Partial fill cavity construction: dead?

Here is a very interesting article ive come across. It should be read by every building contractor and self builder.

The basic premise is that the standard partial fill cavity wall building method is inadequate in todays climate of energy efficiency and low cost heating. At its least, it states that this method should no longer be considered that standard building method throughout the country. Its time building contractors changed their practises or they will be left behind.

Heres a snippet of the conclusion:

'Radical abatement measures must be
implemented immediately to offset further
growth in these emissions over the next
ten years and to prepare for much more
onerous obligations in the longer term'.
EPA Newsletter Vol 7 No 2 October 2000

If one looked at partial fill cavity walling
using EPA's statement as a principle and the
information I have examined above as the
context, the only sensible decision would be
to say that partial cavity walling has reached
its limit and is no longer useful in achieving
this society's goals of improved living
standards while also abating environmental
degradation. There are now ample more
predictable and adaptable technologies
available to replace it.

Intresting article, and it is a bit of an ask these days for a cavity wall to achieve the current u values in part L.
I intend on using a 4" block cavity wall, what would be the best bet to achieve current u values? Is it constructing a wider cavity and more insulation or drylining the inside of the house?

Thats the million dollar question jollyman.

Personally i would specify the following:
1. external sand and cement render
2. 100mm medium density concrete block
3. 125mm cavity
4. blown-in full fill insulation. (whether PS or other approved)
5. 100mm autoclaved aerated concrete block (AAC)
6. internal slabbing of 12.5mm gypsum board with 25mm EPS backed insulation with foil facing
7. internal skim plaster finish

by my calculations, that make up will give you a wall u value close to 0.2
whereas the standard 310 cavity with partill fill kingspan will really give you a u-value in the region of 0.7.

Oh the extra Euro Signs are flashing in front of my eyes €€€€

The worst about slabbing the inside is fixing afterwards for rads and the likes they will all require grounds, may have damage to walls!

Ok so maybe i would be willing to stretch the wallet/budget to that, with the exception of the AAC block would that have much of an impact on the U value?

So is partial fill Masonry block cavity walls in order to meet current Regs just as expensive as its timber frame competitor? I think it would make for an intresting comparsion!

[broken link removed]

have a look at the first table in this pdf. This shows the difference of an inner leaf of AAC or dense concrete.

Perhaps make a choice between AAC inner or Insulation backed plasterboard. Personally i would choose the AAC. Also minimise as much as possible the service holes through your walls.... bring as much through the floor as possible ie sink waste pipes, external tap pipes, etc.....
and dont include passive vents, splash out the extra for a mechanical HRV system, if at all possible.

Hi Sydthebeat, so you still recommend cavity wall? Is it the 'partial fill' element that you don't like, ie. does the full fill blown in cavity insulation plus the AAC block make the difference (in your view)?

Yes barney it does.

my problems with partial fill are:
Theres no inclusion in u value calculation for:
1. thermal looping due to the inherent gap between the insulation and inner block leaf
2. reduction in u value for 'wet' outer block leaf
3. reduction of u value of 'kingspan' insulation due to make-up and inevitable decay of silver foil / brown paper make up..... and the inevitable exhaustion of the inherent gas in the PU foam or PI foam.
4. inherent puncture of this build method by services
5. inherent break of the thermal envelope by bad workmanship.

I dont recommed the cavity wall, but it will always be there. It just shouldnt be the industry standard, it should be considered as an inadequate method. But as long as Kingspan and the concrete lobbyists have the government ear, it will be.

Thanks Syd, well if starting from scratch then what construction method other than cavity wall would you use then? ICF, TF..etc.?

Barney,
thats a hard one.. obviously budget is the main factor here.. plus smaller factors of personal favouritisms....

however you probably should look at it from the point of view of what BER rating you would like to have, thus what elemental u values you need.. and work back from there. The biggest factor is actually looking at the building and all its elements as one entity.. rather than all the individual things people get bogged down in.. ie Under floor heating, geothermal, wood pellet vrs oil etc.

I would have no problem recommending any building system, but like everything, you have a rolls royce version and you have lada versions.
Other factors of going down the prefabricated route is the lack of knowledge in the trades about these new systems. Ask any electrician how you wire a Poroton block house or ICF house and his look will be priceless.

currently these are building systems available:

Cavity Block + drylining
Cavity Wall
Precast Concrete Walls Systems
Conventional Timber Frame
Structural Insulated Panel System (SIPs)
Light Gauge Steel Frame
Insulated Concrete Formwork
Aerated Fire Clay single leaf (Poroton)
Autoclaved aerated blocks (AAC, Ytong)
Vaccuum Sealed Insulated Panel Systems (VIPs)

Theres a myriad of sales-speak and technical data to thrudge through. I dont envy anyone starting out on a self build.

sydthebeat said:

Barney,
I would have no problem recommending any building system, but like everything, you have a rolls royce version and you have lada versions.

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Looks like im Building a lada so! I know im probably being a bit stubborn here, but the standard cavity has done well enough for the past 20 years, i know we wll have to move with the times but surely, the standard cavity house is still (albeit not meeting new regs) sufficent.

Preparing for the onslaught!!!

there wont be an onslaught jollyman

perhaps 'sufficient' might be an acceptable adjective.... but read the article fully and you will see why 'inadequate' is more applicable.

remember that cast in situ concrete was 'sufficient' in the 40's and 50's... cavity walls with no insulation was 'sufficient' in the 60's and 70's
cavity partial fill maybe was 'sufficient' for 80's and 90's...... but no longer. The industry standard is now no longer adequate in todays climate of energy efficiency and sustainable building.

Its like anything, any structure with walls and roof can be considered a dwelling... its the make up of it that determines the comfort of its occupants.

