Insulating the crawl space

Crawl space insulation specialists for more than 40 years



Our total crawl space insulation solution transforms it from a wet, cold space that draws a significant amount of heat from the floor, to a dry space with dry foundations, that keeps the heat in the house. Insulate your crawl space with TONZON. Benefit from warmer floors, energy savings, less moisture in your home and positive impacts on comfortable living and on your health.


The inspection

When you request an obligation-free quote from us, we will first call to carry out an inspection of the crawl space. Our installer examines the situation in the crawl space and decides whether TONZON insulation is possible. Fortunately, in 95% of cases TONZON can be installed. It can sometimes be the case, however, that TONZON can't be installed due to insufficient space, or vermin. But there are solutions for that too. For example you can install grates to keep pests out, or excavate to create more space. A tailor-made quote will be provided immediately after inspection. This is also an excellent opportunity to put your questions to one of our specialists.



As the manufacturer, we guarantee that our products will work optimally for at least 10 years. If you have any problems, contact your installer in the first instance. They can carry out any necessary repairs. If there are any further problems, the TONZON team is always here for you. For more information about our warranty scheme, see our terms and conditions.

With TONZON you get:


  • Free crawl space inspection, with expert advice.
  • A quote tailored to your home.
  • Installation that often takes no more than one day.
  • A 10-year warranty.

The installation


Often the work can be done within a day, depending on the area of the house. For very damp crawl spaces it may be necessary to work in two stages. In that case, step 1 is to cover the crawl space floor with TONZON Soil Foil. This stops moisture entering the crawl space through the soil and allows the crawl space to dry. This may take a week or two. Once the crawl space is dry, we can install the insulation. There is a choice between three-chamber Thermos Cushions and four-chamber Thermos Cushions. The latter provide even higher insulation values. Installing the Thermos Cushions is noise-free and no gases or chemicals are used, so you can simply stay at home while we install the insulation.



Experience the comfort of a well insulated floor



Request information, obligation-free, or call +31 (0)53 - 206 0709


Frequently asked questions

For your convenience

We recommend insulating the foundation walls. Note, however, that this should be done on the outside. This is because if the foundation walls are insulated on the inside, they will no longer absorb heat from the crawl space floor in winter. The lower parts of the walls in the room will then get colder and mould may develop near the edges of the floor.


Installers of sprayed Pur insulation provide the following explanation. Under the Pur foam, everything becomes soaking wet, not only the foam itself, but also the foundation walls. This moisture can migrate up the wall into the house. Therefore, the top of the foundation is sprayed with PU foam.

Learn more about the differences between TONZON and Pur foam.


A floor without a crawl space can be insulated by installing a new floor, raised some distance from the old one. The air space between the old and new floors can then be divided with TONZON Thermosheets into single air layers of up to 5 centimetres.

Read more about insulating floors with no underlying crawl space.


TONZON Soil Film is lighter than water. If the water in the crawl space is limited to occasional puddles, then no additional measures are needed. If there is more water than that, it is advisable to apply a bubble wrap layer first, which helps the Soil Foil to float on the water. The Soil Foil should then be fixed at a level higher than the water. If the water in the crawl space is higher than a quarter of the crawl space depth, other measures need to be taken. For example, a drainage system, a pumping system, or raising the crawl space floor.

Read more about TONZON Soil Foil.


The moisture from the crawl space floor evaporates and condenses in colder places such as on cold water pipes and cold foundation walls. After applying Soil Foil, the soil is sealed off as a source of moisture, allowing foundation walls and cold water pipes to dry. The colder it is outside, the faster the drying process. After installing Soil Foil, the only source of moisture is the outside air in summer. Warm air entering a cooler space (basement or crawl space) cools, thus increasing humidity. This can also make cold water pipes moist and cause a film of condensation to form on the Soil Foil. However, moisture that enters the crawl space with the outside air, through ventilation, is also removed through ventilation when the outside air is colder, e.g. in winter.

It is inevitable that water will sometimes form on the Soil Foil. Basements are damp in summer and dry in winter, and the same applies to crawl spaces. Warm moist air from outside cools in the relatively cold space. In the process, the relative humidity of the air increases, because colder air contains less moisture. This phenomenon causes condensation on other insulation materials, such as wool and foam. In a TONZON insulated crawl space, this condensation will take place on the Soil Foil. It starts with a thin film of condensation that forms during the day and disappears again at night. If the warm period lasts longer, and the nights are also warm, drops of water will start to form, which roll towards depressions in the Soil Foil, forming puddles. This is not a problem. Moisture that enters due to ventilation will also disappear due to ventilation.

Soil Foil limits humidity in the crawl space, and will continue to do this, despite a few puddles of water on the foil.

Read more about TONZON Soil Foil.