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Period homes are often through of as being draughty, and air leakage is responsible for as much as a third of a building’s heat loss. While reducing draughts by sealing up gaps and adding seamless insulation layers is key to making a house feel warmer, in order to prevent condensation it’s important that materials are breathable and ideally able to help control humidity in the atmosphere.

Insulation products made of natural materials work especially well with old buildings. ‘Natural fibres are truly breathable and can help buffer humidity levels, holding moisture in a less harmful way.’ Says Mark Lynn, managing director of Eden Renewable Innovations and a director of the Alliance for Sustainable Building Products. ‘This is particularly important in older homes, where ventilation and humidity levels may be problematic.’

Although natural products cost more than many mainstream options, they are renewable and can even help reduce the levels of indoor pollution. However, don’t overlook man-made insulation as there are some extremely effective, breathable products that are suitable for period homes. Often the best solution is to employ a mix of materials – consult an expert with experience of old properties.

Where to insulate:

LOFTS:

If your loft is not currently insulated, then tackling it should be your first priority – it’s the easiest area to insulate and considering up to a quarter of an un-insulated home’s heat is lost through the roof, it’s an important one, too.

The most cost – effective solution is a ‘cold’ roof, where the insulation is laid on top of the ceilings of the rooms below. This is usually done by layering quilts or batts of insulation between and over the joists. Alternatively, loose-fill insulation, which fills all the gaps, can be used. It’s important to maintain ventilation paths at the edge of the roof to avoid condensation, which can rot the timbers.

If you want to convert the loft into a living space, you will need a ‘warm’ roof, where the roof itself is insulated. If reroofing is taking place, you could insulate above the rafters, although this will raise the roof height. The other option is to insulate between or below the rafters, or a combination of both. A variety of materials can be used, but its important to maintain an air gap beneath the tiles.

WALLS:

It is estimated that 35 per cent of an uninsulated building’s heat can be lost through the alls, but this is disruptive to address. Homes build before 1920 had solid walls, as opposed to including a cavity that can be filled with insulation. Solid walls can be insulated either internally or externally – but both solutions involve covering the existing wall finish, which can mean the loss of period features.

For internal walls, rigid insulation boards can be applied, or a stud wall constructed and filled with soft insulation. Plaster is then applied over the top. This inevitably affects existing skirtying and cornicing. To Insulation external walls, a layer of insulation is applied and covered with lime render or other cladding. This can totally change the look of a house and affect elements such and overhangs, windowsills and door openings, so is not suitable for the beautiful facades of many period homes.

FLOORS:

Around 10 per cent of a property’s heat is lost through the floors, of which there are two types: solid or suspended timber. Solid floors are in direct contact with the ground, so without lifting them it is difficult to add insulation, but topping them with breathable, natural carpets, such as wool or coir, will help. Avoid rubber-backed designs. If the original floor has preciously been replaced with concrete and includes a damp-proof membrane, then laying a floating wood floor on top can improve thermal performance. If there are damp problems with a concrete floor, consider replacing it with limecrete, made of breathable lime and aggregate.

Suspended floors are straightforward to insulate where there is access from below, such as a cellar. Quilt- type insulation can be fitted between the joists, supported with netting. Insulating from above involves lifting floorboards, so think twice if the floor is of historical value. If you do disturb the boards, lift a small number at a time. A variety of soft, insulating materials can be sed. Supported by nets of rigid materials can rest on timber battens.

DRAUGHT PROOFING

Alongside insulating, it’s important to address gaps, as heat is easily lost through them. The Energy Saving Trust estimates that simply filling gaps can save up to £40 per room, per year on bills. Open chimneys are easy to block off with an inflatable Chimney Balloon or removable Chimney Sheep, while gaps between floorboards can be sealed with discreet strips, such as StopGap or DraughtEx.

Narrow gaps around windows and doors can create draughts as well as rattling noises. Avoid silicone sealants and instead use draught strips, which can be removed in the future if required. If you have single glazed windows that make a room feel cold, look at fitting secondary glazing.

