In winter, at least 25% of the heat goes through the roof of the uninsulated building, the losses are compensated by enhanced heating. Of course, the load falls on the heating system and entails increased energy consumption. The budget way to solve the problem is to insulate the ceiling in a private house, the attic remains cold. Overlapping less roof slopes in area, hence the savings. Our task is to tell you how to properly insulate the ceiling, after selecting suitable materials.
The eternal question is to insulate from the inside or outside
Any external fence separating the living room from the street, it is better to sheathe the outside with thermal insulation. Accordingly, the ceiling insulation on the top floor of a private house is done from the attic. Causes:
- Installation is physically simplified, which is important when doing the work yourself. There is no need to make a suspended frame or hem the insulation from the bottom to the ceiling.
- An insulator layer 10–20 cm thick (depending on the region of residence) will not reduce the height of the rooms. This is an important plus for old buildings and "Khrushchev" with low ceilings.
- In an old house or apartment you don’t have to redo the repair.
- If you do not follow the technology of internal thermal insulation, the surface under the insulation will get wet, a fungus will appear. Condensation of moisture inside the "pie" contributes to 2 factors: the penetration of water vapor and the formation of dew points at the junction of dissimilar materials.
About the notorious dew point that ordinary homeowners fear. To avoid condensation inside the structure, it is worthwhile to withstand 2 conditions: prevent water vapor from entering the room and use an insulator of sufficient thickness. Then the dew point will be inside the insulation, where there is nothing to condense. The second way is to organize the removal of moisture using ventilation (read below).
Reference. The dew point is a phenomenon of condensation of water vapor from air at a certain humidity and temperature. The lower the air temperature, the earlier the degree of extreme moisture saturation is reached and condensation begins to precipitate.
There are exceptions to the rules, not every room can be finished with insulation from the outside. Examples:
- ceiling of the upper apartment of a multi-storey building;
- attic;
- balcony, loggia;
- concrete ceiling of the garage above the basement, cellar;
- the need for cost savings, etc.
In these cases, internal thermal insulation of the ceilings is arranged with strict adherence to technology. We will describe the order of work in the form of step-by-step instructions, but first you need to find out ...
The better to insulate the ceilings
For insulation of ceiling structures, 4 groups of materials are used:
- Fibrous - mineral, stone (basalt) and glass wool.
- Loose - sawdust, clay, expanded clay, vermiculite.
- Polymers made of expanded polystyrene and polyethylene.
- Sprayed - ecowool, polyurethane foam, liquid foam - penoizol.
We will not focus on the last group of heaters - liquid mixtures are applied by spraying or filling cavities under pressure, which requires appropriate technological equipment. You cannot do such insulation of the ceiling in a private house with your own hands - you need to hire the masters of a specialized company and pay for services.
Note. Spray materials are the most effective and expensive at the same time. Manually applied only insulating polyurethane foam Polynor with a low coefficient of thermal conductivity λ = 0.04 W / (m • ° C). The price of the aerosol can is 8 oz. e., the coating area is 1 m² with a thickness of 50 mm.Thermal resistance of the layer: R = 0.05 / 0.04 = 1.25 m² • ° C / W - the information is useful to us for comparison.
Let us consider in more detail each group of building materials, then we will choose suitable heat insulation materials for ceilings in various rooms.
Porous fiber materials
For the thermal insulation of roofs and attics under a cold roof, 3 types of fibrous products are used:
- mineral wool with a synthetic binder, thermal conductivity λ = 0.055-0.06 W / (m • ° С);
- non-combustible basalt insulation λ = 0.05-0.053 W / (m • ° С);
- fiberglass-based mineral wool (aka glass wool) λ = 0.044 W / (m • ° C).
Clarification. We provide insulation parameters for actual operating conditions, taken from the normative building documentation. To overestimate the performance of insulators, manufacturers indicate the coefficient λ for the material in a dry state. The lower the thermal conductivity, the better the insulation resists cold.
