Foil has been used in construction for several decades, and during this time it has proven itself to be a good thermal insulation material. Foil for baths and saunas serves as a heat insulator and as protection against steam (vapor barrier, vapor barrier membrane).
It is glued to the ceiling and walls and must be covered with an outer finishing layer (for a bathhouse this is a natural wooden board). The service life of such protection is significant - at least 10 years.
Where is it used?
It should be noted that the heat-insulating effect of foil is not based on the same property as that of other heat-insulating materials. Aluminum foil for a bath, on the contrary, conducts heat very well, but its effectiveness is based on the reflection of heat rays.
Any household infrared heater, electric fireplace, air heater uses an aluminum heat reflector. To eliminate the disadvantage of aluminum’s high thermal conductivity and low strength of foil, manufacturers produce composite materials.
They have a layer of foil (reflective layer) and a layer of thermal insulation, such as polyethylene foam. There are also many options where the foam layer is replaced with plastic film and (or) kraft paper.
Megaflex
This is bath foil that has higher quality parameters compared to its competitors. Megaflex can be used at temperatures above 300 degrees. Bath foil is highly reflective. If the installation technology is followed, this product will help create a sufficiently sealed system, which prevents the spread of steam outside the bathhouse.
Pros and cons
The use of foil in a bath is due to its ability to reflect heat and retain steam. For a bathhouse, these are important qualities; not so many materials have them. When deciding whether foil is needed in a bathhouse, you must take into account that it will serve as a good additional insulation system, but not the main one.
Information. The price of foil is very low. The price is comparable to average wallpaper, which is often changed. Apart from the rolls themselves and foil tape, you don’t need to buy anything additional.
A common myth that works against foil is that to insulate a steam room or an entire bathhouse, it is enough to cover it with a thin layer of foil. It's not like that at all. The bathhouse needs to be insulated exactly the same as if foil had not been used in it at all.
It plays only a supporting role, enhancing the insulating qualities of existing insulation materials. Before covering the inside of the bathhouse with foil, it should already be well insulated, and the entire insulation should be well protected with waterproofing. Communications, water, lighting must also be installed, and a stove installed.
Which one to choose
The basis of the foil is a thin metal sheet. It is made only from aluminum. This is due to its technological feature, which allows aluminum to be rolled into very thin sheets. Not all metals have such a ductility coefficient.
Copper is on par with aluminum, but when rolled into thin layers, it oxidizes. Only aluminum remains suitable, so there are no options for metal. Aluminum already has excellent performance properties. Bath insulation with foil can be produced by the manufacturer in a variety of options.
The main types of foil insulation used in baths
- Foil + foamed polyethylene (Folgisolon), single-sided and double-sided coating, different thickness of the polyethylene layer;
- Foil-coated mineral wool. The aluminum coating is only double-sided.
- Bath foil reinforced with kraft paper (Kraft foil). It does not have an insulating layer.
- Foil + fiberglass mesh (Folar). It is heat resistant.
- Regular construction foil without a base. Requires careful gluing and good protection followed by a finishing layer.
The choice of which foil is best for a bathhouse is made based on design documentation, construction budget and availability on the local construction market. If the requirements for safety and environmental friendliness are the highest, then paper-based foil for a bath or without a base at all is optimal.
If the quality requirements are standard, then the foil thermal insulation for a bathhouse can be anything, as long as it comes from a certified manufacturer.
If the bath already has a good layer of insulation, then there is no point in purchasing foil on foamed polyethylene or mineral wool.
It is for such options that foil is made on kraft paper for a bath or fiberglass mesh.
These additional materials are added to the foil not for insulation, but for strength.
There are a huge variety of specific brands of foil: Alufom, Resurs Megaflex, foil for a bath of any brand should have a uniform surface. There should be no stains, streaks, thinning or untaped areas. This is the main indicator of quality.
Foil is not difficult to produce, and aluminum has a low melting point. This is why there are so many manufacturers of foil and foil materials. It is recommended to pay attention to certified products.
Reviews of foiled mineral wool
Foil-coated mineral wool can be presented in soft rolled and hard mats. According to experts, this expands the scope of use. Among the main advantages of the first of the mentioned types, according to consumers, a high degree of moisture and vapor barrier should be highlighted.
