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 hot water 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 cylinder 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 its the air that does the job. So if 6" of insulation is compressed to 4", it has the insulation value of 4" of material.

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 are now available that provide better insulation value, and are worth using.

Expanded Polystyrene

now we know what polystyrene is shipped in

Low cost insulation available in

slab form
as small beads for loose fill & beanbags
larger chunks for packaging

Mainly used for:

Roof insulation
Wall insulation
Floor insulation
Rarely used for extra fridge & freezer insulation

Polystyrene is flammable, and produces toxic smoke on burning. This problem is worse when painted with oil based paints.

Sometimes used for cavity wall insulation

Can saturate with water and cause damp problems
Beads pour out of any hole made in the wall if not glued

Polystyrene in wall cavities is relatively well protected from fire, and is not considered a fire safety issue. However polystyrene cavity insulation in contact with PVC electrical cable fitted in cavities causes the cable to leach plasticiser and become unsafe.

Historic uses

Insulating decorative ceiling tiles

Dangerous in a fire
Spreads fire rapidly
Generates thick toxic smoke when burnt
Ugly

A thin crack covering layer on walls

Dents very readily
Grim news in a fire

Polystyrene ceiling tiles are best removed for safety, as is polystyrene backed wallpaper.

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
Fireproof
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 airborne fibres, somewhat like known carcinogenic forms of asbestos.
Dust mask should be used during handling
Gloves are also recommended to reduce splinters
Compressing 6" down to 4" gives you the insulation value of 4" of fibreglass.
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.

Polyisocyanurate

Survives temperatures upto 400C
R value for 1" insulation: 5.3
Kingspan is the leading manufacturer

Cellulose

Loose fill
Used in cavities
Plant fibre
Made from ground newspaper
Low cost
Better performance than fibreglass
wikipedia

PVC Cladding

Mainly used on gable wall ends
Keeps rain off the wall
Can make a messy wall look ok too, but not the world's favourite finish

Timber cladding

Timber cladding is used as an interior and exterior finish
Provides a degree of insulation
Several timber designs available

Insulating render mixes

Cement mixes containing polystyrene beads, leca or vermiculite

Fireproof
Paint to prevent water ingress and freeze/thaw damage

Shredded Paper

Sometimes used as loose fill loft insulation
Waste paper is treated with fire retardant and chopped or shredded.
Recycled
Not damp tolerant

Cardboard

Very low cost insulation material
Its low cost helps ensure higher returns on investment by eliminating much of the investment cost.
Fitting used cardboard results in zero extra manufacturing energy use.
Cardboard wall insulation is popular in the US, but seems to have had little takeup here in the UK.
Its flammability can be resolved by painting it with a mixture of borax & boric acid.
Its damp susceptible, and can support mould if damp
Should not be used in situations where damp may occur.
Available free

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 either a specialist mixer to produce or ready chopped paper.

Sheep's Wool

Sheep's wool is sometimes used instead of fibreglass or rockwool.

Natural
Non-irritant, no protective clothes required.
Can absorb and release moisture. Unlike glass/mineral wool where moisture reduces insulation.
Is a carbon sink, over 45% of the weight is carbon
Life 50+ years
Biodegradable
Does not spread fire, but chars.
Treated against insects
Costs more than fibreglass & rockwool
Cheap if you or a nearby sheep farmer has wool they can't sell, unwashed wool is not allowed to be used.

Straw

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

Susceptible to damp & mould, but less so than cardboard
Nest material for birds
Can contain unhatched insect eggs
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.

Non-flammable
Unaffected by damp
Used as loose fill, mainly under floors

Vermiculite

Similar to expanded clay beads

Bubble wrap

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

Degraded by UV light.
Flammable
Used as greenhouse secondary glazing
May last ok in dark places eg lofts & cupboards.

Felt

Felt strip is used as pipe lagging

Its wound around the pipe(s) and secured with tape
Brown, hairy and untidy looking
Best used for pipes out of sight
Good for insulating grouped pipes, where foam jackets don't fit.
Foam tube is much quicker for insulating single pipes

Foamed Concrete

Lightweight concrete blocks have insulation value
Insulation is one of the reasons for their use in interior walls
They don't survive outdoors unless rendered.

Aerogel

Aerogel is a very low density glass/air gel rated at 0.013 W/mK
High temperature resistance
Its high price restricts it to applications where high insulation value per size is necessary
Sold by Spacetherm.

Unsatisfactory Insulation Materials

Carpet

Too thin to give much insulation
Flammable
Reduces draughts

Polystyrene ceiling tiles & wallpaper

Too thin to give much benefit
Very flammable
Dents very easily

Sand

Traps air but is too thermally conductive

Bubblewrap

Degrades quickly from UV exposure

Spray-on Roof Insulation

Traps water, prone to causing rot
Makes the roofcovering non-reusable

By Application

Loft

Rockwool
Fibreglass
Shredded or chopped fire retardant treated paper
Sheep's wool (available in batts as Thermafleece or rolls from www.BlackMountainInsulation.com)

Roof

Polystyrene - cheap
Straw - very cheap
Polyisocyanurate - where depth of insulation needs to be minimised

Cavity Wall Insulation

Fitted to existing wall cavities

Rockwool
Fibreglass
Polystyrene bead

Wall Cavity Insulation

Fitted to retrofitted cavities

Polystyrene slab
Fibreglass
Rockwool batts
Cardboard
Polyisocyanurate

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.
Polyisocyanurate
Polystyrene foam backed plasterboard sheets may also be used

Free insulation options

Waste cardboard sheet
Shredded waste polystyrene
Straw
Bubblewrap for water tanks
Scrap clothing as pipe insulation

Fire

With 69,000 house fires in 2001, the performance of insulation in a fire affects loss of property and life. There are 3 main categories of fire performance:

Fireproof materials such as fibreglass and mineral wool act as a fire barrier if they remain in position.
Fire retardant materials will burn away when flames reach them, but will not spread the fire further. Thus these do not act as fire barriers.
Flammable materials such as untreated cardboard can ignite and spread fire. These products should generally be treated before use with a fire retardant, although there are examples where pattern of use provides another means to prevent spread of fire (eg plastered strawbale construction).

Insulation Values

To be worked into the article

20mm marmox R= 0.60
uninsulated cavity wall R=0.73, U=1.37
50mm celotex U=0.40 R=2.63
Single brick - R = 0.12
Unventilated Cavity - R = 0.18
18mm Plywood - R = 0.70