150 or 175mm cavity - anyone build this width cavity?

gooner99

Hi. Did any of you build with .....

a) 100mm block - 150mm cavity fully pumped with bonded bead - 100 mm block. (No internal slabbing). Plastered inside and out of course?

or

b) a) 100mm block - 175mm cavity fully pumped with bonded bead - 100 mm block. (No internal slabbing). Plastered inside and out of course?


How are you finding it?

Whatwicklow

It wouldn't be a common spec as the costs associated with additional design, special block ties, lintels, trays etc etc would make other 'normal' insulation options more attractive and probably provide a better u value.

Interesting to see if anyone has done it thou.

gooner99

Oh.

I had read that 150mm was the cut-off point where standard wall ties would still be ok and there would be no need for an engineer to design. But it just about meets the regs.

Read that with 175mm there is a need for different wall ties and an engineer is required to design. Also read that 175mm is kind of a sweet spot in terms of u-values exceeding the regs. Wider seems to not make any significant heating savings.

kerry bhoy

I built using 200mm cavity. Got local builders merchants to order in wall ties to suit.
Neither block layer or engineer had a problem with it.
But they did cost close to 1000 Euro's.
Attached photo

gooner99

Looks good. Is that pretty steep though for the wall ties?

How is the house performing?

BarneyMc

Went with a 250mm cavity. Engineer insisted on a 6 inch block on the inner leaf on the ground floor. 200mm would probably have been ok but all went well.

BryanF

gooner99 wrote: »

Oh.

I had read that 150mm was the cut-off point where standard wall ties would still be ok and there would be no need for an engineer to design. But it just about meets the regs.

Read that with 175mm there is a need for different wall ties and an engineer is required to design. Also read that 175mm is kind of a sweet spot in terms of u-values exceeding the regs. Wider seems to not make any significant heating savings.

by 'standard' and sweet spot, do you really mean barely complaint with part L/BER/ building regs ?

kerry bhoy

gooner99 wrote: »

Looks good. Is that pretty steep though for the wall ties?

How is the house performing?[/quot

Ya, expensive alright. But if you're going that big stainless Steel is the cheapest way to go.

House is preforming very well. Even with the current Cold weather comfort levels are excellent.

Bad_alibi

I went with 100mm block, 250mm cavity fully pumped with bead & 100mm block
You need to use stainless steel wall straps/ties, I got mine from vantry engineering in Wicklow.

If I was doing it again I'd go with a 200mm cavity as I had large window opening and once you go over 2m opes your into expensive steel lite lintels
If your engineer says it's more expensive or doesn't understand it, get a new engineer, one thing I learnt building is the vast majority of archs/engineers haven't a clue about new building practices or part L compliance. Most are still pushing insulated slabs on the external walls as their standard/perfected detail

House performs very well but that's because I went with a high level of Airtightness. House takes about a day/day and a half to fully come up to temp but it'd hold the heat for 2/3 days.

4odh4n

100mm-200mm-140mm here. house has some short slabs for upper floor so had to have 140 inner leaf. wall ties are pricey alright, from memory i think the stainless steel ones came in about a euro each

gooner99

BryanF wrote: »

gooner99 wrote: »

Oh.

I had read that 150mm was the cut-off point where standard wall ties would still be ok and there would be no need for an engineer to design. But it just about meets the regs.

Read that with 175mm there is a need for different wall ties and an engineer is required to design. Also read that 175mm is kind of a sweet spot in terms of u-values exceeding the regs. Wider seems to not make any significant heating savings.

by 'standard' and sweet spot, do you really mean barely complaint with part L/BER/ building regs ?

No. From reading boards I had come accross a couple of claims that 175mm was where the benefit of insulation v running costs were most felt and that once you went wider the savings on heating were simply not significant and that the money was better spent on beefing up floor/roof insulation along with airtightness, windows and thermal bridging. Not sure how scientific the calcs were.

