Cavity or EWI?

portwest

I am building a split-level house with concrete retaining walls at ground level on concrete slab,this will be topped with hollow-core and block on the flat to roof,there will be triple glaze aluclad,MHRV and 150mm floor insulation. This house is similar to Tómas O'Leary's "Out Of the Blue" house in design and orientation (southern) so the architect is recommending 200mm external insulation ground to roof level. Would cavity insulation give better value (U+£)?

Carlow52

if block on flat to roof where is the cavity?

sydthebeat

portwest wrote: »

. Would cavity insulation give better value (U+£)?

at a basic level, no it wouldnt.

However, everything is based on a budget. Does yours cover EWI?

beyondpassive

portwest wrote: »

I am building a split-level house with concrete retaining walls at ground level on concrete slab,this will be topped with hollow-core and block on the flat to roof,there will be triple glaze aluclad,MHRV and 150mm floor insulation. This house is similar to Tómas O'Leary's "Out Of the Blue" house in design and orientation (southern) so the architect is recommending 200mm external insulation ground to roof level. Would cavity insulation give better value (U+£)?

The polystryrene external wall insulation and the full fill bead for a wide cavity have a similar Thermal conductivity. You would be best go for 250 cavity as an alternative to 200 EWI. There are lots of tricky details such as the transition from a cold retaining wall to warm superstructure. With wide cavity the window details are more complex than EWI.

BryanF

beyondpassive wrote: »

The polystryrene external wall insulation and the full fill bead for a wide cavity have a similar Thermal conductivity. You would be best go for 250 cavity as an alternative to 200 EWI. There are lots of tricky details such as the transition from a cold retaining wall to warm superstructure. With wide cavity the window details are more complex than EWI.

recently, on a commercial job we went from cavity to EWI to icf, the deciding factors being competitive cost and speed, but of course a compromise by the archs on U-value had to be made (i think we ended up with around 0.2w/mk)

A lot of this debate comes down to site supervision and architectural detailing. You could argue that its easier to get a block layer to build the 250mm cavity and pump (& the straps + closers etc for windows) than get an EWI guy to do the job right.. what I really mean is the better EWI guys are expensive, and convincing a client of why the expensive guy is worth it, can be difficult during the middle of the build when money starts to get tight..

portwest

beyondpassive wrote: »

The polystryrene external wall insulation and the full fill bead for a wide cavity have a similar Thermal conductivity. You would be best go for 250 cavity as an alternative to 200 EWI. There are lots of tricky details such as the transition from a cold retaining wall to warm superstructure. With wide cavity the window details are more complex than EWI.

I had a guy on to me today, says that his 160mm EWI would give me a U-value of 0.18 at a more competitive price than the 200mm EWI. I would be hoping to put drylining on the inside of the retaining walls to help the transition. Overall I would like to shoot for close to passive.

BryanF

portwest wrote: »

I had a guy on to me today, says that his 160mm EWI would give me a U-value of 0.18 at a more competitive price than the 200mm EWI. I would be hoping to put drylining on the inside of the retaining walls to help the transition. Overall I would like to shoot for close to passive.

passive wall requirements are generally lower than .15w/m2k

portwest

sydthebeat wrote: »

at a basic level, no it wouldnt.

However, everything is based on a budget. Does yours cover EWI?

Yes, but within reason, the architect seems to be going on much the same guidelines as the " Out of the blue" house, which has 315mm EWI and a 200mm polystyrene floor slab foundation. Which imo is excessive. I would like this house to be close to passive.

portwest

BryanF wrote: »

passive wall requirements are generally lower than .15w/m2k

Would the 200mm EWI give me this?

BryanF

portwest wrote: »

so the architect is recommending 200mm external insulation ground to roof level.

portwest, have we just gone full circle:) May i ask is your architect doing a phpp and if so, your "shoot for close to passive" should be a calculation done by him giving you an idea of what U-value's you require. just remember in the greater scheme of your build insulation is cheap!!!

here's a simply illustrated passive house heat loss diagram from another self-builder, you can clearly see that even at passive levels, wall insulation and in your case the retaining walls and your detailing (thermal bridges) will impact greatly on your homes overall losses
http://www.boards.ie/vbulletin/showpost.php?p=74762619&postcount=35

Would the 200mm EWI give me this?

ye should be close, depending on product and block. have a look here:
http://www.viking-house.ie/quinnlite-passive-house.html

when your dealing with specific tradesmen that promise you the stars: show the literature to your architect and he'll decipher it.

also if you want a more general understanding of the figures and what they mean, why not start with the passive house website:
http://www.passivhaustagung.de/Passive_House_E/Passive_house_insulation.html

Do-more

I don't know if this is possible but I'm just going to throw it in here for consideration, bear with me!

