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Attic Insulation/ ventillation?

Thommo

I will be insulating a very large attic soon and was wondering what my concerns should be with regard to allowing for appropriate ventillation?For example , after Ive laid down insulation between the joists can I then cover this ove with chip board?

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10-10-20

OK, you'll need to give us more details.
Putting down chipboard implies that you are intending on using the attic for storage, but insulating under the storage area means that you will be running the risk of damp and such entering the stored items. Typically you would insulate above the storage area.

In terms of ventilation of the configuration that you are discussing, the vents around the soffits would be left clear to allow airflow into the attic space. You then insulate every square inch of the ceiling except under the cold water storage tank. You should then lag this (top and sides only) to prevent it from freezing.

Anyhow - is insulation in the roof rafters a possibility?

ennisjim

I'm in same situation, ie. very large attic which I intend to floor for storage and possible play area for kids. I'm planning to insulate between rafters in central space and between joists in the crawl spaces to side (which will be ventilated via soffit). I am also putting in a rad or two to allow for a very low level heat to prevent attic space getting too cold and having a big temp difference between downstairs and attic space.
My question is how much insulation should I put in joists in central space ? Theoretically this could be none I suppose since the central attic space will be insulated above as I said above - but perhaps not to a very high spec I expect (€). But I wouldn't be comfortable with no insulation in joists from noise point of view. I would have thought that some insulation in joists would be a good idea even if attic space is not cold. I'd appreciate any thoughts on this.

10-10-20

Personally, I'm planning on putting in at least 100mm of rock-wool under the liveable attic space, and >250mm else where. Don't forget that a lot of the noise which is transmitted through a surfaced attic floor comes down the joists, so insulation placed between them will have limted function.

Mellor

Thommo wrote: »

I will be insulating a very large attic soon and was wondering what my concerns should be with regard to allowing for appropriate ventillation?For example , after Ive laid down insulation between the joists can I then cover this ove with chip board?

To answer your question, yes you can cover this with chipboard, ply or similar.

10-10-20 wrote: »

insulating under the storage area means that you will be running the risk of damp and such entering the stored items. Typically you would insulate above the storage area.

Not really, most attics are insulated between joists and most are used for storage. Its no different than using an uninsulated garage or shed for storage. In fact the "damp risk" is less in the attic as more heat will pass through it than through a garage or shed.

Mellor

ennisjim wrote: »

I'm planning to insulate between rafters in central space and between joists in the crawl spaces to side (which will be ventilated via soffit).

Are you also insulation behind the walls of the central space. You need to "join up" (for want of a better word) all insulation. So the insulation between the joists need to meet that between the central space. This doesn't apply if the rafter insulation is the full length of rafters and not only above central space.

But I wouldn't be comfortable with no insulation in joists from noise point of view. I would have thought that some insulation in joists would be a good idea even if attic space is not cold. I'd appreciate any thoughts on this.

As 10-10-20 pointed out the insulation will do little here for sound, as sound travels through the joists and solid members anyway.
A floating floor would do much more to lower the noise of impact sounds in the attic.

10-10-20

Thanks for the clarification Mellor.

ennisjim

Hi Mellor, Can you clarify what you mean by 'floating floor' ?

Mellor

ennisjim wrote: »

Hi Mellor, Can you clarify what you mean by 'floating floor' ?

Opps, missed this.

A floating floor where the flooring material (OSB, Ply, T&G etc) is not fixed directly to the joists but to batons that sit on pads on the joists or on a sub-layer of flooring (more osb or similar. The Sheets act act additional bracing creating a more rigid floor, and the pads buffer the impact sound between the two rooms. This is one form of sound the other being airbourne.
Impact is the stamping of kids feet, air bourne is the shouting as they do it.

ennisjim

Thanks Mellor for the explanation.