Insulating 1870's loft - vapour barrier

[MulesMarinair]

Hi
I'm insulating my loft (no insulation up there at all at the moment).
Was going to lay insulation between the ceiling joists over the lath and plaster ceiling.

I've read about vapour barriers - can anybody recommend one (or is one actually needed?)

Sorry, am green as they come.

Thanks a million,

M

 

[biffvernon]

The house has managed for 130 years without a vapour barrier. I wouldn't add one now - it will just stop the moisture getting out.

 

[BMcD]

It's also a very good time to check the condition of your ceilings from above before they get covered. Check that the nibs (the hardened plaster that has been squeezed between the wooden laths) are intact and that the laths are well attached to the joists. Then be careful not to break any nibs off when laying the insulation.

 

[NT]

Vapour barrier is not normally used for loft insulation. All the insulation in such a case is on the low RH side, so should be fine with no extra barrier.


NT

 

[Penners]

I agree with all that's been said above.

However, if you want to be belt-and-braces about this, why not use the insulation that is encapsulated in silverised polythene? (I think it's called something like Space Blanket). That will give you several benefits - it'll add a degree of damp resistance to your insulation, it increases the insulation value (a bit) and it's a heck of a lot less unpleasant to lay than naked fibreglass.

Of course, Thermafleece would be even better - provided you can afford it.

 

[MulesMarinair]

Thanks heaps for all of the info and tips. Its appreciated.

Thanks again,

M

 

[another_richard]

Can I hijack this and ask about loft insulation, please?

I have recently had to cut access to into our loft (1890's Queen Vicky) where none had previously existed. (no treasure up there I am afraid).

I want to lay down insulation, but also some sort of chipboard flooring to enable storage.

I ask:

1: I can simply put the insulation between the joists and plank over it, right? That thin silver stuff?

2: It has been said that there is a minimum thickness of insultation required, is this true and if so would not my planking, once laid, squash this down? Would I need to make the joist higher with 3 x 2 to make space for the insulation?

Any advice please. Also it has to be cheap i.e. silver bako foil and old blankets cheap.
Thanks.
Rich

 

[Nemesis]

Well, I have to say I would consider that condensation could be a problem if some sort of foil covered stuff was used. I would be interested to know what others think about this.

If you mean the thin stuff that has few proven insulation properties you could be wasting your cash.

I would also consider that ceiling joists might not be up to the job of being used to support chipboard then any wieight of stuff stored on top. You could end up with bowed joists and cracked ceilings.

 

[MdB]

If your ceiling is like mine with joists 50x50mm on a wide spacing (1.1m I think) then no as it won't take the weight.

 

[Penners]

condensation could be a problem if some sort of foil covered stuff was used.

Surely not if it's laid between the ceiling joists (ie: cold roof).

ceiling joists might not be up to the job of being used to support chipboard then any weight of stuff stored on top

Absolutely. The size and spacing of ceiling joists is critical.

 

[NT]

quote another_richard

> 1: I can simply put the insulation between the joists and plank over it, right?

yes


> That thin silver stuff?

no, use fibreglass or rockwool. Cheaper, more insulation per £, longer life, and the insulation values quoted are for real.


> 2: It has been said that there is a minimum thickness of insultation required, is this true

no. Deeper than the joists is a good thing, but none is required.


> and if so would not my planking, once laid, squash this down?

Dont squash it down, that would reduce effectiveness greatly and put a lot of downward force onto the ceiling, which isnt a good idea! Just put enough between joists to reach the top of the joists.


> Would I need to make the joist higher with 3 x 2 to make space for the insulation?

Need, no, but if you want more insulation then you can either do that or lay the rest of the insulation on top of the chipboard, moving it aside where you put boxes down (which will themselves insulate)


> Any advice please. Also it has to be cheap i.e. silver bako foil and old blankets cheap.

If its got to be that cheap, there are cheaper options than fibreglass, but the time it takes to lay them goes up a lot. If youre serious about cost I can mention some options, but unless you are I'd forget trying to save a little with cheapskate options, it adds a fair bit of time.

Finally you'd best tell us your joist dimensions and spacing. In some cases such joists can only barely support a person, nothing else.


NT

 

[MulesMarinair]

Hey Another_Richard,
I'm in the same boat as you.
Cheapest thus far seems to be B&Q cos they have an autumn sale on the the stuff at the moment - seems to be 33% off

Depends on your budget - power company might do it for you. Think they quote £240 for 50m2.
PLanned to lay 10cm between joists and then run 15-17cm perpindicular... (big old house, Scotland...) will never use all the attic for storage, might keep a corner by the hatch with only 10cm and lay some chipboard over that.


M

 

[another_richard]

Hey Another_Richard,
I'm in the same boat as you.
Cheapest thus far seems to be B&Q cos they have an autumn sale on the the stuff at the moment - seems to be 33% off

Depends on your budget - power company might do it for you. Think they quote £240 for 50m2.
PLanned to lay 10cm between joists and then run 15-17cm perpindicular... (big old house, Scotland...) will never use all the attic for storage, might keep a corner by the hatch with only 10cm and lay some chipboard over that.


M

Thanks for the tip, will try and get a 'grant' for it and get it done on the cheap, failing that B&Queue. I do plan to put in a window to try and get a sea 'glimpse' too. Joists are 3" x 2"

 

[Penners]

Cheapest thus far seems to be B&Q cos they have an autumn sale on the the stuff at the moment - seems to be 33% off

33% off what?

Having been a supplier to one sector of the retail trade for umpteen years, can I advise you to compare prices, not discounts? The widespread practice is to mark prices up during quiet periods of the year, and then 28 days later (the legal requirement) start a sale and say "XX% OFF".

 

[MulesMarinair]

...sorry Penners, 33% off 28 or 29 quid I think. I only mentioned the discount as I thought Richard would be savvy enough to shop around and see what he gets for his money elsewhere as well.
As to what is in a 28 quid roll of insulation constitutes and the area it covers - better to compare the dimensions on the packs between retailers... Check their websites. Think Wickes and B&Q had similar dimensions and same basic price, so thats why I said B&Q looked like the better deal.
Have no idea what a trade account would get it at from a builders merchants.
apologies for the confusion,
M

 

[Nemesis]

Joists aren't very big, I'd be wary of putting much weight on those.

 

[NT]

Joists aren't very big, I'd be wary of putting much weight on those.

We only got half the info we would need on the joists, but as Nemesis says 3x2 is unlikely to be good for significant storage

If you want insulation plus storage there, adding another 3x2 or 2x2 on top of the existing joists (glue & screw) could turn it into a serious floor structure.

http://www.wiki.diyfaq.org.uk/index.php?title=Strengthen_a_Wood_Floor


NT