No Felt under Tiles

[Beeny555]

I have just insulated the floor of the loft and boarded it, but now need something to prevent the dust coming in from the roof as it has no felt. Can someone suggest what I can use,other than using boards which decrease the headroom and polythene which causes condensation. I also don't want to use the sprayed foam method either. Any ideas?

[noseall]

brown paper.

[masona]

I've used peg board sheets on mine, no dusts through the holes and it's well ventilated

Or you could use breathable membrane

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[redwin11]

Hi Beeny, i'm in the exact same position - how did you end up going about preventing the dust from coming in?

I've just been quoted three grand for the spray foam method - s** that.

[donnamarie]

i want to insulate my roof too - peg board sounds like a simple and easy solution to stop the dust!! know where I can get it from cheaply??

[Greena13]

This must be a Surrey thing as I face the same issue as the original poster. Can anyone explain to me:

Does the pegboard solution work?

Is this with a breathable membrane behind it or not? And if not, how does this stop the dust as it has holes in it...

[GoingDigital]

I have done our loft using celotex/kingspan rigid boards.

Our rafters are 3"(75mm) I have nailed some 15mmx15mm battons down the sides of the rafters against the tiled edge to form an Air Gap. Then cut strips of 60mm celotex and put foil tape over the joins.

The reason I left 15mm is that is what the manufacturers suggest when a breathable membrane (rather than tar felt) is used. So my theory is that no membrane means the roof is completely breathable and should the roof aver be re-done the gap is the correct size for a breathable membrane to be installed.

The trouble is that 60mm is not enough so I will also be adding large sheets of 25mm covering the existing board and rafters so the speak. This seems to me like the best way.

[Greena13]

GoingDigital wrote:

I have done our loft using celotex/kingspan rigid boards. Our rafters are 3"(75mm) I have nailed some 15mmx15mm battons down the sides of the rafters against the tiled edge to form an Air Gap. Then cut strips of 60mm celotex and put foil tape over the joins. The reason I left 15mm is that is what the manufacturers suggest when a breathable membrane (rather than tar felt) is used. So my theory is that no membrane means the roof is completely breathable and should the roof aver be re-done the gap is the correct size for a breathable membrane to be installed. The trouble is that 60mm is not enough so I will also be adding large sheets of 25mm covering the existing board and rafters so the speak. This seems to me like the best way.

Thanks for this - just a couple of questions:

1. Roughly how long did this take to complete?
2. How much did the materials cost?
3. How did you secure the Ceoltex to the 15mmx15mm?
4. When you say '60mm is not enough' - what do you mean (I guess, in terms of insulation)?
5. 'Sheets of 25mm' - do you mean additional Celotex here?

All help gratefully received!

[GoingDigital]

I haven't quite finished the project yet as it is part of a larger project that includes installing solar collectors, velux windows in the roof, installing a new floor and putting boiler in the loft space. But it is a very simple job to do. Cellotex / Kingspan comes in 2.4x1.2m boards and it is very light wight. In some respects it is a bit like a high density polystyrene covered in foil, but has much better insulation properties. The boards have insulation ratings of double that of the same fiberglass/rockwool. It is very quick to use a knife or saw to cut a strip off the board to fit between the rafters.

The cost might be a problem if you are on a tight budget as the 60mm boards cost £23 each.

You don't attach the celotex to the 15 x 15mm as such it is just there as a spacer to stop the celotex from being pushed up against the tiles so you have a 15mm gap betwwen the board and tiles. You need the air to circulate under the tiles to stop condensation and to allow the tiles to dry out when they get soaked with rain. If you imagine putting a block of polystyrene between the rafters it would just stay there as it will be jammed between the rafters, if that makes sense. Then you have foil tape that you put half on the board and half on the rafter if you see what I mean. This seals any small cracks left between the board and rafter, makes a vapor proof seal and helps hold the boards in place.

When I said 60mm is not enough I mean that in my circumstances we need better thermal insulation than you would get from just a single sheet of 60mm celotex. Seeing as how your main concern is just to stop the dust coming through you don't need to worry about the thickness of the insulation as the insulation in your floor will be the main insulation for your house.

If you are on a tight budget you could have thinner celotex boards and wider battons behind it. So if your rafters are 3"(75mm) like mine you could have 25mm battons and 50mm celotex as the boards would then only be £18.

Hope that all makes sense.

[Greena13]

Perfect - thanks again.

[GoingDigital]

Your welcome, It took me a while to find this solution myself, as like you the spray foam idea didn't appeal, so pleased to share.

One thing probably worth adding is that you will still want air to come into the loft space from the eaves. In my case the ventilation will be in the trickle vents in the velux windows, but in your case you should probably leave a gap at the bottom. Don't go all the way down to the eaves or you will completely seal the loft and then any hot damp air that gets up from the house below (through light fittings for example) will have nowhere to go and will condensate on your new boards.

Leaving a gap won't matter as you won't be able to use the shallow space under the eaves so a bit of dust collecting there won't hurt.

[Deluks]

Geena, the original poster faced the problem of dust collecting on stuff. You do not need to insulate the roof as if you were doing a loft conversion. If your loft floor is already insulated to a decent spec then insulating the rafters will be a waste of money, unless you are planning to heat and use the area as a room, aka loft conversion.

Brown paper has been suggested, as has pegboard. You could also just use hardboard which works out at about £4 a sheet.

[Greena13]

Deluks wrote:

Geena, the original poster faced the problem of dust collecting on stuff. You do not need to insulate the roof as if you were doing a loft conversion. If your loft floor is already insulated to a decent spec then insulating the rafters will be a waste of money, unless you are planning to heat and use the area as a room, aka loft conversion. Brown paper has been suggested, as has pegboard. You could also just use hardboard which works out at about £4 a sheet.

Sounds cheap, quick and easy - I like it!

I still don't understand the pegboard option, but if I use hardboard sheets do I just nail across the rafters and leave a gap at the botton for air flow?

[GoingDigital]

I wouldn't say a waste of money as using insulation has two advantages.

First most people who board out their loft for storage have inadequate insulation as they often have 100mm of fiberglass. So insulating the rafters helps improve the loft insulation.

Second the loft space temperature can vary enormously, from below freezing to hot enough to deform some plastics. The items stored in the loft will benefit from the insulation stabilizing the temperature.

[chappers]

Brown paper or hardboard the choice is yours, just never ever ever be tempted to spray foam.