At Ecomerchant we stock a large and complete range of environmentally friendly, natural types of insulation for almost every conceivable application. In addition to walls this includes in-ground insulation, floors, ceilings, roofing, external and interior systems, plus a wide range of acoustic products.

Browse popular, ethical materials for wall insulation below to see our high quality eco products, information on pricing, delivery, application and use, technical datasheets, installation guidance and more.

If you have any questions please call our team on 01793 847444 and we will be happy to advise.

How to insulate different wall types

How and what to insulate a wall with largely depends on the location and function of the wall itself.

All walls in a building can be insulated. Typically external walls are insulated to prevent heat loss; the insulation can be located on the exterior surface, in a cavity if one exists, between timber studs for timber frame, or on the internal face.

Internal dividing walls (structural and partition) can also benefit from thermal insulation but more commonly this will include an acoustic function i.e. noise reduction.

Broadly speaking there are two types of wall, load-bearing and non-load bearing:

Load-bearing walls

  • External walls that support the structure (and themselves) including floors and roofs
  • External walls protect from weather and provide the thermal ‘shell’ of the building
  • External walls are where windows and doors are located interrupting the ‘shell’ of the building, openings must be suitably reinforced to maintain integrity
  • The internal face of an external wall is the optimum location for an airtight layer
  • Party walls divide and support adjoining properties, their function is ‘shared’ between the adjacent buildings
  • Internal walls can be load-bearing and divide and support the structure these are typically supported directly off foundations

Non-load bearing walls

  • Internal walls divide the structure
  • Internal walls provide acoustic and thermal benefits

These two types of wall can be made in various ways. Some of the most common are:

Solid wall insulation

Very common in existing buildings built before 1920 as structural walls, typically masonry, block or brick they have no cavity although can contain voids if rubble-filled. Generally these walls stay dry by allowing moisture to evaporate through the brick (or masonry) and a lime mortar paired with good ventilation and heating.

Modern solid walls include insulated concrete formwork, clay or concrete blocks, cast concrete and some timber frame designs.

Cavity walls

These are made up of two layers with a gap in between (the cavity) joined by ‘ties’ to prevent them moving together/apart either located in the mortar layer or sometimes mechanically fixed. Some early buildings have no ties. These can be installed later by through-drilling and fixing ties with epoxy resin glue. The outer layer is usually made of brick with an inner layer of brick or concrete block.

Cavity walls are common in properties built after 1920 although occasionally can be found in properties built pre 1900. Originally used to protect against moisture penetration and wind-driven rain, the addition of cavity wall insulation was a later introduction as was retrofitting by injecting insulation into empty cavities. Cavity wall construction is the most common way of building a wall today throughout most of the UK.

Walls that contain spaces (a form of cavity but not considered as a ‘cavity wall’) are also fairly common, typically in timber frame construction where spaces are used for ventilation commonly on the cold side of the insulation layer for example beneath external cladding (see notes below). These spaces are designed to protect the fabric of the wall by allowing water vapour to be moved to the outside such spaces are vital to ensure peak thermal performance and building durability.

Party walls

Typically found in terraced or semi-detached buildings they are usually made from the same materials as the rest of the building’s load-bearing walls. They support and divide but are not exposed to the weather.

Internal walls within the roof space, where the masonry or brick ends at the roof plate level, are simply to divide roof spaces. They are often plasterboard and should be constructed to meet current fire regulations.

Protruding party walls above roof level are a potential site for the ingress of water and must be suitably sealed with flashings.

Insulating external walls

Locating the insulation layer will be a function of the type of wall. Cavity walls made from brick and block will be insulated in the cavity either partial or full fill using either rigid boards or vitreous fibre batts. Retrospective cavity fill can be with blown glass wool, polystyrene beads or polyurethane foam, none of which are natural or particularly environmentally friendly. This is one area that cannot be insulated with natural materials.

Insulating solid walls

Solid walls can be insulated on the external or internal face or both. Timber walls can be insulated from the outside, inside and in-between studs or often all three.

Insulation choice depends on many factors which are often out of the control of the occupant of the property. Planning, Listed Building or Conservation Area restrictions may prevent insulation from being installed externally.

There may also be practical restrictions such as:

  • roof overhangs
  • abutting walls
  • lamp posts
  • cable connections
  • complex external surfaces
  • adjoining properties or walls

Any of these could mean that external insulation would either be extremely tricky to install or would be incomplete.

External wall insulation on solid walls will typically achieve higher levels of insulation with little risk of moisture problems either internally or within the wall structure. It also keeps the thermal mass of the building within the insulation envelope.

