Investigating the performance of solid walls with water-repellent surface treatments

A damp solid wall has poorer thermal performance than a dry wall, hence affecting its energy performance. Under future climate scenarios, the moisture content of solid walls is likely to increase, particularly due to higher rainfall intensity. Moreover, solid wall insulation changes the moisture balance of the existing wall; hygrothermal simulations often highlight the need for additional rainwater protection if internal wall insulation is to be installed.
Therefore, providing rainwater protection is often necessary for solid-wall buildings that are facing higher exposure to atmospheric agents. Traditional methods include incorporating additives (e.g. tallow or linseed oil) into limewash, perhaps in conjunction with rendering and bedding mortars, which might affect the aesthetic appearance of the building, e.g. if the building was not previously rendered. On the other hand, there is some evidence on the long-term effectiveness of modern colourless water-repellent surface treatments, which would allow preservation of the aesthetic appearance of the building. If effective, these surface treatments have the potential to be an enabling technology for the improvement of the energy performance of solid-walls.
Although water-repellents can have benefits, in the past, there has been evidence of the poor performance of silicone water-repellent surface treatments associated with the reduction of vapour permeability of the external surface. Recent developments in the chemical composition of water-repellent treatments are claimed to have improved this feature. However, there are uncertainties of long-term performance, particularly on building materials of different mineralogy and porosity.
In a broader level, little evidence is available on the positive and long-term adverse effects of water-repellent surface treatments on building energy performance, occupants' health and durability.
The research aims to investigate the long-term hygrothermal performance and effectiveness of solid walls with water-repellent surface treatments. In particular, the research will address the following research questions, which are in line with both the Technology and system performance and Comfort, health and well-being ERBE themes:
1. What evidence already exists in relation to water-repellent surface treatments in traditional solid walls?
2. What is the influence of these treatments on the pore structure of material usually found in external walls of traditional buildings?
3. What is the influence of these treatments on the improvement of the thermal transmittance of solid walls?
4. What is the long-term hygrothermal performance of solid walls with water-repellent surface treatments?
5. What are the long-term adverse and positive effects on solid walls with water-repellent surface treatments?
a. What are the long-term harmful and positive effects on reapplying water repellents?
6. What is the influence of water-repellent surface treatments on the indoor air quality and energy performance of a solid-walled building?

The low carbon energy systems needed to achieve the Government's carbon 2050 reduction targets promise declining generation costs, but at the price of inflexibility and intermittency. The challenge is to contain costs and improve energy system security, by building in resilience. The opportunities include: more efficient energy conversion, networks and storage technologies; improved energy control and management systems; integration of energy performance into modern methods of construction; improved measurement, display and control systems; and new business models. This will bring pervasive economic benefits: the creation of new intellectual property and expertise; businesses with the ability to compete in the huge new markets for energy efficiency and resilience, both in the UK and overseas; healthier and more productive places to work and live; and a means to address social hardship and inequalities, such as fuel poverty, which affects the health and wellbeing of society's most vulnerable. Seizing these opportunities requires leaders with multi-disciplinary knowledge, skills and whole-system perspective to break down restrictive, sector-specific silos, and drive innovation. The ERBE CDT will train such leaders.

The short and medium term impacts of the ERBE CDT will arise during the training of these leaders and through their research outputs and collaborations. These will include, but are not be restricted to: new approaches to analysis; new insights derived from large datasets; new modelling methods and ways of using existing models; new experimental techniques; field and laboratory measurement techniques; improved socio-technical methods; new manufacturing methods, devices, primary data sets, and patents; and, together with our industrial stakeholders, the integration of research into the business innovation process.

The longer term impacts will be realised over the next 40 years as ERBE graduates take on influential roles in diverse organisations, including:
- national and local governmental organisations that are developing affordable and socially acceptable evidence-based energy policies;
- energy supply and services companies that are charged with delivering a clean reliable and economical system, through deployment of energy efficiency products and technologies within an evolving energy system architecture;
- technology companies that are developing new components for energy generation and storage, new heating, cooling and ventilation systems, and smart digital controls and communications technology;
- industries that are large consumers of fuel and power and need to reduce their energy demand and curb the emission of greenhouse gases and pollutants;
- consultancies that advise on the design of energy systems, non-domestic building design and urban masterplans;
- facilities managers, especially those in large organisations such as retail giants, the NHS, and education, that are charged with reducing energy demand and operating costs to meet legally binding and organisational targets;
- standards organisations responsible for regulating the energy and buildings sectors through the creation of design guides and regulatory tools;
- NGOs and charities responsible for promoting, enabling and effecting energy demand reduction schemes;
- health and social care providers, who need to assure thermal comfort and indoor air quality, especially as our population ages and we adopt more flexible healthcare models.

The realisation of these benefits requires people with specific skills and an understanding of the associated ethical, health & safety, regulatory, legal, and social diversity and inclusion issues. Most importantly, they must have the ability to look at problems from a new perspective, to conceive, and develop new ideas, be able to navigate the RD&D pathway, and have the ability to articulate their intentions and to convince others of their worth; the ERBE CDT will develop these capabilities.