Insulation theory for beginners - question inside

[Will_s87]

Hello,
I have removed the carpet in my living room to reveal some nice floorboards.(timber suspended floor)
To try and prevent it getting too cold over winter I'm thinking about insulating with jablite wedged between joists. However, this will take some considerable effort / pain because the void below the joists is only 1ft tall
Lets assume I manage to insulate 90% of the floor boards.
Will this have any noticable effect on the warmth of the room, or will the cold air simply find its way in through the areas I haven't managed to insulate?

(i dont expect to stay in this house for more than 5years and so I dont want to exert to much time / energy)

thanks,
Will

 

[jeds]

Insulating any part of the floor will have some benefit. If I were you I would consider using a mineral wool rather than jablite. It's easier to install and about the same in thermal value - and it's cheap. If you lift floorboards every, say, 1.5 metres you can push mineral wool along the void with a batten. Fit a small 'T' piece on the end of the batten.

 

[Will_s87]

Do you mean fill the entire void with insulation..? I was under the impression that the insulation would sit tight against the underside of the floor boards withsome air gap underneath for ventilation.

heres our floor

 

[jeds]

Not the entire void. 200mm would be beneficial.

 

[oldbutnotdead]

Yes you need to maintain ventilation under the insulation- which makes it a pain in the bum job as a retrofit. If you do most of it you will feel the benefit- if you have access to a young child they may be induced (with enhanced pocket money) to crawl underneath & do the job that way (or is stuff like that no longer allowed? Didn't do me any harm etc etc etc )

Seriously, the rockwool is much easier to apply but you have to prevent it from dropping out of the gap between the joists. If you can get to the underside of the joists, garden strawberry nets work really well (stapled to joists then stuff rockwool in).

Jablite- you'd have to cut it quite accurately to ensure it stays put, likewise with Celotex etc- since you've got deep joists I'd stick with Jablite or rockwool- price/sq m is lower

 

[theprinceofdarkness]

It all depends on the insulation level of the rest of the house. In the 1970s in a 3 bedroomed semi with solid walls, about 10% of the heat loss was through the floor. if you have got filled cavities and have attended to draft proofing then the percentage is probablely higher, say 20%. To insulate under the floor boards is difficult and time consuming, especially as you can't get underneath them. Because hot air rises, the warmest air in the under floor void is just under the floor boards. The best bang for you buck is to cross line the floor boards with Baco foil, to stop drafts.
Frank

 

[Will_s87]

Hello

thanks for the useful replies. I got some garden netting stapled in and stuffed a load of rock wool under there

hopefully I can tell the difference once it starts getting cold again.

thanks again,