It is expensive to insulate the floor on the ground floor in a home without a basement. In return, you avoid cold feet and drafts. Read how the floor is re-insulated and what you can save.
Why floor insulation?
A lot of heat can escape through floors that lie on the ground floor just above the house’s foundation.
If there is no insulation under the floor, you waste a lot of heat. At the same time, the floor will feel cold, and there may be drafts along the floor.
In some older homes there is no insulation at all between the floor and the ground below, and in some cases mold can develop under the boards as a result of a lack of floor insulation.
People are usually sensitive to cold feet, and many will therefore turn up the heat extra if the floor is cold – even if the rest of the room is comfortably warm.
But if the heat disappears from an uninsulated floor, turning up the heat doesn’t help much.
Cold floors are especially a problem in families with small children of crawling age, where the consequence of cold and drafts at child height can lead to illness.
If you have a home from, for example, the 1960s, there may be uninsulated pipes that run under an uninsulated floor, and here there may be leaks or condensation on the pipes, which form a breeding ground for mold, and you have no chance of seeing that .
Often, however, you can smell the mold. – it smells earthy. You can also see stains in the floor covering if there are pipes that are leaking.
But even without the uninsulated pipes under the floor, mold can form due to condensation on the concrete slab under the floor.
Be aware that re-insulating the floor is not a do-it-yourself job.
When does the house need floor insulation?
As a rule of thumb, the floor needs to be insulated if:
- The insulation layer is less than 100 mm.
- The floor has not already been thoroughly insulated.
Underfloor heating must be installed, a bathroom renovated, or the floor must be renovated in some other way, possibly after water damage.
It is especially when underfloor heating is installed, or where the floor covering is replaced in some other way, that it can be advantageous to re-insulate. When re-insulating, the floor almost always has to be broken up.
Is the floor sufficiently insulated?
Insulating the floor can be expensive, but afterward, you can save money on heating costs and avoid cold feet and drafts.
It rarely pays to re-insulate if the insulation layer is at least 100 mm unless you have to raise the floor anyway.
On drawings of the house, you can usually see how much insulation is under the floor. If you cannot find drawings of the house, you can check the insulation layer under the floor by removing a floorboard. Choose one of the boards lying inside along the wall. Then it is not so much visible that the board has been taken up, and it is easier to take it off and on again.
Get help from an energy advisor
It can be difficult to determine whether the floor is sufficiently insulated, but you can contact a building technical adviser or energy consultant who can assess it.
The energy advisor can take a photo of the floor with a thermography camera that shows if and where the cold penetrates. This should be done during the heating season, as the difference between the outside and inside temperature should be a minimum of 12 degrees.
It is relatively expensive to insulate under the floor when there is no basement. That’s why it’s good to know that what you plan to do will actually solve the problem of cold and drafts and provide the most heat savings for the money. You can get help with this from an energy consultant.
Insulation of the floor in a house without a basement
There are generally 3 different ways to insulate the floor in a house that does not have a basement. You can:
- Insulate under the living room floor.
- Establish a new, insulated off-road deck.
- Insulate from the outside by insulating the house’s foundation and plinth (this provides indirect insulation of the floor).
Insulation under the entry-level floor
It is a good energy solution to insulate the space under the entry-level floor, i.e. between the floor and the ground. But it is also an expensive solution.
You have to remove the old floor in order to install the insulation. If, for example, a very nice plank floor is taken up carefully, it may be possible to reuse it.
Granules can perhaps be blown into the gap instead of laying entire insulation mats. It must be done by professionals – it is not a DIY job and it requires that there is a vapor barrier and that it is intact.
If the ground cover is uninsulated, the cover must be cleaned of organic material, and a vapor barrier must be laid out, where a maximum layer of insulation of 75 mm (and only 50 mm on the outermost meter along the outer walls) must be laid on top, as otherwise, problems can arise with moisture and mold in the floor construction.
If the ground cover is insulated, a maximum of the half as much insulation must be laid on top of the concrete cover as there is under the cover.
This is because the warm, moist air from the house can penetrate through the floor and condense on the cold concrete deck. This happens if there is too much of a difference between the temperature inside the house and the temperature at the concrete deck just above the ground.
Therefore, the insulation layer must not be too thick – unless there is also insulation under the ground cover.
It can be difficult to know with certainty how much insulation is under the concrete layer.
Establishment of a new all-terrain deck
The installation of a new all-terrain deck is often chosen when underfloor heating is to be installed, or because there are problems with moisture and possible water damage after a major downpour.
If the floor under the house is to be effectively insulated, an insulation layer of at least 300 mm must be laid. It is therefore necessary to break up the concrete layer under the house and dig out, so that there is room to lay insulation under the ground cover.
It is an expensive solution and the work should always be carried out by an experienced contractor. Always obtain quotes from three different contractors.
