Roof and Ceiling Insulation
 
Ceiling (and roof) insulation is critical in most buildings and climates. Even if insulation involves lifting the roof, it may be a deserving task and investment.

The benefits are immense. Ceiling-roof insulation is a crucial piece of any insulation - something that in some more extreme cases may avoid 50% of the home's heating and cooling energy losses...


Layers of insulation

In cold climates, the insulation is usually restricted to ceiling (or attic).

In hot and warm climates ceiling-roof insulation involves, usually, two layers of insulation:

- roof insulation (particularly important in hot climates) and...
- ceiling insulation.

Ceilings and attics may also benefit form reflective insulation in hot climates. See, on this issue: Reflective Insulation.


Ceiling Insulation Materials

Most ceilings are insulated with loose cellulose (R-3.5 per inch, loose fiberglass (R-2.5 per inch), loose rock-wool, or batts/rolls of fiberglass (R-3.2 per inch). 

For some tips about choosing the right material, see:

Cellulose insulation
Fiberglass and Mineral Wool insulation
Sprayed foam insulation


Roof Insulation Materials

Roof insulation is based on a reflective material (usually a layer of RFL sarking or foil batts) installed under it.

When installing the reflective material, make sure that there is a minimum gap (of 1 inch / 2,5cm) between the roof and the RFL. In the case of sarking, just install it between the battens and the rafters, with its shiny side facing down.

Note:
Reflective insulation is different from reflective roofing techniques, based on reflective coatings, membranes or high reflective tiles in order to get cooler roofs... See on this issue:
Reflective roofs
Reflective roof materials
 

Ceiling Insulation

If you are skilled enough, you may install the fiberglass batts yourself. Just install it over existing insulation, and take some basic precautions (gloves, eye protection, dust mask...).

In the case of polystyrene boards, you should place it between the joists.

For loose-fill fiberglass, cellulose or rock wool, it's better to hire a professional to install the material.

In colder climates two layers of bulk insulation may be installed to improve the performance, one on top of the other.

Types of roof & insulation

Insulation techniques and materials used in the various types of roofs - tile roofs, metal roofs; pitched roof with flat ceilings, sloping ceilings, cathedral ceilings, vaulted ceilings, and flat roofs – are very alike.

Insulation should be installed with enough space to provide ventilation and necessary air gaps.

Roof Insulation: R-Value

Typically....

- homes in warm-weather climates should have an R-38 Non-SI roof insulation (or R-7 in the SI system)
- homes in cold climates should have a roof insulation around R-49 Non SI (R-9 in the SI System).

To a more precise calculation, take into account:

1 - The R-value (thermal resistance) of the materials used in the roof and ceiling
2 – The R-value you should use in your climate zone: See: Insulation levels and Climate zones
3 – Add the difference between 2 and 1: you should use insulation materials with a R-value equal to that difference.

For details on R-value calculations, see:
Insulation levels and Climate zones
Insulation performance R-value
 

Roof ventilation and insulation in cold climates and humid climates

Roofs need insulation, but in many cases they also need ventilation, to allow heat/moisture dissipation. This is a particularly important element in hot-dry climates and also in colder climates, where a certain amount of ventilation is necessary to avoid moisture.

In this cases, insulation shouldn't damage the ventilation system.

Obviously, insulation shouldn't also damage eventual ventilation systems in other climates, if they exist (in humid climates, ventilation is usually very limited or inexistent, or demand drainage mechanisms: ventilation may become a problem in tropical climates and humid cold climates since it may cause excessive condensation under the roof).

See:
Insulation benefits
Insulation materials
Fiberglass, mineral wool & Home insulation
Reflective roofs
Reflective roof materials
Reflective Insulation
Insulation performance
Walls Insulation
Attic insulation
Ducts insulation
Pipe insulation
Moisture and insulation
How to deal with Insulation contractors and home builders
Insulation in your climate zone
Insulation tips
 


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