make a hole in the lower layer of the deck that facilitates access of the sprayer to the roof frame. The required hole dimensions are usually indicated in the operating instructions for the sprayer, which also specifies the location where it would be more appropriate to obtain such a hole. Before spraying, make sure that the metal tile deck is securely supported by plywood or OSB boards made from compressed chips. Carefully spray foam into the hole. Please note that after spraying the foam will begin to expand, filling the inner surface of the flooring. Once fully expanded, hardened and cured, the hole must be sealed.

Installing the metal tiles can start as soon as the thermal insulation "pie" is prepared.

To ensure long-term effectiveness and durability, selecting the appropriate insulation for a roof covered in metal tiles requires taking into account a number of factors. Foam plastic or polyurethane sheets, foam, and fiberglass are some examples of insulation types. Each has advantages and disadvantages.

Because foam plastic or polyurethane sheets are relatively lightweight and have good thermal insulation qualities, they are easier to handle during installation. They produce a continuous, solid layer that lowers heat loss and can improve a building’s energy efficiency. To prevent thermal bridging, it is essential to make sure the installation is done correctly and without any gaps.

Fiberglass insulation is renowned for being inexpensive and simple to install. It is a good thermal insulator and is made of fine glass fibers. Depending on the required level of insulation, different thicknesses of fiberglass can be installed. To avoid moisture problems, though, extra protective layers or vapor barriers might be needed, particularly in humid climates.

Foam insulation, like spray foam, can fill gaps and effectively reduce air leakage while providing a seamless layer of insulation with outstanding thermal resistance. It can improve structural integrity by lowering the possibility of moisture buildup and mold growth, and it sticks well to uneven surfaces. However, because of how it is applied, it usually needs to be installed by a professional, and it can cost more than other forms of insulation.

The final decision about insulation for a roof covered in metal tiles is influenced by a number of variables, including the building’s design, budget, climate, and intended energy-efficiency targets. Speaking with an experienced contractor or insulation specialist can offer insightful advice catered to the particular requirements of the project and guarantee that the insulation type chosen will function at its best for the duration of the roof.

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