The Materials
BLANKETS AND FLEECES:

Soft batts or rolls of insulation are easy to fit between joists, studs and rafters. The cheapest option is glass or mineral wool, which has good thermal and sound insulating properties, but is irritating to skin. Sheep’s wool, such as Thermafleece, is a good alternative with advantages including being kind to skin and enhanced breathability and sound absorption. ‘Sheep’s wool is made from keratin, which can absorb and release more moisture and even remove indoor air pollutants,’ says Mark Lynn.

The other fleece option is hemp, a sustainable plant crop that is more breathable than mineral wool, can absorb up to 20 per cent of its weight in water and absorb noxious gas. If space is tight, look at Thermablok Aerogel, available in blankets and boards, which uses NASA-developed technology to eliminate cold bridging (which impacts on efficiency) while being breathable. It’s super thin – just a 10mm thickness can increase the insulation factor of a solid wall by up to 67 per cent.

RIGID BOARDS AND FOAMS:

There are a range of board options, the most common being ‘closed cell’ foam slabs, such as PIR (polyisocyanurate) PUR (polyurethane) and phenolic. Most are impervious to moisture. For a natural option, look at wood fibre board, which is made from timber waste, so is largely renewable and recyclable, has some humidity control and offers good acoustic performance. Boards need to be fitted together tightly, but avoid in awkward area’s as cutting around details without gaps is tricky.

SPRAY-ON AND LOOSE FILL:

Ideal for filling every nook and cranny, these insulations form a seamless layer. Cellulose, such as from Thermofloc, is a loose-fill option made form recycled newspaper. It can be poured in place or blown into voids and gaps. It’s eco-friendly, breathable and gives food acousitic and thermal properties, and is suitable for roofs, floors and walls. Also look at lysnene, a spray-on insulation with an ‘open cell’ composition that, on application, expands 100-fold in seconds to seal all gaps, service holes and hard to reach spaces

Period Living June 2018
Feature: Melanie Griffiths
Illustrations: Sarah Overs

Contacts:

Eden Renewable Innovations Ltd,
thermafleece, Natrahemp and SupaSoft (recycled plastic bottle) insulation
Soulands Gate, Dacre, Penrith, Cumbria CA11 0JF
Sales & General Enquiries: 01768 486285

Thermofloc:
Cellulose (recycled newspaper) insulation
www.thermoflocinsulation.co.uk

Natural Insulations
Online retailers of Steico flec (wood fibre insulation) thermafleece, Natrahemp, Supasoft (recycled plastic bottle) Insulation and thermofloc
www.naturalinsulations.co.uk

Supasoft Insulation
Recycled Plastic Bottle Insulation
www.supasoftinsulation.com

Breathability is a measure aimed at complimenting other means of controlling moisture within the building and its fabric. When considering breathability, it is important to mention that the majority of internal moisture should be removed by good ventilation and the majority of external moisture should be eliminated through an effective weather protection surface, good guttering and drainage systems.

Assuming most moisture is controlled in this way, breathability allows for the balanced removal of what moisture is left within the fabric (which although relatively small, has the potential to be very damaging to the building fabric and occupant health over a period of time).

Defining breathability

A breathable structure is one that allows the passage of moisture in order to prevent the accumulation of harmful water within the building fabric or its surroundings.

Harmful water is water that increases humidity to a detrimental level or which alters the physical structure of materials in a damaging way. When water is capable of dissolving things or is capable of supporting microbial growth, it risks causing harm.

Persistent liquid water or persistently high humidity is likely to be harmful. These often go hand in hand. Intermittent wetting, water vapour with a relative humidity below 70% as well as most water bound to a material (bound water) is unlikely to be harmful. Water vapour is a gas and shouldn’t be confused with mist.

The four essential components of effective breathability

A moisture pathway – There must be a pathway for water vapour to move through breathable materials. Moisture can only move through materials that contain pores or holes of sufficient size to allow water vapour molecules to migrate and escape from within the building fabric. Materials or structures with this property are said to be vapour permeable.

Molecules of water vapour are incredibly small (less than 3 millionths of one mm) so very small pores can seem very large in relation to individual molecules. To give some idea of the scale, a water molecule passing through the eye of a needle is like a dingy sailing through the Pacific Ocean. This is why vapour permeable materials can appear solid to the naked eye but still allow large quantities of water vapour to pass through them.

