How and how to insulate the foundation of a wooden house from the inside and outside?

For your home to last a long time, keep moisture buildup at bay, and maintain comfortable interior temperatures, you must insulate the foundation of a wooden house. Every approach to insulation, whether you’re thinking about doing it internally or externally, has advantages and disadvantages.

Applying materials directly to the foundation’s exterior is known as exterior insulation. Using this technique shields the foundation from changes in temperature and moisture intrusion. Insulated concrete forms (ICFs), sprayed polyurethane foam, and rigid foam boards are common materials used for exterior insulation. Adequate installation is essential to guarantee efficient defense against moisture and cold.

Conversely, adding insulation to the walls of the crawl space or basement is the main goal of interior insulation. For existing homes, this method may be more affordable and accessible. For interior insulation, materials like rigid foam boards, fiberglass batts, and spray foam are frequently utilized. In order to avoid mold and decay, it’s imperative to take care of any current moisture problems before adding insulation.

Any insulation project must be well prepared before it is started. Important first steps include evaluating the state of your foundation, locating possible moisture sources, and selecting the right insulation. The effectiveness of the insulation and the energy efficiency of your wooden house can be increased by using proper installation techniques, which include caulking joints and gaps.

Insulation Method	Details
Exterior Insulation	Apply rigid foam board or spray foam insulation directly to the exterior walls of the foundation. This method prevents thermal bridging and keeps the foundation warm.
Interior Insulation	Use insulation panels or batt insulation on the interior walls of the foundation. Ensure proper moisture barrier installation to prevent mold and moisture issues.

Thermal insulation methods

Thermal protection is made from the following materials:

• Penoplex. This product is durable and virtually impermeable to steam. Its characteristics do not change when in contact with water.
• Styrofoam. It has slightly less durability. Due to its simpler installation and low cost, the product is often preferred.
• Expanded clay. Cheap bulk product. It is made by firing clay.

Outside

It is advised to waterproof the base and complete exterior insulation work at the same time.

1. After applying bitumen mastic, cut sheets of material are tightly applied to the base.
2. Holes are made in them for attaching plastic “fungi”.
3. The joints are covered with foam.
4. To improve waterproofing, cover the surface with waterproof material (roofing felt).
5. Then they are fastened with fiberglass mesh and a layer of plaster is applied to it.

Your home’s heating costs can be greatly decreased by this occurrence. Mineral wool is placed underneath ornamental panels or siding to enhance the base’s thermal insulation. By adding expanded clay concrete to the blind area’s base, they further insulate the nearby soil.

From the inside

When external insulation is insufficient to provide adequate heat protection, internal base procedures must also be implemented. While it cannot shield the base, this solution aids in keeping the floor from freezing. There are many different work options; some even turn into part of the interior design. The foundation is always waterproofed first.

Regarding a note. If external protection of the concrete is not a reliable option, then at the very least, water penetration must be stopped. The base doesn’t freeze too much as long as it stays dry.

Selection of insulation materials

Materials made of mineral wool don’t make the best choices because they retain moisture. The properties of thermal insulation are lost as a result. The product shrinks as a result of soil pressure, and its insulation effectiveness quickly drops. However, polymer insulation has none of these drawbacks.

Penoplex

The method of production used is extrusion. In every technical metric, it outperforms polystyrene foam:

• much stronger;
• completely waterproof;
• weakly transmits steam and heat;
• does not allow microorganisms to develop inside.

Penoplex thin slabs work much better as insulation. For dependable thermal insulation of the foundation, 40 mm (or 60 mm in northern latitudes) of material is sufficient. Products have unique connecting ridges and grooves to make installation easier.

Using an adhesive solution, attach the product to the base by using disc-shaped dowels. Slabs may be laid horizontally (if the foundation is slab-based) or vertically (with a strip or column base).

The material perfectly withstands the load from a layer of concrete and does not flatten because of its increased strength.

The type and thickness affect how much one cubic meter costs.

• Penoplex extreme from RUB 11,790.
• Penoplex foundation from RUB 8,600.
• Penoplex comfort from RUB 7,900.

Polyurethane foam

When it comes to foundation insulation, polyurethane foam is becoming more and more popular. With no seams, the material forms an incredibly durable coating.

It completely withstands negative effects. The heat insulator also has the benefit of protecting concrete from moisture and steam at the same time, which makes installation much easier.

Excellent adhesion to any substrate is a useful feature of this insulation. Adhesion to wood, stone, concrete, and brick is just as strong. The product fills even tiny cracks and is simple to apply to even the hardest-to-reach areas.

