Insulating walls with insulation and foil

A vital first step in increasing your home’s energy efficiency is insulating your walls. It lowers your energy costs and improves the comfort of your living space by keeping your house cool in the summer and warm in the winter. Combining foil and insulation for superior thermal performance is one efficient technique.

This method makes use of the advantages of reflective foil and insulating materials. While the foil reflects radiant heat away from your home, the insulation acts as a barrier to heat transfer. This combination has the potential to greatly increase your insulation system’s overall effectiveness.

Gaining knowledge about the fundamentals of wall insulation using foil and insulation is crucial, regardless of whether you’re renovating an old house or building a new one. It’s an easy process that can have a significant impact on your home’s comfort and long-term efficiency.

Insulation Type	Properties
Fiberglass	Good thermal resistance, affordable, easy to install
Foam Board	High insulating value, moisture-resistant, lightweight
Mineral Wool	Fire-resistant, soundproofing qualities, durable
Reflective Foil	Reflects heat, reduces radiant heat transfer, thin and lightweight

Characteristics, pros and cons of foil insulation

Foil insulation is made up of two layers: an aluminum foil reflective layer on top of a base that can be polystyrene foam, extruded polystyrene, glass wool, or basalt wool. Similar to how a mirror functions, this insulation works by reflecting infrared (heat) rays back into the space, while the base insulation holds onto the heat that has penetrated the foil.

As a result, foil insulation is always installed facing the premises, or the heat, with a metallized layer on top.

The most important performance characteristics of insulation with foil

The foil used on the insulation dramatically alters the base’s quality indicators:

• Sudden changes in temperature and humidity are better tolerated;
• the vapor permeability threshold decreases, almost to zero value – 0.001 mg/m*K;
• the thermal insulation capabilities of the insulation increase – up to 97% of the heat is reflected back into the room;
• sound insulation abilities increase even for materials with conditional noise protection properties – up to 68%;
• the service life of the foundation increases almost 2 times.

Pros and cons of foil insulation

Foil insulation for wall insulation has benefits and drawbacks. Among the benefits we ought to emphasize are:

• increase in service life by 25-75% of the type of insulation on which the foil is applied;
• improving the level of thermal insulation;
• appearance (expanded polystyrene) or improvement (basalt wool) of noise protection properties;
• reducing the thickness of the insulation, which leads to a reduction in mechanical loads on the building structure, and also preserves usable space in the house;
• more efficient heat conservation, which, firstly, saves the family budget, and secondly, reduces the load on heating systems installed in private homes. And this, in turn, extends their resource;
• absence of drafts in rooms insulated with heat insulators and foil;
• simple installation – you can insulate the walls yourself;
• moisture resistance – there are no restrictions on use in rooms with high humidity, for example, a bathhouse.

Important: One common misconception when evaluating the benefits and drawbacks of foil insulation is that it is inexpensive compared to other materials. This is true for nearly all materials that are taken into consideration. It is best to avoid mentioning the price factor because there is such a wide range of prices on sale. It may have benefits as well as drawbacks.

First and foremost, among the drawbacks, you should be aware of the following:

• no screed is poured onto foil insulation – the point of using foil for insulation is lost: it simply does not work;
• thin insulation with foil does not provide complete protection against heat loss. It is necessary to pair other thermal insulators with such material;
• to glue the butt seams, you need to buy a special, metalized adhesive tape, which increases the estimated cost of repairs (construction);
• It is undesirable to fasten insulation with foil with nails and dowels – the integrity of the foil layer is compromised, as a result of which the thermal insulation properties of the material decrease.

Which foil insulation is best for walls?

Insulation requirements vary depending on whether it is used indoors or outdoors, and this includes insulation with an applied foil layer.

Inside

Generally speaking, walls can be insulated using any type of foil insulation. Even with sufficient income, a foil stopper. However, experience has brought about its own specialization: cork and extruded polystyrene for warm floors, foam and mineral wool for walls.

When it comes to simplicity of technology or heat retention, cotton wool and foiled polystyrene foam are equal when it comes to thermal insulation of walls in residential buildings. Here, affordability takes precedence over durability in certain situations. Regarding this, we observe that glass wool and foam plastic have shorter service lives than basalt wool.

Foiling basalt wool is necessary in areas with elevated temperatures and high humidity, like steam rooms found in bathhouses or saunas. Polystyrene foam is afraid of high temperatures, and glass wool is afraid of humidity. Because of mice and rats, you should not use mineral wool or polystyrene foam at the dacha.

