Posted By: James Nortonneed an idea about thickness ASAP

When I looked into this a few years back, I seem to remember that you need a 30:1 ratio by mass.
So work out the mass of air you want to thermally stabilise, including leakage/ventilation. Multiply by 30 and that should give you the mass of the thermal mass.

I have no real idea if it will help as I only did a scale model, and life does not scale well, but be interesting to see what you end up with and if it helps any. You putting any temp loggers in the mix to be dig out later?

Inside the thermal envelope is the only place for passive thermal mass.

Not convinced about water walls yet, the SHC is good, the price is good, but have a nagging doubt about something I just can't put my finger on at the moment.

sand and lime or sand cement base-coat with finishing coat, maintain good thermal contact between core and top layers.

Plaster onto EML or wood laths with no air gaps then?

...now taking it a bit further, one of these walls in in a nice location in the living area where the sumptuous clay plastery-ness would be well worth the effort and its a bit smaller too so need to work well... ...where as another one is in a bedroom, is much larger and frankly not worth the effort so am thinking of a earth wall lite solution, say 6mm PB on bed of plasterboard adhesive then a skim coat...?

Any thoughts...?

J

<blockquote><cite>Posted By: James Norton</cite>...now taking it a bit further, one of these walls in in a nice location in the living area where the sumptuous clay plastery-ness would be well worth the effort and its a bit smaller too so need to work well... ...where as another one is in a bedroom, is much larger and frankly not worth the effort so am thinking of a earth wall lite solution, say 6mm PB on bed of plasterboard adhesive then a skim coat...?

Any thoughts...?

J</blockquote>

One idea, take unfired clay bricks and build a wall by dipping them in water and laying them as you would brickwork, without the mortar. as a finish, the wall can be plastered or finished with a damp cloth wiped over the surface, which will blend the bricks into one surface.

For the bricks and stud work, you could think about leaving the timber exposed and plastering up to the timber.
James, your design sound very similair to what I am planning for my house. Where I will use a timber frame stud work with clay block infill, I will use reclaimed oak beams, oiled and leave them exposed.

If you do go over any wood, the key is to use 2 coats, a base and finish coat. put some nails in the wood, plaster over with a base coat, fill any large cracks that develope and then plaster over with a thin finish coat.

Posted By: bot de pailleOne idea, take unfired clay bricks and build a wall by dipping them in water and laying them as you would brickwork, without the mortar. as a finish, the wall can be plastered or finished with a damp cloth wiped over the surface, which will blend the bricks into one surface.

I like those ideas! Thanks, BdP
PS Have you tested them - do they really work as well as I would imagine?

Posted By: bot de pailleFor the bricks and stud work, you could think about leaving the timber exposed and plastering up to the timber.
James, your design sound very similair to what I am planning for my house. Where I will use a timber frame stud work with clay block infill, I will use reclaimed oak beams, oiled and leave them exposed.

You're absolutely guaranteed cracks at the junction, though. So if thinking about airtightness, you'd need a membrane behind the timber.

Posted By: bot de pailleFor the clay plaster, remeber that you can add things to teh finish coat. Quartz or graines of crushed mother of pearl shells look nice on a wall that will have down lighting near them.

Yup, I'm planning on using that trick. I note from elsewhere that adding granite chips is a great way to increase the exhalation rate of radioactive thoron gas from the plaster, so perhaps they wouldn't be such a good idea

This article on the effect of thermal mass on space heating may be of interest to you James.

http://www.constructireland.ie/Articles/Renewable-Energy/The-effect-of-thermal-mass-on-space-heating.html

In my situation the idea is to just knock the edge of the big extremes of temp, particularly in respect of overheating

J

Posted By: SteamyTea

Posted By: Chris P BaconThis article on the effect of thermal mass on space heating may be of interest to you James.

Just got around to reading it.
If I read it right, not much difference between low and medium thermal mass, but high thermal mass is the worse.

Yes, it seems that on balance medium thermal mass is probably best for most situations, giving you the benefit of some smoothing without any possible negative effects on the heating load.

I assume James you are aiming at a medium thermal mass solution and the article gives added confirmation that that is the correct approach.

I was considering whether to add some form of thermal mass to my internal stub walls such as filling with hempcrete or such but I think my floor slab will probably be enough.

...decision time approaches for 'mass walls light' (bad choice of walls but 'mass walls cheap' is perhaps a bit unpalatable, true, but unpalatable )

...further to the above the unfired blocks are not available in the quantities (small) I need, even despite my attempts at charm and talk of high profile demonstration etc, so am looking at possibly cob blocks or to be honest ordinary concrete blocks...

as above for the mass wall in the less prominent location so far I have:

a. win lottery, put family up in 5 star hotel for 6 months then studwork, clay plaster on hemp.
b. 5 number win, studwork with concrete block infill, hessian over studs, 2 coat gypsum base coat plaster and skim
c. partial blockwork in studs with 6mm board on plasterboard adhesive to blocks and studs
d. blockwork wall with head restraint and acoustic ties to studwork party wall beyond
- i. fair faced and painted
- ii. single base coat and skim

any thoughts...?


J

i dont see why you need to win the lottery to do this work, unless you are buying the clay plaster in sacks from a eco building supplier. and why 6 months of work? a week or 2 at most.

what about using sand? build a stud wall, ply wood finish, pour sand into the stud wall cavity.

are the supports for these mass walls strong enough?

Teenage son helps build block wall and gets to finish it himself (within reason)?!

lego?

I'm thinking of using exposed concrete/cob block on my interior walls re thermal mass as I like the 'look' of them but appreciate end user and design review committee not keen.

As one last hurrah, google 'concrete block interior design' select images that may persuade (there is a couple of nice ones - not too brutal), with the caveat that if they really don't like it you can plaster over later - by the time that happens(!) you maybe able to afford the clay plaster.