Above, we calculated the thermal resistance R of penoizole 5 cm thick (1.25 m² • ° C / W). Let us compare the indicator with the characteristics of fibrous materials of a similar thickness by performing a short calculation for each (the method of SNiP is applied):
- minvata - R = 0.05 / 0.055 = 0.9 m² • ° C / W;
- stone wool - R = 0.05 / 0.05 = 1 m² • ° C / W;
- glass wool - R = 0.05 / 0.044 = 1.14 m² • ° C / W.
Conclusion. According to thermal insulation properties, fibrous heaters lose to liquid and foamed polymers. Glass wool shows the best result, the worst - ordinary mineral wool insulators. By the way, the values of thermal resistance R are interpreted the opposite: the higher the indicator, the more efficiently the insulation of a certain thickness works.
We list the remaining, no less important properties of fibrous insulation:
- Cotton wool is produced in rolls, plates and mats of various densities - from 35 to 200 kg / m³.
- The open-pore structure contributes to good vapor permeability of materials.
- Mineral wool absorbs moisture, but with proper ventilation dries quickly.
- Basalt fiber is considered non-combustible because it can withstand temperatures of 600-700 ° C. Conventional mineral wool slabs also do not burn, but are destroyed by strong heating. Glass wool begins to melt at 250 degrees.
- Insulators do not have high strength, are attached to glue or using a frame.
Fiberglass-based cotton wool contains the smallest particles of glass, so it is not applicable inside residential premises. The well-known manufacturer of roofing insulation "Isover" recommends covering glass garret floors from the outside.
Other mineral insulators use a synthetic binder containing formaldehydes. Under certain conditions, these substances can be released and mixed with air. With internal insulation, mineral wool must be well insulated from the living space with the help of a film, drywall and so on.
Loose heaters
All backfill materials are of natural origin, and therefore environmentally friendly. The following heaters are used for insulation of ceilings:
- expanded clay;
- fine chips, sawdust;
- clay;
- vermiculite gravel.
Reference. Vermiculite is much more expensive than expanded clay, so it is rarely used. Clay in its pure form is also not used - it is usually mixed with reeds or sawdust.
The main disadvantage of natural insulation is low efficiency compared to mineral and polymer products. Example: thermal conductivity of expanded clay gravel with a density of 200 kg / m³ is 0.11 W / (m • ° C). The heat resistance of the R layer of 50 mm will be only 0.05 / 0.11 = 0.45 m² • ° C / W. Indicators of expanded clay increased density, sawdust and clay even less.
Briefly about the properties of building materials:
- All bulk heaters pass water vapor well.
- The combustibility of clay, expanded clay and vermiculite gravel is practically zero. Sawdust or reeds mixed with clay mortar also successfully resists fire.
- Long service life (excluding wood chips).
The low price of natural heaters is a relative concept. To create a heat-insulating layer comparable to mineral wool 5 cm thick, you need to fill in expanded clay to a height of 100 mm, that is, spend twice as much.
Characteristics of polymer thermal insulation
To begin with, we give a list of materials used indicating the heat-conducting characteristics in operation:
- polystyrene with a density of 15 ... 35 kg / m³, λ = 0.045-0.041 W / (m • ° С);
- EPPS extruded polystyrene, density - 20 ... 40 kg / m³, λ = 0.039-0.037 W / (m • ° С);
- foamed polyethylene 30 ... 50 kg / m³, λ = 0.044-0.042 W / (m • ° С).
Reference. Extruded polystyrene foam is often called Penoplex by the name of a popular brand. Products made of polyethylene foam are known by the names "Penofol", "Isolon" and "Tepofol".
For comparison with fibrous insulators, we determine the thermal resistance of polymers with a thickness of 50 mm:
- polystyrene 25 kg / m³ - R = 0.05 / 0.043 = 1.16 m² • ° C / W;
- "Penoplex" - R = 0.05 / 0.038 = 1.32 m² • ° C / W;
- “Penofol” - R = 0.05 / 0.042 = 1.19 m² • ° C / W.
