Insulation queries

Ceiling insulation
I have a flat roof house which is unpleasantly hot. The ceiling is above the wooden beams and this leaves little room for ventilation between the roof and ceiling. I am prepared to forego the ‘look’ of the wooden beams. Can you answer the following questions for me?

* Will a second layer of ceiling board with insulation under the beams help to solve the problem? At least that will give a further 20-25cm space between the roof and the ceiling. 

* What type of insulation would best reduce the heat and the noise from the street? The normal ceiling insulation, Think Pink, 40-50mm thick polystyrene sheets or the type that resembles tinfoil? 

* Would it help to make a few ventilation holes between the roof and the ceiling, which could be closed with wire mesh or something to keep birds/bats out?
Marlene Labuschagne, by email

Sharl Bennie, our building expert, replies: 

Try using a combination of the two types of insulation products you mention. First of all, in the space between the beams, I suggest that you first install a ‘BFR D12’ (radiant bubble foil type insulation), which can be nailed up against the underside of the ceiling or branderings of the existing roof. This should be fitted with the reflective side facing upwards to reflect the radiant heat coming through the roof.

Secondly, it is recommended that at least a 100mm thick bulk type (fibre glass insulation) be fitted above the new ceiling board. This can be installed above the branderings for the new ceiling which you are going to install below the beams.
This combination of the two types of insulations will address both the thermal and acoustic problems that you have in the roof. 

The mentioned ventilation holes will only help if it is done at the apex (top side) of the roof structure due to the fact that any trapped heat will always move up and build up at the highest point of the roof cavity. Caution should be used not to create any waterproofing problems in the process.

For further information and assistance on thermal insulation products, you can also contact Michael at Insulation Warehouse in Pretoria, 012-804-5454 or visit www.i-w.co.za