Interiors 1,681 views Oct 09, 2017
Creating happy and healthy living spaces

Poorly-insulated homes can have an adverse effect on the health of the occupants, particularly the very young or elderly during winter months. The issue becomes more acute in multi-occupancy buildings. With a fair chunk of the UK’s social housing stock having been built in the 1960s, much of it is showing signs of age and disrepair. Ben Warren, Managing Director at global building materials manufacturer, Baumit, considers how improved insulation and internal plaster can tackle issues with mould and damp for the long-term benefit and wellbeing of the building and occupier.

Creating better-insulated homes is more than about keeping occupiers warm and dry. It’s equally about facilitating an indoors environment in which residents can live happily and healthily for as long as they remain. Ageing buildings and the UK’s wet, mild climate provide the perfect storm for damp to thrive. This is particularly concerning when multi-occupancy, social housing buildings are affected, as these provide affordable accommodation for many elderly people and young families. Long-term exposure to mould and damp can lead to chronic health issues for the more vulnerable members of society.

Big decisions

The importance of choosing the right insulation is therefore paramount to creating interiors in which occupants can thrive. When it comes to deciding between external or internal wall insulation, it’s very much a case of horses for courses, as any selection will be based upon what the building’s owner is hoping to achieve or the age and type of brick the property is constructed from. For landlords of privately-owned multi-occupancy buildings, financial considerations might conclude an EWI system is more appropriate, and here’s why: from a rental point of view, if you have a room that is 5m2,to provide a decent level of internal wall insulation would require a minimum build-up of 15cm. This would result in a 6% reduction in floor area, which might not sound like a huge amount, but could equate to a significant incremental loss in buildings containing several properties. Loss of floor space equals loss of income for the landlord, therefore in such instances there’s a commercial argument for choosing external wall insulation.

In terms of external wall insulation systems applied to housing association properties, acrylic top coats are very much in vogue. It’s an option primarily based on cost. Local authority funding has been cut to the bone across the board - every pound is being accounted for. It means, although an insulation system specified for a council-owned building might fit the budget, it’s not necessarily best for the property or its occupants’ long-term well-being.

Through everyday living, residents create water vapour. Baths, washing, cooking…it all creates steam - even breathing. Now, consider how much vapour is generated in a multi-occupancy building containing, say, 150 tenants. All that vapour will pass through the building’s elements, but in cases where the EWI contains a non-vapour permeable acrylic topcoat, the vapour will be trapped. This can lead to condensation and the dreaded “d” word – damp. Therefore, an external wall solution that might have appeared cost-effective in the immediate-to-short-term could potentially result in unnecessary and unforeseen expenditure.

Let it breathe

Applying non-breathable EWI to a building causes what might be referred to as the “plastic bag effect” - walls can become cloaked in condensation from non-escaping vapour. To create a breathable outer layer for buildings private or public, a silicon-based finish render, such as Baumit’s SilikonTop, is preferable. Water-repellent, stain and weather resistant, the system provides a robust white or coloured façade. It’s easily applied to mineral renders old and new, providing a decorative, vapour-permeable topcoat that makes for an attractive exterior, whilst optimising occupants’ living environment. 

Another benefit of ‘going external’ when it comes to wall insulation? EWI removes the dew-point - the temperature below which water droplets condense – from the inside of a building to prevent condensation forming. Baumit openSystem provides a perfect example of an EWI system that let’s go of moisture and retains airtightness. Its unique perforated Expanded Polystyrene (EPS) façade insulation boards ensure high vapour permeability, resulting in the release, rather than the entrapment, of water vapour. It has the added benefit of having no effect on a building’s airtightness.

OpenSystem comprises six, high-quality vapour permeable components. It includes Baumit NanoporTop, an innovative self-cleaning topcoat render which uses ‘photokat’ photocatalysis technology to create optimum protection against contamination using the power of light.

The system is also made up of Baumit PremiumPrimer, a superior quality primer for pre-treatment of hard or non-absorbent mineral substrates; and the aforementioned EPS boards. When applied as part of a new-build or refurbishment project, each component helps increase a structure’s ‘breathability’ to collectively offer outstanding levels of insulation. In short: EWI improves the aesthetics on the outside and the building’s thermal performance without affecting the interior space.

Successful wall insulation, whether exterior or interior, is largely dependent on the correct system being specified for the appropriate environment. The consequences of getting it wrong could prove disastrous for building owner and occupant. With interior walls, for instance, this could lead to condensation forming on the surface of the inner face, or even worse, interstitial condensation within the wall that may result in material failures. Vapour permeability is as important to internal wall systems as external ones. Baumit’s range of lime-based, thin-coat plasters offers an excellent option for interior walls. Baumit KlimaDekor, for example, is vapour permeable and low in emissions, making it a high-performance, environmentally-friendly, breathable plaster.

Whilst internal wall insulation might be viewed as a less cost-effective option, particularly for owners of multi-tenanted buildings, for single projects it could provide the aesthetic as well as thermal solution. For example, when installing insulation to a semi-detached house, it might be that you want to retain a brick façade to ensure it mirrors the neighbouring property. An interior system is therefore a great solution. It’s worth being aware, however, that interior wall insulation will incur some disruption for residents, whereas external systems can be applied without installers requiring access to a property’s interior.

External or internal wall insulation? Each has its benefits, but neither will be effective long-term without the vital human element, which means specifying the correct system for the appropriate purpose.