Are ICF buildings compatible with Passive House methods?

SandwichPanel

I'm curious about the ability of an ICF house to conform to Passive House requirements generally?

Since I'm currently looking at Passive House standards and details a lot I see particular U-Values, Energy consumption figures, and concerns about thermal bridging and air tightness pop up frequently and I have a question about ICF.

Solar heat generally influences solid interior surfaces such that Passive house buildings (of various styles, timber, steel, concrete etc) maximise south facing glazing so that more surfaces can receive sun, heating up due to this radiation. Thermal massing is an important consideration in creating/maintaining heat within the house so how does ICF (Insulated Concrete Formwork: Poured concrete between 2 insulated surfaces such as thick polystyrene panels) compare in its ability to create thermal massing?? Is it purely down to the plasterwork over this insulated polystyrene to conduct heat to the air? And is plasterwork/board effective or negligible in doing so? Or is it easily discounted for by using efficient Heat Recovery System?

Is ICF easy to incorporate into a new build or retro fit project aiming for Passive House heating levels and numbers, from an architectural point of view??

sas

SandwichPanel wrote: »

I'm curious about the ability of an ICF house to conform to Passive House requirements generally?

Since I'm currently looking at Passive House standards and details a lot I see particular U-Values, Energy consumption figures, and concerns about thermal bridging and air tightness pop up frequently and I have a question about ICF.

There are PHI certified ICF systems. There is a PHI certified ICF house in Ireland that used an imported german system.

The issue with the ICF systems commonly available here is that none of them offer sufficient u-values to meet the PH standard. That's not to say they can't be used to build really comfortable homes.

SandwichPanel wrote: »

Solar heat generally influences solid interior surfaces such that Passive house buildings (of various styles, timber, steel, concrete etc) maximise south facing glazing so that more surfaces can receive sun, heating up due to this radiation. Thermal massing is an important consideration in creating/maintaining heat within the house so how does ICF (Insulated Concrete Formwork: Poured concrete between 2 insulated surfaces such as thick polystyrene panels) compare in its ability to create thermal massing?? Is it purely down to the plasterwork over this insulated polystyrene to conduct heat to the air? And is plasterwork/board effective or negligible in doing so? Or is it easily discounted for by using efficient Heat Recovery System?

Is ICF easy to incorporate into a new build or retro fit project aiming for Passive House heating levels and numbers, from an architectural point of view??

With respect you appear to be all over the place with this.

The PHI maintain that thermal mass is irrelevant in a passive house. I'm dealing directly with them for my home and have previously asked this question.

I don't see the relevance of ICF for retro fit on the basis that I take retro fit to be an upgrade of an existing structure. If you mean can you build extensions with it and tie them to existing structures then yes you can. The detailing will be important however but this is the case for an extension.

What do you mean by "from an architectural point of view"? My interpretation of an "architectural point of view" would be the appearance\design of the building. So to me your question reads, "Is it possible to build walls with this wall building method?"

For what it's worth, PHI certified ICF was too expensive for my build. There are detailing concerns around windows and issues with wider openings where you'd be constructing insitu lintels. It was things like these that put me off it.

Carlow52

sas wrote: »

For what it's worth, PHI certified ICF was too expensive for my build. There are detailing concerns around windows and issues with wider openings where you'd be constructing insitu lintels. It was things like these that put me off it.

Put u off PHI or ICF?

SandwichPanel wrote:

Thermal massing is an important consideration in creating/maintaining heat within the house so how does ICF (Insulated Concrete Formwork: Poured concrete between 2 insulated surfaces such as thick polystyrene panels) compare in its ability to create thermal massing??

The external walls of any modern construction are rarely if ever going to add thermal mass for interior heating.

Thermal mass is about the inner walls and their ability to attenuate large temp variations.

See here: http://www.boards.ie/search/?q=%22thermal+mass%22&f=876&u=124705&title=&threads=&date_from=&date_to=&sort=

As Sinnerboy has penned here recently thermal mass is also a consideration when looking at projected occupancy.

SandwichPanel

There are PHI certified ICF systems. There is a PHI certified ICF house in Ireland that used an imported german system.

The issue with the ICF systems commonly available here is that none of them offer sufficient u-values to meet the PH standard. That's not to say they can't be used to build really comfortable homes.

Thanks sas that answered my question pretty well for now!
I was aware ICF homes can be comfortable and good. In reference to thermal mass being relevant or not in Passive houses tho I suppose I was more concerned with its potential role in designing passive homes in the Irish climate rather than if it is actually an essential criteria or not when designing a 'passive home' generally, but you have cleared that one up for me nicely in regard to how ICF is employed currently using Irish building techniques. Passive homes CAN be of ICF but may be quite expensive and tricky to work in many cases.

I meant ''architect's'' rather than ''architectural'' point of view, as in: my concern regarding the designing of a good layout, costing and possible concerns when advising a client from the outset, rather than a structural point of view concerning structural soundness.
Yes, 'Retro fit' was used to mean an extension! apologies for vagueness in original post, excuse was tiredness!

Re: Carlow 52

The external walls of any modern construction are rarely if ever going to add thermal mass for interior heating.

Thermal mass is about the inner walls and their ability to attenuate large temp variations.

Thanks for reply but, I did know thermal mass is more about the inner walls ability to attenuate large temp fluctuations, that was the point of my question regarding ICF (using thermal mass of floors and walls on the inside through solar radiation, hence the mention of glazing also). I appreciate your comments tho, both you guys!

sas

Carlow52 wrote: »

Put u off PHI or ICF?

ICF. When looked at in comparison to other systems, I struggle to see what it offers at all except that it tends to be cheaper. You also tend to get less in terms of u-value too though which balances that advantage out for me.

Take external insulation for example.

My thoughts:

Both ICF and EWI have the same issues as regards durability externally imho.

With EWI your external walls are finished with plaster internally with no issues as regards hanging items etc.

There is a myth that ICF is more airtight than other systems. This is simply not true. A section of ICF wall with no openings will be more airtight than a block wall unplastered. Once the block wall is plastered however, it is every bit as airtight in practical terms. In practical terms meaning that you can hit below the PH standard with plastered block walls.

All systems have the same airtightness issues around openings.

I believe it is easier to get a good thermally performing window installation with EWI too. Reason being that with EWI your windows are installed before the insulation. Hence you can ensure the insulation fits snugly around them. With ICF your windows are installed after your insulation which complicates detailing.

Apart from it looking cool as it goes up however (and it does look really cool) I fail to see what it offers.

I'm open to correction here though.

Carlow52

Thanks for the reasoned comments: much appreciated.

What I like about the ICF idea is the the notion that there are less 'moving' parts than the trad cavity wall/ties/internal insulation [ beads/sheets whatever] construction methods.

Once you start looking at PH standards and below then different issues arise, such as u describe.

On ICF one important issue is to make sure that the readymix concrete is mixed properly, particularly at the start of each load where there can be an excess of stone in the first shot.

I always insist on a proper mixing of each lorry once it has arrived on site and a visual inspection into the drum before the first bit is poured from each lorry.

Having cut my teeth on building the items shown in the link taught me a thing or 2 about ready mix!
http://www.sir-robert-mcalpine.com/projects/?id=2523

sas

Carlow52 wrote: »

I always insist on a proper mixing of each lorry once it has arrived on site and a visual inspection into the drum before the first bit is poured from each lorry.

Having cut my teeth on building the items shown in the link taught me a thing or 2 about ready mix!
http://www.sir-robert-mcalpine.com/projects/?id=2523

Yeah, I'm sure working on the likes of that would certainly encourage vigilance.