Just Insulation

Insulating the Exterior of External Walls

Frankly, our area of expertise is interior insulation rather than exterior. We do supply Kingspan Kooltherm K5 External Wall Board, upon which external render may be directly applied. However, all of the other rigid insulation boards that we supply need to enclosed behind a suitable external cladding material.

Insulating the Interior of External Walls

There are many solutions to be insulation of interior side of solid stone walls. Commonly, there is a desire to minimise this space consumed by the insulation, and it can be difficult to balance the need to insulate versus the loss of space to the interior of the property.

Multi-foil insulation

We are often asked if multi-foil insulation is the best solution for insulating the interiors of external walls. A consideration when retro-fitting multi-foils to the interior of external walls is the space requirements inherent in the application of multi-foil insulation, insomuch as any foil insulation is only effective if there is a minimum of a 25 mm air gap on either side of the insulation.

A typical minimum buildup might be … External wall … 25mm Timber Batten … Multi-foil insulation (compressed to a minimum of 7mm ±) … 25mm  batten …  57mm total … before the installation of a 12.5mm foil-backed Plasterboard, or a high-performance insulated plasterboard.

Single-foil or bubble-foil insulation

Unlike multi-foil insulation, which has been specifically developed to inhibit the opportunity for condensation to form, single-foil and bubble-foil insulations  commonly attract condensation in interior applications, posing the risk of dry rot.

Some timber-frame building manufacturers  are experimenting with heat reflecting membranes, such as single foil laminates complemented with layers of dry insulation, However, they are in a position to ensure envelope of the building is sealed. Such controls are quite challenging to apply in a retro-fit situation.

High performance insulated plasterboards and thermal laminates

Perhaps the simplest and fastest means of applying insulation to the interior of an external wall is the use of insulated plasterboard. These boards combine standard plasterboard with rigid dry insulation in a single product.

Commonly, the rigid insulation would be manufactured from (in order of effectiveness – and cost) Phenolic foam, PIR (polyisocyanurate), PUR (urethane foam), XPS (extruded polystyrene) or EPS (expanded polystyrene).  It is advisable to ensure, particularly in areas where moisture or damp are prevalent, that the insulated plasterboard has an integrated vapour barrier … this facility is commonly reserved for the more expensive boards.

While insulated plasterboard may seem at first glance seem to be an expensive solution, the labour costs and the time of installation can be dramatically reduced.

To gain maximum value from this type of insulation, it is preferable if the boards can be fitted directly to the interior of the external wall. This can be done using mechanical fixings or by the dot and daub method, therefore the walls should be relatively smooth. It is, of course, possible to secure wooden battens to the walls and mechanical fix the installation to them.

Rigid insulation boards

Perhaps the most common solution to the insulation or external wall is the use of rigid insulation boards. Again, the boards are manufactured from Phenolic foam, PIR (polyisocyanurate), PUR (urethane foam), XPS (extruded polystyrene) or EPS (expanded polystyrene). Generally, Phenolic, PIR, or PUR, would be used in this application, as the polystyrene option is best reserved for underfloor applications. Typically, there will be a requirement to create timber-frame stud-work to support the dry insulation.

Stone Mineral Wool Slabs

We would consider this option the least desirable solution for insulation of interior solid stone walls, unless the property is situated in a location with lower humidity levels.
Mineral wool slabs are ideal for interior walls where moisture and damp issues are more easily controlled.