It is noticeable that the thermal insulation performance of polymer insulation exceeds the characteristics of mineral and basalt wool. The leader is extruded polystyrene, whose result is comparable only with polyurethane foam applied by machine.
Other properties look like this:
- Thanks to the closed air pores, heaters practically do not allow moisture to pass through. An exception is foams having a meager vapor permeability of 0.05 mg / (m • h • Pa). The indicators of mineral wool are 0.4 ... 0.6 mg / (m • h • Pa).
- All polymers are flammable, no matter what sellers and manufacturers claim.
- Polystyrene-based materials are highly durable and are available in slabs.
- Foamed polyethylene has a soft and flexible structure, sold in rolls. To reflect the infrared heat flux, the insulation surface is covered with aluminum foil.
In terms of accessibility, polystyrene is in the lead - its price is comparable to natural materials. An “extruder” is sold at the price of basalt non-combustible cotton wool or even more expensive.
Useful fact. A good insulator can be a polymer stretch ceiling, forming an air gap under the ceiling. This cavity cannot be called hermetic, but there are very few paths for the penetration of warm air.
Selection tips
A review and comparison of the characteristics of insulation materials showed that each group of insulators has strengths and weaknesses that limit the scope of application. For example, flammable polymers cannot be used for insulation of floors on wooden houses - fire regulations prohibit it. It is not worth ignoring the requirement - with the help of a heater, the fire will easily spread to the next floor.
Reference. When installing wooden ceilings, standards require that the supporting beams be treated with a refractory composition and non-combustible insulators are used. If you follow these instructions, then in the event of a fire, the ceiling will last 30-60 minutes until it collapses. Here is the answer to the question of whether it is possible to insulate a wooden ceiling with foam.
Based on experience in construction and other regulatory requirements, we will give the following recommendations for choosing thermal insulation:
- Ceilings made of wood are better insulated from the attic with basalt wool, expanded clay, vermiculite or a mixture of clay with sawdust.
- The ceilings in the rooms of the bath (especially steam rooms) need to be insulated with environmentally friendly materials. Here the choice is small - the same expanded clay, sawdust, vermiculite gravel, natural moss. No polymers and mineral wool, from strong heating, the release of harmful substances will begin.
- The ceilings of the attic rooms are sewn from the inside with dense basalt fiber, glass wool is not applicable.
- Concrete monolithic coatings are usually insulated with foam or polystyrene foam. In a country house - from the roof, on the balcony of a high-rise building or in the basement of the garage - from the inside.
- It is more correct to insulate flat reinforced concrete roofs with polymers from the outside, before the device of the surfaced bitumen roof. If this is not possible, Penoplex is hemmed from the bottom without problems, but with the observance of technology.
- Foil foamed polyethylene is preferably used as an additional insulating layer. Find out how to properly insulate the ceiling with Izolon and Penofol from a separate manual.
Practice shows that it is better not to combine wood and vapor-proof building materials. The polymer, which adheres tightly to the beam, blocks the access of air; wood does not “breathe”. If steam begins to condense at the junction and has nowhere to leave, the tree will turn black and rot.
The author of the video clearly exaggerates and exaggerates the problem, but the situation shown is, of course, unacceptable. There is only one way out - when using polymers, it is necessary to ensure the contact of wood with air, which is not easy to implement technically.
How to calculate the thickness of the insulation
The determination of the thickness of the insulation layer will be shown by examples. As a basis, we take the formula for calculating thermal resistance (in the previous sections we already used it to compare the effectiveness of different materials):
- R is the heat transfer resistance of the insulating “pie”, m² • ° C / W;
- δ is the thickness of the insulation, m;
- λ is the coefficient of thermal conductivity of the material, W / (m • ° C).
The essence of the calculation: according to the standard thermal resistance specified for your region of residence, calculate the thickness of the insulation, knowing the characteristic λ. The value of R is determined according to the scheme given in the regulatory documents, a map with indicators for the Russian Federation is shown in the photo.
