Attic insulation - Adequate amount

HighWire

Hi there,
Can someone more knowledgable than myself answer a question.

When laying insulation in an attic I always thought you should
go between the joists and then over the top, or am I way out?

We have the attic partially converted for storage, supports
and floor were put in when the house was built.
But the insultion only goes between the joists, I didnt notice until
not cause it is above the joists, but put moved the insulation
and noticed its running in the same direction.

So heres the question, by law should there be more.
If not then what would people recommend to get and is the stuff
you can buy in the local builder providers good enough?
I've seen the type with silver backing, would that be an idea
to put over existing? What exactly should I look for???

We also have a pull down stairs, what would you recommend
for that as I've read there can be a lot of heat loss through there too.

Thanks for any advice.

RKQ

HighWire wrote: »

When laying insulation in an attic I always thought you should
go between the joists and then over the top, or am I way out?

So heres the question, by law should there be more.
If not then what would people recommend to get and is the stuff
you can buy in the local builder providers good enough?
I've seen the type with silver backing, would that be an idea
to put over existing? What exactly should I look for???

We also have a pull down stairs, what would you recommend
for that as I've read there can be a lot of heat loss through there too.

By law there should be a certain depth of insulation if your house was build after July 1992. The depth of insulation was increased over the years, so the date on your Commencement Notice would dictate the Regulations at the time of construction. For example if the attic was a undeveloped Dormer, your joist could be 225mm deep for storage.

250 - 300mm thick insulation is now the minimum requirement, laid between the joists and perpendicular to the joists. Depth of each layer is dictated by joist depth.

Solid insulation boards could be laid over your storage area with plywood sheets over them, to support your weight - depending on joist construction. There are a number of manufactures web sites etc. B&Q also have insulation boards for this purpose, as do most Hardware / DIY Stores.

Its a good ideal to draught seal the opening of the Pull-down stairs. Its probably not possible to lay insulation over the ope with the stair mechanism.

sinnerboy

It is best to stick with the same insulation type in this case . The existing quilt insulation will allow vapour to move trough it ( this is not a defect , but part of the nature of the product ) . The process is referred to as the ceiling "breathing" The attic should be ventilated to to remove excess vapour and condensation - to help the "breathing" .

So placing foil faced insulations ( by which i assume you mean the kingspan type ) over quilt insulation is not a good idea .

you need a total of 300mm quilt with the additional layers to run accross the timbers

now - for storage - usaully only the mid part is of use with the headroom vanishing towards the roof edge

In the middle part of the roof triangle place joists to run across joists . And the important part - breathing - . Dont use ply , with all that resin in its make up it can hinder breathing . Use floor boards , but spaced say 15-20mm apart .

Vital detail - do not choke the roof edge ventilation by stuffing insulation tight to the felt - make sure you leave the vent space open

.

HighWire

Sorry, meant to say there is T&G flooring down, not ply, in the middle only.
Checked underneath and there is insulation under the T&G.

So it would be a good idea to put more insulation at the sides
where its only up to the joists. I'll measure the depth later and see
what it is.
Could be that its the right depth, just not over and back.
House was only built last year by the way.

RKQ

HighWire wrote: »

So it would be a good idea to put more insulation at the sides
where its only up to the joists. I'll measure the depth later and see
what it is.
Could be that its the right depth, just not over and back.
House was only built last year by the way.

Putting fibre glass or Rockwool insulation down over the joists and perpendicular to the joist would greatly improve the attic. There are many threads dealings with attic insulation - pipes, storage areas, cables etc here and on the DIY forum.

The insulation board I was refering to is not "foil" faced.
Proper ventilation will prevent condensation in the attic.
Plywood is easy to cut to fit in the hatch and is very strong. It also survives well in a dark cold attic. It is one of the few materials that Rats don't like to eat. They love wood!