We’ve discussed what a breathable membrane, such as nilvent is previously on our blog – basically a layer fitted to allow water vapour to escape to the outside of the building, removing the need for ventilation directly above the insulation layer. In this post we are going to cover in more detail how to fit this to a timber frame wall so that you get the maximum benefit.
Kingspan nilvent should be fitted to either ply, OSB or insulation sheathing before the brickwork or cladding. When installing you should ensure that the membrane is fixed taut and, if required (for vertical installation), seal the joints with tape.
It can be fitted either in horizontal or vertical runs. In both cases you should make sure that the upper layers of nilvent overlap the lower layers, by a minimum of 100mm so that water is shed away from the sheathing. Make sure that the lowest timbers in the wall are protected by the nilvent.
If you are fitting the nilvent in horizontal runs we recommend that the vertical overlap should be a minimum of 150 mm and that these overlaps are staggered in adjacent strips of product.
For vertical installation, the vertical laps should be 150 mm minimum if the laps are sealed with an acrylic double−sided adhesive tape or vertical battens applied to the outside of the membrane, or 400 mm minimum, if the laps are unsealed.
The breather membrane should be secured at regular intervals to prevent damage by wind, by either nailing or stapling. Staples should be austenitic stainless steel and nails either galvanized mild steel, austenitic stainless steel, phosphor bronze, or silicon bronze.
While you are installing the nilvent, we recommend that you mark the location of the timber studs, usually by fixing tape to the face of the nilvent. This will allow for the correct fixing of wall ties or battens into the timber studs.
Kingspan nilvent resists windblown rain and snow, and will protect the sheathing and timber frame from external moisture penetration. The product can be used as a temporary weather protection during construction, prior to the completion of external brickwork or cladding. This time period must be limited to two months as Kingspan nilvent is not resistant to long term UV exposure.
For all pipe penetrations, the nilvent should be star cut and dressed up the side of the pipe penetrations and then use tape to seal the nilvent securely around the pipe.
For more information on breather membranes, take a look at our website; for information about insulating timber frame walls have a look at our online U-value calculator.