# How to calculate the SD value?

### How to calculate the SD value?

Defined as the thickness of the air layer equivalent to diffusion, expressed in meters. More value SD is low, the more the product is permeable to water vapour. Mode of calculation : SD = the μ of the material x the thickness in m of this material present in the wall.

### What Sd vapor barrier value?

You will therefore need to provide a membrane vapor barrier independent and continuous located under roof. Provide at least one vapor barrier of SD-value > 18 meters.

### What is the SD of a vapor barrier?

The coefficient SD (expressed in meters, it indicates the resistance to the transmission of steam of water) is the benchmark indicator for parriessteam ; more value SD is high, the less the product lets through steam of water.

### Which SD for wood wool?

For installation in accordance with DTU 31.2 (construction of houses and frame buildings drink), it is necessary to regulate the diffusion of water vapor in the wall. In the case of a ventilated facade, DTU 31.2 recommends the implementation of a rain barrier with a SD ≤ 0.18 m and a vapor barrier with a SD ≥ 18m.

### Which vapor barrier for timber frame?

Unlike a parriessteam traditional (cf DTU 31.2), the membrane vapor barrier for House at wood frame Vario Duplex is hygro-regulating: it limits the flow of heat through the walls, thus regulating the risks of condensation, of training of mold or of fungi harmful to wood of

### Which vapor barrier for wood wool?

Highly recommended to bio-sourced or ecological insulation, it will easily accommodate blow-in products such as cellulose wadding or wood wool. For this type of use, it is necessary to use a vapor brake armed!

### How to choose a vapor barrier?

1. Some insulators are more sensitive to steam that others. …
2. the vapor brake is less resistant to the diffusion of steam of water than one parriessteam, his Sd is between 2 and 18. …
3. For high humidity environments, an Sd above 18 is required.

### Which SD for vapor barrier?

Good to know: the minimum value SD with a brake steam is of 18 m according to DTU 31.2 (Unified Technical Documents) in order to of protect the insulators as much as possible and limit parasitic aeraulic exchanges.

### Which rail for wood wool?

– The first recommends a thickness of 50mm: thus no air gap, therefore less noise transmission. The wood wool will compact without any problem. – The second ensures that a thickness of 40 mm is required: the insulation should not be compressed. HE systematically recommends 40mm.

### What R for wood wool?

Thickness : For the insulation of the lost roof spaces, it is necessary to aim at least 35 cm of wood wool for achieve the minimum thermal resistance of R = 7 m². K/W.

### Where is the vapor barrier located?

the vapor brake must be laid on the warm side of the building in front of the last layer of insulation. It features an Sd greater than 18m and no insulation material behind the vapor brake is of a Sd less than 18 m. It must cover the entire building envelope: floors, walls and roofs.