Loft insulation between roof rafters on a pitch roof

littlemoney

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I have loft insulation between the joists by that I mean the floor part of the loft. I then have boards over the joists so I can used the loft for storage. I would like to increase my loft insulation but still be able to have the boards in place. I don't want to raise the joists to add insulation under the boards as I don't have the skills.

I have found refernce to polystyrene blocks which can be fixed between the roof rafters. Is this something fairly simple and do I need to do anything to the roof before hand. I am concerned about moisture occuring between the roof and the insulation. I can't see the tiles so I assume there is some form of lining under them. It looks like a black lose woven material. The house was built in 1950.

What are the pros and cons of this. Is this a good idea generally and is there anything better than polystyrene or can anyone suggest anything else I could try to improve loft insulation.

I level of DIY skills is poor but am willing to learn. I am asking as I don't want to create problems in my loft,and then need to pay someone to sort out the problem,

I hope I have got the terms right but being on my own now I am trying to learn what I can do to reduce my heating bills. Sorry for the long post

steppevos

If your loft space is ventilated (your facia have holes in with little rosters), then there is little point in putting insulation against the roof, because there is already free flowing outside air in your loft so you would only put insulation between outside air and 'outside' air (in your loft). Don't close the holes in your facia either or you are sure to create a damp problem in your loft.
A way forward would be to take up the boarding and put another set of joists down in right angle to the existing joists and fill the space up between with insulation and return the boards on top. I read that you don't want to do this, but I don't see another way. Maybe somebody else will come along with some bright ideas.

screwedagain

Generally speaking, you only need to insulate the underside of the roof if you have the loft converted into a habitable room, with a radiator in it. In which case you wouldn't really need any/much insulation on the 'floor' of the attic.

At the minute (presumably), the source of all your heat is in the house, below the attic, so the insulation you have on the floor of the attic helps contain that heat in the rooms below.

I know it's a pain but it would be much more effective for you to increase the amount of insulation on the floor of the loft, rather than insulate the rafters.

Hope that makes some sort of sense!

adonis

What about loft stilts?

27col

There is absolutely no point in insulating between the rafters. Think about it, any heat that may be prevented from leaving, has already escaped from your house, it is now in the roof. The only time that insulating between the rafters is of any use is if you are using the roof space for a model train layout or an office etc.

steppevos

In reaction to 27col: it would still make sense to insulate between the rafters if the loft was reasonably air tight (but then there is high risk of damp problems in the loft). If the roof is also insultated, the temperature different between the loft and the level below will be less, so less heath will escape through ceiling (the heath loss is a function of the temperature difference and the insulation value of the layer(s) in between).

27col

steppevos wrote: »

In reaction to 27col: it would still make sense to insulate between the rafters if the loft was reasonably air tight (but then there is high risk of damp problems in the loft). If the roof is also insulated, the temperature different between the loft and the level below will be less, so less heath will escape through ceiling (the heat loss is a function of the temperature difference and the insulation value of the layer(s) in between).

True enough, but I doubt that the extra saving will warrant the extra cost. Far better to insulate the floor of the loft properly, even if it's going to be a bit of bother to do it. You need to be keeping the heat in below the upstairs ceiling, not above it. The volume of a roof can be quite high, especially if the roof has a steep pitch and any heat in that volume is heat that has been allowed to escape from the habitable area of the house.

ListysDad

Not withstanding all the other valid comments, there is one other thing to consider - pipework.

By insulating between the spars you create a warm loft space where freezing will be far less likely to take place. If you insulate on top of the joists then you are effectively moving pipework to 'outside' and no matter what insulation (NEVER put the grey polyethelene lagging on as it cannot protect against freezing) you install, in bad conditions it will freeze unless you also install trace heating.

If no pipes in loft there's no problem to consider!

BobBobBuilder

Please accept that in the UK we have millions of homes with no roofing felt, whose roofs 'are open to the wind, rain and snow entry, (don't believe me then Google it) now think what else comes into the loft from the outside - the answer is a million cubic feet per year of COLD AIR (Lets call it January, February and March 8 degrees bitterly cold air) Question: Now where do you think its going to go and end up? ANSWER: Inside your home.

Lets switch the scenario: Think of cold air as cold water, and hot air as hot water, and try to imagine what happens when all that cold air/water hits the bedrooms and downstairs. Its going to be cold for you and yours for 6 months of the year, and to be even marginally warmer you need to increase your expenditure on energy to £3000 per year or more. So what is the answer: You either board and barricade the roof by insulating under it, by inserting a vapour barrier and insulation between the rafters or you freeze. Your choice. Your Health Issue, You're Home.

Facts: Insulation does not store or retain heat, bedroom ceilings are not closed cell structures. Plasterboard should be banned, One inch of insulation is all you need, and do close the 101 gaps found in every home. Loft insulation more often than not is poorly laid and more for show than substance.

TRY THIS TEST: In winter seal the front door jamb with carpet tape, and use the side door to your house. Fact: One £2.00 roll of carpet tape beats £500 worth of insulation. Fact; The average roof contains 2 wide open windows. To renovate your house and to keep warm you need to study the US concept of building envelopes, Roofwrap and Housewrap. Also read up on breathable roofing felt and air vents.