As for foil wool in the form of rigid mats, they have excellent insulating properties and are easy to install. The thickness of soft rolls can reach 10 mm, and the maximum exposure temperature, as home craftsmen emphasize, is quite high and reaches 125 ° C.
Which one is better to use?
When wondering what foil to use for a bath, evaluate the different options. To calculate the required quantity (and, therefore, price), exactly the same scheme is used as for wallpaper.
In stores with wholesale prices you can buy at least one roll. For thin materials it is more than enough for the entire bath. Thick foil insulation is purchased in several rolls.
Technology for laying vapor barrier from foil kraft paper
When installing a vapor barrier in the attic, you can attach foil material:
- on floors;
- along the slopes.
In order for vapor barrier work to be of high quality, you should:
- lay strips of vapor barrier material only horizontally;
- attach the starting strip at the ridge of the building, then, overlapping, attach subsequent strips;
- the vapor barrier must be a solid structure that prevents moisture from entering the room;
- Vapor barrier material should be attached from the inside of the room with slats or a construction stapler;
- When installing a vapor barrier for a room, experts recommend selecting related products from the same manufacturer as the material itself.
The work of arranging a vapor barrier for a room is not as difficult as it seems at first glance. Knowing the installation technology and the main stages of this work, even a novice master will be able to do it.
Thickness
Aluminum allows the production of any sheets. From a few micrometers to centimeters. In construction, options of 30-300 microns are used. Foil for a bathhouse 100 microns is the most durable, and the cost differs slightly from thinner options. It is easier to work with a durable option, but installation still needs to be carried out very carefully.
The thickness of the foil layer is always indicated in the characteristics of the material. If you have a limited budget, you can choose the minimum thickness. The smaller the thickness, the more careful the installation needs to be. The thickness of the foil does not have a significant effect on the efficiency of heat reflection.
Information. Foil without an insulating layer on mesh or kraft paper is sold in rolls, with a thick layer of insulation - in sheets. In terms of price, it is beneficial to immediately purchase several rolls to insulate the entire bath.
Do not think that thickness is the decisive factor in which foil is best to use for a bath. On the contrary, it only affects strength, and not the thermal insulation characteristics. Despite the inertness of aluminum, it is still oxidized to some extent by water.
For some manufacturers, especially in those materials where thin foil is used, it is protected by a polymer film or spraying.
Such insulation is usually more expensive.
Their benefits are noticeable only after many years of use.
Their use is justified only for paired separation.
Reviews of foil in rolls
This material is sold not only in the form of panels. If you want to purchase foil for a bath, you can choose the material in rolls. It is characterized by low cost, which is complemented by ease of installation. Installation of such foil is possible only on fire-resistant heat-insulating material with fastening with metal brackets.
Buyers like that the sheet thickness is minimal and can be 0.5 mm. The roll width is 1500 mm. According to consumers, the temperature range is quite wide and varies from -50 to +75 °C.
Insulation materials
Foil insulation for a bath can have either a porous polyethylene base, or made of mineral wool or basalt. An option is foil foam rubber, foam chips on a mesh, but these are all specialized insulation materials intended for refrigerators.
In construction practice, they can be encountered very rarely. Bath insulation with foil is widely available in only two versions: polyethylene and mineral wool. Here are their main advantages:
- foil on polyethylene foam is a safe material; both components are widely used not only for insulation, but also for food packaging;
- mineral wool or basalt does not burn, but requires caution when working, as when handling glass wool.
Information. The insulation layer does not allow the sheet to be bent under an unacceptably small radius. It greatly facilitates installation, but the footage of foil with insulation in one roll is much smaller. At a price per meter it is more expensive than plain foil.