A driving force – There must be a force to drive the movement of moisture. Moisture always moves from areas of high humidity to areas of low humidity so for moisture to move through the fabric we need different levels of humidity – known as a humidity gradient. It is this gradient that drives the rate and direction of moisture movement.

Asorptive fabric – There must be a way to suppress the harmfulness of any water during its passage through the fabric. In other words, while moisture is moving through the fabric, it should be in a form that is least likely to cause harm. This is done by using materials that are capable of binding and releasing moisture as well as regulating humidity. Materials that can bind and release moisture are commonly referred to as breathable materials

Vapour control – There must be measures to regulate the amount of moisture able to enter and leave the building fabric. This is referred to as vapour control. Vapour control is achieved by ensuring components are organised in the correct order in terms of their resistance to moisture movement (vapour permeability).

Breathability in practice

Breathability is a property that prevents or limits the build-up of harmful moisture within the building fabric. As such breathable structures are most effective when the amount of moisture capable of entering the building fabric is regulated.

Internal moisture is best regulated by effective ventilation, limiting sources of high humidity, using appropriate vapour control measures and preventing uncontrolled air leakage into and through the building fabric. The latter is best achieved by following an appropriate air-tightness and vapour control plan.

External moisture is best managed with effective weathering surface and ensuring that guttering and drainage systems are installed and maintained correctly.

Moisture moves through vapour open materials at different rates making it important to install products in the right combination allowing for appropriate vapour control. This will prevent moisture bottle- necking that can create a damaging build-up of water during its transit. An effective combination of materials and products can be determined through moisture modelling and condensation risk analysis during the design stage.

In a properly functioning breathable structure, it is important that water moves around the fabric in a form that does not risk causing harm. This means that the accumulation of liquid water and persistently high levels of humidity should be avoided. The best way of achieving this is to incorporate sorptive materials which include natural fibre products (such as wood, wool, cellulose, straw and hemp) or mineral products (such as clay and lime) that are capable of binding and releasing moisture.

Sorptive materials temporarily bind moisture and lower humidity significantly suppressing the harmful effects of moisture as it moves through the building fabric. Because of this, the most effective breathable structures incorporate at least one sorptive material. In most cases this involves the incorporation of natural fibre insulation.

Types of breathable materials

Natural fibres – suppress or moderate potentially harmful water by binding and releasing moisture which helps regulate humidity levels as the moisture moves.

Minerals – can provide a porous surface through which potentially harmful water can move and have the ability to capture moisture.

Breathable and moisture variable membranes – are flexible micro-porous or monolithic membranes that keep out liquid water and draughts whilst allowing the passage of moisture vapour.

Conclusions

Breathability is the most effective way of maintaining stable and harmless moisture levels within the building fabric. For effective breathability, all four essential components must be present – a moisture pathway, a driving force, a sorptive fabric and vapour control. Breathability is not a substitute for the main mechanisms of moisture removal and prevention in and around the fabric. Instead it should be seen as an effective mechanism for regulating levels of residual moisture within the fabric. In practice, a degree of moisture will inevitably penetrate the building fabric so having a strategy to deal with this is important for good design.

More price-competitive

While doing some research for a client, our Architectural Assistant Chrissy made an exciting discovery: natural insulation is now price-competitive with the artificial version, and in many cases is actually considerably cheaper.

Natural wall insulation costs far less than industry-standard artificial insulation per square metre. However, natural insulation does require a greater thickness to provide the same thermal performance – about 75% more. Taking this into account, we have found that cavity wall insulation for a timber-framed brick building is significantly cheaper when using natural materials.

Based on quotes for two of the most popular and industry-standard products, the same thermal performance can be achieved with either 80mm thick Celotex FR5000 at £13.36 per square metre, or 140mm thick Thermafleece CosyWool at £10.07 per square metre.

Safer and healthier

Celotex FR5000 wall insulation is made from rigid polyisocyanurate (PIR) board, which is plastic-based with various chemical additives and a blowing agent to make it foam. While not particularly hazardous, it is an irritant to skin, eyes and the upper respiratory system. Thermafleece CosyWool is a natural and safe product which is almost entirely sheep’s wool – you don’t even need gloves to handle it.