Synthetic insulation materials do not manage water in the same way as natural ones. Natural insulation is vapour-permeable, materials such as dense wood fibreboards ensure the safe transfer of moisture from the masonry walls to the exterior of the building. Vapour open materials actively dry damp masonry walls and can keep them dry. Wood fibre boards finished with a vapour-permeable but water repellent render provides a long-lasting, dirt and stain resistant facade.

Insulating wall cavities

There are no suitable natural insulation materials for use in the cavity in a cavity wall.Retrofit however is a different case.

External wall insulation can be used to renovate the exterior of buildings with cavity walls. When correctly installed it will ensure the proper functioning of the cavity wall insulation by preventing water penetration and by moving the condensation point outwards beyond the cavity, meaning the cavity insulation stays dry and functions properly.

Our advice would be to only ever fill an existing cavity wall if you’re going to externally insulate as well. The cavity is there for a reason - it’s there to keep the building dry and it really should not be filled. The reason is very simple – if you fill the cavity, moisture can track from the outer skin all the way through to the inner skin, plus any moisture generated within the building during the winter months which gets into the cavity will condense, wetting the insulation. This will increase the risk that it can migrate back towards the interior, so adding cavity wall insulation retrospectively can create damp problems rather than solve them.

Insulating timber frame walls

For the general builder, the most common way to insulate a timber frame is to use a foil-faced foam board or a glass/mineral wool batt, both of which can be combined with a multi-foil blanket to improve the U-values.

Synthetic insulation

Whenever synthetic insulation is used in a timber frame the design and installation MUST keep moisture out of the structure. As a result, these insulation materials require vapour barriers but also necessitate gaps (cavities) within the construction to ‘manage’ water vapour safely away, in other words to stay dry. On paper and in the lab this works really well but in practice ensuring perfect continuity of these layers and membranes is very difficult.

Building sites are dirty, windy, wet places, timber frames get wet, insulation materials get wet and even prefabricated panels get wet on-site, so it is important to use a system that can dry quickly to help the timber frame to dry.

Natural insulation

Natural insulation materials, especially wood fibre, can absorb water if allowed but, importantly, release it again so the structure dries out again very quickly. Once natural insulation is dry it will continue to take up excess moisture from the studs until both materials reach a similar, low level of humidity. Limiting the pathways for air movement between the insulation and the surrounding surfaces, including studs, boards and membranes, is vital in maintaining (or achieving) target thermal performance)

Insulation needs to achieve a snug fit so eliminating air leakage pathways. Foil boards are almost impossible to fit in this way. It’s worth noting that where the structure is fully ‘vapour open’ from plaster to render gaps are not required. It is only when impermeable elements are included that present a barrier to the diffusion of water vapour that condensation can occur and a gap is needed to allow ventilation to remove the moisture.

Natural insulation used in a breathable (vapour open) structure does not require interstitial gaps or spaces, the wall section can be fully filled. The hygroscopic nature of the wall will then facilitate the safe movement of moisture to the outside surface to be wicked away for example through a lime render or directly from the building surface behind a ventilated façade.

Wood fibre batts

Flexible wood fibre batts, Wool and Hemp are among the best ways to insulate between studs simply because they are compressible. Cut a little larger than the void to be filled they will self-support by being ‘friction fit’, once in place they will spring firmly against the edges of the void, ensuring there are no gaps for warm air to move through.

Rigid fibre boards

Rigid foam boards are very difficult to install effectively between timber studs. Because they are brittle and inflexible it is near impossible to cut a single piece to exactly the right shape to fit between timbers and so air gaps will form. Plus all PIR boards shrink, even a small gap in the structure can be ruinous to the performance of a building. Our advice, don’t use rigid boards between studs in a wall.

Flexible wood fibre batts are a very high-density form of insulation (typically 50kg/m3) that allows fast and effective insulation between timber studs.

The internal face finish can be a rigid plaster carrying wood fibreboard, an engineered airtight racking and vapour control board (not OSB) or plasterboard. Use OSB3 if a service void is to be included. It is important to check if the use of an internal membrane is required.

On the external face a rigid wood fibre sheathing board can be used, there are versions that are render carrying or for slips or masonry or the board can be battened to accept cladding. Wood fibreboards used on the exterior of studs to create a weather-tight shell that keeps the building warm in winter and importantly, cool in summer.

