underventilated suspended ground floor - can using superquilt (or similar) be a solution?

[swimm...@yahoo.co.uk]

I did insulated a suspended ground floor in the past with very poor results - the crawled space was under ventilated and the rockwool blanket installed between the joists used to get soggy under certain circumstances...as a result some fungi started growing on the joists' surface - I decided to convert the floor into a concrete one (the other half of the house had a concrete floor anyway).

I've just stumbled across this product:
http://www.ybsinsulation.com/products_floor_superquilt_crawl_space.htm
By the graphics I'm led to believe that this design should provide a valid alternative to cure problems due to under-ventilated sub floors (like the problem mentioned above)....am I right?

Any feedback appreciated...
If so, would this product provide an even cheaper alternative?:
http://reviews.wickes.co.uk/9987-en_gb/210022/reviews.htm

[Onetap]

On Sunday, October 21, 2012 10:43:34 PM UTC+1, swimm...@yahoo.co.uk wrote:

> By the graphics I'm led to believe that this design should provide a valid alternative to cure problems due to under-ventilated sub floors (like the problem mentioned above)....am I right?

I don't think they say it's an alternative to adequate ventilation. The ventilation is to dissipate moisture coming from the ground through the oversite concrete.

[swimm...@yahoo.co.uk]

well, the product is sold for another function: insulation...still, in my case it would had been a more elegant and less costly solution than converting the suspended under ventilated floor into a concrete one. I wish I'd seen that graph years ago (the superquilt "crawl space" design) - there are other applications but the one which involves stitching the quilt just under the joist is just perfect.

That superquilt would solve 2 problems at once...you get insulation and dry joists - worth every penny if considering how easy is it to install the stuff.

I've used some SILVER FOIL BUBBLE WRAP INSULATION in the past but for a completely different project - happy with this sort of product so far though I don't think they provide much insulation.

[Tim+]

Or ventilate the underfloor space?

Tim

[swimm...@yahoo.co.uk]

>
> Or ventilate the underfloor space?
>
> Tim

isn't that easy in terraces houses - ideally you want two opposite walls where to open small gaps in the wall to provide enough ventilation - I did try with 2 ajacent walls but it didn't work...the bricks were also affected by some rot (maybe dry rot) and I took no chance.
By isolating the joist from the moisture coming from the ground (there was no concrete) and also from a dodgy wall (as I said maybe infected by some form of rot) one is guarantee the joist are kept healthy...the parallel of this form of insulation must be the warm roof (as opposed to the cold roof systems).

[harry]

The U values in the first one seem pretty incredible.
It's quite difficult to fix stuff like this properly especially if the
space is restricted.
The hardest bit is sealing the perimeter. The way they've shown
doesn't seem practical.

[harry]

On Oct 21, 10:43 pm, swimmyde...@yahoo.co.uk wrote:

If there is a ventilation problem, I don't think this stuff will fix
it. May even make it worse.

[swimm...@yahoo.co.uk]

On Monday, 22 October 2012 07:54:26 UTC+1, harry wrote:
> On Oct 21, 10:43 pm, swimmyde...wrote:

I agree with you about the U value declared...I don't believe any material of that thickness can offer such insulation - in fact I'm considering using a similar cheaper product (single foil bubble wrap) just to keep the moisture from the ground away from the joists and radiate the heat from the room above - after all, this is what this type of product is good at, and floor insulation works mostly on radiating heat (celotex and similar would be mostly wasted in this instance).

[swimm...@yahoo.co.uk]

keep the moisture away from the joist then you don't need to ventilate...

[meow...@care2.com]

On Monday, October 22, 2012 11:09:28 AM UTC+1, swimm...@yahoo.co.uk wrote:
> On Monday, 22 October 2012 07:56:24 UTC+1, harry wrote:
> > On Oct 21, 10:43 pm, swimmyde...@yahoo.co.uk wrote:


> > > > I've just stumbled across this product:http://www.ybsinsulation.com/products_floor_superquilt_crawl_space.htm
> > > > By the graphics I'm led to believe that this design should provide a valid alternative to cure problems due to under-ventilated sub floors (like the problem mentioned above)....am I right?

