Attic multiple Insulation

jasgrif11

I'm building a new house and I will be insulating between the rafters on the roof but will I also need to insulate between the attic floor rafters? and if so can I just floor over this area afterwards. Should I get hoods for all my low voltage lights or just leave an area clear around the light.? Will the floor cause a fire hazard with the heat from the recessed lights? What are other people doing? I have installed a breathable felt and there are air vents in the soffit.

Many Thanks
J

10-10-20

Feckin recessed lights again!
You can get Intumescent hoods for these lights, but they do insulate the lamp somewhat and will cause a build-up of heat.
http://www.alertelectrical.com/Light%2Dfittings%2DIndoor/Interior%2DRecessed%2DLight%2DFittings/Recessed%2DLighting%2DIntumescent%2DFire%2DHoods/
The recommendation is that if the attic space is going to be used as storage, then the roof rafters should be insulated and the ceiling un-insulated. This will also suit the recessed downlighters better as you will have an uninterrupted insulation envelope.
If there is no plan on using the attic, insulate the ceiling and install hoods on the lights.
I have serious draft problems with my recessed downlighters, hence my opening line - my downstairs toilet HAD 5 of them in the ceiling - till I removed 2 and insulated above the ceiling (pitched roof above the toilet).

ennisjim

Hi J, I have pretty much the same setup as you. A largish bungalow (2100 sq.ft) with large space upstairs which will be initially storage but is big enough for other purposes in the future, eg. playroom for kids, etc. I also have quite a lot of recessed lights in corridors and kitchen. My current thinking is to go for low-energy rather than halogen. We have decided against dimmers so low-energy is possible. Low-energy is attractive due to longer lifetime and lower power usage. Also I am assuming that low-energy means lower temp and less fire hazard, but at the same time we are of the ultra-cautious variety so we are likely to be using the intumescent hoods also.
I am planning to insulate better the floor joists (9"x2") with fibre-glass, but I am also planning to insulate between roof rafters - mainly to avoid the attic space overheating in summer and getting too cold in winter. With the hoods and low-energy I am assuming that it is OK to insulate between the joists and allow the upstairs to be floored. Hope my assumptions are OK.

jasgrif11

My plan was to put Kingspan between roof rafters and Fibre Glass in between ceiling. My main concern was flooring over the low voltage lights

hopalong_ie

For my Low Voltage Downlighters i made an open ended mdf box to go around them that kept the 10cm of free space all around, the then put a reinsulated my attic, in the floor above the light is a series of small holes to allow the heat to raise away, No fires yet.

10-10-20

The true function of intumescent hoods is to slow down a fire spreading from below into the space above, and not to insulate the fixture as part of the ceiling insulation. So, adding them to an install where low-energy fittings are installed is just adding to the cost over functionality. I found this article to support this... http://www.basislighting.com/home/news/intumescent-fire-hoods.

With normal filament bulbs, when fitted to GU10 or similar holders, a specification relating to the minimum distances from surrounding surfaces is supplied, but this means little when the fittings are using low-energy light sources. I suppose the guidance could be given that if a fitting can be installed under floorboards given that a minimum distance is maintained, this can be assumed more than safe for low-energy bulbs also.

In terms of insulating both the ceiling and the roof structure, I believe that there are situations where this is not recommended, due to dew-point or moisture entrapment in the attic space. You may get further clarification on this from another forum member.