Two methods are used to apply polyurethane foam:

• Fill. It is more expensive and labor-intensive, so it is rarely used when insulating the foundations of private houses.
• Sputtering. Actively used if it is necessary to perform thermal insulation of the entire building, starting from the base and ending with the roof.

Method of spraying:

1. Before application, the mixture ingredients are placed in a foam machine.
2. Then the finished mass is sprayed under pressure onto the surface of the building.
3. After a few seconds, the material hardens, so finishing can be done immediately after work.

The high cost of this insulation option is a drawback. The cost of the material is 400 rubles per cylinder. Additionally, you must pay for an installation, which is costly even for renting. One square meter will typically cost 600 rubles to process.

Styrofoam

The majority of users of this product are developers. It is lightweight, the sheets are rectangular, and even if you install it yourself, it is not very difficult to install.

Since the material comes in a variety of thicknesses and densities, you can choose the specifications you need for a given application. It is essential to buy the thickest sheets—at least 50 mm thick—when insulating foundations.

Foam plastic has a higher heat conductivity than expanded clay, wood, or mineral wool. It is virtually impervious to moisture absorption, deformation resistant, and a superior absorber of noise. It is imperative that the sheets maintain their initial characteristics when subjected to weak acids, alkaline solutions, or chlorinated or salted water.

Contact with bitumen mastics, cement plaster, lime, and aqueous adhesive solutions is easily tolerated by the insulation.

Contact with the insulation is readily tolerated by:

• lime;
• bitumen mastics;
• cement plaster;
• aqueous adhesive solutions.

Use polystyrene foam PSB-S-50 for slab foundations and foundations that are deeply buried in the ground. Because of its ability to tolerate large mechanical loads, it provides dependable protection during soil heaving. When a wooden structure is supported by a strip or columnar foundation, the PSB-S-35 brand should be chosen.

• PSB-S-35 — 4,150 rub./cube.m;
• PSB-S-50 – 5,800 rub./cube.m.

You can use polystyrene foam to insulate the foundation of a wooden house by watching this video:

Expanded clay

Bulk materials may also be used for foundations in addition to the insulating materials listed. This is the best of them all. It is inexpensive, safe for the environment, and has superior thermal insulation qualities. Products are available for both vertical and horizontal foundation insulation.

A drawback is that when expanded clay absorbs moisture, some of its properties are lost.

It’s also a drawback that the workflow takes time and effort. As a result, the substance is rarely used in favor of more potent goods. One cubic meter of expanded clay will typically cost 1,500 rubles.

Differences for different base options

A wooden house needs to have its base veneered and insulated, regardless of the type of foundation. The course of action selected is contingent upon the state of the soil beneath the structure and the kind of foundation laid:

1. At the strip foundation there is a strip of reinforced concrete located under all load-bearing walls. It is buried in the soil. Insulation is done using several methods: vertical, horizontal or mixed:
2. with the first method, the side surfaces of the fill are protected;
3. in the second case, a blind area is built around it to prevent soil heaving.
4. If the climate is not severe, the mixed type is used.

A wooden house’s foundation needs to be insulated in order to remain comfortable and energy-efficient. You can stop heat loss, moisture buildup, and possible structural damage by properly insulating the foundation on the inside as well as the outside.

Materials such as spray foam or rigid foam boards can be applied directly to the foundation walls, beginning with the exterior insulation. By doing this, a thermal barrier is produced that lessens heat transfer and aids in regulating indoor temperatures all year long.

Fiberglass batts or spray foam are two options that can be installed between the foundation walls’ wooden framing for interior insulation. By reducing drafts and cold spots, this not only increases thermal efficiency but also improves the indoor climate overall.

Take into account the local climate, the amount of moisture in the air, and the unique design of your wooden home when selecting insulation materials and techniques. Ensuring long-term durability and optimizing the effectiveness of insulation requires proper installation.

Effectively insulating your wooden house foundation will improve its longevity and energy efficiency while also improving comfort. You can maintain the integrity of your foundation insulation over time by performing routine maintenance and keeping an eye out for indications of moisture or insulation degradation.

The following is a succinct thesis statement for your paper: We look at practical ways to insulate a wooden house foundation’s exterior and interior in this guide. We go over the necessary materials and practical steps for each approach, from stopping moisture penetration to improving energy efficiency. This article offers concise, practical advice to help you safeguard and maximize the foundation of your wooden home, regardless of whether you’re retrofitting an existing structure or dealing with insulation during construction.

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