Loft insulation...

On 17/03/2010 16:18, John Smith wrote:

You wouldn't need to wear a mask/boiler suit just to access the loft. It's when you disturb the fibreglass and it sends up particles that you need a respirator. Once the dust has settled, you'll be fine.
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wrote in message

Surely the particles will settle over everything and any movement will disturb them? Approximately how nasty are these inhaled anyway?

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wrote in message

Once things have settled down, a quick brush on one will not dislodge much. It's when it's being handled in vengeance that things get messy. For normal access, if you are not touching the stuff on purpose, it would be fine without.
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IME a trip to a fibreglass insulated loft isnt a great experience, but nothing terrible. They do get everywhere, but only in tiny amounts. Boarding over it will pretty much solve that though.
NT
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John Whitworth wrote:

I cannot disagree that what you say is theoretically correct.
The central part of my loft is boarded, over insulation level with the joists, with lots of stuff stored on it. Either side has a substantial covering of insulation. One cold day I went all round the house with a temperature measuring gun, to see if I could find any significant cold spots. I could not detect any significant temperature difference between those bits of ceiling beneath central boarded area, and those with thicker insulation.
Perhaps plastic boxes full of books, carpet off cuts and empty cardboard boxes aren't such bad insulation after all.
As my roof has a fairly shallow pitch, lifting the loft boarding would be pretty impractical, as the headroom would no longer be workable.
Chris
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Chris J Dixon Nottingham UK
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John Whitworth wrote:

The central heating was cycling, so the house was being heated, but temperature had stabilised.
Thinking about the physics, and simplifying slightly, if the air space in room and loft both have uniform temperatures, which is practically true, then in any areas where there is more heat flow, due to lower insulation values, the surface temperature of the ceiling will be lower.
Isn't this simply the reverse of examining walls with an infra-red camera? Room and outside world temperatures are constant, but in areas of poor insulation, the wall is warmer.
Basic physics: greater heat flow requires greater temperature gradient.
Chris
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"John Smith" wrote

To provide storage and access consider:
Locate joists and attach vertical timbers between joists and high points on rafters. Above the required insulation level, add horizontal timbers between new vertical timbers and lower/outer point on rafters. Rest boards on new horizontal timbers to provide elevated shortage. (I did this before insulating the loft - much easier)
For the walkway, remove a strip of the fluffy insulation down to top of joist level. Replace this with rigid celotex-type insulation (50 thick) and board over for access walkway.
Phil
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What sort of timber would I need for this and how many? Before the insulation, the weight of the storage was spread across several joists on the chipboard boards and stacked, sometimes 8 banana boxes deep. I don't see it holding the weight myself.
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John Smith wrote:

I wouldn't worry about that. Just think about the number of people that can be in a room at the same time without the floor collapsing.
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Heh, I meant the additional framework I would install would have to carry the load.
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On Wed, 17 Mar 2010 19:13:55 +0000, stuart noble wrote:

I would. Loft "floors" are rarely built to the same strength as a real floor, all it has to do is hold up a bit of plaster board and insulation...
As for the OP it depends what is in those banana boxes. Books weigh a lot, general loose household "junk" much less.
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Dave.




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Some of them are full of books, some are not. Mostly junk though. I have those placed in the centre where the beams run over a stud wall.
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Dave Liquorice wrote:

Neither weight as much as several human beings having sex, or a bath full of water, or a grand piano, which are the typical peak loads a normal floor has to cope with.
I've bent a 5 ton pulley suspended off a 2x4 beam trying to get a car engine out of a car. We raise the car instead..so that's where things BREAK. i.e the typical 6x3 joist will over a short span easily take a couple of tons. It will bow like shit of course.
But it wont break.
So you don't want more than about a cubic meter of books (probably 1/2 ton)on a single joist.
I don't own more than a cubic meter of books., that's about 500 LARGE paperbacks I'd say. Maybe more.
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Heh, my joists look more like 2x3s
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John Smith wrote:

The fibres are very nsastyy. wear dust mask.
what you SHOULD have done, is aaksked first. The BEST way to do this is to fill between existing joist, then screw more at right angles, and fill between those then sheet over with something cheap like floor grade chip to help seal from draughts and carry any loads. And keep dust from the glass wool or water it is, down.
I would still be tempted to install cross joists and plate anyway if you can.
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Another poster says not to use cross joists...
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John Smith wrote:

That's his prerogative. I said what *I* would do.
Cross joists minimise cold bridging and provide a decent structural support for the boarding.
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wrote:

Either method works. Crossed timber is a lot weaker for a given amount of timber than new timber running on top of the existing joists. The latter strengthens and stiffens the floor stucture considerably, and thats a definite good thing if you're using the space for storage - 7cm joists are feeble.
NT
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