Cavity wall full fill insulation!!?

Rock12

Hi everyone, I am at the decision stage of my self build. I have decided to go with a 200mm cavity and full full insulation, my dilemma lies with the type of insulation.I'm torn between pumped and rigid board. Has anyone here used a full fill rigid insulation in this type of cavity and if so how did you find the installation, cost comparison and any info really would be much appreciated! Thanks.

Eoghan Barra

You should look at Rockwool fullfill cavity wall batts (especially with a name like Rock12!), Knauf Earthwool fullfill cavity batts or something similar.

With pumped, you have no way of knowing whether the cavity has been completely filled without voids, you just have to hope for the best - unless, of course, you have the house infra-red scanned at a later stage.

With rigid insulation, there will not be a snug fit between the insulation and the blockwork; even a few mm of a gap will drastically reduce the effectiveness of insulation - google 'thermal looping' or read this:
http://www.century.ie/cent/PartialFillCavity.pdf

Rockwool cavity is semi-rigid so fits tight to the blocks, is very reasonably priced and, as it is built in as the wall goes up, you can be sure there are no gaps.

Something else worth considering are low conductivity wall ties. Qwik-fix do one for a 200mm cavity. These are about 1/100th the conductivity of steel, which most wall ties are made from.

(I have no relationship with these companies, by the way, other than being a satisfied customer.)

bbam

We went with a bonded bead insulation. The problem with the rigid board is the detailing. It is frequent to have gaps and breaks in tight areas that allow are through and ruin the effectiveness.
if done well the pumped insulation is a thorough job and the end result is excellant.

JD6910

with the full fill pumper insulation in a 200MM cavity is there any chance of water ingress?????

Rock12

I have made a few 360's on this wall insulation and it's proving a very difficult decision to make.

I am hoping that with the extra cavity space this will benefit in the moistures movement down the cavity space and not across it. Also with a good coat of render to the external leaf it will keep ingress to a minimum.

With the probability of thermal looping with partial fill cavity insulatIon decreasing its effectiveness by such a degree I feel it's the best of the cavity options. I will use a thermal imaging camera after to make sure all the cavity is filled.

beyondpassive

We've done both types of cavity fill,
a).160 Taped and sealed PIR board with a 40mm residual cavity
b.) 225-275 platinum bead filled cavity.

Our preference would be the full fill. Vapour movement is always to the outside with bead and in the case of failure, water ingress will weep out through the holes between beads. It brings about some complex details and you'd be advised to get your Architect or Technologist to draw up the main details at 1:5 scale. The details are complex but once it is all agreed on paper, the sequencing of wide cavity works very cleanly on site. The big advantage is that you don't have blocklayers messin with insulation.

We tend to use the stainless steel wall ties for robustness, their conductivity is about 15W(mK) thats why we generally use a 250mm cavity, the U value is corrected from 0.136 to 0.16 W/m2K. I'd advise 225mm cavity as an absolute minimum and 250 as sensible. You also need to place a few aerated concrete blocks to eliminate the cold bridges.

You have to be careful in the detailing of cavity trays and use rigid insulation underneath the plastic as the bead can seal before it fills the narrow toblerone shape completely. Thermography wont tell you much untill you're internal structure is up to about 17 degrees and in winter, you have to use drill and borescope to check to bead has filled over lintels.

If going over 250mm, PM me for site photos or details.
Also note that people tend to forget to design the threshold detail for wide cavity. remember to pay attention to that tricky little junction.

kieranhr

JD6910 wrote: »

with the full fill pumper insulation in a 200MM cavity is there any chance of water ingress?????

The bonded bead insulation is Irish Agrement-certified for all situations apart from use with an outer leaf of porous brickwork over the west of Ireland.

So if you have a rendered block outer leaf, then no chance of water ingress, and especially if you're using a 200 mm cavity. Just make sure it has its IAB cert.

Rock12

Thanks for the info! The 200mm cavity with blown full fill insulation, basalt wall ties and internal insulation is giving a u value of .14 but I had heard of a rigid full fill cavity insulation which had a higher u value which I thought may allow for the exclusion of the internal insulation and increase in thermal mass.

Good to hear your views on the blown Insulation beyond passive. I am getting an energy consultant on board to address the insulation required and the thermal bridging issues but I would appreciate any pics on the detailing you have as a practical guide.

fclauson

beyondpassive wrote: »

We've done both types of cavity fill,
a).160 Taped and sealed PIR board with a 40mm residual cavity
b.) 225-275 platinum bead filled cavity.

