Insulation and airtightness

These are two peas in a pod. We had a presentation last year from ProClima about airtightness and its importance and some of the figures were terrifying. The effect that a lack of airtightness has on insulation values is dramatic. When one thinks about it, the correlation is obvious. If cold air is being driven through, or around, the insulation by draughts then it becomes irrelevant. Good airtightness is therefore important for preserving insulation properties as well as managing ventilation effectively.

We have no real appreciation for airtightness in the UK. Our mild and breezy climates has meant that we have learned to live with draughty homes and we sort of accept it. But in these days were energy efficiency is more and more important we really do need to start to get to grips with airtightness and all the various materials that come with it.

We use insulation in a strange way in the UK. Builders rarely follow instructions from manufacturers on how to fit their products as normally this involves some attention to detail with its associated costs and time. So we often see new buildings going up with phenolic boards in cavities, but are the boards taped together? Rarely.

Membranes are also a whole new building material that is not widely understood. Membranes are used commonly on roofs and timber framed buildings, but until recently they were commonly just stapled to the wood and left. No tape in sight and also no thought for how to join it to elements like brick, block and stone. So again little point in membranes if they are not fitted correctly.

Longevity of seal is also overlooked. With many projects the airtight membrane is an integral and hidden element to the building, so it is very unlikely ever to be checked after the build is complete. Many sealants are not very long lasting (especially in certain harsher areas of the house like on the roof – extremes of heat, or in a floor – exposure to damp) and so when they fail after a few years, all the good work of sealing it up may be wasted. A good quality seal and tape is therefore essential to ensure that the property retains its airtightness into the future.

So be careful when having work done. Insist on using airtight tapes and sealants where required, otherwise the warm home that you were hoping for may not fully appear, especially on the cold windy days that we occasionally have in a Welsh winter.

NOTE. I have just been to a large supplier of insulation and membranes to pick up some stock for a customer. They had the membrane that I needed (a breather one for underfloor insulation), but NO tapes or sealants to go with it!! Apparently there is no demand for the tapes etc so they don’t keep them in stock. See how the conventional builder works?!

On the back of that I have now got some ORCON F sealant and TESCON No.1 tape in from ProClima.