Insulation to cut carbon emissions says Remmers UK

Alex Dennis, managing director of Remmers UK, says a new approach is needed to deal with challenges presented by solid walls, with 45 per cent of heat loss resulting from solid walls in older homes.

Installing effective insulation must now be a priority to cut carbon emissions.

It is estimated that some 6.6m existing homes, built before the advent of cavity wall construction after the 1920s, have solid masonry walls - and most are un-insulated.

Add to this the cavity walled homes that cannot be fitted with cavity insulation and you have a substantial part of the UK housing stock that is crying out for action.

But why hasn't more been done already? Solid walls have generally been considered to be complex, problematic and expensive to insulate, however you handle them.

So, a smart approach is needed today to overcome this preconception.

External issues At first sight, adding insulation on the outside seems simplest, avoiding internal disruption for occupants.

Various systems are available involving either overcladding or rendered finishes.

In both cases, the external appearance will almost certainly change as a result and the house will effectively be extended, albeit just by the added insulation and finishes.

As these changes constitute development, planning permission should be required - particularly on the street frontage where permitted development rules don't apply.

Local authorities vary in their approach to this issue and should be approached in any event.

Certainly, any homes that are historic and listed, or in protected locations such as conservation areas, will need separate consent, which could well be withheld.

It is worth remembering that there are half a million listed properties in England and Wales alone, many of which would benefit from insulated walls.

Adding to the outside of walls causes other problems as well with detailing and adjustment of downpipes, eaves and window or door reveals.

And for houses with direct street frontages this addition could constitute an intrusion onto the public highway.

Of course, insulating inside the building avoids most of these problems but it does create other issues, including a small loss of roomspace.

Whether studwork with insulation in between or directly applied panel systems are used, they will probably require adjustments to skirtings, covings, door linings, radiators and electrical boxes.

Inevitably, the work involved will require rooms to be cleared.

But this freedom will allow the most effective system and all associated work to ensure the best energy conservation outcome.

Managing moisture One fundamental problem with solid wall insulation systems in the past has been the approach to moisture control.

External systems aim to seal the outside of the building, but any moisture that does enter is trapped in the old wall.

Conventionally, internal systems have a vapour barrier to prevent warm, moist internal air meeting the cold external wall to avoid condensation - but a number of disadvantages become apparent.

Connections between building elements, pipes passing through walls and structural movement - for example to timber beam bearings - create problems that are difficult to solve.

Also, making walls impervious to try to stop condensation on the inside impairs the ability of masonry to dry out during the summer months - especially after prolonged exposure to driving rain over the winter.

Vapour barriers are susceptible to damage and the durability of the construction to which they are applied is, therefore, questionable.

Breathable systems In contrast, breathable systems allow freedom for moisture to move, providing a high drying potential which is good for the building fabric - even areas already damaged by moisture ingress in the past.

Experience in Europe over the last decade has shown that these breathable internal insulation systems offer the best performance by far.

And this has been endorsed by sophisticated modelling programmes used to simulate thermal and hygroscopic behaviour of facade constructions.

But, until now, breathable interior insulation materials have had two disadvantages: only moderate thermal insulation capabilities and a limited ability to buffer hygroscopic moisture.

The latest generation of smart, permeable, capillary-active interior insulation systems combine thermal insulation, capillarity and air moisture management within a single system.

They enable the building fabric to breathe whilst providing excellent thermal insulation levels within a relatively thin construction.

They can also take up and store moisture from the indoor air during peak loads, helping to regulate and improve the room climate.

Capillary activity ensures fast and effective distribution of any moisture in the system during the winter months and drying is accelerated, so improving the effectiveness of the insulation.

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