Partial fill cavity construction: dead?

cookie1.... what im saying is that the 310 cavity wall itself has passed its 'use by' date. Full fill (blown-in.... NOT full fill board.!!!!) has advantages over partial fill because of the reduction of thermal looping, the guarantee of a more uniform and soild insulation, but its not the way forward either... it will have its uses as tradepeople are always slow to change.

improving u values of construction is all well and good, but this may not solve the problem of heat losses. If someone has a 310 cavity wall house and want to improve performance, the first thing i would advise would be to do an airtightness test and subsequent investigation with a smoke pen and see exactly where leaks and draughts are in the construction. These can then be sealed and the differemce measured.

When air tightness tests become compulsory, a measurement of above 10 m3/hr/m2 will be a failure. I have a very strong opinion that the vast majority of houses built over the last 10 years in ireland will fail this value, in fact i forsee values of 25-35 being applicable to them.
This value of 10 is only a 'lead-in' value... industry requirements will be about 7 and best performace will be about 2-3.....
 
'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.[/quote]

Syd, you will never get accurate information for u-vlaue on window and doors, only estimates. It changes with so many factors, i.e. u value of oak is different to larch, sipo, pine etc and then the chosen glass package varies depending on glass spec. Safety glass by law must only be safety on one side, laminated glass(the best for safety/security) reduces the volume of Argon as the overall glass package remains the same 24 or 28 mm the norm. Good practise using eg. pine with a 24mm glass package (4-16ar-4) in 78mm frame (pine) 1 mtr x 1mtr should deliver overall u = 1.4. This for sure would go up if safety glass used. Essentially to certify accurately u value for a window then that window would need to be tested. There are no accurate formulas as timber values can really only estimate
 
osho said:
Syd, you will never get accurate information for u-vlaue on window and doors, only estimates.
Click to expand...

what you will get is 'declared' u-values and once it can be shown that these values have been calculated using accrediated testing methods, its good enough to use in say, BER ratings etc. It may not be specific from one frame to another, but it will be good enough.
 
I’m looking at the best cavity wall construction. I do not want to "dry line" with internal insulation. Here’s the proposed wall makup:

1. Outer wall – standard 100mm concrete block

2. Cavity 100mm with:
A. Kingspan Kooltherm K8 only 60mm – U Value 0.25 or
B. Bonded Beads 100mm only - U value of 0.27 or
C. Kingspan Kooltherm K8 60mm – U Value 0.25 plus 40mm Bonded Beads (beads on their own in a 40mm cavity gives U value of approx 0.57) - any ideas what the overall U value is for this combination?
​
3. Inner wall – Quinn Lite B5 150mm block – U Value 0.17

Note: I want to use pre-fabricated concrete floors so have been recommended by Quinn to use the 150mm B5 block. Overall wall width = 350mm.

What’s the overall U value for this entire wall? Any comments and suggestions for improvement?
 

Hi,

Ok, the B5 has a thermal conductivity of 0.17, not a u-value. The u-value of a 150mm B5 is 0.94.

The u-value of 60mm of K8 is 0.33, not 0.25. This is based on a thermal conductivity of 0.021.

I use the SEI u-value calculator which is available at [broken link removed]

I'm no expert but I make the u-value for this wall (option A) to be 0.25. I haven't allowed for the air cavity because I have no idea what the conductivity of air is. I assumed 1.13 for the outer dense block.

This is not a good result. I've read a thread over on boards.ie this week where one of the posters stated that he can't get any building to meet the incoming regs. unless the wall has a u-value of 0.22 or better.

You should download the u-value calc. from the above link (assuming you have access to a copy of excel). I've found it really helpful.

Good luck
 
sas said:
Hi,

I've read a thread over on boards.ie this week where one of the posters stated that he can't get any building to meet the incoming regs. unless the wall has a u-value of 0.22 or better.

Good luck
Click to expand...

What are the incoming regs ?
 
hope these screen caps help:


[broken link removed]


[broken link removed]
. Note: your concrete floor does not require anymore that 100 inner leaf, there are plenty of manufacturers out there that do a panel to suit this.
 
Last edited:
sas said:
I'm no expert but I make the u-value for this wall (option A) to be 0.25.
Click to expand...

I would think the vast majority of existing houses come nowhere near U value of 0.25. I agree however that it's not great.

It's really option C I was thinking of. Will try the U value calculator to see what value option C gets. Hope I do it right!!
 
Syd and SAS, thanks so much for this.... really helpful!

