Breathable paint: what is it and why does it matter?

When choosing paint, we tend to focus on colour, finish and durability. But there’s another quality worth considering, particularly in older buildings: breathability.

Walls naturally absorb and release moisture as conditions change. The paint we apply can influence how easily that moisture moves through the surface, which is why choosing a breathable finish can be especially important for traditional building materials such as lime plaster.

But what does breathable paint actually mean, how can you tell if a paint is breathable, and does it matter in a modern home?

What is breathable paint?

Breathable paint allows water vapour to pass through the painted surface rather than forming a highly resistant barrier.

Despite the name, breathability isn’t about air circulating through walls. It’s about water vapour permeability: the ability of moisture in vapour form to move through a material.

Traditional building materials, including lime plaster, lime mortar and some forms of masonry, are designed to accommodate moisture movement. When these materials are finished with a compatible, vapour-permeable paint, they can continue to release moisture as conditions change.

A less permeable coating can restrict this process, potentially contributing to moisture becoming trapped within the wall.

Why is breathable paint important for older buildings?

Many period properties were constructed before modern damp-proofing methods became widespread. Their walls often manage moisture through a combination of absorption, evaporation and ventilation.

Materials such as lime plaster play an important part in this process. Unlike some modern construction systems, they are intended to accommodate moisture rather than exclude it completely.

Applying a highly impermeable finish to a traditional wall can interfere with its ability to dry. Over time, this may contribute to problems such as blistering paint, flaking finishes or deterioration of the underlying plaster.

For this reason, breathable paints are particularly worth considering when decorating:

• Lime-plastered walls and ceilings
• Traditional solid-wall buildings
• Historic and listed properties
• Older masonry where moisture movement is an important consideration

The right paint should work with the building materials beneath it, rather than against them.

Can breathable paint help with damp?

One of the biggest problems with conventional plastic-based paints is the way they can restrict moisture movement through walls. Many modern paints use acrylic or vinyl binders which, as the paint dries, form a plastic film over the surface. On traditional, breathable materials such as lime plaster, a relatively impermeable coating can act rather like wrapping the wall in cling film, making it harder for moisture to escape.

When moisture becomes trapped beneath the paint, it can contribute to blistering, peeling and damage to the underlying plaster. Simply painting over the problem with another coat of plastic-based paint may conceal it temporarily, but it does nothing to address the cause.

Our natural emulsion works differently. Made with a plant-based binder rather than conventional acrylic or vinyl, it forms a highly vapour-permeable finish that allows moisture to pass through the painted surface. Instead of sealing a traditional wall beneath a resistant plastic film, it helps preserve the wall’s ability to release moisture naturally.

This is particularly important in older properties, where lime plaster and traditional masonry rely on moisture movement to function as intended.

Of course, breathable paint cannot fix a leaking pipe, penetrating damp or inadequate ventilation. The underlying cause must always be addressed. But once it has been resolved, choosing a genuinely breathable finish can make an important difference to how the wall performs over time.

How can you tell if paint is breathable?

The most useful way to assess breathability is to look for a technical measurement rather than relying on the description on the tin.

One commonly used measure is the Sd value, expressed in metres. This describes a material’s equivalent air-layer thickness in terms of resistance to water vapour diffusion.

Put simply, the lower the Sd value, the more readily water vapour can pass through the coating under the test conditions.

For reference, the European standard EN ISO 7783 classifies coatings with an Sd value below 0.14 m as having high water vapour permeability (Class V1).

If breathability is important for your project, ask the paint manufacturer for the relevant technical data and check that the finish is suitable for your particular surface.

How breathable is Edward Bulmer Natural Paint?

Our natural paints are formulated to allow water vapour to pass through the finished coating.

The original technical figures published for our paints are:

• Natural Emulsion: Sd value below 0.14 m
• Water-based Eggshell: Sd value below 0.3 m

These figures demonstrate the different levels of vapour permeability offered by the two finishes. As with any technical specification, it’s important to consult the latest product information when choosing a paint for a particular application.

Our natural emulsion also uses a plant-based binder rather than conventional fossil-derived acrylic or vinyl binders, alongside our carefully selected earth and mineral pigments.

Explore our natural paint finishes.

Do modern homes need breathable paint?

Breathability is particularly important for certain traditional building materials, but it can also be a useful consideration in modern homes.

The appropriate finish will depend on how the wall has been constructed, the materials beneath the paint and the conditions in the room.

Modern buildings typically manage moisture differently from older solid-wall properties, using combinations of insulation, ventilation and vapour-control layers. A breathable paint is therefore not a substitute for an appropriately designed building system.

It’s also worth remembering that applying breathable paint over an existing impermeable coating won’t necessarily make the entire wall finish breathable. The layers underneath still influence how moisture moves through the surface.

Choosing the right paint for your walls

Whether you’re restoring a period property or decorating a modern home, understanding the materials you’re painting is a good place to start.

For lime plaster and other traditional surfaces, vapour permeability can be an important factor in protecting the building fabric. For other walls, it may be one of several considerations alongside durability, finish and ease of application.

At Edward Bulmer Natural Paint, we believe paint should be chosen with the same care as the materials beneath it. By understanding how a finish performs, you can make a more informed decision for both your home and the walls you’re decorating.

If you’re unsure which finish is suitable for your project, our team can help you explore the options.