Suspended Floor Insulation????

[Naithan2013]

Hi,

hope someone can give me some advice??

Ive lived in my house now around 2 years and its really cold during the winter months, Ive installed new windows and doors (A rated) and a multifuel stove to try and generate and keep some heat in!!

Im looking to insulate under my suspended floor, i have around a 3-4ft void beneath so will be able to work from below, Im looking to install 150mm Knauf loft insulation, (also while doing this im installing 200mm extra loft insulation as i currently have 100mm or less in the loft)..

Is it as simple as putting the insulation between the joists and stapling a breathable membrane after this??? im guessing you will need to expandy foam the ridges first as you wouldnt want this butting up against the exterior wall?? is it really worth it?? has anyone done this??

i understand that adding extra insulation to a house which has none is going to offer some sort of saving but if im going to do it, i want to do it right and not have to go back down and do this again!

also the radiator pipes can i pin theses under the floor boards before i put the insualtion which will help retain heat??

any help or advice appreciated

 

[Lusi83]

I've done this in my living room - stapled up loft roll with garden net - and I think it makes a difference...
I am going to do the same in the house I'm renovating - but it only has a small crawl space so using kingspan (110mm) so it doesn't protrude under the joists too much and isn't such a horrible job in a really limited space.

Anyway I've been looking into it and talking to 'people' ... this what I think...
I think new builds need to aim for a U value of 0.35 ...with ideal being 0.25
Assuming you are just mineral wool roll (with a k rating of 0.044) 150mm will give you a U value of 0.29 - so acceptable ( I calculate that I will get a U value of 0.2 ) if you made that 200mm it would be a U value of 0.22 - it can hang down a bit if you have the space -don't cover under the joists though
Insulation tight to floor boards, not compressed and fill edges with loft roll or foam - it can touch wall - cos it should be above dpc. Make sure your air bricks are clear- air can easily flow underneath.
Apparently in some areas you should inform building control ( here I don't have to - but they were very helpful) - one thing he said - if I found I was getting mould anywhere in the house - have a look under floor and make sure it wasn't damp etc (in fact a good idea to check every so often anyway)

Finally - and this might be a real long shot - but my local council (Fife) were offering free underfloor insulation installation - I couldn't get them to do it because they needed a minimum underfloor height (I think 90cm (and I don't have that) - also a minimum access hole - so it might be worth phoning someone like the Energy saving trust -or even your council for more information ..

 

[Lusi83]

Oh and radiator pipes - you can put them in the insulation if you can - or buy decent (class 0) pipe insulation for them (which is the route I took - and will take again)
(Started an argument on here years ago about whether you should insulate microbore or not - argument being insulation increased the surface area and therefore increased the heat loss - in the end instinct told me to insulate - could have been a waste of money or not - don't know how I would every find that out! )