BryanF

gooner99 wrote: »

No. From reading boards I had come accross a couple of claims that 175mm was where the benefit of insulation v running costs were most felt and that once you went wider the savings on heating were simply not significant and that the money was better spent on beefing up floor/roof insulation along with airtightness, windows and thermal bridging. Not sure how scientific the calcs were.

?

175 pumped cavity is ~0.19wm2k
Building regs require 2.1wm2k
So your 'sweet spot' is just Just meeting min building regs for a new build since 2011

The 'sweet spot' in Imo is the passive standard at 0.15 wm2k
150mm PIR will achieve this standard or ~225mm beads.

gooner99

I thought is was 150mm = 0.20u, 175mm = 0.18u, 200mm = 0.15u

a_noodle_jenny

We have 150mm cavity. Build started in April of 2016. Hired a insulation consultant in August and he told us 200mm would have been far better. We hired this expert as i was not happy with approach to airtighness and insulation as per building spec. I don't know anything about 250mm but I know he said in our build he would prefer 200mm but we could have gone up to 250mm...
I would say hire an expert, we are so glad now we did even if we have made the mistake of the cavity being 150mm - our house will still be so comfortable. It's my last winter in our drafty cold 2006 build rented timber frame house... we won't know ourselves when we get in hopefully by early summer.

gooner99

a_noodle_jenny wrote: »

We have 150mm cavity. Build started in April of 2016. Hired a insulation consultant in August and he told us 200mm would have been far better. We hired this expert as i was not happy with approach to airtighness and insulation as per building spec. I don't know anything about 250mm but I know he said in our build he would prefer 200mm but we could have gone up to 250mm...
I would say hire an expert, we are so glad now we did even if we have made the mistake of the cavity being 150mm - our house will still be so comfortable. It's my last winter in our drafty cold 2006 build rented timber frame house... we won't know ourselves when we get in hopefully by early summer.

Glad your build is going well now. Let us know how the building performs when you get in.

What are you going with for floor and roof insulation?

What air-tightness measures did you take?

Can you PM me the experts details please.Thanks

a_noodle_jenny

No problem gooner-
Here's a few pics from early October showing the taping and membrane. Going with heat recovery, air to water Hp and underfloor heating. Temps this week on site were minus 7 and minus 5 on Thursday morning... so some suppliers saying underfloor won't be needed but area is like mini Narnia-type climate.
So many decisions and I've given up on trying to save money on absolutely everything - our kids are very young and this will be our home. The comfort in told we will have due to our change in arrow has since August will be huge... fingers crossed it will pay off for us...

fatty pang

Bad_alibi wrote: »

I went with 100mm block, 250mm cavity fully pumped with bead & 100mm block

How were you windows and doors fixed to a 100mm concrete block ?

Bad_alibi

fatty pang wrote: »

How were you windows and doors fixed to a 100mm concrete block ?

Windows were fitted to external block and fixed with metal straps back to a plywood Box cavity closer. This was then taped and sealed for Airtightness

gooner99

I need to do a quick spec to get a few perliminary quotes on a plan. So I'm going to spec block with 200mm fully pumped cavity. What did you guys that built 200 go with for floor/ roof insulation and what minimum airtightness value should I spec.

I will probably get replies to get a ber done. So I'll note again that it's only for a perliminary tender on a plan to see what we can afford.

Thanks.

gooner99

What are the current options for wall ties in a 200mm cavity and pros and cons with them?

ht9zni1gs28crp

gooner99 wrote: »

What are the current options for wall ties in a 200mm cavity and pros and cons with them?

You really shouldn't be basing decisions on boards.ie input.

The cost difference between a 350mm tie and say a 375mm tie is probably a night on the beer. Larger cavities require more ties per sq/m than the old way of doing it.

Builders and 'professionals' really do need to forget the old regs......

tvisdead

BryanF wrote: »

?

175 pumped cavity is ~0.19wm2k
Building regs require 2.1wm2k
So your 'sweet spot' is just Just meeting min building regs for a new build since 2011

The 'sweet spot' in Imo is the passive standard at 0.15 wm2k
150mm PIR will achieve this standard or ~225mm beads.

