We are commonly asked ...

"What is the best product for the job?" It would be truly great if there were a simple answer. However, the solutions multiply as each of the multitude of types of insulation are added to the equation.

The information that follows is only our personal opinion, and is given without prejudice. Always check with your architect, designer, building control officer, and/or read the product literature and datasheets before making your decision to install or purchase.

Why can't kitchen aluminium foil be used instead of expensive alternatives?

Aluminium foil must have a long-lasting coating to avoid corrosion  ...

Aluminium can only reflect infrared heat if it is untarnished, so untreated aluminium foil would become useless within a mater of weeks.

Aluminium foil has little inherent strength ...

Even if the aluminium foil could be coated with some spray type varnish, it is not strong enough to use as an effective insulation material.

Can single foil aluminium insulation products be used instead of multi-foils?

Multi-foil insulation was developed to overcome the inherent problems of single-foil insulation products in temperate climates  ...

Single foil insulation can be used in temperate climates ... but their are risks!

Temperature changes on a single foil insulation product can react in a manner identical to that of a single-pane glass window ... when distinct temperature fluctuations occur, the result is unwanted and potentially disastrous condensation.

Consequently, if single-foil is installed incorrectly, or is not supported by the appropriate use of, and levels of, traditional dry insulation products ... single foil insulation will condensate and lead to dry rot in wooden rafters and joists.

To quote Gerald Cole, Selfbuild and Design Magazine, May 2008 ...

"in fact, aluminium foil would operate very effectively as an insulator, reflecting 97% percent of the radiant heat striking it. Unfortunately in Britain's dank climate, using it to insulate lofts would also produce a great deal of condensation, depositing moisture in the loft space and eventually causing the roof timbers to rot."

Should you choose multi-foil over more traditional products?

The Pros ... Multi-foil insulation ...

Multi-foil insulation can reduce space requirements over traditional insulation products.

Multi-foils can seal the envelope of the property, thereby excluding draughts.

Infra-red energy is reflected back into the building in winter, and reflected back into the atmosphere in summer.

Installation time (and costs) are dramatically reduced with multi-foil insulation.

Traditional boards, slabs, batts and rolls can be combined with multi-foil to enjoy the benefits of both types of insulation.

Unlike mineral wool, the effectiveness of which can fall off over time due to dampness and accumulated dust and grime, multi-foil's effectiveness does not deteriorate.

Once in place, multi-foils double as an airtight vapour barrier which, unlike ill-fitting closed cell PIR boards provide a continuous barrier that seals the envelope of the roof, or indeed, the entire building.

Multi-foils promise much more effective protection against solar gain, which is a worry in these times of increased summer temperatures.

 The Cons ... Multi-foil insulation ...

Not all building control departments support the use of heat reflecting membranes or thermo reflective foil insulation, so we always recommend checking before purchasing.
Multi-foil insulation does not provide the same acoustic performance as as the glasswool equivalent, so it is worth combining the benefits of both, if like us, you are locted next to an airport.

 

When acoustic insulation is a priority ...

Multi-foil insulation solutions may not be an appropriate choice.

Consider Universal or Rockwool slabs at 33kg, 45kg or 60kg per cubic meter

Sound studios commonly opt for 60kg/m3 x 50mm thick, then double up to 100mm thick, using the outer layer to overlap the joints of the inner layer.

What’s the better option, insulation boards or slabs?

Benefits ... PUR/PIR Insulation Boards such as Celotex and Kingspan ...

Thermal performance can be better when compared width for width with Glasswool slabs.

Boards come in many more width variations than slabs.

Boards are lighter and easier to fit in lofts and roofs.

Aluminium foil facings can and should be taped to provide seamless joints.

Benefits ... Glasswool Slabs or Batts ...

The acoustic performance of slabs can be better due to the structure of the fibres in the product, and the varying level of densities available.

Slabs are more flexible than boards which need to be cut accurately, they can therefore provide a superior fit against joists, rafters, blockwork, et cetera.

Slabs may be preferred in retro-fit above ceiling situations due to ease of application.

Slabs can be tissue faced to provide improved acoustic and fire performance.

The difference between PUR and PIR ... increased fire performance.

PUR/PIR insulation products give the optimum choice for most insulation applications within the building and construction industries.

With their impressive thermal conductivity and high strength to weight ratio, rigid polyurethane (PUR) and polyisocyanurate (PIR) rigid foam products are very effective and lightweight. They have the ability to bond to most materials in the manufacturing process.

Rigid PIR differs from PUR, in that it is produced using an excess of the MDI component (see below). In the presence of an appropriate catalyst the excess MDI reacts with itself to form isocyanurate which is characterised by greater heat stability.

The resultant PIR insulation products exhibit increased fire performance and reduced combustibility and higher working temperature limits compared to PUR and when incorporated into building products, can meet some of the most demanding fire performance requirements.

For the 'Techies' ...

Rigid PUR insulation products are made by reacting a liquid polyol component with a liquid polymeric isocyanate, Methylene Diphenyl di-Isocyanate (MDI), component in the presence of a blowing agent and other additives.

The mixed components then react exothermally to form a rigid thermosetting polymer and since the blowing agent evaporates during this exothermic reaction a rigid closed cell low density insulation product is created.

Excellent insulation is achieved because the gas trapped within the closed cell structure has a very low thermal conductivity and there is minimal heat conduction through the solid cell walls due to the low density, where approximately 97% of the volume of the foam is trapped gas.

When is insulated plasterboard a better choice?

Insulated wallboards and thermal performance plaster boards are ideal ...

12.5mm foil-backed duplex plasterboard is an ideal product where even the remotest chance of condensation is a possibility. It is entirely appropriate for under rafter and loft conversion use.
Performance insulated plasterboards are available from just-insulation.com in widths from 22mm through to 65mm

They can be used as stand-alone products that do not require additional structural support ... internal dry lining and insulation solutions in just one fixing operation that saves time and money.

Are there downsides to bubble foil insulation?

When and when not to use bubble-foil ...

One of the most appropriate places to use bubble foil is between the outer and inner skins of a building, where the plays the double roll of acting as a reflective barrier, and excluding draughts.

Bubble-foil can be used in other areas of a property, but care must be taken to ensure the installation does not allow the possibility of condensation.

Like single foil insulation, bubble foil is susceptible to the creation of condensation in temperate climates if not properly installed and combined with the appropriate dry insulation condensation may occur and lead to dry rot.

Page last updated Monday, April 16, 2012