Example 1 It is necessary to calculate the warming of the cottage with an attic located in the suburbs. We find the R characteristics for Moscow, select the indicator 4.7 m² • ° C / W (for coatings), take the coefficient λ of basalt wool equal to 0.05 W / (m • ° C) and calculate the thickness: δ = 4.7 x 0.05 = 0.235 m ≈ 240 mm .
Example 2 We determine the thickness of the insulation layer from "Penoplex" for concrete floors, location - Cherepovets. The algorithm is as follows:
- We find on the Internet or reference literature the thermal conductivity of reinforced concrete λ = 2.04 W / (m • ° C) and find out the thermal stability of a standard slab 220 mm: R = 0.22 / 2.04 = 0.1 m² • ° C / W.
- According to the map, we find the standard value of R for Cherepovets, we take the overlap index - 4.26 m² • ° C / W (the figure is highlighted in green).
- We subtract from the required heat transfer value the found resistance of the plate: 4.26 - 0.1 = 4.16 m² • ° C / W.
- We calculate the thickness of polystyrene foam insulation λ = 0.037 W / (m • ° С): δ = 4.16 x 0.037 = 0.154 m ≈ 160 mm.
Comment. The algorithm does not take into account the heat resistance of the interior decoration and attic floors, therefore it gives a result with a small margin. If we take away the resistance of the floorboards and gypsum plasterboard hemming, the thickness of the EPSS will decrease to 135 mm.
We warm mineral wool flooring
As mentioned above, mineral wool is used to isolate wooden ceilings and ceilings of attic rooms. So that the material is not saturated with moisture and does not lose heat resistance, it is necessary to withstand 3 conditions:
- protect cotton wool from water vapor from inside the premises;
- provide ventilation of the outer surface, so that the resulting moisture is eroded from the thickness of the insulation;
- the vapor permeability of the materials used in the “pie” should increase towards a colder room or street, as shown in the diagram.
Plate or roll mineral wool is located in the space between the ceiling beams, as shown in the insulation scheme. When installing thermal insulation with your own hands, observe the following procedure:
- Roll out a vapor barrier film from the bottom of the beams, laying adjacent sheets with an overlap of 100 mm wide. Lap on the walls 10-15 cm wide. Carefully glue the joints with tape.
- Glue film overlays to walls with silicone sealant.The goal is to cut off room moisture from penetration into the attic.
- The work is carried out by the cold roof. Therefore, first make a rough padding of the ceiling, which subsequently will be covered with cotton wool.
- Lay the mineral wool slabs as shown in the photo. The rolled material is neatly cut and inserted between the lag, it is unacceptable to crush cotton.
- On top of the insulation, spread the waterproofing canvases - a diffusion membrane that allows moisture to pass only one way - out. Perform an overlap of 10 cm and sizing the joints.
- Across the lag, randomly lay the attic floors from edged boards. Solid flooring is optional.
An important point. Between the surface of the cotton wool and the waterproofing, a ventilation duct is necessarily provided. Thanks to the air gap, moisture is removed from the insulation.
Sometimes builders lay the first waterproofing film on top of the boards of the draft ceiling, bypassing each beam. We do not recommend using this approach - vapor barrier will close the air access to the log wood, and from below it will remain open for steam saturation. Further it is clear - the tree will rot.
How to lay mineral wool on the ceiling, if the thickness of one layer is not enough. In such cases, a second tier of heat-insulating plates, shifted by 30-50 cm relative to the first row, is made. If the height of the load-bearing beams is not enough to organize the air, the frame of the battens of the crates is built up, then a second layer of insulation and waterproofing are arranged.
The attic insulation scheme of the attic is very similar to the thermal insulation of a wooden floor:
- A counter-lattice is provided on the roof, a diffusion membrane is rolled from above along the rafters. If there is no external frame, the waterproofing can be fixed from the inside, bypassing each rafter leg and shooting the edges of the paintings with a stapler.