More sustainable

Thermafleece insulation is natural, non-toxic, made in the UK, low-carbon and recyclable. Other natural insulation types such as wood-fibre or hemp-fibre are non-toxic, low-carbon and recyclable too – although the place of manufacture will vary. The Celotex product is free from ozone-depleting substances and is an energy-efficient insulator. However, the manufacturing process causes pollution and the product causes more pollution at the end of its life as it is difficult or impossible to recycle. Arguably, relying on plastics-based products is also inherently unsustainable as it supports the climate-disruptive oil industry.

Article published by Koru Architects. www.koruarchitects.co.uk

When it comes to more significant works, however, there is much conflicting information around what is the best course of action to take with an old home, especially if it is listed or located in a Conservation Area. The biggest issue is when inappropriate, non-reversible changes are made, or when breathable materials are not specified.

Consider carefully what advice you follow when tackling areas such as heating and insulation, and only work with companies that have experience of dealing with period properties. Where possible, repair rather than replace and check with your local authority before introducing any energy-saving measures that may have a physical or visual impact on your property.

See the article in full at Real Home: https://www.realhomes.com/advice/ways-to-save-energy-in-a-period-home

As a result, the emphasis on effectively insulating your home now couldn’t be greater.The choice of insulation available on the market is varied, but there is much more to insulation than simply saving heat! Your choice of the type of insulation you use is an important decision, a decision that can have economic and environmental consequences for your home, workspace and the planet.

So consider. . .

BREATHABILITY:

Ensuring that your house is breathing, and moisture is able to escape is essential to the health of the building as well as the occupants.Wool breathes through its’ very fibres, packed together creating millions of pockets, these fibres trap air and ensure homes are kept warm during the winter and cool in the summer.
MOISTURE CONTROL:
When wool absorbs moisture it emits energy that warms the wool and so helps reduce condensation and can actually draw moisture out from timber and other building materials where condensation might otherwise be a problem.

AIR QUALITY:

As a chemically very complex fibre, wool is also able to readily bind and fix many airborne chemicals, thus making the air within the building cleaner to breathe. The fibres fix carbon during their formation, providing a mechanism to remove atmospheric CO2 .Fibres such as wool and hemp contain approx. 50% carbon meaning that every tonne converted into insulation fixes the equivalent of nearly 2 tonnes of CO2 which can dramatically outweigh any carbon consumed in manufacture.

SAFETY:

Another thought to consider is the safety aspect. Wool is a kind fibre, itch free, safe and easy to install.  Therefore, there is no need for protective clothing when installing and it does not release damaging fibres into the atmosphere when cut.

SOUND QUALITY:

The sound insulation properties of natural fibres are far superior to those of man-made materials due to their much higher density and the irregular nature of the natural fibres themselves.

PERFORMANCE:

The thermal conductivity of wool insulation products is equal to and often higher than conventional materials. Thermafleece CosyWool for example has a thermal conductivity of  0.0039 W/Mk.

ENVIRONMENT:

Transporting low density insulation carries an environmental impact that can be reduced by compressing the materials. Here at Eden Renewable innovations Ltd, recycled polyester is combined with wool which enables a compression level of 60%.  This has distinct and significant bearing on transport costs and fuel consumption whilst retaining the functional benefits of the wool.

IN A NUTSHELL

Wool fibres not only trap escaping heat, they radiate heat when they absorb airborne moisture.
Wool absorbs toxins emitted from building materials such as formaldehyde
Wool insulation can reduce carbon dioxide emissions in a typical house by 1 ton per year.
Wool insulation is far more effective at absorbing noise than synthetic counterparts
Wool insulation is easy and safe to install!

The solution was found in using SupaSoft.  With its’ recycled content of over 95%, and made almost entirely from recycled plastic bottles it fit the environmental bill perfectly.  Whilst the crimped polyester fibres provide loft and maintain durability which ticked the weight and lack of bulk boxes. With the warmth and comfort provided by polyester fibres widely used to fill duvets and pillows it also meant that the insulation would help to keep the van warm and cosy even in the coldest of weathers.

To find out more about SupaSoft – Itch-free insulation made from recycled plastic bottles visit www.supasoftinsulation.com