> > > > > If there is a ventilation problem, I don't think this stuff will fix
> > > it. May even make it worse.

> keep the moisture away from the joist then you don't need to ventilate...

You're not going to get anywhere near a perfect seal in practice, so you've then got the same level of damp plus even less ventilation.

Multifoils also don't insulate as advertised at room temp, the figures are more applicable to radiant heat loss, which isn't the issue in houses.


NT

[swimm...@yahoo.co.uk]

>
>
>
> > > > > > If there is a ventilation problem, I don't think this stuff will fix
>
> > > > it. May even make it worse.
>
>
>
> > keep the moisture away from the joist then you don't need to ventilate...
>
>
>
> You're not going to get anywhere near a perfect seal in practice, so you've then got the same level of damp plus even less ventilation.
>
>
>
> Multifoils also don't insulate as advertised at room temp, the figures are more applicable to radiant heat loss, which isn't the issue in houses.
>
>
>
>
>
> NT

I have to disagree with you on some points here:
1) radiant heat is very relevant for floor insulation tough some marketing propaganda try to push certain products which aren't that suited for the task and are at most an overkill - I might find some interesting links on the subject but feel free to do your own search on that...
2) a perfect seal isn't required as the temperature of the joist's area is similar to the one on the room above - the dew point became less of an issue = less risk of condensation...by the way, the design states that the foil sections should be stapled and overlapped but not sealed under the joist - this allows any residual moisture to drip down safely (so it implies that a complete seal isn't required nor desirable).

but I agree with you on the performance of multifoils - it's grossly overrated so I rather spend less (aluminum bubblewrap stuff) and make the most of the radiant heat properties of aluminum...(basic science really - I trust that).

The more research I do the more I'm convinced this is a very effective way to solve the problem of under ventilated suspended floor - still, a real life example would put any residual doubts to rest...is there anyone out there who can provide some valid examples? (no just theory).

[The Natural Philosopher]

I had a long argument with a friend about this.

I reckoned with adequate ventilation you should treat it as a colad roof
- i.e. lift the floor, stick celotex between joists, foil tape over and
re-lay floor.

He reckoned the better place for the vapour barrier was actually under
the joists allowing any moisture to be driven upwards into the room . I
didn't like that as the vapour barrier itself could get very cold and
condensation would happen on the inside of it.




--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

[swimm...@yahoo.co.uk]

>
>
>
> I had a long argument with a friend about this.
>
>
>
> I reckoned with adequate ventilation you should treat it as a colad roof
>
> - i.e. lift the floor, stick celotex between joists, foil tape over and
>
> re-lay floor.
>
>
>
> He reckoned the better place for the vapour barrier was actually under
>
> the joists allowing any moisture to be driven upwards into the room . I
>
> didn't like that as the vapour barrier itself could get very cold and
>
> condensation would happen on the inside of it.
>
>

I wouldn't try the first solution...not on under-ventilated floors on terrace houses...
The foil under the joist is something I'd like to have a go...the key point here is RADIANT HEAT - the area around the joists isn't going to be that colder than the temperature above...if condensation is formed it should drain safely on the crawl space.
I would pay £££ to check a real life example of this particular design (aluminium under floor joists)...and why haven't I thought about that before? nor have I come across any publication/diagram to show this system? Maybe is a new idea? For less than £40 per room one can solve a very common plague of suspended ground floors (especially in terrace houses).

[Grimly Curmudgeon]

On Sun, 21 Oct 2012 15:26:56 -0700 (PDT), swimm...@yahoo.co.uk
wrote:

>By isolating the joist from the moisture coming from the ground (there was no concrete)

Conscientious builders used to spray the underfloor soil with a layer
of tar to keep the moisture levels down. Adequate ventilation was
still needed, of course.