Joe Ragdale, Technical Manager for Wetherby Building Systems, discusses how to combat the issues with installing EWI in winter weather conditions
“As winter approaches, many refurbishment projects are likely to be delayed as winter weather conditions cause setbacks on site. This is a particular issue with external wall insulation (EWI) installations as these systems cannot typically be installed in cold, wet conditions.
The majority of EWI render solutions can only be applied in dry conditions with temperatures above 5°C, which poses a major problem for contractors and installers, who cannot afford downtime on projects that are delayed or for render systems to fail in poor weather.
With the government outlining a need to dramatically increase EWI installation levels to meet carbon budgets, delays simply cannot be afforded putting increased pressure on installers and contractors to meet deadlines. Wetherby Building Systems is advising there are a variety of techniques and processes that contractors should be considering to help ensure the correct conditions for EWI application to meet project deadlines and maintain the required level of EWI installations.
It is vital that EWI is applied in optimum weather conditions and it is advisable that a job is only started in the correct climate, as if a projects starts and the system then fails due to being installed in bad weather, it will increase the time and costs on the project in the long-term.
Contractors must ensure products are applied suitably and cure correctly to prevent wash offs or damaged render that will need replacing, causing further setbacks. There are a number of ways this can be monitored and recorded on site to ensure the quality of the installation.
Moisture meters are easily available and should be used to test the moisture content of the basecoat or substrate in application. The substrate and basecoat must have a moisture content of less than 1.5% to ensure primers and finishing coats can cure correctly and the systems are not adversely affected by the conditions.
Humidity was a huge problem in the industry last year, with 2012 the second wettest year in the UK since records began; the total rainfall for the UK during 2012 was 1,330.7mm, just 6.6mm short of the record set in 2000. With analysts stating that the frequency of extreme rainfall in the UK is increasing, this problem is only set to continue for EWI applicators, so it is vital installers are aware of the humidity before commencing an EWI project.
Humidity needs to be below 90% to allow renders to cure correctly, if it is above this level it will prevent the render from drying out, leaving the finish wet on the wall, which will cause a sustained negative effect on product properties if this continues for several days. Humidity readers and thermometers are highly recommended for use on site to avoid such problems and ensure conditions are appropriate for application.
Product selection is also an important consideration when working in winter conditions, as certain systems can cope better with cold, wet weather. It is the finish, rather than the insulation board that needs to be thought about, as it is the final finish that gets exposed to the elements. Mineral render and polymer modified finishes, such as dry dash, are the most suitable as they are far more durable and less susceptible to failures in the colder and wetter conditions. In contrast, silicone and acrylic renders are less tolerant to wet and cold climates and trapped moisture, or finishes frozen soon after application will be far more likely to fail.
Ensuring the right conditions during application is the only way to guarantee EWI systems cure correctly to enable them to perform effectively. Protecting working areas is one solution, but this can be difficult to achieve. Sheeting scaffolding and using heaters to provide consistent temperatures above 5°C is possible and can help ensure the successful application of EWI enabling contractors to meet tight deadlines.
Cold and wet weather will always be a problem for EWI installations in the UK and a period of poor conditions will inevitably cause delays. Contractors and installers need to be working with EWI system manufacturers to find ways to combat the issues of installing EWI in winter conditions and ensure failures are kept to a minimum.”
For further information on Wetherby Building Systems or any of the products in its portfolio log onto www.wbs-ltd.co.uk or call 01942 717100.