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

Stockists:
Thermafleece:
Sheep’s wool, hemp and SupaSoft (recycled plastic bottle) insulation:
www.thermafleece.com
Tel: 01768 486285

Thermofloc:
Cellulose (recycled newspaper) insulation:
www.thermoflocinsulation.co.uk
Tel: 017684 86285

Natural Insulations
www.naturalinsulations.co.uk
Tel: 01768 485050
Online Suppliers of Steico flex (wood fibre) Thermofloc, Natrahemp, Thermafleece and SupaSoft (recycled plastic bottle) insulation.

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.

A sorptive 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.

ASBP Briefing Paper – March 2018

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