How to avoid compressing insulation when flooring loft?

Yorky

I have read in several places, most recently an SEI guide, that loft insulation should be laid in between the joists and then another layer across them and this should not be compressed if laying flooring for storage purposes.

If this is the case, how would it be possible to actually lay flooring without compressing the insulation? It also says that battens may need to be fixed to the joists in the proposed flooring area to raise the flooring in order not to compress the insulation. Again, how could this be done without breaking the second layer of insulation.

Any advice/tips would be appreciated.

ardara1

Fill depth of joists with fibre - then ply then Kinspan/xtratherm - then ply.

You''re supposed to have a total of 270mm fibre in two layers to meet regs.

Remember - this si min levels - if you do store materials up there and compress the fibre - you will lose more heat/have to replace it with more fuel/create more carbon -

Do the right thing - BUY A SHED

Yorky

Fill depth of joists with fibre - then ply then Kinspan/xtratherm - then ply.

The insulation is already in place - two layers of fibreglass at right angles. Would the above method not be very heavy on the floor? Also, could you walk on the top layer of ply without crushing the insulation?

You''re supposed to have a total of 270mm fibre in two layers to meet regs.

I think its 200mm

ardara1

ardara1 wrote:

Do the right thing - BUY A SHED

If you can't, then you should install some additional floor joists up there to maintain the depth or lay a floor then cover it with flooring grade Kingspan (or similar) then cover with another layer of chipboard.

Best not to use the loft for storege.

Viking House

Instead of all the plywood and Kingspan use 60mm of breathable softboard on top of the joists for a much greater effect. Softboard is the heaviest of all insulations and holds onto heat 10 times longer than Kingspan lowering your heating costs. Here is the research http://www.viking-house.net/decrement-delay
Kingspan/Plywood will not allow your roof to breathe and will trap moisture in the insulation. Using the Plywood/kingspan combination on top or the rafters is the same mistake that most timber frame manufacturers are making by putting the OSB on the outside of the frames trapping moisture in the frames.
The outside layer should be 10 times more breathable than the inside layer.

arghh

I am thinking of using the plasterboard with the insulation at the back I know that kingspan does one with about approx 40/50 mm of insulation. I am going to use rockwool between the joist as well but this Breathable Softboard sounds good. I find at the end everything comes down to price is the Breathable Softwood expensive and is it easy to get in Ireland?

Yorky

Kingspan/Plywood will not allow your roof to breathe and will trap moisture in the insulation.

But will the fibreglass underneath not stop the moisture entering the insulation in the first place?

Softboard is the heaviest of all insulations and holds onto heat 10 times longer than Kingspan lowering your heating costs. Here is the research http://www.viking-house.net/decrement-delay

Prima facie, this seems to be the best solution - a composite board which will floor and insulate in one but can it be walked upon? How much does it cost and is it readily available?

Viking House

But will the fibreglass underneath not stop the moisture entering the insulation in the first place? Yes! the moisture will get into the fibreglass from below, it would be better to remove the insulation between the joists, put in a breather membrane and put the insulation back in, then put the softboard on top.

Prima facie, this seems to be the best solution - a composite board which will floor and insulate in one but can it be walked upon? How much does it cost and is it readily available? We are bringing in a load of it next week from Poland for using on top of the rafters before we put on the battens & slates. I will know the m2 price tomorrow. The 50mm boards are suitable for light traffic but plywood would be harder.

Yorky

Yes! the moisture will get into the fibreglass from below, it would be better to remove the insulation between the joists, put in a breather membrane and put the insulation back in, then put the softboard on top.

But if the softboard is breathable, will it not allow the moisture which is passing through the fibreglass insulation to pass through it also?

The 50mm boards are suitable for light traffic but plywood would be harder.

Would it be a good idea to cover the softboard with a hard wearing surface then, such as Plywood, or what that diminish the breathability of the softboard?

antoinolachtnai

Well, if you're just using the floor for storage, you shouldn't put much wear on it! If I were going to spend a lot of time up there, I wouldn't insulate the floor.

Would be interested to hear the price on the softboard.

Viking House

antoinolachtnai wrote:

Would be interested to hear the price on the softboard.

It looks to be about €10/m2 plus Vat for the 50mm sheets.

Yorky

So, just lay this on top of the fibreglass and screw through it into the joists then? Is it flexible to allow for this and will screws hold it alright?

I am only using the loft for storage so the traffic will be light-would the boards be alright to walk on, say, once or twice a week?

Viking House

So, just lay this on top of the fibreglass and screw through it into the joists then? Is it flexible to allow for this and will screws hold it alright? Yes

I am only using the loft for storage so the traffic will be light-would the boards be alright to walk on, say, once or twice a week? Yes no problem

stiofanD

So, is it possible to get these softboard sheets in Ireland, or do we need to source them in Poland also ? I am also in the process of insulating/flooring the attic to allow me to store the christmas decorations up there

Viking House

Ecological Building Systems have it I think but I think it is dear, I remember getting a quote for a roof from them last year.
There was another company at one of the building shows called www.sensibuild.com
We will have it in our factory Ashbourne at the end of January in 30mm and 50mm tongue and groove.
Let me know what the other prices are please. Thanks

Vinneyboy

Viking House wrote:

Ecological Building Systems have it I think but I think it is dear, I remember getting a quote for a roof from them last year.
There was another company at one of the building shows called www.sensibuild.com
We will have it in our factory Ashbourne at the end of January in 30mm and 50mm tongue and groove.
Let me know what the other prices are please. Thanks

has anyone got any other prices for this softboard?

Reyman

Viking House wrote:

Ecological Building Systems have it I think but I think it is dear, I remember getting a quote for a roof from them last year.
There was another company at one of the building shows called www.sensibuild.com
We will have it in our factory Ashbourne at the end of January in 30mm and 50mm tongue and groove.
Let me know what the other prices are please. Thanks

What's the measured u value for the 50mm sheet softboard?