Insulate roof from the inside or outside?

Insulate roof between rafters

Even if costs are already saved in the house or apartment by modern heating technology and a sensible heating plan, expensively paid heat can still disappear into thin air. Where we don't need them.

Namely if the roof is not properly insulated or not insulated at all. A lack of insulation of the roof cladding is particularly noticeable if you have living quarters in the attic. This can even become really really annoying.

Because not only do you then heat the winter air out there, but the walls also get dirty irregularly. Strongest where the wall is coldest. This can result in really ugly stains on the freshly painted wall after just one winter. Wallpapering yourself doesn't really help.

So – if not already done and somehow feasible, you should take care that your roof is properly insulated. Costs quite a bit, but pays off in the end not only in quality of living, but also in your wallet – shrunken heating bill.

First screen, then dam

Before you set out to insulate your roof, browse, resp. Use a thermal imaging camera to see where the weak points are in your roof.

As a rule, it will be cheaper if you hire a termographer, who will examine the whole house with the thermal imaging camera and then also professionally evaluate the images for you. Cost about 100 euros.

In the case of a new building, in contrast to old buildings, you are also bound to comply with the official specifications of the german energy saving ordinance (enev) with regard to the heat transfer coefficient (U-value) of the relevant building component (e.G., roof insulation).B. Pitched roof).

The U-value measures the amount of heat flowing through a building component. This means: the lower the value, the more efficient is the insulation. Your choice of the insulation method and also the insulation materials should of course be based on these legally determined values, even for older buildings.

After all, they were not invented out of harassment, but also make sense for you as an energy consumer – in the sense of saving energy. And: in particular with old buildings and older real estates should be insulated anyway apart from the roof also walls, hot water pipes and windows, so that the warmth remains also really in the house.

Insulate roof – with which method?

Insulating the roof from the inside or from the outside – that is the question on which the further procedure depends.

Depending on the results that the termograf gives you and depending on your living situation, different methods of insulating the roof come into consideration. Advantages and disadvantages have you all, wants to be thus well considered. And depending on the situation, only one of these options may even be considered at all.

Above-rafter insulation – insulating the roof from the outside

For this, the roof must be covered, so that the insulation can be installed.

  • Advantage: perfect thermal insulation possible and your rooms remain untouched in the meantime.
  • Disadvantage: expensive, because you have to hire a professional roofer.
  • Conclusion: worthwhile itself only, but then in any case, if the roof is to be covered straight anyway again.

Insulation between rafters – insulate from the attic

Here, the insulation material is installed between the rafters. – see picture on the right.

  • Advantage: you can do a lot yourself with patience and skill and thus save costs. And: here, too, the living spaces are not changed and can continue to be used.
    Disadvantage: there can be weak points or. In technical jargon: thermal bridges are created – namely at the rafters, which are not insulated with this method.
    Conclusion: if your house is built in such a way that you can get to the rafters from the inside, there is a lot to be said for this option. Especially if you can also disguise the rafters from the inside. How much is really necessary is best told by the analysis of the thermograph.

Under-rafter insulation – insulating the roof from the inside

The insulating material is applied from the inside, i.E. From the inhabited room.

  • Advantage: well, what is left for you, if the other two variants are out of the question for you, either for financial reasons, or for construction reasons – for example, the retracted wall is almost directly under the roof cladding. Compared to intermediate savings insulation, you also have the advantage here that you do not install any thermal bridges, since the walls are completely insulated throughout. Compared with insulation from the outside, this option is also relatively inexpensive.
  • Disadvantage: your living space is reduced – by at least the thickness of the insulation material. Of course, your rooms are not habitable for the time of the reconstruction.
  • Conclusion: if there's no other way, you'll have to bite the bullet. Not a problem if the rooms are large enough to reduce.

Floor slab insulation – for unoccupied roofs

Covering the roof from above – the floor of the attic is insulated.

In the picture to the right – here not the roof, but the floor of the attic is insulated.

  • Advantage: the most cost-effective and least time-consuming method, of course. The effect of thermal insulation is also very good – so no thermal bridges.
  • Disadvantage: none, except:
  • Conclusion: only comes into question if the attic is not inhabited. But then it should be the choice nr. 1 be.

Costs and financing

If the roof insulation is carried out in parallel with other renovation or refurbishment work, the costs can add up quite a bit in any case, even with careful planning.

Taking out a loan is then quite obvious. The only question then is how to get a favorable loan. But it's often not that difficult with construction projects.

The respective terms and conditions of the providers of personal loans, which are very suitable for renovation work, depend on several factors, such as the total amount, the term and the purpose of use.

In order to find the most suitable provider for your situation, a free comparison check with the help of online providers is worthwhile. A personal loan for renovations is a special form of real estate loan and may only be used for this purpose.

If the insulation of the roof is part of a series of energy renovations, you may receive government financial assistance. With lenders of renovation loans are credit amounts of 500 € to 250 €.000 € possible – here a term between 12 and 84 months is common.

Minimum costs for roof insulation

If you don't want to take out a loan, probably only option 2 or 4 will work for you. In addition, a few key data:

The total cost of insulating your roof depends on the method chosen, but also on the insulation materials selected for the roof and the additional materials required, such as vapor barriers, vapor retarders and the battens.

In terms of insulation materials, styrofoam is usually the cheapest, hemp and sheep's wool are the most expensive.

It also makes a difference, of course, whether you buy the insulating materials in a DIY store or have them supplied by a specialist company. Depending on the dam material – that is, without labor hours electricity, tools and odds and ends, you can expect to pay between € 100 to € 150 per square meter to insulate.