I'm building in timber frame at close to passive spec. The shell of the house is delivered and erected as per a "normal" TF house with closed panel 145mm wall with windows and doors already fitted in the factory. On site there is then a passive upgrade kit fitted which consists of a 145mm layer of dense rockwool and then a 70mm stud wall with more rockwool between the studs.

You could build your retaining wall and then a cavity and then build the entire house in TF?

Or you could build the shell in ICF allowing you a concrete first floor if you want one and then fit the "passive house upgrade" similar to mine to bring your wall u values down to around 0.1 with good cold bridging details due to the ICF's?

Not sure if the latter would throw up any issues such as with interstitial condensation etc., but as I say I'm just throwing it in here for discussion and consideration.

BryanF

Do-more wrote: »

I don't know if this is possible but I'm just going to throw it in here for consideration, bear with me!

I'm building in timber frame at close to passive spec. The shell of the house is delivered and erected as per a "normal" TF house with closed panel 145mm wall with windows and doors already fitted in the factory. On site there is then a passive upgrade kit fitted which consists of a 145mm layer of dense rockwool and then a 70mm stud wall with more rockwool between the studs.

You could build your retaining wall and then a cavity and then build the entire house in TF?

Or you could build the shell in ICF allowing you a concrete first floor if you want one and then fit the "passive house upgrade" similar to mine to bring your wall u values down to around 0.1 with good cold bridging details due to the ICF's?

Not sure if the latter would throw up any issues such as with interstitial condensation etc., but as I say I'm just throwing it in here for discussion and consideration.

there's a passive house in Carrigaline Cork, just built like this

just do it

sydthebeat wrote: »

at a basic level, no it wouldnt.

Interesting. Leading on from this can I take it the greater depth of insulation one goes for the better value there is to be had from EWI.

It's just a pity its so expensive here. Hard to see why given that all it appears to be is securing large blocks of insulation to the wall!

sas

just do it wrote: »

Interesting. Leading on from this can I take it the greater depth of insulation one goes for the better value there is to be had from EWI.

It's just a pity its so expensive here. Hard to see why given that all it appears to be is securing large blocks of insulation to the wall!

It took 2 - 3 guys the bones of 4 weeks to just secure the insulation on my home. Cutting it so that it's gap free is VERY time consuming. A gable with no windows can be done quickly. They did one of my gable ends (both stories) in a day. Cutting for window overlaps etc is very time consuming work.

The plastering took nothing to 6 days for everthing i.e beads, plint, base cost mesh and finish. They literally flew around the house doing that.

It's massively time consuming to do correctly and hence it's the price. If you're paying less you're getting less. I absolutely believe this and is the reason that I absolutely believe wide cavity is significantly more easily achieved and represents more bang for buck without the long term concerns on durability.

BryanF

just do it wrote: »

It's just a pity its so expensive here. Hard to see why given that all it appears to be is securing large blocks of insulation to the wall!

Its labour intensive and the materials are expensive and the expertise to get the finishing render correct seems to flummox a lot of installers.. maybe because some aren't very diligent plasterers, or possibly because short-cuts are taken to get the business from people who expect their EWI done cheap..

just do it

sas wrote: »

It took 2 - 3 guys the bones of 4 weeks to just secure the insulation on my home. Cutting it so that it's gap free is VERY time consuming. A gable with no windows can be done quickly. They did one of my gable ends (both stories) in a day. Cutting for window overlaps etc is very time consuming work.

The plastering took nothing to 6 days for everthing i.e beads, plint, base cost mesh and finish. They literally flew around the house doing that.

It's massively time consuming to do correctly and hence it's the price. If you're paying less you're getting less. I absolutely believe this and is the reason that I absolutely believe wide cavity is significantly more easily achieved and represents more bang for buck without the long term concerns on durability.

As with everything quality of workmanship is key. I suppose with wide cavity you'll get away with less exacting detail.

Do you think as EWI becomes more established and lads like you've used get more experienced the time involved will decrease enough to make a difference on price?

sas

just do it wrote: »

As with everything quality of workmanship is key. I suppose with wide cavity you'll get away with less exacting detail.

Do you think as EWI becomes more established and lads like you've used get more experienced the time involved will decrease enough to make a difference on price?

The guys that did mine are a big company that did big commercial jobs e.g. garda headquarters

Their head man trained\worked in germany for years. They are very experienced.

No matter how many babies you have, the next one will still takes 9 months

portwest

sas wrote: »

The guys that did mine are a big company that did big commercial jobs e.g. garda headquarters

Their head man trained\worked in germany for years. They are very experienced.

No matter how many babies you have, the next one will still takes 9 months

sas, is your EWI 200mm, are you happy with the job, can you pm the company?

sas

portwest wrote: »

sas, is your EWI 200mm, are you happy with the job, can you pm the company?