I have gone with the 150mm PIR board from one of the main suppliers starting using the product onsite today.
Like BryanF pointed out the the cavity width is only part of it, the materials being used is critical. The PIR boards looked to me like the superior product, and one which I can inspect daily visually.
Finally of course is workmanship. The lab quoted U values will be ineffectual if the workmanship is crap.
If you decide to go PIR the reps will be happy to talk you through inspection methods etc.

gooner99

Thomas Better Broccoli wrote: »

You really shouldn't be basing decisions on boards.ie input.

The cost difference between a 350mm tie and say a 375mm tie is probably a night on the beer. Larger cavities require more ties per sq/m than the old way of doing it.

Builders and 'professionals' really do need to forget the old regs......

Thanks for the reply. Sorry I should have been more clear. I wasn't asking for advice on cavity design or width with my last post. I was just trying to get up to date info on what wall ties were on the market for a 200mm cavity, brands and products. There may be ones that I am not aware off. Thanks

gooner99

oops double post

gooner99

Just did a very quick check there. Local merchant has 12" stainless steel which he says are suitable for 200mm cavity and the only ones they supply at the minute @ €140 for 300. Teplo on twistfix have 10 @ €37.38 = 300 @ €1121.40

mjp

Engineer had drawn construction drawings earlier this week but when asking him about expected BER he was saying we be getting C2 which too low for my liking for newbuild. Told him I wanted A3 rating or similar so he has suggested changing cavity from 150 to 200mm aswell as increasing depth of floor insulation.

Would these changes alone bring me near A3 level if I try get a good level of airtightness around windows and all floor/wall joints with pumped cavity insualtion. Will be going for A2W heat pump and UFH with MVHR system.

Also what are the additional costs with 200mm cavity size?
Guessing a 33% increase in cost of pumped ins. due to increase in cavity area aswell as added costs of wallties.
Will blocklayer's charge more per block than if using 150mm or is it much more of an inconvenience for them. Will be going looking for prices in month's time for this but trying to preempt what they might say back to me.
Father is thinking that 200 mm size is excessive but would be quite old school in relation to these types of things.

gooner99

mjp wrote: »

Engineer had drawn construction drawings earlier this week but when asking him about expected BER he was saying we be getting C2 which too low for my liking for newbuild. Told him I wanted A3 rating or similar so he has suggested changing cavity from 150 to 200mm aswell as increasing depth of floor insulation.

Would these changes alone bring me near A3 level if I try get a good level of airtightness around windows and all floor/wall joints with pumped cavity insualtion. Will be going for A2W heat pump and UFH with MVHR system.

Also what are the additional costs with 200mm cavity size?
Guessing a 33% increase in cost of pumped ins. due to increase in cavity area aswell as added costs of wallties.
Will blocklayer's charge more per block than if using 150mm or is it much more of an inconvenience for them. Will be going looking for prices in month's time for this but trying to preempt what they might say back to me.
Father is thinking that 200 mm size is excessive but would be quite old school in relation to these types of things.

I'm not an expert on this. I guess going from 150mm to 200mm you will need more wall ties and more expensive ones and the bonded bead will be about 25%+ more expensive.

Not sure what price bonded bead is at the minute, maybe someone that's priced both can give a rough price difference.

Quick look at teplo basalt wall ties.......

6mm x 275mm long Teplo wall tes are a class 2 tie suitable for a cavity width of 105 - 150mm , qty 10 @ €28.25

6mm x 325mm long Teplo Tie is a class 2 wall tie suitable for a cavity width of 155 - 200mm , qty 10 @ €37.38

I'd imagine there are other associated costs like different sills, cavity closer and other details. Other's may be able to give a better insight to the differences between 150 and 200 cavity.

BryanF

mjp wrote: »

Engineer had drawn construction drawings earlier this week but when asking him about expected BER he was saying we be getting C2 which too low for my liking for newbuild. Told him I wanted A3 rating or similar so he has suggested changing cavity from 150 to 200mm aswell as increasing depth of floor insulation.

