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Floor insulation
jacko - 6/2/09 at 08:09 PM

Hi a house near me was flooded last year and know the builder is re-fitting the floor boards he has put lathe's under the joists then looks like loft insulationwith silver foil on one side between the joist then floor boards is this a common practise ?
I thought that would stop the floor / boards breathing
Jacko

Guinness - 6/2/09 at 08:24 PM

I don't know about common practice, but it can be done. I guess most people don't insulate because of the difficulty of doing so.

The foil will be an attempt at vapour control / stopping condensation. The air underneath the floor will be cold, assuming your neighbour has air bricks front and back. The air movement will evaporate anything coming up through the soil. Keeping the floor boards protected from the cold air seems pretty sensible.

We had a damp proof course installed in our Victorian Terrace a couple of years back. When it was being installed we discovered we had damp in the floor joists / floor boards.

So we took up the whole ground floor, put dpm beneath the new floor joists, insulated between all the joists, then put new / reclaimed floor boards back down.

The 50mm of insulation beneath the floor boards has made a massssssivvvveeeeee difference to the temperature of our house. We used to have the heating up between 4 > 6 during the winter. Now we have the heating between 1 > 2 even in the middle of winter.

Also we have real floor boards that you can walk around on barefoot without them being chilly.

Just got to sort out the loft now. It doesn't have any heating at the moment, but I just super insulated it in multifoil and composite boards. It's holding a steady 15 degrees C even without radiators!

Cheers

Mike

nick205 - 6/2/09 at 09:26 PM

I've seen new builds being insulated in this way and my parents recent extension was fitted with similar insualtion (Kngspan IIRC). Has to be a good move if done correctly IMHO.

Well worth having a look at modern building insulation practices, the materials and their performance have come on massively over the last few years.

zilspeed - 6/2/09 at 10:35 PM

There's now a requirement for the U value of the floor - it's 0.25 in Scotland.

Our old house, built in the 1980s feels as if the floor is thermally transparent and it is definitely an area I would like to improve upon. Would also like to upgrade the loft insulation to 250mm as well.

jlparsons - 6/2/09 at 10:41 PM

I think you can get something similar which you can put a tiled floor over. I'd like to do that if I ever finally get around to doing our kitchen-diner knock-thru.

stevebubs - 7/2/09 at 03:18 AM

quote:
Originally posted by zilspeed
Our old house, built in the 1980s feels as if the floor is thermally transparent and it is definitely an area I would like to improve upon.


Ditto - amy easy options?

zilspeed - 7/2/09 at 09:11 AM

quote:
Originally posted by stevebubs
quote:
Originally posted by zilspeed
Our old house, built in the 1980s feels as if the floor is thermally transparent and it is definitely an area I would like to improve upon.


Ditto - amy easy options?


Not really.

1) Deep Solum / Cellar ?
Get under there and secure batts of insulation between the joist.

2) Shallow Solum ? Crawl around on your back doing the same.

3) Hopelesslely shallow solum like most modernish houses ? Lift the flooring one room at a time and either lay insulation on netlon mesh or secure batts of solid insulation.

I have no idea how much space I have but suspect it is very little. Our underfloor area is well ventilated but has no insulation and there are certain areas in the kitchen where you can actually feel the cold because of this. My preference would be kingspan or similar secured right underneath the existing flooring.

DarrenW - 9/2/09 at 09:42 AM

There must be a big space under the floor to fit lathes.


Ive been in a house with ventilated floor spaces before and they can be bloody cold in winter. Insulation sounds like a good plan and as long as there is still space under the joists etc then i guess it will be fine. No real difference to insulating your loft with the ventilated bit above the insulation.