Outside

It is meaningless to use foil insulation to prevent heat loss from the facade. We need to use complex reasoning to understand the nature of infrared rays, their length, their capacity for reflection, etc. in order to explain this. P.

Let’s ignore all of this and demonstrate with a few straightforward examples how the opposite happens in cold weather: the cold is transferred inside the insulation.

1. The way foil reflects heat is exactly the same as how a mirror does it. The reflected bunny is incredibly bright and easy to see in direct sunlight. Reflected light on a cloudy day will create a dim area. There is virtually no light reflection at night.

The same is true with foil. The polished surface of a thin layer of aluminum works more effectively, reflecting a large flux of thermal radiation, the higher the thermal energy flux. This example already demonstrates that the foil has nothing to reflect at below-freezing temperatures because there aren’t many infrared rays and they’re long, which is also significant because long waves can easily pass through a thin layer of foil.

2. Let’s carry out a quick test. Arrange a mirror, a piece of metal (or construction foil) for wall insulation, and a sheet of mirror facing the sun on a sunny day.

After three to four hours, touch your hand in turn to the foil (warm), the metal (you risk burning yourself), and the mirror (you feel cool). The same procedure will then be performed in extremely cold temperatures. Let’s touch each material once more, one by one (those who are particularly curious can do this with their tongue). They’re all the same temperature. Or did someone wish for aluminum to be heated?

In summary, the foil cools to the same temperature as the outside air during cold weather. Adhered to the insulation, it actively transmits the cold to the insulation’s substrate. Insulation in reverse occurs as a result: rather than providing protection, the foil layer lessens the facade’s insulation’s capacity to withstand heat.

Required materials and tools

The retail chain uses a variety of foil materials. Different supplies and equipment are needed for their installation. As a result, we offer a comprehensive inventory of the necessary tools along with information on their location and timing of use.

Supplies you’ll need:

• foil insulation;
• wooden beam 50×50 mm for lathing;
• spacer bar (20×50 mm) for installing a counter-lattice;
• plasterboard or OSB for covering the frame;
• primer;
• adhesive for insulation – individually for a specific type of substrate (“CERESIT CT 190” for basalt wool, “CERESIT CT 85” for polystyrene foam);
• metal corners, self-tapping dowels for the wall and wood screws – fasteners for assembling the sheathing.

The equipment you ought to carry with you is:

• homemade sawhorses or stepladder (you can use a strong table);
• a hammer drill or electric drill – will be required when attaching the sheathing trim to the wall;
• screwdriver;
• mixer attachment for stirring glue;
• glue container;
• wood hacksaw;
• construction knife with replaceable blades;
• putty knife;
• level;
• roulette.

Preparatory work

As previously mentioned, foil thermal insulation for external walls is essentially money thrown away in the cold. Therefore, before we discuss the technology of preparing walls for insulation, we note that we will only consider internal work.

The "wet" method of insulation is rendered unnecessary when a layer of foil is present for multiple reasons:

• additional fastening of the slabs with dowels is necessary, which destroys the integrity of the metallized layer, reducing the effectiveness of thermal protection;
• decorative plaster will not adhere to foil;
• when the outer layer of the reflector is in close contact with any other materials, the effect of reflecting infrared rays disappears: the material in contact with the foil will heat up, in turn heating the aluminum, and it, along the chain, will give off heat outside to its substrate, and not to the room. That is why the instructions for using foil materials for insulation provide for the installation of a ventilation gap. In this case, the reflected heat rays will heat the skin. In this case, the foil itself does not heat up much.

There will be lathing because there isn’t a "wet" way of thermal insulation. All of the preparation work is concentrated here. Essential:

• remove from the wall everything unnecessary that interferes with work: switches, sockets, lamps, various fasteners, etc.d.;
• remove old finishes and, if necessary, plaster;
• clean the surface from dust, dirt, soot and grease stains;
• repair small and large cracks;
• prime the wall in two passes.

The insulation will conceal everything, so there’s no need to carefully level the surface.

The procedure for carrying out the aforementioned tasks is described in further detail in the article "How to prepare walls for wallpapering."

Sheathing installation can start once the primer has dried. The document "Wall insulation with stone wool" contains comprehensive instructions for this particular work stage.