Mine is 300mm. What's the fascination with 200mm of EWI?

I am happy with the job.

PM on the way.

portwest

sas wrote: »

Mine is 300mm. What's the fascination with 200mm of EWI?

I am happy with the job.

PM on the way.

SAS, thanks for the pm. Is their much of difference financially between 300mm and 200mm (%)?

sas

portwest wrote: »

SAS, thanks for the pm. Is their much of difference financially between 300mm and 200mm (%)?

My system was supplied as an adhesive only system.
So the only difference on mine was the price of the additional 100mm

If your system was also mechanically fixed then it will get more expensive. The primary reason being that the fixings for 300mm cost alot.

I'm going passive so I never fully explored the thinner systems and the price to performance ratio.

portwest

I can't get more than a five to ten year guarantee from any of the EWI suppliers for durability, I am 500m from the sea here in the west, I am concerned, my phpp consultant says the alternative is a 300mm beaded cavity to a 250mm Ewi. I spoke to a builder and he says there will be very little difference in cost. I thought a wide cavity is a cheaper option?

beyondpassive

Wide Cavity and EWI on Block and flat are inseparable on cost and in any SWOT analysis

The main advantage is its perceived robust inside and outside and the fact that the insulation is pumped after the windows are in and sealed can give assurance that the insulation is continuous .

wide cavity photos

about2build

Hi Guys Beyondpassive....I have heard it said that the pumped bead will not necessarily create a continuous insulation barrier and that some spots may be missed that will only show up later on a thermographic camera??? Worried about this though my insulator said there would be no prob the arch is not so sure and feels pumped cavities are not suitable for new builds but more as an addition to existing board insulation

beyondpassive

about2build wrote: »

Hi Guys Beyondpassive....I have heard it said ........

I've heard it said that Micheal Jackson is alive and well and stackin shelves in Aldi Tullimore. :-) I' wouldn't rely too much on heresay. Bead is perfectly fine for wide cavity, but you need to check under cavity trays where you have a corner window. I don't think blown bead is well suited to partial fill.

portwest

beyondpassive wrote: »

Wide Cavity and EWI on Block and flat are inseparable on cost and in any SWOT analysis

The main advantage is its perceived robust inside and outside and the fact that the insulation is pumped after the windows are in and sealed can give assurance that the insulation is continuous .

wide cavity photos

yes, but sas has stated in a previous post that if he was doing it again he would go with a wide cavity as more cost effective option, is my situation different because of block on the flat?

BryanF

portwest wrote: »

yes, but sas has stated in a previous post that if he was doing it again he would go with a wide cavity as more cost effective option, is my situation different because of block on the flat?

its about the on site quality of tradesmen with cavity, and trades + product section/application with the EWI and of course the detailing for both options

just do it

portwest wrote: »

I spoke to a builder and he says there will be very little difference in cost. I thought a wide cavity is a cheaper option?

There isn't much difference in cost - that is if you go for the cheapest EWI option. What ever about quality of build on wide cavity, it is crucial on EWI. Are you willing to take that chance?

portwest wrote: »

I am 500m from the sea here in the west, I am concerned, my phpp consultant says the alternative is a 300mm beaded cavity to a 250mm Ewi.

I'm a similar distance with an exposed site on the west coast. I'm more willing to take a chance on the build type used for all houses around here, with the modification to wide cavity
vs
a novel build type where you need perfect junctions between each of the EWI panels, and a large level of trust in external render lasting 30/40/50 years.

just do it

I originally also had ICF as an option but, amongst other reasons, I went away from it when I read posts from quite a few different self-builders mentioning they "only had 1 or two blow-outs"! Surely these are huge thermal bridges?!

I see similar problems occuring with EWI with air gaps between panels. Who's to say there is perfect contact to whole depth of 250mm between each and every panel?

Then there is the post-build test using a thermal imaging camera. If there are gaps in the full-fill cavity these are easy to fill. What if there are gaps in the EWI? How easy are these to remedy?

For me 300mm wide cavity seems to win out and subject to phpp calculations that is what I'll be building with.

In theory EWI is better, but from a practical and cost point of view wide cavity wins hands down.

sas

beyondpassive wrote: »

Wide Cavity and EWI on Block and flat are inseparable on cost and in ...

I'm going to have to ask you to back this statement up I'm afraid. I'd be happy to be wrong on this one.

Anecdotally:

SoldSold extended his original home. The extension as I recall was actually larger than the original house. He externally insulated the original house and built the large extension with wide cavity for financial reasons if I recall correctly. He got one of the cheapest prices I've ever seen for EWI and it was still more cost effective to do wide cavity for the extension.

FClauson and I recently compared numbers on my build costings versus his proposed wide cavity and the price difference was very large.

Can we see some actual numbers for comparison.

SAS