Price for foil for bath insulation
Table. Popular foil heat insulators for baths.
| Name, photo | Characteristics, description | Average market value, in rubles |
| 1. “Annealed” foil | A fairly soft material, the thickness of which is 100 microns. Sold in rolls of 10 square meters. As for the total length of one roll, it is equal to 10 meters. Complies with GOST. | From 1400 rub. (per roll) |
| 2. “Isover Sauna” | The brand of insulation mentioned above, 5 centimeters thick, is also sold in rolls 12.5 meters long. The total area of one roll is 15 square meters. It is characterized by the fact that it also has soundproofing properties. | From 2200 rub. (per roll) |
| 3. “Steam MAT ALUCOAT 35” | High-quality Finnish heat insulator, still sold in rolls. The thickness of this material is 3 centimeters, and the length of one roll is only 8 meters. In addition, the total area of one roll of insulation is 7.2 square meters. | 1800 rub. (per roll) |
| 4. Rockwool Sauna Butts | And this is foil-coated mineral wool, which is sold in slabs. The thickness of this material is 5 centimeters, and the dimensions of one plate are 60x100 centimeters (WxL). The total area of one slab is 0.6 square meters. | 750 rub. per package (8 slabs) |
| 5. URSA GEO M-11F | High-quality roll insulation - mineral wool with foil coating. What is typical is that this bath foil is laminated with kraft paper. The thickness is 5 centimeters, and the length of one roll is 12.5 meters. The optimal operating temperature is +270 degrees. | 2100 rub. (per roll) |
As you can see, the cost of foil varies and depends not only on the variety, but also on the specific manufacturer.
Vapor barrier
Even a thin aluminum sheet tens of micrometers does not allow water vapor to pass through. This property is very important for baths and saunas. Foil vapor barrier for bathhouses is produced by many manufacturers, and it is very convenient. You stick on a universal layer that will perform two functions at once:
- Reflective thermal insulation for a bath is a layer that effectively reflects IR rays;
- Vapor barrier made from food safe material.
The ability to effectively reflect even the thinnest sheets of foil, such as food grade foil, can be easily verified. Look at the leaf in the sun against the light. It shouldn't show through at all.
At the same time, much thicker and more reliable foil is used for construction than for the food industry. The thickness of aluminum foil for vapor barrier in a sauna (in a sauna the vapor barrier is always more powerful than in a bath) can be any.
In this case, you should only use construction foil, not food grade foil. The quality of the vapor barrier is more influenced by the accuracy of installation and the absence of cracks it ensures, rather than by the thickness of the material.
Installation
Information. The general rules for attaching foil in a bathhouse are as follows: it is necessary to glue all joints with foil construction tape, the work must be neat, installation must be done without tension, with an allowance and sagging of the roll of 1-2 cm in each cell of the frame.
Sheathing a bathhouse with foil is done at the stage when the main layer of insulation on the inside of the frame has already been laid. Moreover, such a stage of readiness should exist for the ceiling. Foil on the bathhouse ceiling is even more important for reflecting heat, as warm air rises straight up. The coating on the ceiling and walls must be continuous and without cracks. Only in this case will it be effective.
Any aluminum foil for baths and saunas is mounted with acrylic glue. There is no point in using toxic epoxy. Its strength is excessive for such a task. The same applies to polyurethane and other polymer adhesives with solvents. Acrylic glue is bought in cans, and construction tape is also covered with it. Masking tape should not be used.
Important! Be sure to check the characteristics of the glue to determine whether it is approved for interior use, whether it is moisture resistant, and whether it is suitable for foil. Gluing can be done not by the foil itself, but by a layer of polyethylene. In this case, purchase the appropriate glue option.
The first stage is preparing the base of the walls and ceiling. You can spread rolls of foil over a layer of mineral wool, basalt or any other insulation. You can put an additional membrane for insulation.
Layers of plywood, thick film and other materials are used.
Exact adherence to technology at this stage is not so important.
The main thing is that there is good waterproofing of the insulation in front of it from the interior of the bathhouse.
That is why this separating layer is most often made of good waterproofing material. When preparing the surface, we take two points into account:
- We remove all sharp corners and protrusions;
- We provide the possibility for further installation of the subsequent finishing layer (lining, block house).
The second stage involves the main way to attach the foil in the bath - using glue. All other methods will be worse. Self-tapping screws, nails, studs from a stapler - all of them lead to a violation of the tightness of the layer and the effectiveness immediately decreases. In addition, during intensive use of the bathhouse, condensation is possible on the vapor barrier layer of foil. The metal here will rust.
Attention! Do not stick foil on large wooden surfaces, logs, beams and linings. These materials have too much dimensional variability. And if you glue foil on them over its entire area, then when it swells it will simply tear.