- The insulation is placed between the rafters completely. If the width allows, we put the plates in 2 layers with a dressing, otherwise we mount a horizontal counter-lattice.
- We beat the vapor barrier to the rafters through the rails, to which the interior finish of the gypsum board or lining is subsequently attached.
It is extremely undesirable to insulate concrete ceilings with cotton wool from the inside, especially in humid rooms - the kitchen and the bathroom. The porous material will freeze and lose its properties if effective ventilation is not provided. Another thing is to fix the mineral wool in the space behind the stretch ceiling, where water vapor hardly penetrates.
Styrofoam sheathing technology
Polymers are usually used to insulate reinforced concrete floors and ceilings, on both sides. To isolate the structure from the inside, the surface must be prepared - to close the joints of the plates, level with a solution and thoroughly treated with a primer.
The second stage of internal thermal insulation is the installation of a subsystem of wooden blocks or metal profiles. The frame plays the role of a platform for the finishing device - drywall, suspended ceiling and so on. Polystyrene plates are attached to the concrete surface directly with an adhesive mixture and dowels, umbrellas.
Reference. Performing thermal insulation of balconies and loggias with extruded polystyrene, masters often dispense with the subsystem - they stick or screw plates to the ceiling in a continuous layer. The slats for the inner lining are attached to the concrete floor through the insulation with special screws - nails.
How to insulate a reinforced-concrete ceiling in a private house from the inside:
- After preparing the surface and assembling the frame (or without it), prepare the adhesive mortar according to the instructions on the container.
- Apply glue to the foam plate and press it to the surface, hold for a while. Fasten the next element end-to-end with the previous one, do the adjacent row with a shift relative to the first.
- When the mixture hardens, additionally fix the polymer plates with dowels in the form of umbrellas. It is desirable to blow off joints with polyurethane foam.
- Block the ceiling with vapor barrier, observing overlaps and gluing joints. The film or "Penofol" is aimed at the subsystem with a stapler.
- Fill the edges of the film on the walls and glue with construction sealant. Install the battens of the battens and proceed to the finish.
Tip. Do not screw the Penoplex to the ceiling without glue. Firstly, there will be gaps under the insulation, and secondly, you need to perfectly level the surface. Otherwise, at the joints of the plates, differences of 1-3 mm will appear.
External insulation of reinforced concrete slabs with polymeric materials is used on flat roofs and exploited attics. The “pie” on the roof is formed as follows:
- The prepared surface is covered with a vapor barrier film in accordance with all the rules.
- Polystyrene foam is tightly placed on top, fixed to the ceiling.
- A cement screed is poured, playing the role of waterproofing and a solid foundation, so that you can walk on the roof.
- A surfaced waterproofing with roofing felt with flycars is arranged to remove air and water vapor from under the “pie”.
Of course, you can insulate reinforced concrete with mineral wool from the inside, and the floor of the log house with polystyrene foam. Then take additional measures: isolate the mineral wool very carefully from the room, and blow foam between the polymer and the wood - it lets air through and prevents rotting.
Finally about filling the attic
The use of bulk materials is the simplest option for insulating the ceiling of a country house, although not the most effective. Thermal insulation is made on top of the floor in various ways:
- The space between the beams is covered with expanded clay, sawdust or vermiculite gravel at the highest possible height. The flooring boards are laid on top.
- Chips and sawdust are mixed with pre-soaked clay. The solution fills the space between the lags.
- A screed of sawdust is arranged - the waste is mixed with cement and sand in a ratio of 5: 1: 1.
If you have a screw concrete mixer at your disposal, you can prepare a more modern insulation for the ceiling - polystyrene concrete. A cement-sand mortar is mixed with polystyrene balls and laid on a ceiling with a layer of 200-300 mm. It is not necessary to lay the flooring - the monolith has sufficient strength.
Note. There was a mistake in the video - there is no need to lay the film under bulk materials. Water vapor (especially in the bath) should freely go out through expanded clay or sawdust concrete to the outside, and the tree should dry thoroughly.