I've had a go with the calculator and got the following U Values (based on Syd's thermal conductivity values):

http://i259.photobucket.com/albums/hh293/brianmcskane/UValues-1.gif

All thermal resistances are as per Syd's previous post and the Quinn B3 block = 0.12W/mK and B5 block 0.17W/mK. (www.quinn-lite.com)

Conclusions (if correctly calculated!!)
1. Cheapest (assuming std blocks are cheaper than Quinn Lite blocks) and almost best U Value is row 9 (as per Syd's conclusion), i.e. U Value of 0.15 (0.13 can be achieved with Quinn Lite B3 100mm block)

2. Difference in the Quinn Block 100mm v 150mm is just U value of 0.01 - e.g. compare row 13 and 14 or row 16 and 17

3. Difference in the Quinn Lite B5 100mm v Std 100mm concrete block is marginal - compare row 9 and 15 and 18 [Can someone confirm this as it doesn't make sense.... did I calculate wrong???]

4. Increasing the cavity from 100mm to 150mm (and filling with EPS) is more effective than increasing block width from 100mm to 150mm - compare rows 17 & 18 (cavity width) with rows 16 and 17 (block width)

5. Overall the obvious option is row 9, i.e. standard 100mm concrete blocks with 150mm cavity filled with EPS (this is platenum bonded beads I assume?) as per Syd's earlier post.

Comments and corrections welcome!
 
Had a quick look at Syds 0.15 option. The thermal conductivity of Ecobead Platinum as per the IAB cert is 0.033, the regular ecobead is 0.04.

These will give worse u-values obviously. Haven't checked the other pumped insulation types. You should take a look on www.nsai.ie under "thermal insulations" in the Agrement Board section.
 
I was at the Homebond "Right on the Site" seminar in Kilkenny last night; I'd recommend that anyone interested in the implications of the forthcoming Part L 2007 go along to the next one in their region. Air tightness will be a huge industry in itself(and the construction industry thought that radon was a headache!). SEI and Ecoheat gave excellent presentations on renewable energy options.
 
Is there any issues with moisture through walls with
- bonded bead insulation with/without board insulation (e.g Kingspan Kooltherm K8 60mm)
- as compared to normal cavity wall (with board insulation only).
 
KBREN said:
Is there any issues with moisture through walls with
- bonded bead insulation with/without board insulation (e.g Kingspan Kooltherm K8 60mm)
- as compared to normal cavity wall (with board insulation only).
Click to expand...

For all above options there are none that i've ever heard of and know people who have employed all those methods.

According to Syd the best results are got from fully pumped bonded beads. When calculaed (see above posts) this did indeed prove correct.

Also you should save on the building of the house as your builder has no insulation boards to deal with and slow him down. Also less chance of him just wacking them in without care when you're not looking!!
 
Barney, im going to completely change my opinion on pumped in insulation.. sorry....

there were some assumptions made in the above calculations that turned out to be incorrect on my part. My TC values were incorrect. Im actually going to take out the pumped in insulation calculation above....

For a regular cavity block wall 100mm, pumped in will only get you 0.3 u value.
To achieve miniumum regs (0.27) u values you need to use AAC blocks on the inner leaf of a 100 cavity.

there is one company who claims a u value of 0.2 with a 150mm cavity... but that doesnt state whether the (more expensive) AAC blocks need to be used.

My preferred cavity construction is as follows:

external render
100 dense concrete block
50 cavity
100 AAC block
100 PU board mechanically fixed
47.5 Composite plasterboard
skim finish

With this relatively easy construction you are looking at a construction u value of 0.13. There are also added advantages of having the thermal insulation within the structure which i can go into later.
 

This construction does fall down though anywhere there is a junction between an external and an internal wall. Unless of course you intend dryling everywall in the house!
 
if AAC blocks are used, thermal bridges are kept to a 'practical' minimal....

a TC value of 0.18 for AAC is a hell of a lot better than 1.15 for dense concrete blocks.
 
sydthebeat said:
if AAC blocks are used, thermal bridges are kept to a 'practical' minimal....

a TC value of 0.18 for AAC is a hell of a lot better than 1.15 for dense concrete blocks.
Click to expand...

Ok, fair enough I missed that.

Wouldn't the lack of cavity insulation make hollowcore on the first floor a substantial cold bridge?
 
sas said:
Ok, fair enough I missed that.

Wouldn't the lack of cavity insulation make hollowcore on the first floor a substantial cold bridge?
Click to expand...

... we would detail that out if it came to it..... we still have a 50mm cavity to play with
 
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