Hi Syd,
You really know your stuff about new building methods.
I would love your comments on this product which i was considering using in my self build.It has a IAB cert and you can get a 300mm single panel which would reach a u value around .11 according to the manufacturers(would imagine the bridging from the steel would reduce this.)
i also noticed the bridgeing where the floor meets the ring beam on the first floor.Do you think this would be a big issue?
I have no association with the company.
Thanks

[broken link removed]

sydthebeat said:

there wont be an onslaught jollyman

perhaps 'sufficient' might be an acceptable adjective.... but read the article fully and you will see why 'inadequate' is more applicable.

remember that cast in situ concrete was 'sufficient' in the 40's and 50's... cavity walls with no insulation was 'sufficient' in the 60's and 70's
cavity partial fill maybe was 'sufficient' for 80's and 90's...... but no longer. The industry standard is now no longer adequate in todays climate of energy efficiency and sustainable building.

Its like anything, any structure with walls and roof can be considered a dwelling... its the make up of it that determines the comfort of its occupants.

Click to expand...

Ok point taken thats me put firmly in my place! I suppose its down to the age old battle of the QS V the Architect/Engineer spec We always have that battle in our offices, as one of the posters in my office says "Quality will be remembered long after cost has been forgotten" (Erected by one of the cheeky contracts managers)

Hi sparky,
im familar with the M2 emmandue firm, i know the development they built in Portarlington, Riverview, ive done a snag list on of the units.

I also had a good chat with them yesterday at the PlanExpo. Theyre fully IAB certed. Therefore i have absolutely no problem in recommending them. AFAIK theyre one of only two ICF dealers that are IAB certed. the other is amvic from kildare. the IAB cert shows that the system is suitable for the irish climate and regulations.

I assume you are planning on using the single panel system. I am happeir with the 35mm sprayed conc finish that the thin bed plaster finish on other systems. I also think their system would be perfect for the thin brick finish ive seem on other systems.
I personally would prefer the double skinned system because of the reduction of cold bridges. There is a possibility of a large cold bridge at the ringbeam level of the single panel system.

my only advice would be to perhaps get a quote from both systems and see how competitive they are.........

i have no association with either system.

As Sydthebeat said the u value is the one of the most important considerations, so what about the new baby... Passive House. Concrete / timber etc... at the end it is all about heat loss and cost.
If one if building a new house BER is important.

Though interesting reading, this article is utterly biased IMO and read like the timber frame vs traditional concrete built house rage.

Just have to check who wrote it....The above mentionned web-site home page starts with

"This web site gives you a wide choice of Timber Frame to choose from, whether it's a Dormer, Two Storey, Semi-Detached or large scale housing developments. "

Click to expand...

humm.....


How is all this above u-value wall theory stuff impacted by the overkilled Building Regulation Part F "Ventilation"? and the windows/doors u-value? and the roof (which is where heat loss occur most)?
Is it not like trying to build a Ferrari car fitted Jolly Man Lada's engine?

The article was sourced from centurys website... but was actually published in Construct Ireland Magazine in February 2005. The article holds no bias to any industry. The author is a project Architect who is able to give unbiased opinion based on experience and available technical data.

The ventilation regulations (part F) are a necessary requirement to ensure the health of a building and its inhabitants. Without proper ventilation we would become very sick due to inhaling exhausted gases, co2 and co3. Our buildings would crumble due to mould, fungal growth and rot.
It is widely accepted that to have as low energy a dwelling as possible you should be incorporating a mechanical Heat Recovery ventilation system, the 'hole in the wall' passive vents are inadequate from an energy efficiency point of view and shoul dnot be used as the industry standard any more.
bacchus, i dont understand what issue you have with window/door u values?? and the roof??? the lowest u value is required in a conventional roof (0.16).... and the vast majority of contractors and self builders out there still cannot insulate the roof properly to comply with the regs.....

sydthebeat said:

The ventilation regulations (part F) are a necessary requirement to ensure the health of a building and its inhabitants.

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I did not say there were not necessary, simply that there are OTT IMO ( this is why Irish houses are so drafty and struggle to keep any heat in)

I completly agree that the "hole in the wall" should not be used as the industry standard any more, but it still is. Because it is a quick and cheap solution to a dangerous issue.

sydthebeat said:

bacchus, i dont understand what issue you have with window/door u values?? and the roof??? the lowest u value is required in a conventional roof (0.16).... and the vast majority of contractors and self builders out there still cannot insulate the roof properly to comply with the regs.....

Click to expand...

my point exactly.. one needs to take into account the u-value of all the elements that makes a building rather than just the u-value of the wall.
Take windows for instance.. many people/companies just talk about the u-value of the glass/glazing, and forget about the rest that makes a window.

bacchus said:

my point exactly.. one needs to take into account the u-value of all the elements that makes a building rather than just the u-value of the wall.
Take windows for instance.. many people/companies just talk about the u-value of the glass/glazing, and forget about the rest that makes a window.

Click to expand...

When a dwelling is being 'certified' to comply with building regulations the overall heat loss is calculated... if it fails then it cant be certified. every element of the build is included in this. The regs also give elemental u values that, if not exceeded, should comply with the overall heatloss. ie wall = 0.27 roof =0.16 window / door = 2.2.
Its interesting to note that some elemental u values may be exceeded and the dwelling may still comply with the overall heatloss and thus comply with the regs.

any delared u value for a window / door must include its frame. If people only consider the glazing u value then they are incorrect and frankly uneducated. Whether or not the frame is thermally broken is a huge factor in the u value of a window.

Hi sydthebeat,

If full cavity fill is the way to go would you recommend filling the remainder of a partially filled cavity in an already constructed house as a method of improving the u-value of the walls?