Would these changes alone bring me near A3 level if I try get a good level of airtightness around windows and all floor/wall joints with pumped cavity insualtion. Will be going for A2W heat pump and UFH with MVHR system.

Also what are the additional costs with 200mm cavity size?
Guessing a 33% increase in cost of pumped ins. due to increase in cavity area aswell as added costs of wallties.
Will blocklayer's charge more per block than if using 150mm or is it much more of an inconvenience for them. Will be going looking for prices in month's time for this but trying to preempt what they might say back to me.
Father is thinking that 200 mm size is excessive but would be quite old school in relation to these types of things.

You need a second opinion. Your engineer is way off compliance with 2011 building regs with a C3 rating!

chillit

this page will give you some basic info on the u-value you get from various cavity widths and wall types when using pumped beads. 
http://www.kingspanecobead.com/index.php/u-value
as Bryan mentioned your engineer should really have this covered for you. Or if he doesn't do BER type stuff then hire someone to do a DEAP for you. Doing the DEAP early in your planning process will likely save you more than it costs.

sydthebeat

mjp wrote: »

Engineer had drawn construction drawings earlier this week but when asking him about expected BER he was saying we be getting C2 which too low for my liking for newbuild. Told him I wanted A3 rating or similar so he has suggested changing cavity from 150 to 200mm aswell as increasing depth of floor insulation.

Would these changes alone bring me near A3 level if I try get a good level of airtightness around windows and all floor/wall joints with pumped cavity insualtion. Will be going for A2W heat pump and UFH with MVHR system.

Also what are the additional costs with 200mm cavity size?
Guessing a 33% increase in cost of pumped ins. due to increase in cavity area aswell as added costs of wallties.
Will blocklayer's charge more per block than if using 150mm or is it much more of an inconvenience for them. Will be going looking for prices in month's time for this but trying to preempt what they might say back to me.
Father is thinking that 200 mm size is excessive but would be quite old school in relation to these types of things.

i know its been said already, and im assuming this is a new house build, but i cant believe there is an engineer in 2017 who prepared construction drawings for a dwelling which was no where near building regulation compliant. C2 wouldnt have been acceptable 8 years ago!

In order to know what specification complies with minimum building regulations you first need to have a Preliminary DEAP assessment carried out.

I have yet to come across any dwelling which complied with minimum regulations which had a BER rating lower than A3.

I have come across some A3 rated dwellings which havent complied !

Moggaman

kerry bhoy wrote: »

I built using 200mm cavity. Got local builders merchants to order in wall ties to suit.
Neither block layer or engineer had a problem with it.
But they did cost close to 1000 Euro's.
Attached photo

Can i ask did you have to thicken your inner leaf to 140mm and if so were the blocklayer able to lay the wall as normal due to it being so wide
Thanks

Count Mondego

Moggaman wrote: »

Can i ask did you have to thicken your inner leaf to 140mm and if so were the blocklayer able to lay the wall as normal due to it being so wide
Thanks

There is no need. 100mm--200mm bead---100mm is perfectly fine with the right ties. I have hollow core on this too.

BryanF

Count Mondego wrote: »

There is no need. 100mm--200mm bead---100mm is perfectly fine with the right ties. I have hollow core on this too.

what is the width of the cavity?

Calahonda52

BryanF wrote: »

what is the width of the cavity?

Looks like 200 from the 200 bead, with HC on a 4" inner leaf

Count Mondego

BryanF wrote: »

what is the width of the cavity?

200mm. I should have mentioned that I've only 5 or 6 rows of blocks on the 2nd floor, not full 2 storey :-)

I swear an engineer did the spec!

ht9zni1gs28crp

I had stainless steel ties thermally modelled from Varty Engineering. Should anyone require a cheaper option than the Teplo or Basalt ones. Get in touch with them. up to 375mm to suit a 250mm cavity.

That's based on 5 ties per m2 as opposed to 3 for standard cavity.

All worked fine, and passed passive certification.