Floors and Ceilings Insulation
From a thermal point of view, there isn’t much point in insulating between floors as the heat flow will move freely via the stairway. From an acoustic viewpoint though, much can be gained by good design consideration and reference to some of the proprietary plasterboard systems.
Air borne vs Impact noise
The main problem with 2 story construction comes from the floor above sitting directly on top of the floor/ceiling joist that then supports the lining underneath. The transport of ‘air-borne’ noise through such a system is limited and significantly muffled with the addition of a layer of batts between the joists held in place temporarily with twine or strapping pre-sheeting.
The ‘impact’ noise where vibration is involved is more difficult and for this to be dealt with effectively, the lower ceiling lining needs to be independent from the floor structure above. This can be done by suspending the ceiling independently or by using the concept of adding furring channels (battens) that are attached to the joist above using the ‘resilient-mount’ that acts as a cushion against impact noise transfer.
Ceiling constructions and their insulation
Many commercial buildings and offices have suspended grid ceilings without any form of insulation. These premises tend to be uncomfortable with the extremes of temperature. Enormous saving can be made with air-conditioning running costs by simply placing insulation batts atop the ceiling tiles. An added benefit of ceiling insulation in offices is a direct reduction in acoustic flanking paths that may have had office conversations leaking over the top of a partition wall.
Clear access is required for a scaffold platform or stepladder for smaller areas. On many occasions we access the premises outside normal work hours for ease of operation. It is suggested to have a few spare ceiling tiles available in case of accidental breakage during the installation process.
Cathedral & Raked ceilings
To achieve satisfactory thermal insulation in these situations, installation must occur in the construction phase. Typically we string our batts in place temporarily with twine or strapping prior to the ceiling being fixed. Care needs to be taken where the ceiling system meets a conventional flat ceiling as these constructions can lead to thermal leaks. Access can be a problem with some entry foyers in structures rising to a second level and ceiling following the roofline some 6.0 mtrs above. Scaffold may be needed and installation will take a little longer.
Pitched roof ceilings
For new structures, it is beneficial to pre-load the ceiling with bags of insulation distributed evenly throughout. Some areas may have very restrictive access and may even require material to be strung in between the ceiling joists prior to sheeting. Steel framed structures with wider truss spacings should have a ‘catwalk’ to allow primary access from one end to the other.
We cut around ceiling penetrations, and re-position down-light transformers atop the insulation if they are loose fitted in the ceiling. In some cases, during other parts of the construction phase, the insulation may have been moved aside. To ensure the insulation is optimally spread and for the best results, we usually return to spread the ceiling batts after all other trades have completed.
Please note the Building Code of Australia restricts the number and total area of cut-outs in insulation for penetrations. The gaps down grade the performance of the insulation barrier and careful thought need to go in to how this issues is managed. I have noticed recently that there are now some Downlights that can be insulated over with the additional bonus being they are also sealed to prevent draughts. Check with your Electrician.
In existing structures the access and the spacings between the ceiling timbers are important. Older structures tended to be built with the ceiling lining spanning 450mm whilst modern structures have slipped out to 600mm spacings. Skillion roofs normally deny internal access and it may be necessary to lift the existing exterior skin, open the roof space and lay insulation from on top. Replacing all the roof screws if tackling a metal roof is highly recommended.
Ceiling Insulation ranges from R2.5, R3.0, R3.5, R4.1, R5.0 & R6.0 . The BCA again sets out what is required in various Zones across Australia for Instance in Zone 5 (Newcastle and Surounds) it nominates a total Roof & Ceiling insulation of R 4.1 for light a coloured roof up to R5.1 for a darker colour. We can typically achieve this by adding R3.5 batts at ceiling level which would then add to the various elements such as plasterboard, roof tiles and the air gap between to give a system rating of R4.1 and comply. If it were a metal roof with blanket R1.3, you could get away with R2.5 for a light coloured roof. Obviously the darker colours would need a higher R value. Care needs to be taken to ensure adequate framing for the higher R values.