Feedback on Calistherm board for internal insulation?

H.E. Pennypacker

I'm looking for feedback/opinions on Calistherm Climate Board as an option for internally insulating the interior walls of a solid wall extension. The sales blurb -snip- says that mould is unlikely to grow on it and it manages moisture levels, reducing condensation risk.

I have a somewhat complicated problem - a bungalow with '60's cavity wall and an extension to that with solid walls. The extension was dry lined maybe 30 years ago but is always cold. External insulation is one option but money is an issue so we'd prefer to limit works to the extension if possible. The extension is a continuation of the main house (ie not at right angles to it) so externally insulating just the extension would look odd. I've seen other posts here that say that the cavity walls would need to be pumped before external insulation would be effective which makes externally insulating the entire house a much more expensive job. In any case, the cavities aren't completely clear - lots of mortar etc.

Would Calistherm be a workable and uncomplicated solution to warming up the extension? As it appears to be fixed to the external wall there doesn't appear to be an air gap so less risk of mould on the inside surface of the exterior wall

Calahonda52

If you do an advanced search here on boards.ie for "Calsitherm" which is the correct spelling of the product, you will find lots of posts about it.

I don't have the spec sheet to hand but it may not have a decent enough U value for ur application. It is, as you know more used in locations where damp walls and lots of condensation is an issue.

It is not cheap either, nor are all the bits and pieces required to fit it.

Are you 100% certain it is a cavity wall: unusual for '60's, more usually cavity block

Do you intend removing the dry lining?

This product works best with a lime based substrate, so if the extension walls are skimmed with gypsum you can't use it.

BryanF

We're talking about calcium silicate boards http://en.m.wikipedia.org/wiki/Calcium_silicate

calistherm is a good product

Drylining ia not as good a solution as Ewi (covered on numerous threads here)

H.E. Pennypacker

Calahonda52 wrote: »

Are you 100% certain it is a cavity wall: unusual for '60's, more usually cavity block

Do you oppose removing the dry lining?

This product works best with a lime based substrate, so if the extension walls are skimmed with gypsum you can't use it.

Thanks for the info. The walls were drilled for vents some years ago. When we remove the vent covers, the cavity is clearly visible in the original house whereas the extension vent holes don't have a cavity. The extension walls are 1" thinner. I know that this doesn't prove for certain that the extension walls are solid and I agree that it would be an odd approach but its all I know so far.

We plan to remove the existing dry lining.

Calahonda52

Grand, any chance of a few fotos of the respective walls inside the vents.

Meant intend as to oppose

kkelliher

A very good product but approx 5 times the cost of standard drylining boards so keep this in mind.

H.E. Pennypacker

Calahonda52 wrote: »

Grand, any chance of a few fotos of the respective walls inside the vents.

Meant intend as to oppose

I guessed that's what you meant - predictive text is a nuisance sometimes.

I've attached the photos (see next post, they went missing....)

I'm starting to think that I may be wrong about the walls being solid, despite what the vent openings show. I went up into the attic and checked the extension gable wall. Its block built but I've no idea if its cavity or flat block. That would make it somewhat unlikely that the other walls are solid given the wall width. When I examined the cavity wall vent in the original house more closely, I noticed that the cavity stops at that point. There is a layer of something that looks like slate over the cavity with reinforced concrete above that (maybe poured, hence the slate?). This is at the level of the top of the window. When I stood back and thought about it, I noticed that the windows in the extension are lower than the other windows so even though the vents are at the same height in relation to the ceiling, if the same approach was used in the extension then that area would be reinforced concrete.

I removed an electric socket but its inset into the drylining so the back plate doesn't go into the brick.

I guess the next step is to drill a hole in the gable wall and see what happens.

H.E. Pennypacker

Photos mentioned in last post

Calahonda52

Guessing a little here pending the arrival of the experts
the slate is a cavity closer and then perhaps they cast a ring beam all the way around to help tie the roof together and stop it splaying out.
It also sounds as if they had no precast lintels so the killed two birds with the one stone.

Is the second foto through the ring beam?

BryanF

H.E. Pennypacker wrote: »

. External insulation is one option but money is an issue so we'd prefer to limit works to the extension if possible. The extension is a continuation of the main house (ie not at right angles to it) so externally insulating just the extension would look odd. I've seen other posts here that say that the cavity walls would need to be pumped before external insulation would be effective which makes externally insulating the entire house a much more expensive job. In any case, the cavities aren't completely clear - lots of mortar etc.

I don't understand the cost comment regarding pumping the cavities. Have you priced Ewi?
Get 3 prices for the whole house, pumping whatever wall cavities you have would be only 10% or so.

Ask each tenderer how they will insulate the plinth, eaves, window reveals, door thresholds, move out & fix rainwater goods etc

H.E. Pennypacker

Calahonda52 wrote: »

Is the second foto through the ring beam?

I think so although there's no evidence of any reinforcement in that particular area.

BryanF wrote: »

I don't understand the cost comment regarding pumping the cavities. Have you priced Ewi?
Get 3 prices for the whole house, pumping whatever wall cavities you have would be only 10% or so.

Ask each tenderer how they will insulate the plinth, eaves, window reveals, door thresholds, move out & fix rainwater goods etc

The much more expensive reference in my original post is an exaggeration on reflection. I got a quote previously for EWI - approx 12k after grant so 10% additional for the cavity is there or thereabouts. I didn't have any confidence in the guy who gave that quote so spoke to another installer via the ESB scheme. That installer seemed a bit better but still not great on detail. Neither of them saw filling the cavity as necessary. The third one that I tried did a job locally but didn't turn up for their appointment to have a look at the house and quote. TBH I gave up at that stage. It seems to be an area full of people who have just turned their hand to a new money making area, like aluminium windows were years ago. I know its the ideal solution but that may be in the longer term when installers have more of a track record..