Select the right Mechanical Insulation Fixing for Structural Performance.

Insulation frequently forms the part of a buildings external-envelope which maximise its thermal performance;  examples include external wall insulation (EWI) and over-rafter warm roofing systems.

These systems need to be held securely to the structure to resist significant wind-loads and stop the insulation from being torn from the building.  Failure of an external insulation system can occur if pull-out loads wrench the fixing system from the building or pull-through loads cause the insulation to fail and pull over the heads of the fastener.  Establishing the suitability of a fastener to anchor into a specific building material is an essential part of planning an insulation fixing system.

The first thing to identify is the type of background material to which the fastener needs to anchor. In houses and apartments, the substrate may be wooden joists, concrete panels, or masonry walls.  Some bricks and blocks may include hollow or perforated voids.  The nature and condition of the building components are likely to have a significant impact on the pull-out resistance of the fixing.

The next consideration is the size of the fasteners head; this is the part of the anchor that clamps the insulation to the structure.  Insulating materials are made from a diverse selection of materials and are available in a variety of thicknesses.  Some of the most common building insulation sheets are those made from mineral wool, such as those made from strands of glass or rock, foam (PIR, PUR or phenolic), and extruded or expanded polystyrene (XPS or EPS).  The weaker and thinner the insulating material, the greater the head-diameter or washer needed to hold it in place and to resist pull-through forces.

Composite insulation boards are generally two-part thermal laminates.  These laminated linings combine sheets of foam, polystyrene, or mineral wool topped by a rigid layer of plywood, oriented strand board (OSB), cement-particle board, or plasterboard.  Fixing solid composite insulation boards to the structure of a building requires fasteners more traditional sized heads.

Best Insulation Fixings for Thermal Performance

The purpose of insulating a building is to maximise its thermal benefit. The majority of insulation-fastening plugs are of plastic or nylon composition and are poor conductors of heat.

Many synthetic mechanical fixings make use of a central drive-pin that operates an expanding mechanism at one end of the fastener to deliver an enhanced anchorage. The pins are generally in the form of nylon or thermally-broken steel nails or screws that drive into the hollow plastic plug.

Several fastening systems are set up such that upon installation, the head sits in a shallow recess, slightly beneath the surface of the insulating material.

The use of such synthetic fasteners helps to fulfil the objective of retaining the utmost insulation values of a building by mitigating potential heat loss at fastening positions.

The advantage of using plastic insulation fixings is that they help retain the insulation values of a building by mitigating potential heat loss at fastening positions. The disadvantage of using plastics and nylons is that they are combustible and are incompatible with an insulating system where fire-resistance is a constraint.

Best Insulation Fasteners for Fire Performance

The devastation fire causes can be catastrophic. Particular types of fire-resistant composite insulation boards can safeguard a building from fire hazard by providing passive fire protection. Passive fire protection system aims to contain the fire and smoke to prevent them from moving from one part of a building to another.

Plastics fasteners tend to be slow to ignite but once ignited they can melt and lose their ability to hold the insulation in place. Melting fasteners present many hazards including the release of smoke and toxic gasses, flaming droplets which spread the fire, and fallen insulation boards that block escape routes.

There are many instances where non-combustible fixings are preferable or mandatory for use when fitting insulation to a building. Examples may include securing composite insulation boards to a concrete ceiling or soffit, insulated plasterboard sheets to the communal areas of a building, and external wall insulation slabs on multi-storey structures.

In contrast, metal fixings maintain the stability of the boards in the event of a fire. Metal fixings comply with BS EN 13501 as a Class A1 non-combustible fastener. Class A1 fasteners will not contribute to a fire at in any stage nor will they present a smoke hazard.

The upside of using metal insulation fasteners is their dependability to continue to function in the event of a fire; the downside is that metal is a good conductor of heat and can provide a thermal bridge through the insulation, resulting in potential heat loss at fastening positions.

It is common for pragmatic designers to specify an insulation fastening system that combines the attributes of both plastic fixings and steel anchors. In external wall insulation systems for low-rise buildings, the designer may prescribe the use of the more thermally efficient plastic fasteners, supplemented by using fire-safe mechanical fixing per board.

Select the Appropriate Type of Non-Combustible Mechanical Fixings

Fire-resistant insulation fixings are available in zinc plated carbon-steel and stainless-steel. When insulation needs fitting externally, consider the use of stainless steel, which offers excellent resistance to corrosion. When fixing insulation internally, and rust potential is not an issue, carbon-steel fasteners, which cost less, are generally suitable for use.

To limit heat loss caused by thermal-bridging, contemplate using metal fixings having a small cross-sectional area and those that have the least area of contact with the background material. Also consider that stainless-steel conducts just 25% of the heat conducted by zinc-plated carbon steel, making the former up to four times as thermally efficient.

Twistfix supplies an assortment of high integrity mechanical fixings for securing insulation in new construction or retrofit building upgrades. Where fire-safety is an issue, choose from the Insofast range of non-combustible insulation anchors for fastening fire-proof insulation panels, insulated plasterboard and warm roof boards to brick walls, concrete soffits and timber roof rafters.

Fixings for External Wall Insulation

Twistfix offers a selection of insulation anchors for fastening EWI boards to brick walls, including easy to use plastic insulation fixings and, for where fire-safety is an issue, non-combustible Insofast ISF35 metal fixings to supplement or replace the synthetic anchors. The ISF35 is available in zinc plated steel and in corrosion-resistant stainless steel.

Fasteners for Internal Wall Insulation

The Insofast ISF18A is a non-combustible helical nail specifically adapted tor fixing all types of plaster­board-laminated insulation sheets to brick and block walls. The insulated plasterboard fastener has a spiral shank and a shallow sunken-dish head. Use three fixings per board in conjunction with 'dot and dab' adhesive or twelve fixings per panel in place of place the adhesive.

Helical fixings for pitched warm roof insulation

Thor Helical Super-7 warm roof fixings are ideal for use in pitched warm-roof construction systems, securing insulation boards between rafters and a counter-battens.­ When hammered in, the stainless-steel 7mm helical fasters corkscrew into the timbers when hammered in to firmly hold the insulation in place. Use our online calculator to find out how many you need?

Fasteners for flat roof composite insulation boards

The stainless steel Insofast ISF18 is a similar fixing that includes an 18mm head. It is perfect for fixing plywood or OSB faced insulation sheets to rafters in warm flat roof appli­cations. The ISF18 is also available in zinc-plated steel.

Non-combustible fixings for fastening insulation to concrete soffits

Insofast ISF35 fixings are a superb option for fixing slabs of insulation beneath concrete soffits and car park ceilings. Available in a choice of stainless steel or zinc-plated steel these high-performance insulation anchors are quick and easy to fix.

Twistfix supplies top-quality Insulation Fixings at a discount price.