INSULATION

The Lone Ranger

OK,
140 MM CAVITY WITH PUMPED BEAD INSULATION.
2 STORY WITH UNDER FLOOR HEATING DOWN STAIRS AND UP.
HAD HEARD THAT A SAND AND CEMENT FINISH ON INSIDE WOULD BE A GOOD THERMAL STORE BUT NOW I HAVE BEEN TOLD I SHOULD USE INSULATED SLABS ON INSIDE.
ANY SHED SOME LIGHT ON THIS PLEASE.
THANKS

bbam

Don't know about thermal store but the sand/cement finish will improve resistance to air passing through the wall structure..

As to pumping the cavity and insulated boards.... We did this two years ago and are massively impressed with the results, there are however many who are of the opinion that it's not a good idea...

Carlow52

The Lone Ranger wrote: »

OK,
140 MM CAVITY WITH PUMPED BEAD INSULATION.
2 STORY WITH UNDER FLOOR HEATING DOWN STAIRS AND UP.
HAD HEARD THAT A SAND AND CEMENT FINISH ON INSIDE WOULD BE A GOOD THERMAL STORE BUT NOW I HAVE BEEN TOLD I SHOULD USE INSULATED SLABS ON INSIDE.
ANY SHED SOME LIGHT ON THIS PLEASE.
THANKS

whats with the caps, no need to shout:(

skim coat better for airtightness than sand cement.
insulated slab will make house a low thermal mass/store gaff
more here re the shed question
http://www.freefoto.com/preview/11-12-52

dos29

Carlow52 wrote: »

skim coat better for airtightness than sand cement.

I'm curious as to where you draw this info from, cos all the internet trawling I've done states the opposite?!?! :eek:

Carlow52

dos29 wrote: »

I'm curious as to where you draw this info from, cos all the internet trawling I've done states the opposite?!?! :eek:

did u not read the small print:)
Went on 2 air-tightness training courses and both recommended a skim coat on the interior block face before doing the blow test.

If I am wrong in relation to it better to use sand cement for this purpose then please throw up a few links.

I will mea cupla.

sas

I can give you an example. This is a friend of mine and the results of the airtightness test are listed at the top.

Www.mypassivehouse.com

Test was done after scratch coat applied.

One example does not a case make I appreciate. It is my plan to test at this stage too.

dos29

Carlow52 wrote: »

Went on 2 air-tightness training courses and both recommended a skim coat on the interior block face before doing the blow test.

You've lost me now.
Here's my thoughts from my admittedly limited internet research.
Best practice for airtightness in block build, is sand/cement scratch coat. This is generally finished with skim coat, which should add to airtightness, but is not the main contributor. It can sometimes be finished with a floated sand/cement finish coat, which gives a slightly rougher finished surface than skim, but would also add to airtightness.
Now, if we bring insulated slabs in, (as in the OP), unless you put scratch coat under the insulated slab, you are relying on the slab, which will only take a skim coat, for your airtightness. And this combo of only slab and skim is supposed to be nowhere near as good for airtightness as a scratch coat.
Then the next dilemma.
Once you bring insulated slabs into the question, is there not a worry at the moment that if its onto a scratch coat, you create a dew point behind the insulation where mould can be an issue?
As I say, the only knowledge I have on this subject is what I've gleaned from the internet.

sinnerboy

Concrete blocks are porous. And Blockies NEVER fill the perps.

Any continuous and joint-less coating of the nature of skim or sand and cement counters the porosity.

If not dry lining one needs the durability of sand and cement ( or "full coat" gypsum plaster ) to the internal.

If dry lining this would be wasteful - thus skim.

sinnerboy

@ the OP

High thermal mass delays your heating system response time

Low thermal mass speeds it up .

In and of itself Thermal Mass is neither good nor bad. Like the missus , just needs to be understood better.

Whether you require insulated plasterboard or not to comply with building regulations is a query for you Architect or Engineer . Or BER Assessor .