Insulation for a sauna with foil and for a bath are attached in the same way. The supporting surface is the wooden frame bars to which the insulation is attached.
Insulation boards must be laid so that they are all below the level of the lattice bars.
All protruding parts must be compacted, additional slats and adhesive seams must be laid.
Finishing a bathhouse with foil is very similar to wallpapering walls.
Anyone who knows how to hang wallpaper can handle it.
Steam room cladding
Foil for steam rooms is usually purchased on kraft paper or polyethylene. It is not recommended to use foil mats with mineral wool due to their low moisture resistance.
The ideal option is safe and environmentally friendly kraft paper. The steam room differs from other rooms in the bath due to its increased temperature and humidity. This imposes corresponding requirements on all finishing materials.
Important! Pay attention to each area. Carefully seal the joints of the rolls and the joints near the ventilation window, grilles and doors. You should not save foil tape.
Foil is always used in conjunction with other insulation and finishing materials. The moisture resistance of all materials is the main condition that must be taken into account before choosing foil for the steam room.
Kraft paper has good moisture resistance, although it is an organic compound. The same applies to polyethylene. An exception should be made only for mineral wool and basalt.
Apply insulation for the steam room with foil with an overlap.
Thin sheets are joined with tape overlapping, thick sheets - end-to-end.
The ideal option for joints, especially for thick materials, is to seal the entire seam with foil tape on both sides.
If this is not possible, then glue the joints on one side.
In a steam room, special attention should be paid to the fit of the foil insulation to the frame of the ventilation window, to the valve and door.
These are weak points where steam rushes and condensation forms. Thin foil in these places can be applied in several layers.
How to sheathe a ceiling
Before covering with foil, the ceiling must be almost 100% ready. Only the wooden face layer needs to be hidden before this. The structural component that carries the load (beams, flooring) must be completed, insulation must be completed, and all communications must be installed. Pasting with foil does not take much time.
Information. The ceiling is sheathed with foil in an almost completely built bathhouse, at the stage when communications are separated and there is no interior decoration yet.
Ceiling sheathing differs from wall sheathing in that there is a different pattern for attaching the insulation. The scheme with fastening slabs in the cells of a wooden frame is rarely used. It is difficult to glue the slabs securely enough to prevent them from falling out.
In this regard, continuous flooring is used on the ceilings. It is made from clapboard or thin wooden boards. The use of OSB board is extremely undesirable, since at a high ceiling temperature (in a sauna it reaches 70 C with almost every firebox), it begins to release harmful compounds.
OSB boards are a good material, and they are quite acceptable outside the bathhouse, but inside they are undesirable, especially on the ceiling.
On the ceiling, do not stick foil over its entire surface.
As already noted, this can lead to its rupture, especially if the ceiling is made of swelling boards.
Lining the inside of the bathhouse with foil for the ceiling and walls should be done without tensioning the foil.
It is glued to strips of glue and should have an overlap of 1-2 cm. Strong sagging weakens the structure; it should not exist. In the same way, with a margin for distance fluctuations, electrical wires are hung on supports.
Attention! When covering the ceiling, use safety glasses. The ceiling is covered with the same type of foil (or foil insulation) as the walls.
What should be the thickness of thermal insulation in a bathhouse?
Here, a lot depends on the thickness of the walls, as well as on the material from which they are made. So, for brick/concrete walls with a thickness of 25 to 35 centimeters, it is necessary to use a heat insulator 10-15 centimeters thick. For the same walls, but with a thickness of more than 35 centimeters - within 8-10 centimeters. If we are talking about wooden walls with a thickness of 10-15 centimeters, then the thickness of the heat insulator should be approximately 6-8 centimeters, if 15-20 - then approximately 4-6 centimeters, and finally, if over 20 - then about 2-4 centimeters . As you can see, there is nothing complicated here, so let’s move on directly to the installation work.
Pasting aerated concrete
Aerated concrete is a material with thermal conductivity identical to natural wood. Despite the fact that it is a mineral material, aerated concrete floats in water. It is suitable for a bath, but subject to careful protection from water. It must be remembered that it actively absorbs moisture. Its resistance to moisture is much lower than that of wood.
On the other hand, getting wet does not lead to the destruction of the aerated block, but it is very undesirable.
The method for attaching foil in a block bath should take this into account.
