insulating under suspended timber floor

[abr]

Hi Daniel

That is a good point about the potential increase in condensation. It is one of my worries because we do not have trickle vents on our wooden DG windows.

However we have to find solutions to that if it because a problem.

On the subject on the VB and ensuring airtightness the Green Building Store and Ecomerchant suggest using Pro Clima tape or Orcon F adhesive to stick it to the wall. These are really expensive and only available by delivery. Is there a similar product that is cheaper and that I could buy in the local builders merchant? We are doing the job this Sat.

Cheers
A

 

[stewill]

Hi A,

Was wondering how you got on with the insulation of your suspended timber floor and what way you chose to go with the vapour barrier in the end? I had the same thinking as yourself and am gearing up to do the job in the coming weeks.

Any advice??

Regards
Stew

 

[geraldthehamster]

Hi A,

Was wondering how you got on with the insulation of your suspended timber floor and what way you chose to go with the vapour barrier in the end? I had the same thinking as yourself and am gearing up to do the job in the coming weeks.

Any advice??

Regards
Stew

Take up floorboards, fit 50mm Celotex between joists, fill gaps between it and joists, and edges of wall, with expanding foam. Ensure any air bricks are not blocked and that they still ventilate the under floor space.

You don't need a vapour barrier, although the foil on the Celotex provides one anyway.

I've done this and it works.

Cheers
Richard

 

[Beefpotnoodle]

I just wanted to hi-jack thus thread a bit, I'm doing an underfloor job on my house, plenty if space to work even walk underneath the floor! The problem I have is, I'm cheap! I'm looking for a cheap alternative to insulation and am not expecting miracle. Is there any issue with simply stapling bubblewrap to the underside of the t&g floorboards, with a slight overlap onto the beam?

 

[Beefpotnoodle]

After very briefly looking into it, bubble wrap degrades quickly do forget that, cheers

 

[freddiemercurystwin]

Its alright, we never took it seriously in the first place!

 

[dhutch]

You don't need a vapour barrier, although the foil on the Celotex provides one anyway.

So how do you know you dont need/want one?

Daniel

 

[geraldthehamster]

So how do you know you dont need/want one?

Its purpose would be to avoid condensation in mineral fibre insulation, which is unlikely to be an issue in a well-ventilated under-floor space.

Cheers
Richard

 

[Perry525]

There seems to be some degree of misunderstanding here.
You have a floor with cold air rising through it.
Why? Because warm air rises, the wind blowing over a roof, sucks the air from inside a building.
The air that is pulled in is colder and drier than the warm wet air in the home.

The solution, find the holes in the ceilings and walls and block them. This will keep your warm air in.

Then think about the floor, very little heat will escape downwards, as heat from radiators is radient, projected forwards into the room, and backwards into the walls, then the warm air rises, hits the ceiling cools and falls back to the floor, is dragged along the floor, loosing heat as it goes, then rises up the radiator again.

If you want to stop the heat, from passing through the floor boards, fit sheets of polystyrene between the joists, keeping in mind that little heat will move downwards, and the tight fitting polystyrene, helped by spray foam in any gaps will stop the cold air from being pulled into the home.

If you manage to make your home fairly air tight, this will save a lot of money.
It is a simple matter to open a window from time to time, to let your water vapour out and cold dry air in.

Remember heat always moves to cold, and water vapour also moves to cold.

 

[geraldthehamster]

There seems to be some degree of misunderstanding here.

I should say so

Cheers
Richard

 

[AronSearle]

On a timber frame wall, with celotex, you should have a vapour control layer. Otherwise the concern is that the only passage for vapour is through the studs, or gaps between the insulation and studs. Some work has shown this "can" be an issue, depending on specifics.

I'm not aware of any definintive source that says this also applies to floors, it's a subject that no one can seem to agree on, as everyone seems to have different ideas as to how vapour moves downwards compared to horizontallaly or upwards.

Oh, and Perry525 has some funny ideas about which way *heat* radiates.

 

[EddieM]

if using expanding foam remember to use gloves. You only makw that faux pas once!

 

[kbdiy]

as heat from radiators is radient, projected forwards into the room, and backwards into the walls, then the warm air rises, hits the ceiling cools and falls back to the floor, is dragged along the floor, loosing heat as it goes, then rises up the radiator again.

eerrr no - most heat produced by radiators is in fact, convection, so the bit about rising warm air and then cooling describes convection, not radiant heat.