Converted attic - 5 rules for filling the space

There's a vitamin cure for a house that gains volume without the need to expand. Withattic conversion, well-thought-out work can create rooms that are ideally proportioned.

1st rule

A well-structured roof

A house's attic space lends itself to a wide range of conversion scenarios, but only if the roof structure is designed for the purpose. Ideally, the house should be fitted with beams forming a "traditional" framework that leaves enough space to create rooms. This is an assembly of wooden trusses that supports the entire roof and rests on load-bearing walls.
If this isn't the case, we're talking about an industrial framework made of prefabricated elements called fermettes. Although this type of framework is renowned for its solidity, it is not suitable for converting attic space. In this case, and without getting too technical, it's best to use self-supporting beams to reinforce the parts called "crossbeams". This structure is needed to support the weight of the roof structure and the ceiling and floor created.
If the work does not involve altering the pitch of the roof or replacing the roof covering, simply submit a declaration of work to the town hall. Otherwise, you need to apply for a building permit.

Reduced-rate VAT on renovation work
Renovation work carried out in a dwelling completed more than 2 years ago benefits from a lower VAT rate than the standard 20% rate:
- reduced rate of 5.5% for renovation or energy improvements ;
- an intermediate rate of 10% for improvements, conversions, fittings and maintenance.

2nd rule

Well-insulated eaves

Warm in winter, cool in summer - that's the comfort we're entitled to expect from the new rooms that will be added to our home. That's why we need to ask the right questions aboutattic insulation. It's a key element in the proper use of this floor. It's even more important in terms of energy bills, since 30% of heat loss occurs through the roof.
While glass wool is the leading insulator in 3/4 of all homes, other materials are beginning to make their appearance, including :

- plant-based wool(cotton, hemp, linen) ;
- animal wool(sheep) or feather ;
- expanded polystyrene (EPS) insulation: made up of balls bonded by compression;
- cork: composed of air-filled cells, it's a great attic insulator...

For maximum efficiency with glass wool, you need to aim for a high thermal resistance to achieve a coefficient of R = 8m².K/W. This generally requires double-layer insulation. The first layer, laid between the rafters, has a high thermal resistance, given the limited space available (6 to 8 cm). The second layer is fixed between the purlins, with its vapour barrier facing inwards to complete the insulation. A metal frame is used to fix the plasterboard covering the insulation.

You've got to fit in?
Converted attic space is 2 meters high under the roof structure, and the roof pitch must be greater than 30%. These are two criteria to be taken into account if the rooms are to be comfortable.

Rule 3

Well-lit rooms

The charm of a converted attic lies in its natural light. This comes from gable windows and roof dormers. If these openings aren't enough, a roof window can be installed to provide plenty of light. This installation must be planned before installing insulation. Advantage: no major structural work required. Disadvantage: this window limits opening in case of rain.
Let's not forget that to enjoy a well-earned rest, you need to create total darkness. Roller shutters and awnings on Velux-type frames make a major contribution to this. Ideally, this roof window complements another opening window, but it can also stand on its own.
When it comes to lighting, spotlights are the best choice. Thanks to their LED technology, they produce a beautiful play of light while limiting electricity consumption.

Worth knowing
As with conventional windows, you'll need to obtain prior planning permission from the town hall before installing a roof window. This planning permission is not required for the replacement of a velux window with the same characteristics as the previous one.

4th rule

A well-organized space

If there's one place where closets and dressing rooms are well accommodated, it's in the attic. Attics can be used to organize closets with shelves to create storage areas and add character. Sliding doors, for example, are ideally suited to a room that needs to be flush with the eaves. Similarly, areas with low ceilings are ideal for dressing rooms or shelving. Here's a space dedicated to storage that lets you get rid of a few bulky items...

Decoration
A mezzanine at the end of the staircase leading upstairs offers inimitable charm. It also brings light into the adjoining rooms and reinforces the cocooning dimension of the rooms created under the roof. A perfect place to rest or read...

5th rule

A well-heated and ventilated surface

Before you even think about air-conditioning your attic, you need to preserve its natural coolness with good thermal insulation and efficient ventilation such as VMC (controlled mechanical ventilation). This allows air to be renewed, while the dual-flow version recovers heat from extracted air.
As for heating, the solution is often to extend the existing network (such as the central heating system) or to install new convectors. If this was not foreseen when the house was built, underfloor heating cannot be installed at a later date.
There's also the question of air cooling, much appreciated during the summer months. Reversible air-conditioning, which uses a heat pump to lower the temperature by 3 to 4 degrees, is the preferred choice. A split air conditioner consists of at least two units, one outside and one inside. More powerful, this system can cool several rooms by installing a multisplit (several indoor units).

Using the sun to produce cooling?
You need solar panels to generate electricity to run the reversible heat pump. In this case, the heat recovered by the unit is not released indoors, but outdoors. The temperature is lowered by an average of 3 to 4 degrees.

Eco-PTZ

To finance work at zero interest

The zero-rate eco-loan (éco-PTZ) helps finance energy-efficiency renovation work on homes. The loan is available to landlords and occupants of older homes until December 31, 2021. By carrying out a package of 3 works - thermal insulation of the roof, installation of renewable energy heating and replacement of half the windows - the amount reaches 30,000 euros.

Christophe RAFFAILLAC