The Liquid Roofing and Waterproofing Association (LRWA) has appointed a new director to its board, which has reinforced its pledge to maintain and encourage the highest standards of quality within the liquid industry. With over 37 years of experience in the liquid roofing market, Mark Flello will work with the existing LRWA board members to lead the strategic direction of the Association. Mr Flello began his career in the laboratories of Evode, before transferring to its subsidiary firm Evode Roofing as a roofing technician, which later became part of Briggs Amasco. He now works at and jointly owns Dove Technology, a business that makkes a range of adhesives specifically designed for the flat roofing sector. As a supplier to the liquid roofing sector, Dove Technology holds Associate Membership at the LRWA and Mr Flello brings his wider sector knowledge to the association, being the only associate member on the board. Mr Flello has also previously played an active role as chairman of the European Liquid Roofing Association (ELRA), which changed its name to European Liquid Waterproofing Association (ELWA) in 2005 when he became vice chairman of the ELWA technical committee. Speaking about his new position at the LRWA, Mr Flello commented: “I’m joining the board at such an exciting time, with the liquid roofing and waterproofing market growing we’re firmly focussed on raising awareness of the excellent liquid systems and products that are available, and making sure operatives are being trained properly to use them. “I think the main challenges ahead are combating quality control of those products being sold without any testing or certification which are simply not fit for purpose, and advising contractors on how to make the right choices when specifying systems. “I’m looking forward to working with the rest of the team at LRWA and bringing my skills to the table.”

Andy Swift, national sales manager for window and door foam sealant company ISO-CHEMIE considers the trade-off between airtightness and ventilation in sealing products. The legal requirement to consider airtightness in building design has been around for more than 10 years (2006) and falls within the orbit of UK Building Regulations. The measurement for calculation air loss out of, or ingress into, a building is measured in cubic metres (m3), per hour (h), per square metre of building envelope (m2) and at a differential pressure of 50 Pascals (Pa) between internal and external air pressure. The back stop maximum leakage is 10, equivalent to 10m3 (h.m2) at 50Pa. When designing to Passivhaus standards, this gets a little more complicated as they refer to airtightness as so many changes of air per hour. This relates more to the cubic capacity of the building or room, rather than the surface area of the envelope of the building. Notwithstanding this, to give some comparison it is generally agreed that Passivhaus is looking for a goal of 0.6m3 (h.m2) @50Pa, or less. Initially, not too much notice was given to the requirement to have a maximum air leakage, as in reality an air loss of 10m3 (h.m2) @50Pa could not really be called an airtight building, so the designs and detailing did not have to change radically to achieve it. However, building standards have progressed with the requirement to conserve more and more energy. Although the legal backstop of 10 has not changed the target air leakage for SAP, separate target values set by the house builders themselves have both significantly reduced. This helps to save heat loss out of the building, thus requiring less use of heating systems to maintain a comfortable temperature within the building, and in turn leading to greater energy efficiency and lowering CO2 emissions. This brings us to the question about air quality within the building. The more airtight we make our buildings the less fresh air we get into them through random unwanted gaps within the building fabric. Such problems can cause other issues for people with respiratory problems or young children, so proper ventilation is crucial.  Build Tight, Vent Right ‘Build Tight, Vent Right’ has been a popular mantra relating to building design, particularly to those concerned with the Fabric First strategy, rather than just throwing ‘Eco Bling’ at a building design to achieve the relevant Standard Assessment Procedure credentials. It is often argued that if by reducing air loss you then need to build-in designed ventilation, then why bother in the first place? The answer, apart from the fact that legislation must be complied with, can be summed up in one word: control. It is the difference between controlled air loss, or ventilation, and uncontrolled air loss and draughts, which is the nub of the whole issue. How is ‘Build Tight, Vent Right’ achieved? With regards to ventilation, this generally falls into two major camps – natural ventilation and mechanical ventilation. If you achieve an air loss of 3m3 (h.m2) @50Pa or less, then it is a necessity to use mechanical ventilation. With an air loss of more than 3m3 (h.m2), it is generally considered that well designed natural ventilation is sufficient for most domestic dwellings. For unwanted air loss, it is generally acknowledged that the air loss between the junctions of windows and doors to walls, walls to floors and walls to ceilings accounts for more than 50% of the air loss in a house. Other common factors of air loss relate to fabric of the building itself and the various holes knocked through the fabric for an assortment of reasons such as drainage, heating flues, electrical cables etc. There are many products on the market claiming to be airtight seals. But the key is to use the correct products in the correct environment, and the extent to which they degrade over time. In addition, if one of the major requirements of airtightness is to reduce heat loss out of the building, then thermal resistance to these air leak sources surely needs to be considered as well. Certainly, being airtight will reduce or stop heat loss by convection, but what about heat loss by conduction – often referred to as non-repeating thermal bridges? The industry is starting to understand that airtightness is only half the story for the sealants. That is why the thermal insulation of joints between window, doors and walls is now included in the latest SAP calculations, where previously it had simply been ignored. When choosing a suitable airtight seal, the full requirements necessary to create a long-term solution must be considered. If it is simply to seal the edges or overlaps of an internal airtight membrane, then movement and thermal insulation are unlikely to be major factors to consider as any number of various stick on adhesive strip tapes are likely to be suitable. As there are technical differences between them, some specialist knowledge or advice is always helpful. A different story However, when sealing an actual construction joint between similar or different materials, it is a different story. An illustrative example is the movement between joints created by the junction of different construction materials, such as windows to walls or walls to roof etc. Even joints between the same materials can move, such as brick or concrete expansion joints. The initial drying out of the building must also be considered. In this respect, the differential movement between timber frame buildings and the external masonry facades is well researched and documented. But the different coefficient of expansion factors of different materials is less well known. When selecting an airtight seal for this type of application, consideration must be given to several factors to assess if it’s correct for the joint-type. This is based on: The need to accommodate movement Any need to allow for conduction heat loss, to maintain the thermal integrity of the abutting materials The suitability of the active adhesive system for both initial application and long-term use on