Be aware that window and door openings are covered in slats beneath the mineral wool. Not under foam plastic is this done. But with foil foam, the holes will also need to be cushioned, so to speak. Reinforcing polystyrene foam’s ends and outer corners presents significant challenges.

The key phases of the sheathing installation can be enumerated as follows:

• vertical trim posts are adjusted to the height of the ceiling and attached to the wall;
• horizontal strapping is screwed to the fixed racks using metal corners;
• vertical internal slats are installed. The pitch is equal to the width of the insulation sheets;
• horizontal slats are installed. They are only needed for drywall. Vertical posts are enough for OSB boards.

Insulation technology

The same guidelines apply to work done on foil-insulated facades and interior walls. But there are some subtleties that we will discuss.

Inside

Nearly the same technology is used to attach foil for insulating walls from the inside of a house with different substrates to the sheathing, with modifications for the type of insulation base.

Styrofoam. An adhesive layer that has been applied beforehand to the back of polyfoam is optional. The slabs are cut to fit the cells in both situations. After using glue to separate the protective film from the insulation, the insulation is pressed up against the wall and left there until the adhesive composition starts to polymerize (the exact time will always be specified on the packaging or on special inserts).

To repair polystyrene foam without the use of glue, a few additional steps must be taken:

• dilute the glue, strictly following the instructions on the package. Stir with a mixer until you get a homogeneous mass without lumps;
• give the glue time to mature. Minimum – 5 minutes;
• apply glue to the back of the polystyrene foam;

Crucially, the only kind of insulation that requires secrets when using glue is polystyrene foam. All the subtleties of an apparent straightforward process in the article "Using polystyrene foam to insulate walls."

• insert the plate into the cell, then fix it with glue;
• all gaps and cracks are blown out with polyurethane foam or polyurethane foam glue;

Crucially important: make sure to observe how the polystyrene foam responds to the polyurethane foam before using it. Many companies use their own solvent to melt polystyrene foam.

• after completing the insulation work, fill the counter-batten;

Be aware that there is no need to perform vapor barrier work because the foil itself acts as a great vapor barrier.

• sheathing is being installed.

Glass wool. The glue used for attachment uses the same technology as polystyrene foam. There is a subtlety here, though. One day prior to the commencement of work, every roll of glass wool is laid out and left there until the cutting to size process commences.

Wool made of basalt. In contrast to earlier materials, basalt wool is randomly inserted into sheathing cells after being cut to a larger size. It suffices.

In addition, the sheathing is mounted on the mineral wool and positioned on top of it.

The walls of cool steam rooms and saunas are insulated with a frameless system. All that needs to be done is glue basalt wool to the wall and use specialized tape to seal the seams. No finalizing tasks.

There is a chance that kids using the sauna could get burned. After that, the wall’s vertical frame posts are fastened, basalt wool is adhered to, the majority of the sheathing is installed, and finishing touches are applied.

Outside

Because of the way he is made, man prefers to learn from his own mistakes rather than those of others. We refer to the works on our website, "Insulation of walls with foam plastic" and "Insulation of walls with stone wool," where the procedures for facade insulation are detailed, for those who are among them and still wish to use foil material for external insulation (by the way, there are many of them, which is confirmed by numerous photos on the Internet). Every operation is carried out precisely, without modification or exception.

Nonetheless, it is preferable to take lessons from the errors of others. I would like to ask the owner, by the way, how he plans to apply decorative plaster. Based on the picture, the facade looked ready for it.

Enhancing your home’s energy efficiency can be done simply and effectively by insulating the walls with foil and insulation. You can decrease heat loss and raise indoor comfort levels considerably by selecting the appropriate materials and installing them correctly.

To ensure that the insulation fits snugly between wall studs and that the foil side faces the right direction to reflect heat, don’t forget to measure and cut the insulation carefully. To stop air leaks and get the most out of the insulation, seams and edges must be sealed properly.

In addition to lowering energy costs, taking the time and making the effort to insulate your walls makes your home a more environmentally friendly and sustainable place to live. You can lessen your carbon footprint and enjoy a cozier home with the appropriate strategy.

Insulating walls with foil and insulation is a practical and affordable way for homeowners to improve the thermal performance of their home. It creates a barrier that decreases heat gain in the summer and loss in the winter, making it an extremely effective way to improve energy efficiency and maintain comfortable indoor temperatures.

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