Our preference would be the full fill. Vapour movement is always to the outside with bead and in the case of failure, water ingress will weep out through the holes between beads. It brings about some complex details and you'd be advised to get your Architect or Technologist to draw up the main details at 1:5 scale. The details are complex but once it is all agreed on paper, the sequencing of wide cavity works very cleanly on site. The big advantage is that you don't have blocklayers messin with insulation.

We tend to use the stainless steel wall ties for robustness, their conductivity is about 15W(mK) thats why we generally use a 250mm cavity, the U value is corrected from 0.136 to 0.16 W/m2K. I'd advise 225mm cavity as an absolute minimum and 250 as sensible. You also need to place a few aerated concrete blocks to eliminate the cold bridges.

You have to be careful in the detailing of cavity trays and use rigid insulation underneath the plastic as the bead can seal before it fills the narrow toblerone shape completely. Thermography wont tell you much untill you're internal structure is up to about 17 degrees and in winter, you have to use drill and borescope to check to bead has filled over lintels.

If going over 250mm, PM me for site photos or details.
Also note that people tend to forget to design the threshold detail for wide cavity. remember to pay attention to that tricky little junction.

I am building a 250mm cavity - DO NOT UNDERESTIMATE THE LEVEL OF DETAIL NEEDED as mentioned above - every window type and every door type is a little different.

One other point - make sure you block builder understand what is required - we had absolute craftsmen doing ours with the only complaint that lifiting blocks another 6 inches out over the walls (i.e. from 4in to 10in cav) gave them back ache. Next time they would have asked for scafolding both inside and out to save their backs.

Duffman1

Hi Beyondpassive

I am going to be going down this road myself very soon and was thinking of a 250mm cavity and i would be very interested in the correct detailing of junctions etc. could you send me the pics you have of these areas. Thanking you in advance

Regards
Ger

sydthebeat

Duffman1 wrote: »

Hi Beyondpassive

I am going to be going down this road myself very soon and was thinking of a 250mm cavity and i would be very interested in the correct detailing of junctions etc. could you send me the pics you have of these areas. Thanking you in advance

Regards
Ger

nice try

kieranhr

sydthebeat wrote: »

nice try

Ha-ha, saw that coming!

I'm going to paraphrase here for Duffman1. A set of standard details are easy come across, but there's no such thing as a standard project. It's the unusual details that will get you. What happens when there's a window post in the wall? What about that balcony that's exposed on top but internal living space underneath? What happens at the bay window? To answer these questions properly, you need to retain (and pay for) a competent and insured professional to do a proper set of working drawings.

adrianegan3

Hi sorry for dragging up an old post just wondering how did the 200 250 mm cavity’s work out for everyone was it a good job would you do anything different.

adrianegan3

Hi sorry for dragging up an old post just wondering how did the 200 250 mm cavity’s work out for everyone was it a good job would you do anything different.

Duffman1

I went with the 250mm cavity fully pumped with bead. Block on edge on the outside and block on flat for inner leaf. All I can say is the house sits at 22 Deg all year round.

Casati

Duffman1 wrote: »

I went with the 250mm cavity fully pumped with bead. Block on edge on the outside and block on flat for inner leaf. All I can say is the house sits at 22 Deg all year round.

That’s a really wide wall though? Did that reduce the size of the rooms or did you build the house out?

Duffman1

Casati wrote: »

That’s a really wide wall though? Did that reduce the size of the rooms or did you build the house out?

I knew that was the way I was going to build the house so I took that in consideration when drawing up the house. It does make the foundations very wide, benefit of that is have basically no settlement cracks. Block on flat carries hallow core as well the block on flat also acts as a heat sink, walls absorb heat during the day and release it at night.

fclauson

Duffman - was you single or two story

I went for block on edge - 250mm full fill - block on edge

you need to do ALL your detailing before the blocks arrive on site - there is a lot to think about around windows/doors etc

you need to think about sliders vs step over doors
ensure you cater for disability access and how you will detail the ramp up to the door and flat into the inside
and how you will separate the inside lintels from the outside
if you are using steels in some of ops. then you need to think about how you will thermally break them

details - details - details - details - and then start laying blocks

would I do anything different - no !!

€150/annum (+HRV running costs) to heat 300sqM