BRE report into unintended Consequences of solid wall insulation

We are seeing an alarming increase in problems with old buildings which people are being pursuaded to insulate.  When this daft idea first started to become mainstream, we shouted from the rooftops that it would cause huge dampness problems.

Now that millions have been spent insulating houses all over the country, both internally and externally, Dr Colin King, of the Building Research Establishment has been asked to investigate.  His report on the unintended consequences of insulating solid walled buildings says exactly what we have been saying.

In theory, insulating a building sounds good.  In practise, the moment you put something onto a wall, you prevent it breathing. You shift the Dew Point within the wall.  You create condensation.  You create a damp wall. This is no different to what the damp industry have been doing for years - tanking walls, applying impervious compounds like tar, membranes, cement slurries - they all stop the movement of moisture within the wall.  Insulation is worse,  in that it prevents heat escaping, or alternatively, insulates a wall, making it cold.  

BRE Report into unintended consequences of SWI

If you insulate a wall internally, you prevent heat from reaching the wall.  Your house stays nice and warm - SO LONG AS YOU HEAT IT.  The only problem is that the moment you turn the heat off, there is nothing to hold the heat, and it cools down.  If you don't insulate internally, the wall itself will heat up. It's like a storage heater - it warms up and holds heat, so long as it is dry. This brilliant system only breaks down when your walls are subjected to the damp industry, under the expert guidance of their Property Care Association.  For years they have been tanking and re-plastering in impervious materials to trap moisture.  This then transmits heat very quickly, cooling the wall.  Damp walls are cold walls. Damp houses are cold houses.  It thus follows that internally insulataing a house is fraught with danger. You need to really know what you are doing if it is to succeed - and there is very little research available to support internal insulation.  If in doubt, don't do it.  

External insulation is a different kettle of fish.

The wall of your house is kept warm - so the dewpoint shifts to the outside.  This means that moist warm air diffuses through the fabric, and can condense near the outside of the wall, between it, and the insulation.  We've seen this a great deal now.  The problem then is that water builds up into the wall, and eventually the base of your wall just gets wet and cold.  You then start seeing 'damp' symptoms internally - mould, plaster coming off - and of course the house loses heat quickly through the wet wall. The end result is a colder and damper house than you started with.  If there is a ventilated cavity between the insulation and wall, you may avoid the problem. But then where is the benefit of the insulation if it's vented?

This whole subject is very poorly researched - if you read the report by Dr King in the link above, it goes some way to showing just how many potential problems there are - and how it's very ill advised to go slapping any form of insulation on solid walls unless you really know what you are doing.  Experts, surveyors, scientists, building control people - none of us really know how to advise on the subject.  If WE don't, then you may have a problem if you just read a few articles aimed at selling insulation and try it.


Damp and Condensation
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