The Future Lies Off-Site

  • Building Design Expert
  • 7 years ago


Traditional construction methods have served us well. Have they? Or, actually did they pass their sell by date a long time ago? But has tradition conditioned us not to really notice. Take a step back, and a good long hard look; because traditional methods of building have actually left us with a very literal monumental problem where now the future actually lies off-site.

The building stock of this country, let’s stick to the UK for the moment, is traditionally ‘good solid stuff’. But even the post war prefabs still survive, as indeed anything can with a good maintenance regime. However, they have left us with buildings that are so poorly insulated, that even with a complete insulation make-over, the construction still provides all to often insurmountable ‘cold bridge’ issues that can generate mould and ultimately produce air quality problems that often won’t go away. Yet we keep on building them. It’s like we’re banging our heads against our own masonry walls.

Masonry – there’s the problem. One could argue that it goes back to Englishman’s castle days. Naturally, we have developed and refined our construction techniques overwhelmingly since we stopped needing to repel common invaders, but we have retained this desperate need to cling to the principles of solidity and mass as the basis for the vast proportion of our vernacular building design and construction, and so this is why our building traditions are so tied up in ‘bricks and mortar’.

Here’s the rub: We tried our best (that’s our construction industry term ‘best’) to embrace developments in structural technology to take advantage of ‘matchstick’ like timber frames (cheap) that we could insulate so much more effectively (green), whilst at the same time maintaining the external appearance of solid masonry cladding using brick, and, or stone. Fantastic, everyone’s a winner. Or so we thought. But in pioneering this technology, the attention to construction detail didn’t transfer in the move from the last school. We fell foul of incomplete, damaged, or even missing vapour barriers; because few contractors understood the entire schedule of consequences as a result.

Early contemporary timber frame housing attracted a very poor press, and if you were one of the home owners, with very good cause. The late 1970’s and early 80’s had rotting frame members making up the longest list, closely followed by rampant mould growth and poor air quality. We didn’t really understand that the increased insulation, and greater ambient building temperatures could hold onto far greater quantities of moisture in suspension. When it found a cold bridge (via an incomplete) vapour barrier, the release of moisture was that much greater that over time provided horrific repercussions, not only to the framed structure, but to the internal finishes as well.But these panels were manufactured ‘off-site’, and this blog is all about such processes holding the key to the future, so 70’s timber frames remain there, and technology has developed to avoid repetition.

The factory production methods were and are completely sound. Much finer tolerances in manufacture, and assembly of parts in the clean and dry has got to promote greater overall quality; compared to laying bricks in the biting cold of a British winter – even contractors are only human after all. Therein lies the problem. The problem being the human element and the myriad variations that go along with that.

Despite the recent government slow down on the train to destination ‘zero carbon’, circumstances concerning the price of energy has led to the industry, to a small extent, picking up that gauntlet and showing that we understand the need. But it will ultimately take legislation for the volume house builders and developers to comply. If they don’t have to do it history has demonstrated that they won’t.

Terrance Conran coined the phrase “Pile ’em high, and sell ’em cheap”. It worked for him with curtains and cushions, but applying similar principles to housebuilding will never cut it; certainly not on an industry level. But unfortunately as a nation, at consumer level it just seems we are grateful for whatever is thrown at us. It has become a way of life for many to move into a brand new house or apartment, and then start fighting to have all the defective work put right.

Maybe ‘snagging’ will never change; after all it can be largely subjective. But improve the overall quality of the build, and the snags will reduce by default. How do we do this? – We know from the scars on our foreheads that what we are doing now isn’t going to get us close. Fifty years ago the industry could not conceive we would be happy with buildings built in a factory environment and shipped to site to simply be bolted together. But today we know it works. Pioneers have gone out on a limb to prove that. The quality of the build, the specification of materials and the use of technology can and has produced extraordinary results.

Structural insulated panels (SIPS), like most construction forms, are not new, but the technology behind them has suffered from the reticence that goes with our industry, in accepting a construction methodology that threatens other established and existing construction forms. After all this is just another construction panel, as was stick built timber frame. But we already know what happened with that one.

The majority of the still niche SIPS market leaders utilise polyurethane foam as their core material, but other successful cores are made up using both expanded and extruded polystyrene. The price? – sustainability. The bonding between the outer sheathing boards and the core insulation material is key to the panel’s strength and performance. So substituting a more sustainable insulation material within the core, such as sheep’s wool, isn’t going to work at the same level, or indeed at all.

So we are back to that old chestnut argument that buildings constructed using SIPS have a number of performance attributes in their favour, which means the embodied energy is paid back many times over the lifespan of the building, in terms of the high insulation performance, high degree of air-tightness and ease and accuracy of construction. That is the antidote to the complaint that a significant proportion of the core ingredients to SIPS are petro-chemical based.

Modern SIPS owes a great deal to the finite resources our planet is still able to offer, but using them in this way will limit our reliance on those resources; – a strange and double edged sword. but the most effective damage limitation lies for the moment in reducing our reliance on energy, and the future for that lies in the development of off-site construction methods that will provide the best route to energy efficient buildings.