Hi

Has anyone any experience of fitting rigid insulation board to the underside of a suspended wooden ground floor? Which? magazine says that 15% of heat is lost through the floor so I'm wondering whether it is worth doing. My house has a five foot space under the floor where you can walk around with a bit of a stoop so installation wouldn't be too difficult. Any input would be welcomed. Cheers.

:wonder: Looking at some internet prices. You're looking at about £400 for 40 square meters at 75mm thick. Which is just enough to do the ground floor of my house (Which isn't big, so you'd most likely need more)

So lets presume you do the work yourself, meaning labour is free.

My gas bills are roughly £45 per quarter, so £180 per year. of which £27 (15%) is supposedly lost through the floor.

400/27=14.81 years for the saving/installation costs to break even.

Do you plan on staying in your house for over 15 years?

That's just a rough guide, because obviously some of my gas goes into heating hot water, but at the same time the calculation presumes kingspan is 100% efficient.

:norty: Please feel free to check my maths:thumb:

Why use rigid? Why not use loft insulation and use some mesh netting to hold it up between the floor supports? A damn site less expensive surely ..?

Dave

:wonder: Looking at some internet prices. You're looking at about £400 for 40 square meters at 75mm thick. Which is just enough to do the ground floor of my house (Which isn't big, so you'd most likely need more)

So lets presume you do the work yourself, meaning labour is free.

My gas bills are roughly £45 per quarter, so £180 per year. of which £27 (15%) is supposedly lost through the floor.

400/27=14.81 years for the saving/installation costs to break even.

Do you plan on staying in your house for over 15 years?

That's just a rough guide, because obviously some of my gas goes into heating hot water, but at the same time the calculation presumes kingspan is 100% efficient.

:norty: Please feel free to check my maths:thumb:

You didn't make any allowance for lost interest on the £400, which makes the payback period even longer... ;)

Seriously though as the point John was making, it is considered unusual for retro-fit insulation to be cost effective.

John.

Well I guess the rigid stuff is much less nasty to work with than the loose loft insulation. I know I'd avoid that stuff if possible!

Payback might not add up but if the floors feel cold or draughty maybe the investment is worth it for the comfort factor?