One of the most popular and effective ways to reduce energy bills is make your building less leaky (draughty in other words). The word “airtightness” wasn’t even a word used in connection with domestic buildings, until it was introduced and formalised through building regulations in the early 2000’s, it is now an established part of Part L (Conservation of fuel and power) and mandatory throughout the UK.
It applies to new buildings and certain types of work in existing buildings, and is there to enforce minimum standards of energy efficiency.insulation is an obvious way to improve performance but doesn’t cure leaks; evidence shows that leaky buildings are a major source of wasted energy and this is why reducing air leakage within a building is a key component of reducing bills and improving building efficiency. This reduction in the uncontrolled passage of air either into or out of a building is generally referred to as airtightness.
So how do you reduce wastage and increase the energy efficiency of a building, in simple terms insulate well and prevent leakage….. and that sits right at the heart of what needs doing.
However it needs to be understood that this is set in the context of building regulations, which are complicated, and interpreted by technical experts, which adds complexity; regarding a vast range of products all searching for their own place in the market and making their own verified performance and quality claims, yet more complexity; then installed by builders who buy what they are told to or what is available from their local merchant. Wow……. no wonder one of the most common observations we come across is a form of information ‘paralysis’ from our self build customers.
There is a saying that if you do something well you tend to make it look easy. Take a company which has spent over 30 years making products for a single purpose (airtightness) it would be reasonable to assume that they may have got it right, and you would be right in thinking that way, in addition the same company has won awards, robustly tested and retested their products, achieved all major accreditations and has the benefit of post occupancy monitoring for the last 30 years. This company is Pro Clima.
In order to arrive at some basic elements that would apply to most building situations we asked Steve Gurney from Ecological Building Systems could he come up with a simple list of the “workhorses” of airtightness. Could he find six to eight products that would cover most eventualities? The answer came back as a yes.
First two very pared down observations about airtightness.
- Airtightness is effected on the inside of a building, on the warm or internal side of the insulation; the function is to prevent leakage. Variously called vapour check, vapour barrier, vapour control, or airtight membrane
- Wind and weather proofing is effected on the outside of a building the function is to prevent adverse weather penetrating the building fabric and reducing the insulations capacity to perform and prevent deterioration in the building fabric. Variously called vapour control, breather membrane, vapour open membrane, vapour permeable membrane, vapour open underlay and sometimes additionally described as being diffusion open.
Together this ‘wrap’ for the insulated layer allows moisture control geared to our climate with protection from the elements on the outside and leakage prevention on the inside. The airtightness won’t increase the U value of the insulation but it does ensure that the insulation functions to its optimum performance and more likely to achieve designed U Value. It cannot be over emphasised that airtightness and vapour control go hand in hand they work together to solve different problems but with a single end result – better building performance.
Airtightness means designing and installing a continuous seal around the internal fabric of the external envelope to eliminate unwanted draughts. Once the airtightness layer is in place and sealed with flexible and durable tapes, seals and glues, it ensures that the insulation functions to its optimum performance, saving energy and drastically reducing carbon emissions for the lifetime of the building. The airtight layer also ensures that interstitial condensation risk is minimised, ensuring no structural damage from moisture, mould, rot and damp.
Here is the workhorse list
- Internal airtightness membrane Intello Plus
- External roofing membrane Solitex Plus
- External wall membrane for use with timber frame Solitex Fronta
- Universal jointing tape Tescon Vana
- Sealing tape for windows Tescon Profil
- Sealing tape for masonry and integrating into plaster Contega Solido
Six products that cover pretty much all the basic requirements, there are various accessories such as grommets, stoppers and glue that may be required but the bulk of the work is done with these six products.
If you start with the basic principles and keep the products to a proven few then you will be less susceptible to industry ‘noise’ creating confusion or quandary over what product to choose. It would be disingenuous to say the there won’t be times when technical advice is be needed and that is easily available through our technical support team. What it does mean is that for those manufacturers who do it well and make it look simple, take them on trust you are benefiting from years of robust and thorough testing and R&D arriving at a proven and purpose specific product. Their expertise should be your comfort.