Checking out the loft insulation in a recently purchased house, I found the builder had installed the regulation 100mm (house built about 1997) so I have added another 100mm layer over most of the loft.
However the main bedroom has 5 flush mounted light fittings in the ceiling, and the installer had cleared an open space in the insulation above each light, presumably to allow for the lamp heat to escape.
Is this space really neccesary? Is fibreglass insulation inflammable?
Is it OK for me to lay my extra layers over these voids?
No but your light fittings won't like being self-cooked even more than allowed for in the strictly marginal design-down-to-the-last-penny and are likely to fail even sooner than they might otherwise.
On Sun, 01 Nov 2009 17:43:41 +0000 someone who may be David J wrote this:-
That's the problem, crappy light fittings. These nearly always produce uneven light, which is mostly directed at the floor. Useful for illuminating a romantic tussle, but not much else. Removing them and replacing them with something more useful for providing general lighting is the best solution.
You don't say what sort of lamps are installed in these crappy fittings.
I imagine the answer you want to hear is, no. However, the answer is yes, except in unusual conditions which are most unlikely to apply here.
Inflammable is a word the meaning of which can be confused. Flammable and non-flammable are better words to use.
To make up for the poor light distribution these sorts of fitting tend to have high powered lamps in them, which give off a lot of heat. If you insulate over them the insulation probably won't catch fire, but you will shorten the life of the lamps dramatically as they will overheat. You may also cause parts of the fitting to melt.
There is another question. What sort of cable is used to the fitting? If it is ordinary twin and earth this is likely to melt if overheated. The twin and earth should terminate near the fitting and a heat resisting cable run to the lamp. Even that will only resist a certain amount of heat.
There are flowerpot like hoods which can be fitted over these contraptions. They are intended to keep insulation away from the fittings, not to allow it to be run over them.
Well, these lamps are all 240v 40W K1 spotlights. As most of the 40W is light and is ventilated into the bedroom, that leaves just a small fraction of the wattage in heat that will rise vertically into the loft. So how much air space does that need to disipate itself?
Since most of the time the lights are off and the real issue is cold entering the bedroom from the loft, my thinking is that an extra layer of glass fibre insulation over these existing voids would not cause a problem either to the lamps or to the fibre glass.
Removal of these particular lamps is a possibility, but the existing holes would leave a nasty scar on the ceiling.
The comment provided above is smart but not particularly helpful...
On Sun, 01 Nov 2009 21:54:57 +0000 someone who may be Timothy Murphy wrote this:-
Unless the fittings will only take low energy lamps it is reasonably foreseeable that someone will replace them with incandescent lamps in the future, which must be allowed for.
Anyway, low energy lamps are not all equal. For example, compact fluorescents give off more heat than LEDs.
AIUI, in these highly regulated times, you must either add a further
180mm or none at all. By adding just 100mm you have "interfered with a thermal unit" so you must bring it up to current building regs (280mm); it's not enough just to improve it. Adding loft insulation is a building control matter, so there will also be a =A3100 or so to pay for the BC application and inspection.
Houses are bought and sold 'as is', and they don't need to meet any particular standards at the time of sale. The thing is not to lie about its condition when selling - but all that might be needed is an adjustment of the price, or the taking out of a 'building regs' insurance policy, which apparently aren't all that dear.
SWMBO and I spent three sessions in the loft increasing the insulation from 25mm to 125mm,and it was such fun we won't be rushing back to add any more.
Our inefficient back boiler manages to keep this smallish 3-bed sixties jerry-built semi warm, with the lounge at 23 degC, for a whopping cost of £500 a year at current rates. I have no intention of spending £1000s on Class A boilered replacement system.
Final update on the issue.. ... and thanks for all the comments.
I was wrong about the lamps in use in my bedroom. I took one out, and they are actually 12V 20W BAB Halogens. There must be a mains Tx up there in the loft somewhere. So the waste heat being generated up there is even less than I thought. I'm going to take up TOF's suggestion of using a plantpot over each unit and insulate around it.
I picked up some more loft insulation at B&Q today in their 2 for 1 offer. Excellent value at about £1/square M.
It's amazing what can be made out of old wine bottles, isn't it?
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