A new all-terrain deck can be built in several ways, but typically it goes like this:
- The existing floors are removed.
- Excavating is done.
- A capillary breaking layer is established.
- It is insulated with pressure-resistant insulation
- A new radon-proof concrete layer is poured.
- Vapor barrier is laid out.
- It is possible to isolate between the beams.
- The new floor is laid.
If the finished floor covers tiles, the moisture/radon barrier is laid under the concrete cover.
Radon, moisture, and vapor barriers must be carefully sealed at the sides – see if applicable. manufacturers’ instructions.
Insulation of the house’s foundation and plinth from the outside
An alternative solution is to insulate the house’s foundations and plinths from the outside. The plinth of the house must be excavated from the ground so that there will be a workplace to get insulation mounted on the plinths. In the same way, you can install drains around the house if the house is on damp ground.
Foundations and plinths are smeared in a waterproof membrane, and the insulation is mounted on the outside of it. It is finished at the top with a steel profile so that water and moisture do not penetrate into the insulation. On the outside of the insulation, gravel, and stones are first laid as a drainage layer and in the end, soil.
How much does floor insulation cost?
There can be very large differences in prices for floor insulation. This can be due to geographical location, demand for craftsmen, and sometimes also demand for materials. Therefore, you will always need to get a quote from local craftsmen to be sure.
You should always expect that it may be necessary to replace pipes for the domestic water or for the radiators, which in some cases are under the floor.
The heating pipes should also be insulated with technical insulation.
Can you carry out the insulation of the floor yourself or get craftsmen to do it?
You should have craftsmen do the work if you want to insulate the floor from above.
You should always get a professional company to handle the work if you want to insulate with granules. It is definitely not do-it-yourself work and also requires special tools and machinery.
You should also get a professional construction company to handle the work if you need to install a new ground cover under the house or have the foundation and plinth insulated. Serious damage can occur to the house if the work is not carried out correctly.
Choice of materials
If you want to insulate under the entry-level floor yourself, you can use virtually any type of insulation, as in most cases there are no problems with moisture.
Moisture problems tend to occur when the dew point changes and the dew point changes if you insulate with too much insulation, and without taking vapor barrier and/or ventilation conditions into account.
If you want to have granules blown in under the floor, you should get craftsmen to do the work and acquire the materials.
If you need to install a new ground cover or insulate the foundation and plinth from the outside, many different materials must be used and combined. Since it is not a task you should do yourself, it is also best here to get the craftsman to buy materials and do the work for you.
Retrofitting of existing decks
Insulation between the joists in the floor takes place as follows:
- The existing floor is taken up. If it is done carefully, for example, a nice plank floor can be reused.
- Any old insulation and organic material are removed.
- A moisture barrier is installed, which must lie under the insulation against the ground cover. Remember to stick the moisture barrier to the back wall and inner walls. Possibly. edge insulation of 10-20 mm.
- The space between the floor and ground deck is insulated with a maximum of 75 mm of insulation, and for the last meter along the outer walls, there must only be 50 mm due to moisture problems.
- There should be at least 50 mm of air between the insulation and the underside of the floorboards.
- The old floor – or a completely new one – is laid.
Establishment of a new deck
Contact a company with extensive experience in establishing terrain decks under an existing house. It’s not do-it-yourself work. It is usually a contractor that carries out tasks like this.
It is a good idea to have an impartial construction expert assess which method and which materials should be used in your house. It depends, among other things, of the soil conditions on your site, how deep the groundwater is and the depth of the foundation.
This is how the work is typically done:
- The floors on the ground floor are removed.
- The existing flap layer (concrete layer) is broken up.
- The drainage layer (capillary-breaking layer) and insulation are excavated.
- A capillary-breaking layer is established that prevents water from being sucked up from the subsoil.
- A minimum of 300 mm of pressure-resistant insulation is laid.
- A new concrete layer/terrain deck is poured, which is radon-proofed.
- A moisture barrier is installed between the insulation and the concrete layer if it is to be finished with tiles.
- A radon/vapour barrier is installed on top of the concrete deck if a wooden floor is to be installed.
- There may be further insulated between the joists – there should be at least 5 cm of air between the insulation and the underside of the floorboards.
- The old floor is reused or a completely new floor is laid.
Contracts and agreements
Get a detailed, written contract drawn up with the company that will carry out the task. You are better off legally if the work carried out does not correspond to what was agreed in the contract.
The contract should, among other things, contain:
- A detailed description of the work to be done and the materials to be used.
- Deadline for when the work must be completed.
- Agreement on who purchases materials and protects them from rain etc. during the construction period.
If you don’t have a lot of craftsmanship experience, it might also be a good idea to hire a property inspector who is an architect or structural engineer to review the work once it’s finished. It’s called a construction inspection.
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