Recently many timber frame constructors have moved towards ever simpler designs often walls contain no more than 4 or 5 elements. A typical make-up might include an airtight internal racking board, flexible natural insulation batts in between the timbers and an external wood fibre sheathing board either rendered to or battened to support cladding. Simple, uncomplicated, easy to fit and a secure way to deliver thermal performance comfort whilst providing superb protection from the elements.

Insulating internal walls

Internal wall insulation tends to be used less than external mainly because of the disruption it causes to the occupants, although it can be simpler to install and can offer really noticeable improvements to winter comfort. Internal insulation is not subject to the weather so can be less robust than external; this has the consequence of making it cheaper.

Internally applied insulation disconnects the plaster layer from the masonry beneath allowing the plaster to warm up to somewhere near the internal air temperature. Internal plaster will radiate heat back into the room which is picked by our skin and makes us feel warm. This is especially true of lime plaster.

Bricks, concrete and masonry tend to absorb infra-red radiation without this being emitted back from into the room; the result is we feel cold. This means that higher U-Values can be designed for internal walls whilst still achieving big improvements in internal comfort.

Internal wall insulation must be installed carefully, completely and must not create a situation where the moisture levels in the wall rise which then has implications for any timber beams/joists buried in the wall.

Wood fibre insulation has been shown to be the safest form of internal wall insulation to use in all levels of weather exposure, and should be the first consideration for above ground insulation. Wood fibre allows a certain amount of drying towards the interior of the building, meaning external walls stay dry improving the longevity of timber in the walls.

Issues with incomplete insulation

It may be assumed that adding any insulation must help however there are plenty of examples that show incomplete insulation can cause moisture and mould issues, negatively affect indoor air quality and can seriously affect the health of the occupants.

A good way of thinking about this is to imagine the flow of water: it will always seek out the path of least resistance, the dam has to be complete and unbroken. Gaps in the dam are the equivalent of thermal bridges which lead to the problems above. Just like the water behind a dam the same volume will try to get through smaller gaps, increasing its pressure and speed to do so. This is why ‘how insulation fits and is fitted’ is so important.

A recent survey of UK builders found that over 54% of respondents thought that insulation was only about keeping the heat in and nothing else.

How did we get to the stage where the industry knows so little about a fundamental part of building design, construction and comfort? Maybe there is a reason, maybe a little bit of history might help shed some light on this.

Insulation in the UK – a timeline

Insulation timeline for the UK

Today, the most common impression people have about insulation is that they only have a choice of glass, mineral wool or foil-backed board.

Comparison of wall insulation materials

You would think it would be sensible to compare insulation materials in order to consider all the possible features and benefits but this process is largely ignored. The entrenched attitudes towards insulation specification and application mean that the same products get used time and time again even when better products are available.

There is also widespread use of insulation in inappropriate locations where consequential performance issues can arise. A good example would be the use of rigid PIR boards between timber studs leading to excessive air movement through poor fitting and gaps caused by post-installation shrinkage.

The results from the Ecomerchant survey revealed just how little awareness there is about insulation, even in the trade. The Protexion Campaign aims to open up the possibilities for natural insulation materials. Here you will find information to help you explore how natural insulation works and the benefits that it can bring to realise the possibility of building better. Globally, wood fibre is the most common natural insulation material that is commercially available. It works just as well as petrochemical insulation, however, it additionally offers (as do many natural insulation materials), features and benefits which are not found in synthetic insulation. Most importantly, it adheres to all the eight roles insulation should contribute to a building.

The multiple roles of natural insulation

The 8 Roles of Insulation

Within the eight roles there are a wealth of features provided by wood fibre that contribute to fulfilling the role, for example ‘breathability’ an inherent capacity of wood fibre to absorb, attenuate (store) and release moisture with no prejudicial effects at all. This feature is a key part of delivering improved comfort, health, durability and thermal performance.

Why choose natural wall insulation?

Conventional wall insulation typically includes materials that require a lot of energy to produce, such as fibreglass, mineral wool and multi-foils, and can contain numerous chemicals such as blowing or foaming agents, dust inhibitors, fire retardants, binders and adhesives. Vitreous and foam insulation is widely available and inexpensive, these products are often favoured based on the publication of U Values in the Building Regulations where compliance is the target criteria.

Synthetic insulation materials like these also argue that the benefits gained from their use outweighs any unwelcome environmental consequences from production, such as embedded energy or potential to pollute, so they can be sold as ‘green products’.

However, modern consumers, designers and specifiers are more discerning and are not won over by such simplistic claims. The emergence of low carbon construction as a new driver of regulation and the campaign to reduce plastics have highlighted the need for better choices of insulation and adaptation of building design to meet our changing demands.

