Insulating the loft is necessary not only because, in winter, heat dissipates through it, but also to prevent the summer heat from penetrating inside the house.
For these reasons, the loft is an extremely sensitive area of the house and a good insulation must necessarily start from here.
It does not matter if it is a habitable or non-habitable attic, this area of the house must be insulated to avoid higher heating costs in winter and higher cooling costs in summer.
But be careful: insulating does not mean hermetically sealing the room so that not even a single draft of air can get in or out, quite the contrary.
A well-insulated loft must also be well ventilated at the same time.
However well thermally insulated, attics must be ventilated because, when there is not enough air circulation, their temperature can rise considerably on summer days, keeping the house warm long after dark.
In the winter, on the other hand, water vapor can rise from inside the house and condense on the cold, inner part of the roof.
If this moisture is excessive, it can end up souring any wooden structures or damaging plaster and insulation.
A regular flow of air through the attic, through the creation of ventilation openings, can avert both problems.
But let's get back to talking about loft insulation and the materials that can be used, making a necessary premise.
The area in which to lay the insulating material differs considerably in the case of a habitable or a non-habitable attic.
If the attic is not habitable, the insulation material should be laid on the floor, it would make little sense to place it on the inner or outer pitch of the roof.
When the attic is habitable, on the contrary, it is the pitch of the roof that must be insulated.
How to insulate the non-habitable attic
When dealing with a non-habitable attic, and perhaps not even floored, the most suitable materials are fiberglass or rock wool mats.
There are also bulk materials that are simply poured on the floor, between joists, if any, or by creating a perimeter curb that can hold these types of materials.
Expanded clay pellets are the most commonly used bulk material for non-habitable attics.
It is simply tipped onto the floor and then evened out with a straightedge.
Leca (the trade name for this product) is particularly suitable for corners that are difficult to reach or where the spacing between joists is irregular.
The mats, on the other hand, can be sold in rolls or in pre-cut rectangles.
The thickness of these insulating mats is variable: the greater the thickness, the greater their insulating power.
Keep in mind that the material of the mats sold in rolls is highly compressed.
This means that, once opened, the material regains its original thickness, which can be up to four times greater.
For this reason, it is best to open the rolls only at the place of use and one at a time.
If the loft is not habitable and therefore has no finishing touches of any kind, nor a walking surface, it will be necessary to install temporary lights and, possibly, a makeshift scaffold.
Some rafters and boards to be placed on top of it, will allow you to have a sufficiently stable plane on which to work (almost always on your knees).
Insulate a non-habitable attic is something that can be done even by a simple DIY enthusiast, you do not need many materials or specific equipment.
As tools you will only need a serrated knife, or a handsaw, and an upholsterer's stapler.
Remember to always wear personal protective equipment, primarily gloves and a mask, to avoid breathing in the tiny particles of fiberglass with which the mats are made.
How to insulate the habitable loft
A fairly recent law makes it possible to make the attic habitable, provided that it has certain characteristics, then better identified and defined, region by region.
Having said that an attic, to be considered habitable, must have a minimum height and a certain ratio between lighting and floor area, it follows that all those areas that can not meet these characteristics must be closed in a stable manner.
Insulating a habitable attic, therefore, may require not only the insulation of the pitch but also that of any infill walls.
Also in this case, the ideal material to use is glass wool or rock wool, to be inserted between the roof beams, whether they are made of wood or reinforced concrete.
It goes without saying that the insulating material will end up in the cavity, which will then be closed with a wooden matchboard or plasterboard sheets, in the case of wooden beams.
If the beams are made of reinforced concrete, they are probably prepared for the installation of brick planks that will then be plastered.
The good news, for the insulation of a habitable attic, is that this can also be done in the external part of the roof, that is, by inserting the insulating material between the roof slab and the various types of tiles with which the roof is covered.
The consistent advantage of insulating the roof from the outside, is that you do not lose even a centimeter of height inside, and this could make the difference, compared to the legislation, between the possibility of making the attic habitable or not.
Where it is not possible to anchor the insulating material and pre-existing joists, it will be necessary to create a plasterboard false ceiling, after having installed the anchoring frame.
Inside all the spaces that will be closed due to the lack of legal requirements, all the systems can be run, from electrical to hydraulic.
For this reason, choose insulating materials that have good characteristics, both from the point of view of thermal insulation but also from the point of view of acoustic insulation, to avoid the creation of problems, for example with noisy drains.
The advice, especially for the insulation of the walls, is to choose carefully the insulating material, assessing its technical characteristics, and then choose the one that has the best performance with the same thickness.
It is very important, in the laying of the insulation, not to create thermal bridges, or areas of discontinuity in the insulation that will then favor the emergence of mold and moisture.
Get advice on the choice of materials and, if necessary, contact a specialist who can then guarantee the issue of the certificate of improvement of the energy class of your home, a certificate that you will need in case of sale and through which you can get a better sale offer.
Above we have mentioned some materials, among those most used for the insulation of the attic, both habitable and not.
The materials, however, are really many, from the most ecological (such as coconut fiber) to the most technological (such as rubber combined with lead).