Anyone used Thermawall or Koolwall over hebel blocks?

Hi all,

we are planning to build a new house and we are trying to make it nice and warm in winter and nice and cool in summer. We were looking at EcoBlock and other insulated concrete form (ICF) products but a number of the builders we are talking to don't like to work with it.

As an alternative, one of the builders suggested Hebel blocks with render instead. So I was thinking if we used foam insulation and maybe sarking over the Hebel, under the render we should be able to achieve the benefits of ICF. Has anyone done something like this with Therawall of Koolwall?

Comments or suggestions would be greatly appreciated.

It’s interesting you cannot find a builder who likes ICF.

This is not uncommon with many building products.

Builders, Tradies, Draft person, etc usually work with what they know works.

Because many products come and go, which has its negatives and positives probably more negatives.

Have seen Koolwall and thermawall which seem to look good.

I'm sure once rendered would like a normal monolithic house and they would replace Hebel.

Would I use either, hmm unlikely as just extruded Styrofoam would be cheaper I imagine.

I would unlikely put this on the outside of Hebel because of cost.

I would look to put further insulation on the outside of Hebel as I feel insulation is not that good.

My parents just built a home in Hebel and my BIL has some experience with Hebel but both are ambivalent about doing the same again.

But then again I'm currently building my house in ICF (Thermacell) and am not sold as to whether this is the best option, nor do I know what is.

Anyway getting back to your initial comment, I would research products you are interested in.

Then contact manufacturer and ask to recommend some builders and draftsperson using their product.

Finding a product then the builder.

Good Luck

Pulpo

Can’t comment on Hebel as I have no experience with it.

However, I think ICF is definitely the way to go!
I used Zego for my build and can highly recommend it.

Where are you located felicity?
I can recommend my builder (he is able to work Aust wide)

Any questions feel free to ask…

In the meantime, you can go and take a look at my blog: www.rlay1.blogspot.com

Thanks guys for the comments...

we are trying to keep the cost down so we have been talking to the project builders that will do a custom build. The trouble is they either won't use ICF (but suggested Hebel) or we did find one project builder that will do ICF but they pretty much just added the total cost for the ICF on top of the normal build cost... making it way too expensive...

I was trying to get the benefits of ICF with the Hebel styrene combo and hoping to use a project builder...

Pulpo do you have an idea of the cost of the Thermawall or Koolwall? I was just wanting to insulate the Hebel with it but it also needs to be a suitable surface for render...

rlay1
We were looking at Ecoblock in particular since they only use the one expert supplier / installer and I was worried about concrete pour issues.... I would consider using other ICF such as Zego with an experienced ICF builder. One issue for the ICF is that have been told we need to have the plans drawn up specifically for the brand of ICF before we can get a quote. So we would have to commit to a product before we know if we can afford to build with it. It's a bit of a chicken and egg situation...

Your house looks amazing so I would definately like to talk to your builder about quoting for our house... we are in SE metro Melbourne and we are doing a single story demolition rebuild.... Which builder did you use?

Maybe I should start a thread "looking for an ICF builder in Melbourne? "

Hi Felicity,

ICF is always going to be a more expensive option than brick veneer. I would say about somewhere between the cost of brick veneer and double brick costs.

You also need to factor in rendering costs (not cheap) and double glazing is a necessity.

Yes, it is best if the plans are drawn up for the width of the ICF that you will be using. Most only use ICF for external walls and internally standard stud walls.

You only need to factor in approximately 200mm for external ICF walls. I think you’ll find that regardless of what ICF brand you go with they will all have a ~200mm option. Regardless, if any builder is willing to work with ICF, they will be able to supply you with a quote for it.

For details of my builder and other tradies take a look at: viewtopic.php?f=38&t=13950&start=28

I do not know the cost per m2 for Koolwall or thermawall at a guess $45. (guess) call for a quote of supplied.

Extruded 50mm, I have forgotten, hmm $20m2, it was a good price.

ICF, Thermacell 200mm series (not sure if still available) Cost m2 $45, Concrete $20, Render $10, steel $10,

Now that is materials only, so for a fully finished filled rendered wall it would cost the above plus labour and concrete pump.

I would have thought that is comparable with hebel as the powerpanels are around $45 m2 plus render and a timber or steel frame.

If interested in ICF call Geoff at Thermacell based in Vic and have a chat he is an old bloke doing it for many years, he can recommend some builders and draftsperson.

Project homes would not be set up to build in new materials their margins are tight and new things creates uncertainty.

What would be the best building material, who knows. ICF I think is better than hebel.

Take your time, it will take longer than you plan regardless, so in 5 years time you will look back and realise that an extra few months made little difference.

Good Luck

Pulpo

Not all ICF systems are ideally constructed for energy efficiency.

If you live in a temperate climate (i.e. not desert or tropics) then the most effective configuration is:

Inside - Thermal mass - Insulation - Outside

This has been validated by research performed in the 1970s.

Do not leave mass uninsulated. If the mass sits outside the insulation then it performs no useful thermal function.

The main function of the thermal mass is to store heat from the winter sun. The insulation stops the heat leaking out at night.

Thermal mass can be anything like concrete, AAC (Hebel), brick, water tanks, stone.

Insulation can be batts, loose fill or foam.

Your construction detailing makes sense but I can't comment on cost.

AFAIK the only ICF which uses the correct configuration is Thermotech but there may be others on the market now.

Hi Dymonite69,

Very interesting information about the Thermotech.

Most of the ICF is: Inside - Insulation - Thermal mass – Insulation – Outside
How would a configuration of: Inside – Thermal mass – Insulation – Outside, make it more effective?

Thermal mass faqs

Thermal mass myths

Recommended thermal mass volumes

Your Home Technical manual - Thermal mass

looks like Envirotalk is goooooone.

the last link you've posted works though.. interesting stuff as something I've been contemplating is if it'd be worth cladding the exterior of a brick veneer building with another layer of Hebel..

It also depends on how high an R-value you are looking at for your walls and roof. It comes down to the laws of diminishing returns where to go from an R-value of 4 to 6 may cost you another $20,000 to build. It will take quite a long time to pay that back in terms of lower energy bills.
I've drawn up some options for us with this in mind when we do our build this year. We are in a different scenario too as I'll be building the place myself and our climate is more temperate than yours.
I should post up the sections of the walls I've drawn.

Stewie

I've drawn up a couple of ICF homes in Melbourne and have shown very little benefit over brick veneer in terms of cost or energy efficiency. This is partly due to the lack of design theory applied by the owners.
I should stippulate that I am a Drafsman and most of my work with owner builder has be purely as a drafting technician rather than a designer.
It takes a lot of research and knowledge to get the most out of these types of products they have negatives and positives depending on how and where they are used. (ie. location of site and positon in home/construction.)
I guess what I'm trying to say, swapping one material such as brick veneer for ICFs or Hebel makes very little difference to the whole energy efficiency of the building, but using the right material in the right location can have dramatic effects in both directions (good or bad).
All I can say, is look at your site, research the properties of the product you wish to use and implement a design that get the most out of these products. A good design will always pay for itself (in re-sale) rather than efficiency pay-offs as every house usually has a kid that leaves all the doors and windows open, heater on, and blinds open at the worst possible time, to negate the latter.

can you elaborate on some of the design theory faults you've experienced?

On top of those costings above, don't forget a decent price psqm for the render. I doubt you'll find a renderer for $10 a sq metre.