The use of natural insulation materials in the appropriate situations not only fulfils the thermal and acoustic benefits required but bring a host of other welcome attributes such as being safer to handle and fit, breathability, thermal mass, no off-gassing, no waste disposal issues.

The main benefits

Below are just some of the main benefits which go far beyond just preventing heat loss:

  • Natural fibre insulation materials can deliver thermal and acoustic insulation comparable to other insulation materials
  • They have a lower or potentially a negative carbon footprint
  • Fewer health issues during installation as they do not present a problem for eyes, skin or the respiratory system
  • Low to zero toxins
  • Easy to reuse
  • Significant health benefits throughout the lifecycle
  • Offer some thermal mass
  • Natural fibre insulation materials are comparatively more robust in handling than synthetic products
  • Natural fibre insulation off-cuts do not require specialist waste streams and typically can be composted so avoid unnecessary landfill

Natural fibre insulation also tends to have very good hygroscopic qualities and are all vapour-open. Vapour permeable systems are particularly useful where the building is vulnerable to moisture decay. This would be the case for timber frames, timber roofs, lightweight steel constructions and older buildings often made from traditional materials.

They can also assist in regulating relative humidity, and can provide a vapour-permeable system. When used as part of a vapour-permeable system they can reduce the risk of moisture build-up and consequent moulds and bacterial activity which can be injurious to health and costly to rectify.

Customers want alternatives to synthetics

Most of the market growth is driven by customers wanting healthier products that function on a number of levels and compliment the higher performance levels that are being designed into modern buildings and into refurbishing existing properties.

Terms such as ‘breathable’ and ‘airtight’ have created awareness that natural products have multiple and consequential benefits, plus they do not degrade or pollute the environment.

Wall insulation as part of sustainable construction

What kind of wall Insulation you use contributes to meeting an ethical, environmentally friendly project in two broad ways:

  • Does what it’s made of have an impact on the environment or your health in a negative way?
  • Does it reduce or eliminate the need for fossil-based fuels to heat a domestic or commercial property?

The UK home insulation market alone is huge and worth over £800 million per year. Of this, a staggeringly small amount is made up of natural insulation products – probably less than 1%. This is improving and needs to improve further.

Figures are hard to come by but there is one common factor across the market, natural insulation products are growing their market share. For a while, the manufacturers of synthetic insulation focused on embodied energy as their meter for comparison but the overall benefits of natural insulation products cannot be ignored.

Building regulations and carbon targets?

Carbon reduction both embodied and operational will become part of the regulatory framework for construction, Part L of the Building Regulations is being toughened up and The Future Homes Standard will require new build homes to be future-proofed with low carbon heating and world-leading levels of energy efficiency; it will be introduced by 2025. Up to 50% of a new build properties’ lifetime carbon footprint is already there when you are handed the keys so what a building is made of is a significant carbon contributor, meaning what you build from will become much more important.

Natural insulation materials not only reduce carbon through their energy reducing properties (insulating against heat loss or gain) but also through what they are made from, especially wood based insulation, they sequester and store carbon as a valuable contribution to meeting the new targets. We believe that current proven options using natural insulation materials to deliver the proposed reductions should be adopted much more widely now, there is no need to wait. Talk to us about how you can use natural insulation materials to meet or exceed the proposed new standards.

Why choose Ecomerchant as your supplier?

We only sell natural insulation products

The Ecomerchant vision is to lead the move to low carbon living through sustainable construction, energy efficiency (which reduces energy bills) the elimination of waste and pollution and to reduce our overall environmental impact.

We engage with all our customers in a straightforward and understandable way, to sponsor a permanent long-term behavioural shift in our attitude to how we build and live.

We save you money

We carry large stocks of natural insulation materials and cover the whole of the UK. We are happy to supply any of our insulation products in any quantity from a single board or pack up to full loads. You can also buy online it couldn't be easier, just one click and the goods are on their way, just when you need them and no need to waste or store any surplus.

We offer guidance on wall insulation

Every home and every wall installation will be different but the methodology for calculating important considerations is tried and tested:

  • How much wall insulation is required
  • How it will perform
  • What material/type you need

These considerations are a well-trodden path for our experts. If you’re unsure or need a hand figuring out what you want, just call us and ask for help. This is what we do day in, day out. Our manufacturer partners and our team will always be able to help you to work out what is the best available option for your particular job.

Ask an expert today

If you know what you need then why not buy online? You can shop when you want and all of our products are delivered directly to you from stock. If you need help please call and ask on 01793 847 444 or email and we will do the work for you.