There are two ways of installing ceiling insulation under the program:
This is the more traditional way of installing ceiling insulation whereby segments are fitted between the ceiling joists (timber supports holding up your ceiling). Pieces are cut to size and fit snuggly into place. The end result is the top of the joists are left exposed.
While this system will work well, two issues arise from installing in this way. The first is that heat escapes through the exposed ceiling joists because wood is a poor insulator (ie there is an incomplete thermal envelope of insulation across the roof space). Secondly the spacing between joists tend to be inconsistent in older homes meaning pre-cut product does not necessarily fit and requires a lot of cutting and fitting. The net result of these two issues is that a higher grade of material needs to be used to achieve the same level of overall performance as a blanket system. On the plus side leaving the ceiling joists exposed makes walking across the ceiling and accessing wiring and services a lot easier. There is also no gap between the product and the ceiling meaning less chance of heat loss if the insulation is disturbed.
Installing insulation in blanket format is the more modern method. It creates a very complete thermal envelope in the ceiling as the insulation is rolled out over the top of the ceiling joists essentially ‘blanketing’ the whole ceiling. The insulation comes in roll form rather than pre-cut segment. With the blanket system it is very important that the cavity under the blanket is filled in before the blanket is laid. If you are starting with no insulation we recommend installing a lighter layer between your joists first (thus filling the cavity) and then laying another blanket layer completely over the top. The cavity left by just installing a blanket over the top of the joists can easily be compromised resulting in significant heat loss.
Whilst more insulation material is used to insulate the ceiling, the grade of material can be dropped to achieve the same level of performance as segment insulation. The major disadvantage of blanket insulation is that it can become hazardous to walk across the ceiling as the joists are no longer visible. Secondly because the insulation sits on top of the joists, and not hard against the ceiling (ie Gib or plasterboard) there is a pocket of air trapped between the insulation and the ceiling. If this pocket is compromised, for example when one portion is moved, then thermal performance drops. What this means in real terms is that it becomes more important that insulation is fixed up by tradesmen or others working in the ceiling space when they have finished.
Fiberglass is very much the traditional mainstay of insulation in NZ. It is a very common product both here and around the world used in both new and older homes. The product is manufactured from glass and usually contains around 30% recycled glass. The following is some advantages and disadvantages of fiberglass.
There has been a lot of publicity around downlights and insulation, especially with the spate of fires in Australia. The bottom line is that downlights covered with insulation are a fire risk. All downlights need a minimum of 150mm clearance between the outside of the light and the insulation to keep them safe. Yes this does compromise the insulation but it’s better than burning your home down!
From our research it’s not the insulation that catches on fire when a downlight is covered. Most of the products out there are very safe. What does happen however, is that when a downlight is covered the heat generated cannot escape and therefore builds up. If a downlight is too close to a ceiling joist (wooden supports) or has a buildup of debris around it (such as leafs) then this can catch on fire. The transformers also become very hot and keep switching off which can be frustrating.
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