Invest in thorough waterproofing and do it according to all the rules.
Only in this case will the aerated concrete bathhouse serve you for a long time and be fireproof.
The use of foil in an aerated concrete bath is desirable not so much because of insulation, but because of its excellent vapor barrier properties.
In terms of technology, all the methods for making foil in a bathhouse made of aerated concrete do not differ from the standard ones described in detail in this article.
Foil should not be installed directly on aerated concrete walls. A layer of insulation must be laid. Exactly the same wooden grids with cells and insulating boards are used here.
Information. Aerated concrete and foam concrete absorb water more easily than wood. Protection from water and steam must be done even more carefully than in wooden baths. The corresponding article on our website talks about waterproofing.
Features of bath ventilation
As noted earlier, the installation of a high-quality ventilation system is mandatory for the normal functioning of the thermal insulation cake. This should be taken care of in advance - even before proceeding directly to insulation. There are several layouts of holes for ventilation; let’s take a brief look at each of them.
First
We are talking about the circuit indicated in the illustration above by the letter “a”. This is natural ventilation, the supply vent for it is installed at the bottom of the wall next to the heating device, and the exhaust vent is located on top of the opposite one. The option is simple, but its effectiveness leaves much to be desired. For example, some open doors to enhance such ventilation.
Second
Option “b”, in which both vents are located on the same wall, and the heating device is located on the opposite wall. Suitable for baths with one outer wall. To strengthen the system, a fan is used (in the inlet).
Third
As for option “c”, it must be implemented during the construction of the bathhouse, since in this case the air will move under the finished floor. The location of the ventilation windows is the same as in option No. 1, but the fan should be located in the exhaust hole (the one on top). It's a fairly effective system, it's worth noting.
Finishing
The insulation for the walls inside the bathhouse with foil cannot be left uncovered. Foil has low strength. In addition, the material can never be installed without a single wrinkle, so this coating looks very mediocre. To eliminate this, a fine finish is applied.
For bathhouses this is traditionally wood. In front finishing it is used in the form of lining (thin board) or block house (thick board with imitation of a log house or timber). Foil under the lining in the bathhouse is an economical and practical solution. The fastening of the front trim is adhesive and with self-tapping screws, which are recessed and sealed with wooden plugs.
Self-tapping screws pierce the foil layer, but you can’t do without it, and the vapor barrier is only broken by a fraction of a percent. How to cover a steam room with foil and clapboard (or block house) is described in detail in other articles on our site.
conclusions
Foil is an inexpensive means of providing good additional insulation for a bathhouse. It is safe (even used in the food industry for direct contact with food) and easy to use. The only difficulty is the need for great accuracy in work. For foil insulation to really work, we remind you of some conditions:
- foil covering should cover all walls and ceiling;
- foil is only suitable as additional insulation, not the main one;
- All joints must be taped with foil tape.
Insulation with foil does not take much time and quickly gives high-quality results. We recommend it for your baths.
Selecting a foil coating based on the recommended layer
In order to achieve high-quality coverage during installation work, you should adhere to the thickness of the foil thermal insulation. It will depend on the material and thickness of the wall. If the base is brick and the thickness of the steam room wall reaches 37 cm, then the recommended layer should be from 8 to 10 mm. If the base is concrete or brick, and the wall thickness varies from 25 to 35 cm, then the foil insulation should have a thickness of 10 to 12 mm. In the case of a wooden frame from 10 to 15 cm, you must use foil thermal insulation, the thickness of which varies from 6 to 8 mm.
When using the same material, but increasing the wall thickness to 20 cm, you should use a foil layer from 4 to 6 mm in thickness. Foil for a bath will have a layer of 2 to 4 mm if the wooden frame is more than 20 cm thick.
Glass wool or basalt wool can be used as an additional heat-insulating layer. Similar mineral heat insulators are also suitable. Aluminum foil or similar coatings will reflect heat into the room, so it is better to install such a layer in a steam room insulated like a pie. This recommendation is relevant for saunas and baths made of concrete or brick. The advice is also suitable for frame buildings. If the external walls of wooden log houses are sufficiently thick, the layer of additional thermal insulation can be neglected, but when choosing a foil material, you should not give preference to thin sheets of kraft paper in foil.
