Loft insulation - in the pitch or lift existing floor


Postby CuteNic » Tue Oct 26, 2010 4:15 pm

I hope you guys can help. I am a woman, but I'm up for any DIY task. My ex husband, can only be described as "a man down", so I've done my fair share of DIY.

I've moved house and want to make sure my house is insulated. The loft has good access and has been floored. However, the insulation (what I can see from the hatch) is thin and old. So I was wondering should I lift the floorboards and put an additional layer of insulation down? If I do this, how do I get the flooring back down? Or whether I should look to put insulation boards between the joists in the pitched roof? At least this will take away the issue of lifting the floor. The house is 25 years old (if that helps).

Let me know
Nic :wink:
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Postby welsh brickie » Tue Oct 26, 2010 8:18 pm

I would lift the floor and lay more insulation on top.Take up a section of floor first, lay the insulation and relay the floor.That way its more managable
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Postby Perry525 » Wed Oct 27, 2010 9:50 am

May I say that my wife and daughters are all good at DIY, it can be cars, bikes, homes whatever....you are not alone.

The thing with insulation is that you are trying to save money on heating!
Therefore, the smaller the space to heat, the lower the cost.
From which you can see that letting your expensive heat go up into the loft, is a waste of heat, unless you live up there.

The problem? Heat always moves to cold.
Most people think that laying a bit of insulation between the joists is all that is required.

They don't seen to realise that wood, joists are not a very good insulator by today's standards, they were years ago compared to bricks and single glazed windows, now they drain your heat.

The heat loss is mainly by conduction = heat the room, the air, the ceiling, joists, rafters, roof, slates/tiles, floor boards in loft, sky, all these are joined together.

The best way to insulate is as close to the warm air in the room as possible. That means below the ceiling. Fixing two or three inch thick sheets of polystyrene below/across the ceiling, keep the heat in the room.

It stops that loss by conduction, heating so many parts of the home and sky.

I have a bedroom with 5 inches of insulation, 3 inches between the joists and 2 inches below the joists.

To put this into perspective, last winter night 3-4/1/2010 it got down to minus 28C on my lawn with an air temperature of minus 8.1C.

That bedroom never went below 20.3C with no heating, other than that from the hall outside, (the bedroom door was open,) that is kept at 22C 24/7.

On the 25.6.2010 when it got up to 44.6C outside, the bedroom stayed at 23C.

Lever up the floor boards, if nailed. You may be lucky, they may be screwed down.

Carefully fit sheets of polystyrene between the joists, making them as tight a fit as possible and fill the whole space.

If you buy one inch thick sheets they are easy to cut with a sharp knife, thicker sheets cut with a hand saw.

To make it easy, buy an electric resistance cutter, this will slice through polystyrene like a hot knife through butter. These are expensive but make the job quicker and cleaner. They are used in hand crafts to make polystyrene models.
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Postby CuteNic » Wed Oct 27, 2010 11:09 am

Thanks Welsh Brickie. That seems like the obvious, but best solution. I was just worried, more so, about the flooring going back down on top of the thicker layer of insulation. Hopefully it will squash down to allow this. But section at a time is good advice
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Postby Mark(Miller Pattison) » Fri Oct 29, 2010 9:20 pm

It's always recomended to raise the joists with 2x4 rather then lay the boards on top of the insulation. If your going to use the boards as storage just make sure not to put anything really heavy on them as it could compact the insulation to the point of cracking your ceiling. ;)
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Postby tomhat » Sat Oct 30, 2010 9:39 am

Is there a limit to the thickness of insulation that should/could be used in the loft? And does anyone know of an easy way to insulate the tight sections of the loft where the roof meets the floor and in nooks and crannies?
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Postby welsh brickie » Sat Oct 30, 2010 3:43 pm

[quote="tomhat"]Is there a limit to the thickness of insulation that should/could be used in the loft? And does anyone know of an easy way to insulate the tight sections of the loft where the roof meets the floor and in nooks and crannies?[/quote]
There is no limit,But you need airflow near the eaves to dry out any moisture
so keep the insulation clear from the edges
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