Insulation

Insulation reduces heat transfer, thus

• Reduces heat loss in winter, saving on heating costs and improving comfort
• Reduces rate of heat gain in summer, saving on ac costs.
• Prevents freezing of pipes
• Reduces run cost of HW systems

Main DIY Applications

• Wall cavity insulation (for either original wall cavities or a retrofitted cavity behind plasterboard)
• Solid wall insulation (fitted to wall surfaces)
• Loft insulation
• Pipe insulation to prevent freezing or heat loss
• HW tank insulation
• Underfloor insulation

Types of Insulation

Trapped Air

Still air is a good insulator, and is the basis of more or less all insulation products currently used in housing. One way or another, each insulation product traps air, and it is the air that does the job.

Cavities

Cavity walls insulate much better than solid walls, and are an early example of domestic trapped air insulation. Walls with no cavity can have a trapped air cavity attached using battens and plasterboard.

Large cavities allow some air movement, hence foamy and woolly insulation products give better insulation than a cavity alone.

Battens and other barriers to air movement can be used to improve an empty cavity's insulation a little, but denser insulation products provide better insulation value, and are worth using.

Expanded Polystyrene

Low cost insulation available in slab form and (still?) small beads for loose fill.

Mainly used for:

• Roof insulation
• Wall insulation
• Floor insulation

Also used for beanbags, and rarely for extra fridge & freezer insulation.

Polystyrene is flammable, and produces toxic smoke on burning.

Historically used for

• Cavity wall insulation
  • Can saturate with water and cause damp problems
  • Beads pour out of any hole made in the wall
• As insulating decorative ceiling tiles
  • Dangerous in a fire
    • Spread fire rapidly
    • Generate thick toxic smoke when burnt
  • Ugly
• As a thin crack covering layer on walls

Polystyrene ceiling tiles are best removed for safety, as is polystyrene backed wallpaper. Polystyrene in wall cavities is relatively well protected from fire.

Fibreglass

Comes in roll form and also loose fill.

• Lasts the life of the building no matter what life throws at it.
• Waterproof
• Insectproof
• Verminproof
• Springs back to shape if squashed
• Lightweight
• Loosefill can be blown about in a draughty loft
• Produces prodigious loose glass fibres
• Tiny spiky glass fibres cause splinters
• Concerns about its safety are occasionally expressed on the basis that it releases miniature sharp spikey non-dissolving fibres, somewhat like some forms of asbestos.
• Dust mask should be used during handling
• Gloves are also recommended to reduce splinters

Much used for loft insulation

Rockwool

A mineral fibre similar to glass fibre, but denser, so much less airborne fibre.

• Popularly used for loft insulation
• Comes in roll form and also loose fill.

Insulating render mixes

Often cement mixes containing polystyrene beads

Shredded Paper

Sometimes used as loose fill loft insulation

Waste paper is treated with fire retardant and chopped. It may also be shredded

Cardboard

Cardboard is a very low cost insulation material. Its low cost helps ensure higher returns on investment by eliminating much of the investment cost.

Cardboard wall insulation is popular in the US, but seems to have had little takeup here.

Its flammability can be resolved by painting it with a mixture of borax & boric acid.

It is damp susceptible, and can support mould if damp. It should not be used in situations where damp may occur.

• Very low cost
• Damp susceptible
• Flammable but easily fireproofed

Papercrete

A relatively novel building product, low density papercrete has good insulation properties and is made mostly out of waste paper and cement, with a number of possible additions including expanded polystyrene and fire retardants.

It is not on general sale and requires a specialist mixer to produce.

Sheep's Wool

Sheep's wool is occasionally used for house insulation.

• Non-irritant
• not damp resistant
• Fire retardant
• Vulnerable to insects
• Expensive to buy as an insulation product
• Cheap if you or a nearby sheep farmer has wool they can't sell.

Straw

Straw has long been used as insulation, and is another low cost option.

• Susceptible to damp & mould
• Nest material for birds
• May contain unhatched insects
• Flammable, which can be resolved by plastering over the straw to deny the admittance of air for combustion.
• Low cost
• Used to be available in slab form, which is occasionally seen in use.

Clay beads

LECA expanded clay beads are occasionally used as house insulation.

Vermiculite is a similar material.

Bubble wrap

Only rarely used in houses, wrapped round water tanks or used as an insulating window blind.

• Degraded by UV light.
• Flammable
• Also used as greenhouse double glazing
• May last ok in dark places eg lofts & cupboards.

Felt

Felt strip is used as pipe lagging, wound around the pipe(s)

• Brown, hairy and untidy looking
• Best used for pipes out of sight
• Good for insulating grouped pipes, where foam jackets would be difficult to fit.

Other Insulation Methods

As well as fitting sheet insulation material or loose fill, 2 other methods are also used to improve house insulation

Cladding

Wood & PVC cladding are both applied to house exteriors, often gable end walls for some reason, to add a little thermal insulation.

Unsatisfactory Insulation Materials

• Carpet
  • Too thin to give much insulation
  • Flammable
  • Reduces draughts

• Polystyrene ceiling tiles & wallpaper
  • Too thin to give much benefit
  • Flammable
  • Dents very easily

• Sand
  • Traps air but is too conductive

• Bubblewrap
  • Degrades quickly from UV exposure

By Application

Loft

• Rockwool
• Fibreglass
• shredded or chopped fire retardant treated paper

Roof

• Polystyrene
• Straw

Cavity Wall Insulation

Fitted to existing wall cavities

• Rockwool, blown in
• Fibreglass, blown in
• Polystyrene bead, poured or blown in

Wall Cavity Insulation

Fitted to retrofitted cavities

• Polystyrene slab
• Fibreglass
• Rockwool batts
• Cardboard

Solid Insulation for Walls

Fitted to the surface of solid walls, and rarely to cavity walls to increase insulation level further.

• Proprietary hard surfaced insulating sheets are mostly used.
• Polystyrene foam backed plasterboard sheets may also be used

Minimum cost options

• Waste cardboard sheet
• Shredded waste polystyrene
• Papercrete
• Straw

See Also

Borax Fire Retardant

Papercrete

Thermalcheck insulated plasterboard